MANTECH FAQ Library

  • What does high BOD indicate?

    BOD indicates the amount of putrescible organic matter present in water. Therefore, a low BOD is an indicator of good quality water, while a high BOD indicates polluted water. Dissolved oxygen (DO) is consumed by bacteria when large amounts of organic matter from sewage or other discharges are present in the water.

  • What happens if COD is high?

    Higher COD levels mean a greater amount of oxidizable organic material in the sample, which will reduce dissolved oxygen (DO) levels. A reduction in DO can lead to anaerobic conditions, which is deleterious to higher aquatic life forms.

  • What causes high COD in wastewater?

    COD increases as the concentration of organic material increases. It also increases if inorganic compounds susceptible to oxidation by the oxidant (typically dichromate) are present. Water with high COD typically contains high levels of decaying plant matter, human waste, or industrial effluent.

  • What is the BOD of raw sewage?

    BOD can also be defined as the amount of oxygen required by the micro-organisms in the stabilization of organic matter. The results are generally expressed as the amount of oxygen taken by one litre sample (diluted with aerated water) when incubated at 20 degree for five days. BOD of raw sewage is 300-600 mg/litre.

  • What is the COD to BOD ratio in domestic sewage influent?

    BMS have recorded average ratios of 2-3 mg/l COD to 1 mg/l BOD over its 30 years of business. Influent COD in normal domestic sewage is therefore generally 600 – 900 mg/l and it is then treated to at least 30 -100 mg/l before discharge to minimize pollution potential.

  • Why is COD higher than BOD?

    COD is normally higher than BOD because more organic compounds can be chemically oxidised than biologically oxidised. This includes chemicals toxic to biological life, which can make COD tests very useful when testing industrial sewage as they will not be captured by BOD testing

  • How do I store my PeCOD sensor?

    On a day to day basis, the PeCOD sensor inside the Analyzer head, in the same location as it is placed for operation. At the end of each analysis and calibration, the PeCOD primes the sensor line with blank solution to provide a clean environment similar to operating conditions for storage. An alternative to this is to prime DI water manually through Port A of the PeCOD at the end of a day’s operations.

    When the PeCOD is not going to be used for some time, for example a week or longer, it is good to remove the sensor from the unit for long term storage. This is done by first removing the Port A and B tubes from liquid, then priming those lines with air. Then, press on the front latch to open the analyzer head and access the sensor. The sensor can then be lifted off the alignment pins. Once removed, it is important to use a syringe to “dry” the internal channels of the sensor. Fill a 10mL syringe with air, then press the syringe (without a tip) against the holes in the back of the sensor. Push the syringe down to push air through the sensor channels. Perform these steps on each of the holes in the back of the sensor, in the following order:

    Once dry, place face down on a dry surface to finish the drying process. Next, place the sensor in a cool, dark place for long-term storage. The sensor packaging works as a suitable package for long term storage after properly drying the sensor.

  • What is the method for Hot Acidity determination?

    Hot acidity is a variation of the standard Acidity titration using NaOH, with some pretreatment steps performed before the titration. It is outlined in Standard Methods SM2310B, officially called “hot peroxide treatment procedure for acidity determination”. This method is applicable to mine wastes and other samples containing large amounts of metals such as heavy industrial WW.

    From SM2310B:

    • Use the hot peroxide procedure to pretreat samples known or suspected to contain hydrolysable metal ions or reduced forms of polyvalent cation, such as iron pickle liquors, acid mine drainage, and other industrial wastes.
    • Hot peroxide treatment acidity method:
      • Pipet sample volume into vessel
      • Measure pH
      • If pH > 4.0, add small increments of 0.02N H2SO4 to reduce pH to 4.0 or less
      • Remove samples from MANTECH system
      • Add 5 drops of 30% H2O2 and boil for 2 to 5 minutes
      • Cool to room temperature
      • Place samples back on MANTECH system and titrate with standard alkali (NaOH) to pH 8.3
    • The calculation for hot acidity is shown below:
      • Acidity = [((mL NaOH consumed)*(Normality of NaOH)) – ((mL H2SO4 consumed)*(Normality of H2SO4))*50,000]/Sample volume

     

  • What is the measuring range for Dissolved Oxygen on MANTECH systems?

    MANTECH systems utilize one of two dissolved oxygen probes from YSI for automated dissolved oxygen determination. The measuring ranges of both probes are listed below, along with a link to the complete specification sheets.

    YSI FDO 4410 IDS Sensor

    • Dissolved Oxygen Range: 0 to 20 mg/L
    • Air Saturation Range: 0 to 200%
    • Temperature Measurement Range: 0 to 50°C
    • Technical Specifications

    YSI ProOBOD Sensor

    • Dissolved Oxygen Range: 0 to 50 mg/L
    • Air Saturation Range: 0 to 500%
    • Temperature Measurement Range: Ambient 10 to 40°C; Compensation -5 to 50°C
    • Technical Specifications

     

  • How does the PeCOD Analyzer determine oxygen demand?

    The PeCOD® Analyzer performs advanced oxidation on a small volume of sample. As the reaction proceeds, electrical charge is generated proportional to the oxygen being consumed. The PeCOD® analyzer captures this generated charge, plotting the output current from the reaction over time as shown below. The area under the curve generated by plotting current over time is proportional to the oxygen demand of the sample. A blank charge is also determined for each sample, and subtracted from the total charge to ensure accuracy.

    View the detailed overview of peCOD technology and calculations here.

    peCOD Oxidation Profile

     

  • I have an Error Code displayed on my PeCOD Analyzer, what does it mean?

    For information about what the error code displayed on your PeCOD Analyzer represents, click here.

     

  • How can I make Calibrant and Check Standard solutions?

    View our instructions for producing 1L calibrants, check standards and for more information on these solutions: https://mantech-inc.com/wp-content/uploads/2020/09/1-L-calibrant-instruction.pdf

     

  • How does the PeCOD method compare to BOD, TOC, and conventional COD?

    There are several common methods to test wastewater and drinking water for organic pollutants, natural and chemical.  Chemical Oxygen Demand (COD), Biochemical Oxygen Demand (BOD) and, Total Organic Carbon (TOC) compromise the three main methods of testing water samples.  BOD and COD methods differ from TOC because they measure the amount of oxygen that is depleted by organic species in water.  Moreover, TOC is a measure of all carbon (both organic and inorganic), rather than the oxygen that is reduced by these species.  As written by a TOC manufacturer, “TOC on its own sheds no light on the oxidizability of the measured carbon or the amount of oxygen needed for its biodegradation.  Specific to COD, it measures the reactive fraction of the TOC.  This is also known as oxidizability in the European Union.

    View the full article: Comparison of COD, BOD and TOC Methods for organics, which summarizes the advantages and disadvantages of the COD, BOD and TOC methods, and compares them to the PeCOD method.

     

  • Why did my PeCOD calibration fail?

    It is possible that a PeCOD will fail it’s calibration. If this occurs, the PeCOD will notify you of the reason it did not pass. Common reasons are that the M value or C value are out of range. Please refer to page 19 of the PeCOD Pro Operation manual for more information.

     

  • What is your warranty policy?

    MANTECH Instruments are warrantied for a period of one year (unless otherwise specified) from the date of shipment. This warranty covers defects in material and workmanship (parts and labour), under normal installation, use and maintenance, within the region of installation, as described in the operator’s instructions. Please refer to the user’s manual. This warranty does not cover Computer products, YSI branded products, consumables, expendable items or items with physical damage. Computer warranty/service is handled direct by the endusers through the manufacturer. YSI warranty/service is handled direct by the endusers through the local YSI distributor.

    For MANTECH’s warranty policy for electrodes, CLICK HERE.

  • What does the change from ManSci to MANTECH mean for existing customers?

    We have released new 2021 pricing, please contact us at quotes@mantech-inc.com for pricing details and quotations.

    Orders should now be placed with MANTECH.  We are ready to complete vendor registration requirements, simply send requests for information to orders@mantech-inc.com.  Ordering directly with MANTECH provides you a one stop shop ensuring efficient fulfillment, shipping and communication.  Orders placed by USD credit cards are welcome.  If required, orders can still be placed with ManSci as well.

    We continue to appreciate your trust and investment in MANTECH products. We look forward to supporting your automated analysis requirements.

     

  • Why did ManSci change their name to MANTECH?

    ManSci has been MANTECH’s distributor for over 10 years.  Following the acquisition in October 2020, ManSci is now MANTECH (USA) Inc. and a a wholly owned subsidiary of MANTECH.  The exceptional ManSci and MANTECH Teams have now joined forces under one MANTECH brand ensuring outstanding quality, service and support to our customers directly from the manufacturer of MANTECH analyzers.  Our North American Team is fully committed to our mission, specifically to “Optimize Your Results and Protect Our Environment.” 

  • Where can I find our certificates of analysis?

    All certificates of analysis can be found on our Dropbox. Please click here to be redirected to the C of A page, then choose the appropriate folder.

  • What computer specifications are required to run MANTECH software?

    Please see this technical bulletin for the minimum requirements.

  • Where can I find our SDS's?

    The SDS’s to all solutions are posted on our Dropbox. Please click here to be redirected to the SDS page, then choose the appropriate folder.

     

  • How do I contact for support?

    To get in contact with a representative regarding support for MANTECH products, please send an email to support@mantech-inc.com or call us at +1-519-763-4245.

  • How do I contact MANTECH?

    To contact MANTECH regarding product information and general inquiries, you may call us at +1-519-763-4245 or send an email to info@mantech-inc.com. You may also reach out to us directly through our website from the page linked here.

    If you would like to inquire directly about a new or existing quotation, you may email our sales team directly at quotes@mantech-inc.com.

  • What is our mailing address?

    Our mailing address in Canada is 5473 ON-6 N, Guelph, ON N1H 6J2.

    Our mailing address in the USA is 6925 Lake Ellenor Drive, Building 1, Suite 136, Orlando, Florida 32809.

  • Do we accept credit card payments?

    Yes, we do accept credit card payments. To make a payment with credit card please call us at +1.519.763.4245.

  • How do I place an order?

    To place an order, please email us at orders@mantech-inc.com or call us at +1.519.763.4245 . To ensure quick processing, orders should reference a MANTECH Quotation number. To inquire about pricing and receive quotations for MANTECH products, please send an email to quotes@mantech-inc.com.

  • How does PC-BOD calculate BOD when samples have failed BOD Method criteria?
    • If all samples fail the final DO rule, the software will report the value for the sample with the highest dilution (lowest sample volume) and display a greater than (>) symbol.
    • If all samples in a set fail the depletion rule and the BOD of the bottle with the lowest dilution (highest sample volume) is greater than the minimum detection, the software will report the value for the sample with the lowest dilution (highest sample volume) and display a less than (<) symbol.
    • A less than symbol (<) will appear when all samples in a set have a depletion of less than that specified in the BOD Method.  If the BOD of the bottle with the lowest dilution (highest sample volume) is less than the minimum detection for a given sample condition, the average will be displayed as follows:
      • Diluted samples with no seed added < 2 mg/L
      • Diluted samples with seed added < 1 mg/L
      • Undiluted samples with no seed added < 0.1 mg/L
      • Undiluted sampled with seed added < 0.0 mg/L

     

  • How long does it take to measure initials and finals on a MANTECH AM300 series multi-rack system?

    The length of time to measure initials and finals on a MANTECH AM300 series multi-rack system varies depending on the method of sample preparation, sampler size, and probe style. For an example of a typical MANTECH BOD system click here.  For an individualized estimate contact us at support@mantech-inc.com.

  • What information is required to automate biochemical oxygen demand?

    Automating the biochemical oxygen demand (BOD) test can greatly increase the efficiency and production capacity of a laboratory. In order to automate this analysis, the following information is required:

    • How many bottles on average do you set up for an initials batch?
      • (For example, this accounts for all samples and all dilutions per sample, plus blanks, GGA’s, etc.)
    • On what days of the week do you set up for initials?
      • (For example, many laboratories set up Initials on Wednesday, Thursday, and Friday then Finals on Monday, Tuesday, and Wednesday since the laboratory is closed on weekends)
    • What is the maximum number of bottles in your incubator at any one time?
    • Do you analyze BOD, cBOD, or both?
    • What is the range of BOD concentration?
    • What type of samples are you analyzing?
      • (For example: industry type, river, etc.)
    • Who are the clients or users of the BOD information?
      • For example industrial pre-treatment, WWTP effluent compliance, WWTP engineers, etc.

     

  • What is biochemical oxygen demand?

    Biochemical Oxygen Demand (BOD), also often referred to as biological oxygen demand, is a test performed to measure the potential of wastewater and other waters to deplete the oxygen level of receiving waters. In other words, the BOD test is performed to determine what effect dirty water, containing bacteria and organic materials, will have on animal and plant life when released into a stream or lake. Learn more here.

  • What are the dimensions of MANTECH BOD Autosampler Racks?
    Part Number Rack Size Bottle Style Width Depth Rack Height Rack Height w/ Bottles
    PB-10138 11 x 300mL Plastic

    337 mm

    13.25 inches

    234 mm

    9.19 inches

    88 mm

    3.13 inches

    8 mm + bottle height

    0.313 inches + bottle height

    PB-10139 11 x 300mL Glass

    337 mm

    13.25 inches

    234 mm

    9.19 inches

    88 mm

    3.13 inches

    8 mm + bottle height

    0.313 inches + bottle height

    PB-10162 23 x 300mL Glass

    488 mm

    19 inches

    307 mm

    12.06 inches

    71 mm

    3.81 inches

    9.5 mm + bottle height

    0.375 inches + bottle height

    PB-10163 23 x 300mL Plastic

    488 mm

    19 inches

    307 mm

    12.06 inches

    71 mm

    3.81 inches

    9.5 mm + bottle height

    0.375 inches + bottle height

    PB-10060 (discontinued) 24 x 300mL Glass/Plastic

    485 mm

    18.82 inches

    315 mm

    12.38 inches

    193 mm

    7.60 inches

    5 mm + bottle height

    0.188 inches + bottle height

    PB-10133 (discontinued) 24 x 300mL Glass/Plastic

    485 mm

    18.82 inches

    315 mm

    12.38 inches

    131 mm

    5.125 inches

    5 mm + bottle height

    0.188 inches + bottle height

    PB-10185 18 x 300mL Glass

    487.68 mm

    19.2 inches

    236.22 mm

    9.03 inches

    63.5 mm

    2.5 inches

    2.69 mm + bottle height

    0.106 inches + bottle height

    PB-10186 18 x 300mL Plastic 487.68 mm

    19.2 inches

    236.22 mm

    9.03 inches

    63.5 mm

    2.5 inches

    2.69 mm + bottle height

    0.106 inches + bottle height

     

  • How do I configure the YSI 4010 MultiLab IDS meter for PC-BOD?

    To use the YSI 4010 MultiLab IDS meter with PC-BOD, the appropriate driver, computer settings, and software settings must be applied.  Download the Technical Bulletin for more details.

  • Why does the barometer reading on my YSI 4010 MultiLab IDS meter not match the reading documented by my local weather service?

    The YSI MultiLab IDS meter outputs a true barometric pressure reading of its location, which is dependent on elevation above sea level.

    Local weather services typically use a corrected barometric pressure reading, which corrects the reading to sea level.

    To approximate the true barometric pressure reading from a corrected barometric pressure reading, use the following equation:

    True barometric pressure [mmHg] = Corrected barometric pressure [mmHg] – (0.025 * local altitude [feet] )

  • Can I calibrate the internal barometer on my meter?

    The internal barometer on the YSI MultiLab IDS meter is calibrated upon manufacturing and is designed to last the lifespan of the barometer sensor. The sensor is very stable and can last many years. Standard Methods does not specify a requirement for an adjustable barometer for dissolved oxygen measurements or biological oxygen demand testing.

     

  • How do I calibrate my DO probe with the YSI 4010 MultiLab IDS Meter?

    Unless otherwise specified in company or site-specific procedures, specifications, and regulations, a water vapor-air saturated calibration should be sufficient for probe calibration.  For full calibration procedures, please refer to the following pdf.

  • How do I set the sensor cap coefficients in my YSI 4010 MultiLab IDS meter?

    Follow the step-by-step instructions in the pdf.

  • How do I set the date and time in my YSI 4010 MultiLab IDS Meter?

    Follow the step-by-step instructions in the pdf.

  • What is the difference between BOD and cBOD?

    Biochemical oxygen demand (BOD) is a way to assess the amount of oxygen required for aerobic microorganisms to decompose the organic material in a sample of water over a specific time frame. It is the oxygen uptake demand of a source of water. Carbonaceous biochemical oxygen demand (CBOD) is the same method as BOD, but the nitrifying bacteria in the sample are inhibited. Nitrifying bacteria consume nitrogenous materials (compounds with reduced forms of nitrogen) and add to the oxygen demand of the wastewater. Nitrogenous materials are often seen as interference because the purpose of the BOD test is to measure carbonaceous material.

  • How do I store my MANTECH Electrodes?

    MANTECH recommends storing pH and other electrodes immersed in a 1:10 dilution of pH 4 buffer in Tap Water. Conductivity electrodes can be stored in air for system configurations that do not place it on the same holder as another electrode.

  • How does MANTECH account for temperature compensation and correction in pH measurements?

    As the temperature of a solution changes, the actual pH changes. This is not an error of the probe or meter being used, but is the actual pH of the solution at that particular temperature. The temperature effect on the pH value is 0.003 pH units per oC away from 25oC, per pH units away from pH 7. This effect can be either negative or positive, depending on if the temperature is above or below 25oC, and if the pH is above or below pH 7. At 25oC and pH 7, there is no change in the pH value.

    The chart below shows how the actual pH changes with temperature and pH, which allows you to correct the pH reading to 25oC. As an example, if a sample measured pH 5 at a temperature of 5oC, the chart indicates this a negative effect, therefore the sample pH would be 5 – 0.12 = 4.88pH corrected to 25oC:

    MANTECH software accounts for temperature by recording the temperature during calibration via a thermistor probe, then it corrects the pH reading at the time of measurement to account for the difference in measured temperature of the sample vs. the calibration buffers. The reported pH value is the corrected value @ the sample temperature. The equation below shows how the PC-Titrate software calculates pH:

    pH equation

    EMeas  =  Voltage measure by electrode at the time of titration (mV)

    EInt  = Voltage of the Intercept value calculated from the calibration equation. (mV)

    Slope = slope of the line calculated from the calibration equation. (mV)

    TMeas = temperature measured at the time of pH measurement (K degrees)

    TCal = temperature taken at the time of last calibration. (K degrees)

     

    MANTECH also offers the option to report pH values corrected to a set temperature, such as 25°C. This is implemented in the software as an additional step after the sample pH is recorded. MANTECH offers this as a feature for new MT-Series systems, or as an upgrade to existing MANTECH systems.

    For more information please follow this link or contact us at support@mantech-inc.com.

     

  • What are the benefits of IntelliRinse?

    IntelliRinse™ is beneficial because it uses real-time measurement to provide confirmation that your probes are 100% clean, eliminating chances of cross-contamination.

    Active IntelliRinse™ systems allows users to set user-defined values (e.g. rinse to a specific conductivity value) or to adjust the rinse intensity based on previous sample concentrations before moving to the next sample. This is beneficial as it improves the rinsing of probes/electrodes to ensure that cross-contamination does not occur even with particularly dirty or high-strength samples. There is also the option to have the final value measured during rinsing shown in a column on the results report, for a visual confirmation directly with sample results.

  • Do I need a stirrer for my conductivity measurements?

    MANTECH utilizes rapid dipping of conductivity probes into sample tubes to mix samples and ensure a stable analysis of conductivity from the probe. This style of mixing is applicable to systems featuring a 12mm conductivity probe dipping into 50mL sample tubes, and systems featuring a 5mm conductivity probe dipping into 15mL sample tubes.

    For all other combinations of probe and sample vessel, a stirrer is required to ensure proper mixing is achieved.

     

  • What is the recommended type of standard for automated Turbidity Calibrations and Quality Control?

    MANTECH recommends the use of turbidity standards made with suspensions of microspheres of styrene-divinylbenzene copolymer for all turbidity applications. Standard Methods dictate that “Secondary standards made with suspensions of microspheres of styrene-divinylbenzene copolymer typically are as stable as concentrated formazin and are much more stable than diluted formazin.

     

  • What is the wavelength measured for Turbidity by Standard Methods (White Light)?

    Standard Method 2130B (Nephelometric Method) specifies that a laboratory or process nephelometer should have a detector system with a spectral peak response of 400 to 600 nm. MANTECH’s T10 Turbidity meter and automated turbidity applications conform to this requirement.

     

  • How do I clean my conductivity probe?

    For water soluble contaminants, rinse probe in deionized (DI) water.  If ineffective, soak probe in warm DI water with household detergent for 15 – 30 minutes.

    For oil-based contaminants, rinse probe in ethanol or acetone for short (5-minute) periods.

    After cleaning, rinse probe in DI water to remove residual cleaning reagents.  Perform a meter calibration before proceeding with sample analysis.

     

  • What is the Time of Analysis for Different Parameters?

    The timing for analysis of different parameters depends on a few different factors, like the concentration of the sample and the equipment used.

    Another factor is the total available sample volume in the vessel on the AutoMax Autosampler bed. With some combinations of parameters, larger sample volume allows for simultaneous measurements, resulting in faster total analysis time than sequential measurement.  A larger sample volume may require a larger sample cup, which decreases capacity on the same model Autosampler.  For example, an AM73 can accommodate 73x50ml tubes, or 30x125ml cups.  In some, the cases the same set of parameters can be analyzed in 2-5 minutes faster when using the 125ml cups vs 50ml tubes.

    It is important to understand your customers’ requirements in terms of capacity and throughput speed, total batch capacity required and/or daily sample loads and if overnight, unattended analyses will be applicable.

    Individual Parameters

    Combined Parameters

    MT-10 & MT-30 Models

    * If alkalinity is combined with turbidity and/or colour an MT-100 System must be quoted

    MT-100 Model

     

     

  • What are the Different Types of Calibration Profiles?

    Calibrations can be linear, logarithmic, single-line, and multi-line fit. 

    The calibration method used depends on the method required.

    pH and Color calibrations are linear, single-line fit calibrations.

    Conductivity and Turbidity calibrations are multi-line, linear type calibrations.

    ISE (Fluoride, Chloride, Ammonia, etc.) use a logarithmic multi-line calibration type.

     

  • How do I change the buret IP address?

    Mantech Burets have a static IP address assigned to them. These addresses can be changed if there are communication issues between the Buret and the software.

    If an IP address needs to be changed, then you can manually change it using the following steps:

    1. Open the Network and Sharing Centre on your computer through the advanced network settings, or through searching on the Control Panel.

    2. Open Command Prompt on your computer by searching it in your Windows Search Engine.

    3. Extract this folder to your computer.

    4. Plug in the burette. In the Network and Sharing Centre, find the active network for the buret (ethernet connection) and open the properties by selecting the blue “Ethernet”. Open the properties.

    5.Internet Protocol Version 6 should be unselected, and Internet Version 4 should be selected. Click OK and open the Details for the ethernet status. The Value for IPv4 Address should be 192.168.1.1. If not, change the IP address in the Internet Protocol Version 4 properties.

    6. In Command Prompt, type in ping and the IP address found on the back of the buret and then the enter key. For example, “ping 192.168.1.50” without the quotations and the enter key. The buret should reply.

     

     

     

     

     

    7. Open the Buret_IP_Change folder now on your computer and open the application that is in the bin subfolder.

    8. Type in the IP address and “Connect”. Click OK. Then type in the new IP address and select “Set IP”.

    9. In Command Prompt again, ping the new IP address to ensure it works.

    Specific notes:

    • If the IP address is not known, then in command prompt, type in “arp -a” without the quotes and the IP address for the buret will be given as the first line under the IPv4 Address Value. This can be done after Step 5.

    • If using PC-titrate, ensure that the version used is 889 or later. Previous versions do not support the ethernet Burets without an upgrade. Contact support@mantech-inc.com for the ethernet buret software upgrade.
    • If using Mantech Pro, you can find the IP address of the buret (if it is not the one already in the address line) in hardware configuration using the “Configure Adapter”. The software will find the IP address that works for that buret and can be used to test the ping as well for buret response.

     

  • Why is my conductivity analysis reporting negative values?

    The reason you may have negative conductivity values at the low end is that there is a PC-Titrate software calibration being applied on the raw conductivity values from the meter. They are not wrong and it means the value is zero (0). You see this often with DI water measurements. If you turned off the software calibration then you would get the exact same values as displayed on the conductivity meter.

     

  • How do I remove my electrode for maintenance?

    Most MANTECH electrodes are connected to the Interface module via a BNC cable with a detachable S7 connection. This S7 connection is located at the electrode cable junction, allowing for easy detachment from the cable, and removal of the electrode while leaving the cable in place. This applies to all electrodes except the Ammonia Electrode and all Conductivity electrodes. See below for pictures of a pH electrode with the S7 connection attached, and detached.

     

  • How is a Method Detection Limit (MDL) defined?

    A Method Detection Limit (MDL) is defined in slightly differring ways by the US EPA, and the APHA. The definitions are briefly described below:

    MDL as per US EPA:
    The method detection limit (MDL) is defined as the minimum measured concentration of a substance that can be reported with 99% confidence that the measured concentration is distinguishable from method blank results.

    MDL as per APHA:
    (MDL) is defined as the constituent concentration that, when processed through the entire method, produces signal that has a 99% probability of being different from the blank.

  • How does MANTECH account for temperature compensation and correction in conductivity measurements?

    Conductivity is a temperature dependent measurement. All substances have a conductivity coefficient which varies from 1% per °C to 3% per °C for most commonly occurring substances. The automatic temperature compensation on the MANTECH Conductivity meter defaults to 1.91% per °C, this being adequate for most routine determinations.

    Temperature-corrected Conductivity is calculated by:

    1. Subtract the current temperature of your standard from 25°C (or whichever reference temperature applies).
    2. Multiply the result by 1.91% which is your default temperature coefficient.
    3. Multiply the result by the uncorrected conductivity value.
    4. Add the result to the uncorrected conductivity value. If the sample temperature is higher than the reference temperature, the result of step 1, 2, and 3 are negative numbers so it is a subtraction from the uncorrected conductivity value.
    5. The result is the corrected conductivity value.

    Example: Uncorrected conductivity value is 1200uS, current temperature is 21.4°C, reference temperature is 25°C, default correction factor of 1.91%

    1. 25.0 – 21.4 = 3.6
    2. 3.6 * 0.0191 = 0.06876
    3. 0.06876 * 1200 = 82.51
    4. 1200 + 82.51 = 1282.51uS  <— Temperature Corrected Value for Reference Temperature 25°C

    Conductivity readings varying with temperature may be due to the substances under test having a coefficient other than the typical value of 1.91% per °C. To eliminate this variation it is necessary to maintain all samples at the reference temperature by use of a thermostatic water bath or equivalent.

    Adjustment may be made by entering the 4510 conductivity meter SETUP menu and selecting COEFF. The reading can then be adjusted to the required value (0.00 to 4.00) by using the keypad. A setting of 0.00 will mean that there is no temperature compensation being applied.

     

  • What is the difference between 2-pole and 4-pole conductivity probes?

    4-pole sensors have a much broader linear measurement range and are not sensitive to contamination.

  • What is the minimum total liquid volume that can be measured for pH, conductivity and alkalinity with the MT Systems?

    When using 50mL sample tubes, the minimum total volume can be as small as 6 ml using the TitraPro4 pH electrode and the MANTECH 5mm conductivity probe. This is due to the lower immersion depth of these electrodes and precise autosampler coordinate specifications. When using 125mL sample cups, the minimum total volume can be as small as 15mL.

     

  • What should I do if my titration standard is measuring too high or too low?

    If your titration standards are not reading the correct concentrations, for example, the alkalinity standard reading is low, first make sure the titrant has been standardized. Secondly, the precision of the results can indicate if this is a mechanical or chemical problem. If the results are precise, it is likely a chemical issue. Check your standards and titrant standardization. It is also possible that the sample volume may be incorrect.

     

  • What is the sample capacity for each AutoMax Sampler based on available tube and cup styles?

    Each of our AutoMax samplers are compatible with a variety of common sample cup and tube styles to accommodate up to 4 probes. To view available sample vessels and AutoMax sample capacities, read our technical bulletin here.

     

  • Why is the pH electrode slope and measuring characteristics different for higher pH values, for ex pH 13?

    Changes to slope at higher pHs

    Alkaline Error or Sodium Error occurs when pH is very high (e.g. pH 12) because Na+ concentration is high (from NaOH used to raise pH) and H+ is very low.

    Electrodes respond slightly to Na+ and give a false low reading.  This is related to the concept of selectivity coefficients where the electrode responds to many ions but is most selective for H+.  This problem occurs because Na+ is 10 orders of magnitude higher than H+ in the solution.

    High pH electrodes use a 0-14 pH glass.  This electrode will read pH 14 (1 M NaOH) to be around pH 13.7 with a 0.3 pH sodium error.

    A standard pH electrode uses a 0-12 pH glass.  The electrode will read pH 14 (1 M NaOH) to be around pH 12.4 with a 1.6 pH sodium error.

     

    Alkaline error

    The alkaline effect is the phenomenon where H+ ions in the gel layer of the pH-sensitive membrane are partly or completely replaced by alkali ions. This leads to a pH measurement which is too low in comparison with the number of H+ ions in the sample. Under extreme conditions where the H+ ion activity can be neglected the glass membrane only responds to sodium ions.  Even though the effect is called the alkaline error, it is only sodium or lithium ions which cause considerable disturbances. The effect increases with increasing temperature and pH value (pH > 9), and can be minimized by using a special pH membrane glass.

     

    Sodium Ion Error

    Although the pH glass measuring electrode responds very selectively to H+ ions, there is a small interference caused by similar ions such as lithium, sodium, and potassium. The amount of this interference decreases with increasing ion size. Since lithium ions are normally not in solutions, and potassium ions cause very little interference, Na+ ions present the most significant interference.

    Sodium ion error, also referred to as alkaline error, is the result of alkali ions, particularly Na+ ions, penetrating the glass electrode silicon‐oxygen molecular structure and creating a potential difference between the outer and inner surfaces of the electrode. H+ ions are replaced with Na+ ions, decreasing the Hion activity, thereby artificially suppressing the true pH value. This is the reason pH is sometimes referred to as a measure of the H+ ion activity and not H+ ion concentration.

    Na+ ion interference occurs when the H+ ion concentration is very low and the Na+ ion concentration is very high. Temperature also directly affects this error. As the temperature of the process increases, so does the Na+ ion error.

    Depending on the exact glass formulation, Na+ ion interference may take effect at a higher or lower pH. There is no glass formulation currently available that has zero Na+ ion error. Since some error will always exist, it is important that the error be consistent and repeatable. With many glass formulations, this is not possible since the electrode becomes sensitized to the environment it was exposed to prior to experiencing high pH levels. For example, the exact point at which the Na+ ion error of an electrode occurs may be 11.50 pH, after immersion in tap water, but 12.50 pH after immersion in an alkaline solution.

    Controlled molecular etching of special glass formulations can keep Na+ error consistent and repeatable.

    This is accomplished by stripping away one molecular layer at a time. This special characteristic provides a consistent amount of lithium ions available for exchange with the hydrogen ions to produce a similar millivolt potential for a similar condition.

     

  • What is the acceptable dilution factor to measure alkalinity, especially for small volume availability?

    1:2 ratio (1 sample: 2 DI) is the acceptable dilution factor. This means that a sample volume as small as 2 ml can be diluted in 4 ml of Deionized water (DI) for a total of 6ml, when measured in a 50ml tube using the TitraPro3 pH electrode.  Note that since the sample is diluted, the pH should not be reported as the sample initial pH value.  Only undiluted samples should be measured and reported for initial pH. Dilutions factors that are greater, for example 1 part sample to 3 parts DI, were found to produce incorrect, lower alkalinity results.  It was also noted that on higher dilutions, the pH dropped below 7, indicating a change over to the acidic side.

     

  • Why do I need to standardize my NaOH titrant?

    NaOH is highly hygroscopic, meaning that it absorbs water from the air. Therefore, over time the titrant will become more dilute as it absorbs water. NaOH can be standardized by titrating into a sample of potassium hydrogen phthalate (KHP) of known concentration. For example, titrate 0.05 N KHP with 0.1 N NaOH to an endpoint, and using the volume of NaOH added, the precise concentration of NaOH can be calculated. For more information on standardizing NaOH titrant, please refer to Standard Methods 2310. To limit the amount of water being absorbed, a glass drying tube with a cotton ball inserted should be used to prevent moisture going into the tube.

     

  • How do MANTECH systems measure and record temperature?

    The standard method for measuring temperature is with a USB-connected stainless steel thermistor probe. The specifications for this probe are below:

    • Communication: USB controlled by MANTECH Pro Software
    • Sheath Material: Super OMEGACLAD XL/ Stainless Steel/Inconel
    • Temp Range: 0 to 1038 Degree C.
    • Diameter: 0.062in
    • Length: 6 inch
    • Measurement to 3 decimal places
    • Autocalibration feature in MANTECH Pro software

    Alternatively, when measuring conductivity, one can measure the temperature directly from the conductivity probe. This temperature is also displayed directly on the conductivity meter screen.

    MANTECH has the ability to use either of these measurement methods for pH temperature compensation, depending on customer preference and system configuration.

    MANTECH temperature sensors are available in both PT1000 and 10kNTC styles. PT1000 sensors have a linear positive-slope relationship between resistance and temperature with a resistance of 1000 ohms at 0°C, and 10kNTC sensors have a curved negative-slope relationship between resistance and temperature with a resistance of 10,000 ohms at 25°C. Both these models of temperature sensor perform well and comparably within the 0-100°C temperature range that liquid samples exist in. If you require a specific type of temperature sensor, please feel free to let MANTECH know and we will accommodate.

  • What is conductivity?

    Conductivity, also known as electrical conductivity, is used to measure the concentration of dissolved solids which have been ionized in a polar solution such as water. Read MANTECH’s conductivity method abstract here.

     

  • What is a titration?

    Titration uses a solution of known concentration to determine the concentration of an unknown solution. The titrant (the solution with a known concentration) is added from a buret to a known quantity of the analyte (the solution with an unknown concentration) until the reaction is complete. Knowing the volume of titrant added allows the concentration of the unknown solution to be determined.

  • What is pH?

    The potential of hydrogen (pH) is a measure of hydrogen ion (H+) concentration. Solutions with a high concentration of H+ ions have a low pH (acidic). Solutions with a low concentration of H+ ions have a high pH (alkaline). Read MANTECH’s pH method abstract here.

     

  • What is alkalinity?

    Alkalinity refers to the capability of water to neutralize acid, also known as an expression of buffering capacity. A buffer is a solution to which an acid can be added without changing the concentration of available H+ ions (without changing the pH) appreciably. In other words, a buffer absorbs the excess H+ ions and protects the water body from fluctuations in pH. Read MANTECH’s alkalinity method abstract here.

     

  • What is the time of analysis per parameter and for multi-parameter analysis?

    The timing for analysis of different parameters depends on several different factors, like the concentration of the sample and the equipment used.

    Another factor is the total available sample volume in the vessel on the AutoMax Autosampler bed. With some combinations of parameters, larger sample volume allows for simultaneous measurements, resulting in faster total analysis time than sequential measurement.  A larger sample volume may require a larger sample cup, which decreases capacity on the same model Autosampler.  For example, an AM73 can accommodate 73x50ml tubes, or 30x125ml cups.  In some, the cases the same set of parameters can be analyzed in 2-5 minutes faster when using the 125ml cups vs 50ml tubes.

    It is important to understand your requirements in terms of capacity and throughput speed, total batch capacity required and/or daily sample loads and if overnight, unattended analyses will be applicable.

    Individual Parameters

    Combined Parameters

    MT-10 & MT-30 Models

    * If alkalinity is combined with turbidity and/or colour an MT-100 System must be quoted

    MT-100 Model

     

     

  • What are Nitrates?

    Nitrates (NO3) are formed from the two most common elements on earth, nitrogen and oxygen. Their presence in soils comes from nitrogen-fixing bacteria in the soil, decay of organic matter, industrial effluents, human sewage, and livestock manure. Nitrates are a serious problem since they do not evaporate, and hence remain dissolved and accumulate in the groundwater. Read MANTECH’s nitrate method abstract here.

     

  • What is oxidation reduction potential (redox)?

    Oxidation-reduction potential (ORP), also known as redox potential, refers to the capacity of a solution to oxidize (accept electrons) or reduce (donate electrons). ORP sensors work by measuring the voltage across a circuit formed between the indicator and reference electrodes. When an ORP electrode is placed in a solution containing oxidizing or reducing agents, electrons are transferred back and forth on the measuring surface, generating an electrical potential. Common applications for the ORP method include monitoring water chlorination processes for water disinfection, distinguishing between oxidizers and reducers present in wastewater, and metal screening. Read MANTECH’s redox potential method abstract here.

     

  • What is Turbidity?

    Turbidity is defined as the amount of suspended particles in a solution, measured in nephelometric turbidity units (NTU). It is used as a general indicator of the quality of water, along with colour and odour. The US EPA has a maximum contaminant level (MCL) of 5 NTU for drinking and wastewaters. Read MANTECH’s turbidity method abstract here.

  • What is Salinity?

    There are two types of salinity, absolute salinity and practical salinity. Absolute salinity is a ratio between the mass of dissolved material in seawater and the mass of the seawater. Practical salinity is the ratio of the electrical conductivity of a seawater sample to that of a standard potassium chloride (KCl) solution at the same temperature and pressure. Read MANTECH’s salinity method abstract here.

     

  • What is Ammonia?

    Ammonia is a colourless gas that is soluble in water and has a distinctive odour. It is a mild environmental hazard because of its toxicity and ability to remain active in the environment. Direct measurement of ammonia using a calibrated ion selective electrode (ISE) is a quick, accurate and precise way to easily determine ammonia levels. Read MANTECH’s ammonia method abstract here.

     

  • What is Hardness?

    ‘Hardness’ is defined as the total concentration of alkaline earth ions (Ca2+, Mg2+, Sr2+ and Ba2+) in water. The Ca2+ and Mg2+ ions dominate the alkaline earth ions. Therefore, one can refer to total hardness as the total concentration of the Ca2+ and Mg2+ ions in solution. Hardness is expressed as mg CaCO3/L water sample (ppm CaCO3). Read MANTECH’s hardness method abstract here.

     

  • How is alkalinity speciated into carbonate, bicarbonate and hydroxide fractions?

    The main compounds of alkalinity are: hydroxides (OH), carbonates (CO32-), and bicarbonates (HCO3).  The alkalinity, or buffering capacity, of a solution depends on the absorption of positively charged hydrogen ions by negatively charged bicarbonate and carbonate molecules.  When bicarbonate and carbonate molecules absorb hydrogen ions, there is a shift in equilibrium without a significant shift in pH.  A sample with high buffering capacity will have high bicarbonate and/or carbonate content, and a greater resistance to changes in pH.  For more information on MANTECH’s method for automated alkalinity measurement and how the species of alkalinity are calculated, download the pdf.

  • What is Gran analysis and why is Gran alkalinity important?

    Gran analysis is an effective alternative method for endpoint and pKa detection. Using a series of mathematical manipulations, standard titration curves are transformed into linear data called ‘Gran functions’. Endpoints and pKa’s are determined by performing a linear regression on these functions. In many cases, Gran analysis provides a more accurate endpoint, or identifies endpoints not evaluated in Standard Methods.

  • My conductivity meter is not communicating with PC-Titrate. What can I do to troubleshoot?

    Checking the interface communication and software settings is a good place to start when troubleshooting a conductivity meter which has lost communication.

  • How many PeCOD samples can be analyzed with the reagent starter kit I recieved?

    New PeCOD Analyzer orders typically include a reagent starter kit providing the consumables to run the PeCOD analysis. These kits consist of Electrolyte, Calibrant, and Secondary Standard reagents. Electrolyte is the reagent that is mixed with each sample, therefore it is typically the reagent to be used up first, requiring the user to purchase more from MANTECH. It is useful to know on average how many samples can be run with the electrolyte provided in the standard reagent starter kits, therefore we provide this information below.

    You will need to know the color operating range of your PeCOD (Adv. Blue, Green, Yellow, or Red). If you plan to run a single analysis per sample, use the left column for 10mL total volume. If you require duplicate or triplicate analysis per sample, use the right column for 20mL total volume. Depending on how many samples are run per calibration, these numbers may vary.

    10mL Total Volume – Single Analysis 20mL Total Volume – Duplicate and Triplicate Analysis
    For Advanced Blue range (3:1):

    • 7.5mL sample required
    • 2.5mL electrolyte required
    • 2L electrolyte provided in starter kit
    • 800 samples can be run
    For Advanced Blue range (3:1):

    • 15mL sample required
    • 5mL electrolyte required
    • 2L electrolyte provided in starter kit
    • 400 samples can be run
    For Green range (1:1):

    • 5mL sample required
    • 5mL electrolyte required
    • 2L electrolyte provided in starter kit
    • 400 samples can be run
    For Green range (1:1):

    • 10mL sample required
    • 10mL electrolyte required
    • 2L electrolyte provided in starter kit
    • 200 samples can be run
    For Yellow range (1:9):

    • 1mL sample required
    • 9mL electrolyte required
    • 4L provided in starter kit
    • 444 samples can be run
    For Yellow range (1:9):

    • 2mL sample required
    • 18mL electrolyte required
    • 4L provided in starter kit
    • 222 samples can be run
    For Red range (1:49):

    • 0.2mL sample required
    • 9.8mL electrolyte required
    • 4L provided in starter kit
    • 408 samples can be run
    For Red range (1:49):

    • 0.4mL sample required
    • 19.6mL electrolyte required
    • 4L provided in starter kit
    • 204 samples can be run
    Number of samples that can be run with 1L bottle of electrolyte:

    • Adv. Blue range, 400 samples
    • Green range, 200 samples
    • Yellow range, 111 samples
    • Red range, 102 samples
    Number of samples that can be run with 1L bottle of electrolyte:

    • Adv. Blue range, 200 samples
    • Green range, 100 samples
    • Yellow range, 55 samples
    • Red range, 51 samples
    Number of samples that can be run with 10L bottle of electrolyte:

    • Adv. Blue range, 4000 samples
    • Green range, 2000 samples
    • Yellow range, 1111 samples
    • Red range, 1020 samples
    Number of samples that can be run with 10L bottle of electrolyte:

    • Adv. Blue range, 2000 samples
    • Green range, 1000 samples
    • Yellow range, 555 samples
    • Red range, 510 samples

     

  • What temperature should my PeCOD samples be analyzed at?

    The temperature range that PeCOD samples should be analyzed is between 10 to 30°C. For samples that are outside of this temperature range, the addition of electrolyte (which is stored at room temperature) prior to analysis will help to bring the sample solution to an acceptable temperature range.

  • What is the shelf life of a PeCOD sensor?

    If left unopened and sealed in the package, PeCOD sensors have a shelf life of 12 months. Once opened and in use, sensors can be expected to last for approximately 1 month or 200 samples (whichever comes first).

     

  • Will PeCOD® correlate with my BOD results?

    The PeCOD® measures COD through a rapid 10-minute photoelectrochemical oxidation, allowing for the accurate monitoring of a wide range of concentrations in real-time. These COD readings can be used to reliably estimate BOD by applying a correlation coefficient. When compared to the standard BOD test, the PeCOD can estimate BOD concentration within a 95% confidence level.

    Some examples of correlation coefficients of PeCOD/BOD that have been determined for different types of industrial wastewater are provided in the table below.

     

  • What is used as a quality check standard for PeCOD?

    A separate standard produced by Sigma Aldrich is used for quality control testing of PeCOD systems. This allows for verification of results and ensures that the system in use produces trusted values. This secondary standard can be diluted into different concentrations, making its use applicable to all COD ranges of solution used with the PeCOD analyzer. The Sigma Aldrich SKU number for this standard is QC1130.

     

  • What is the difference between the benchtop and portable peCOD?

    The L50 PeCOD® Analyzer is applicable for benchtop and portable use, with the incorporation of an external battery and carrying case.  The L50 weighs less than 7kg and measures 280mm x 210mm x 260mm.  Its rugged carrying case, equipped with wheels, makes it easy and safe to transport the unit between the field and the laboratory.

    Person wheeling the Portable PeCOD L100 Carrying Case.

    Person wheeling the portable peCOD carrying case.

     

  • What is the typical initial peCOD shipping weight and dimensions?

    An investment in the safe, green, and fast PeCOD Analyzer and method includes the PeCOD L50 Analyzer, starter kits, and consumables. This is typically packed in two cartons with the following weight and dimensions:

    Box 1 (starter kits and consumables)
    16” x 15” x 14”, 32lbs
    41cm x 39cm x 36cm, 15kg

    Box 2 (PeCOD L50)
    16” x 15” x 16”, 21lbs
    41cm x 39cm x 41cm, 10kg

  • How much bench space do I require for a typical PeCOD L50 set-up?

    The typical benchtop L50 set up requires 36 inches x 18 inches of bench space, as shown in the figure below.

     

  • Why does my PeCOD plot more than one curve during calibration and sample analysis?

    For calibration, the PeCOD® Analyzer goes through the following phases:

    1. Normalization Phase. This is where the PeCOD® Analyzer is adjusting the LED lamp output, trying to achieve a baseline of 20µA.
    2. Burn-In Phase (port B). This is where the pre-mix blank solution is brought into the sensor cell.  It is oxidized to remove contaminants from the cell.
    3. Pre-Burn Phase (port B). This is where a new aliquot of pre-mix blank solution is brought into the sensor cell.  This phase removed more contaminants from the cell and conditions the cell for the pre-mix blank.
    4. Oxidation (port B). A new aliquot of pre-mix blank is brought into the sensor cell and is oxidized.  This value is used in the peCOD calculation.  The area under this curve is used to calculate the ‘blank charge’, which corresponds to the C value determined by each calibration. This is the small amount of COD contributed by the electrolyte reagent, which is then subtracted from all future COD analyses to give the final COD result.
    5. Pre-Burn (port A). A new aliquot of pre-mix calibrant solution is brought into the sensor cell where it is oxidized.  This removes contaminants from the cell and conditions the cell for the pre-mix calibrant.
    6. Oxidation phase (port A). A new aliquot of pre-mix calibrant if brought into the sensor cell.  This value is used in the peCOD calculation.  The area under the curve is used to calculate the reference charge, which is used with the blank charge to determine the relationship between charge and COD. This corresponds to the M value determined by each calibration.

    For sample analysis, the PeCOD® Analyzer goes through the following phases:

    1. Burn-In phase (port B). The pre-mix blank solution is brought into the sensor cell and is oxidized.  This removed contaminants from the cell.
    2. Pre-Burn phase (port A). An aliquot of sample is brought into the sensor cell and is oxidized.  This removes contaminants from the cell and conditions the cell for the sample.
    3. Oxidation phase (port A). A new aliquot of sample is brought into the sensor cell and is oxidized.  This value is used in the peCOD calculation.  The area under the curve is used to calculate the charge generated by sample oxidation.  The blank value will be subtracted from the sample value to determine the sample COD.

     

  • How does the PeCOD benefit water treatment optimization?

    A common benefit of peCOD implementation for this application is optimization of coagulant dosing.

    The traditional method up to this point has been consistent dosing based on laboratory testing results (jar testing is a very common method of developing coagulant dosing requirements). They then increase their dosing for events that they know to cause NOM spikes. The problem is they often don’t know the extent of the NOM spikes, so they increase their dosing to what has been deemed as ‘enough’. More often than not this is over-dosing, not really causing downstream issues but incurring more cost than is needed for these events. However, when the extra dose is not enough and they under-dose, NOM gets through and reacts with the disinfection chemicals creating DBPs.

    The missing ingredient is knowing when these NOM spikes occur, and to what extent. The events could be anything from seasonal variation based on climate to rapid spikes from storm events, but the benefit of knowing is the same. Plants that have enough funding to do so monitor UV and TOC online, however research has shown that this is not enough. peCOD is another piece of the NOM puzzle and is truly the more important measure when looking at how NOM will react and be affected by treatment. If you know the COD of the NOM coming in and can match it to known dosing requirements, you minimize the possibility of DBPs forming.

    The speed and ease of use of the peCOD is also key here, you are placing this knowledge directly in the operators’ hands, rather than having it be a result they wait to get back from an external lab. When they can truly understand the technology and it’s value, it has a secondary effect of getting them more involved with optimizing the treatment processes. We see with numerous cases (mostly in WWTPs at this point) this occurring, where they get the peCOD for measuring one or two points then realizing the benefit it can have through monitoring their whole plant.

     

  • What is total organic carbon?

    TOC (Total Organic Carbon) is the amount of carbon based organic contaminants in a water system. TOC does not identify each specific organic contaminant present, but rather an absolute quantity of all carbon-bearing molecules. In other words, TOC is a way to measure organic contaminants that may pose a threat to drinking water or wastewater systems.

  • What are THMs?

    THMs (trihalomethanes) are disinfection by-products (DBP’s) formed when residual chlorine reacts with elevated levels of naturally occurring organic matter found in water. THMs are present in most drinking water supplies and are dependent on several factors such as type of organic material present and chlorine dosage.

  • What is UV254?

    UV254 is a water quality test which uses ultraviolet light of 254nm wavelength to measure natural organic matter in water and wastewater.

  • What is natural organic matter?

    Natural organic matter (NOM) is a critical target for drinking water treatment because it causes a negative effect on water quality by color, taste and odor, and can react with disinfectants to form disinfection by-products (DBP). There are several tools for measuring NOM in source and ground water that include total organic carbon (TOC), dissolved organic carbon (DOC), UV absorbance at 254 nm (UV254), specific UV absorbance (SUVA), and chemical oxygen demand (COD).

  • What is oxygen demand?

    OD (Oxygen Demand) measures the chemical reactivity of organics by the demand for oxygen, as shown in the diagram below. It can be used as an additional tool in the characterization of NOM (Natural Organic Matter) to predict DBP (Disinfection by-product) formation. This metric also allows for rapid feedback and optimization of coagulation and disinfection dose requirements.

  • How does the PeCOD Analyzer calculate COD?

    The PeCOD Analyzer performs advanced oxidation on a small volume of sample. As the reaction proceeds, electrical charge is generated proportional to the oxygen being consumed. The PeCOD analyzer captures this generated charge, plotting the output current from the reaction over time as shown below. The area under the curve generated by plotting current over time is proportional to the COD of the sample. A blank charge is also determined for each sample, and subtracted from the total charge to ensure accuracy.

    View the detailed overview of PeCOD technology and calculations here.

    peCOD Oxidation Profile

     

  • What is the primary mechanism of PeCOD chemistry?

    The primary driver of the peCOD method chemistry is advanced oxidation induced by photocatalysis with Titanium Dioxide (TiO2). Pure TiO2 is only photo-active at wavelengths below 380 nm. This is because a certain amount of light energy is required to bump the electrons around and cause the behaviors that we associate with photocatalysis. The UV LED in the PeCOD® COD Analyzer operates at a peak wavelength of 365 nm, with a minimum 360 nm and maximum 370 nm, ensuring that efficient photocatalysis is achieved.

    peCOD Sensor Technology

     

  • What is the difference between chemical oxygen demand and biochemical oxygen demand?

    Chemical Oxygen Demand (COD) analysis is a measurement of the oxygen-depletion capacity of a water sample contaminated with organic waste matter. Specifically, it measures the equivalent amount of oxygen required to chemically oxidize organic compounds in water. The traditional COD method is the wet chemistry method, dichromate COD (CODCr). This involves a two hour digestion at high heat under acidic conditions and involves hazardous chemicals such as mercury and dichromate.

    Biochemical Oxygen Demand (BOD), also often referred to as biological oxygen demand, is a test performed to measure the potential of wastewater and other waters to deplete the oxygen level of receiving waters. The BOD test involves taking an initial dissolved oxygen (DO) reading and a second reading after five days of incubation at 20°C. For this reason, this test is often written as BOD5 for short.

    MANTECH has developed an automated COD method utilizing a new, rapid and green technology called the PeCOD® COD Analyzer. This method directly measures the amount of oxidizable material in a sample via photoelectrochemical oxidation in a microcell, eliminating the need for time-consuming digestion and hazardous chemicals as only an electrolyte solution is required for analysis.

     

  • What pH range can the peCOD method measure in?

    pH Range: 4.0 – 10.0  (after mixing with electrolyte)

    The peCOD method requires that the pH of a sample AFTER being mixed with electrolyte must be between 4 – 10. To determine if a sample must be pH-adjusted, mix the sample with peCOD electrolyte at the proper mixing ratio for your COD range, then test the pH of the mixture.

    For example, the sample may have a pH of 3.0, but then after preparing with electrolyte, the pH is in the required range, therefore, it is acceptable for immediate peCOD measurement.

    If samples have been preserved in acid, they should be neutralized using sodium hydroxide prior to analysis to avoid a low reading, as well as damage to the sensor. When the sample pH is below 4, the photocatalytic oxidation at the TiO2 sensor is affected, leading to poor reproducibility and charge values below theoretical expectation. Below a pH of 2, the TiO2 displays instability. When the pH is above 10, the charge measured for the reference and sample solution yield lower than expected values, again caused by interference at the TiO2 sensor. Sulphuric acid should be used to lower the pH of samples with a pH of 10 or more.

     

     

  • How should COD samples be stored?

    MANTECH recommends storing samples in the laboratory fridge vs preserving samples. If you do choose to preserve your samples, use H2SO4 to adjust the pH of your samples to ~2.

  • What are the PeCOD electrolyte and calibrant solutions composed of?

    The PeCOD electrolyte solution is mainly composed of a low-concentration lithium nitrate solution. The PeCOD calibrant and check standard solutions supplied by MANTECH are composed of sorbitol.  These solutions contain a trade recipe preservative that allow for the longer shelf life, compared to solutions prepared manually. Calibrant and check standard solutions prepared manually, following the PeCOD Standard Recipe, can be used for up to two weeks.

    View the PeCOD electrolyte SDS here and EU compliant SDS here.

    View the PeCOD calibrant SDS here and EU compliant SDS here.

    View the PeCOD check standard SDS here and EU compliant SDS here.

    View the PeCOD pre-mixed blank SDS here and EU compliant SDS here.

    View the PeCOD pre-mixed calibrant SDS here and EU compliant SDS here.

     

  • What does the Class 3B warning label on the PeCOD COD Analyzer head mean?

    The PeCOD COD Analyzer has a warning label on the analyzer head “DO NOT OPEN ANALYZER LID WHILE IN OPERATION” and “CAUTION: CLASS 3B INVISIBLE LASER RADIATION. AVOID EXPOSURE TO BEAM.” See Image 1.

    The lid / cover of the PeCOD COD Analyzer has a warning label stating 'Do not open analyzer lid while in operation. Caution, Class 3B invisible laser radiation. Avoid Exposure to beam. Mantech COD Analysis. UV LED light laser. harmful / non-harmful.

    Image 1: Warning label on analyzer lid

     

    There are two normal LED lights (one red, one green), and one (invisible) Class 3B UV LED laser.  See Image 2.

     

    The red LED light is an error indicator and is a non-harmful light.  The green LED light is the power indicator and is also a non-harmful light.

     

    The Class 3B UV LED laser is a catalyst for TiO2 oxidation of organics.  Class 3B UV LED lasers are harmful to your health, however, there are safety measures put into place to avoid exposure to this invisible UV LED laser on the PeCOD COD Analyzer.  The PeCOD has an automatic laser shut off built in so the laser will turn off when the analyzer lid is opened.  This lid should not be tampered with or modified as the Class 3B laser is hazardous to your health.

    Image of under the lid / cover of the analyzer head showing normal red and green LED (normal) lights representing an error indicator and power indicator. The Class 3B UV LED invisible laser automatically shuts off or turns off / shuts down when the lid is opened to avoid exposure as this invisible UV LED laser is harmful to your health if exposed. The hard cover of the PeCOD COD analyzer instrument unit provides protection from this invisible laser. There are arrows pointing to the Red (normal) LED light, the Green (normal) LED light, and the Class 3B UV LED laser.

    Image 2: Analyzer head with 2 (two) normal LED lights, and 1 (one) 3B UV LED Laser

     

  • Does PeCOD conform to regulatory standards?

    The PeCOD conforms to regulatory standards such as the ASTM International Method D8084, the Ministry of Environment, Conservation and Parks, Ontario (MECP) method E3515, and the Health Canada Guidance on drinking water.

    The ASTM International method for photoelectrochemical oxygen demand is approved for measuring organics in freshwater sources and treated drinking water. More details about this method can be viewed here.

    The Ontario MECP method E3515 replaced the standard dichromate methods due to the fact that no harmful chemicals are used in the PeCOD method. This method now includes PeCOD as an approved alternate COD method in the Municipal and Industrial Strategy for Abatement (MISA). The MECP method can be viewed here.

  • What are the COD/BOD ranges for the PeCOD and what are the mixing ratios?

    There are 4 COD ranges for the PeCOD. The advanced blue range is the lowest range and analyzes samples up to 25mg/L with a mixing ratio of 3:1 (sample to electrolyte). Green is the second lowest range and measures up to 150mg/L with a mixing ratio of 1:1. The yellow range determines COD up to 1,500mg/L with a mixing ratio of 1:9 and the red range can analyze samples up to 15,000mg/L and has a mixing ratio of 1:49. For more information, read MANTECH’s technical bulletin here.

     

  • What is the allowable COD/chloride concentration combinations for PeCOD analysis?

    There are limitations to ensure that, after dilution with electrolyte, the chloride concentration will be <200mg/L. This means that the allowable chloride concentration of the original sample varies depending on the COD range (as illustrated below) since each range has a different ratio of sample to electrolyte. For more information, read MANTECH’s technical bulletin here.

     

  • What are the reasons for differences between the PeCOD COD and Dichromate COD results in some cases?

    Chemical Oxygen Demand (COD) results may differ when measured via the PeCOD COD method versus the traditional dichromate COD method for certain sample matrices. There are various reasons for this difference. One is that chloride, ammonia, and some heavy metals have been known to interfere with PeCOD readings and provide inaccurate results. Another reason could be the time delays between analyses. It is best to analyze samples via PeCOD and dichromate on the same day to limit uncertainties due to sample degradation. For additional reasons and more information, read MANTECH’s  technical bulletin here.

  • What are calibration values, C, M, and Iterm, and what values are acceptable?

    A C value is reported after a calibration. It is measured in μC, and indicates the raw charge generated during the blank oxidation. In PeCOD Pro, the C Value can also be referred to as the Zero Charge (Z1). The expected C value ranges depend on the color range you are working in (advanced blue and green ranges have lower C values than yellow and red ranges). The acceptable values are 50-300 µC for advanced blue range, 150-700 µC for green, 200-750 µC for yellow range, and 250-800 µC for the red range.

    An M Value is also reported at the end of a calibration. It is a ratio of the expected COD to the charge generated during the reference oxidation (of the calibrant solution). It is expressed as COD/μC. The acceptable M value range for the green, yellow, and red ranges is 0.02-0.06 COD/μC. The advanced blue range has an acceptable M value range of 0.01-0.08 COD/μC.

    The Y-axis of the oxidation graph is defined as the Iwork (reported as μA) which is a measure of current. The Iterm is essentially the Iwork at the end of each oxidation curve as it levels off. The acceptable Iterm value for advanced blue and green ranges is >16 μA. For the yellow and red ranges, the Iterm value needs to be >14 μA.

     

  • What is the difference between the L50 and the L100?

    The L50 is the newer, more cost efficient model of the PeCOD. It uses the same method, reagents, and software as the L100. Improvements were made with the fluidics and space requirement in the L50 model. For more information, see the news section.

     

  • How do I store my electrode block?

    If only storing the electrode block for a short period of time (less than 4 weeks), rinse DI water through the PeCOD and leave the electrode block inside. Make sure all of the sample has been washed through by priming Port A several times. If storing for more than 4 weeks, put DI water through the PeCOD and then remove the electrode block to store outside the PeCOD. Flush the channels with 20-30 mL of DI water before pushing through about 10 mL of NaCl, leaving the channels filled. Tape the ends of the channels to ensure no leaks or crystallization occur. For more information, read the storage instructions here.

  • How do I change the number of calibrations and QC checks the PeCOD does during each QC regime?

    Click ‘File’ in the top left corner, and select ‘Preferences’. The ‘General’ tab will pop up, select the ‘QC Regimes’ tab. Here you can see how many calibrations, QC checks, and recalibrations the PeCOD® will preform for the ‘Startup (Daily) Regime’. To see the other regimes, select the ‘Startup (New Sensor)’ tab, or the ‘QC Routine’ tab in the second row. To edit the number of calibrations or QC checks, click the arrows beside the numbers to choose how many of each the PeCOD® will perform.

  • How long does a sensor last in a PeCOD® Analyzer?

    Sensors are expected to last 150 runs when used consistently for an average of 50 samples per week (samples, calibrations and QC checks). However, should a sensor be intermittently used, it is recommended that it be changed after 3-4 weeks of use regardless of the number of completed runs, or based on consistently failing calibration values. When analyzing higher sample concentrations (especially red range) the sensor life expectancy is likely to be shorter, ranging from 60 – 150 total measurements. For more information, read MANTECH’s technical bulletin here.

     

  • Will PeCOD correlate with my Dichromate COD results?

    There is a strong correlation between the PeCOD COD results and the dichromate COD results. To determine this, the two methods were compared vs. the theoretical oxygen demand (ThOD) for 34 organic species. See MANTECH’s technical bulletin for more information on the study.

  • How long will the PeCOD® Electrolyte, Calibrant, and Standard solutions last?

    Both Calibrant and Standard Solutions are good for one year after they are made. Electrolyte has a shelf life of two years after it is produced. All labels have the expiry date in the box just above the MANTECH logo.

  • How do I replace the sensor in my PeCOD® Analyzer?

    Open the top plastic door by pushing down firmly on the front centre of the door until a “click” is heard, then release the door. Open the PeCOD analyzer module by pressing firmly down on the fixed bar, and lifting the front latching bar (should unlatch), then lift up the PeCOD sensor lid. Remove the old sensor by lifting it off of the pins and place the new sensor on the same pins with the “THIS SIDE UP” surface (blue side) facing you.

     

  • How is the PeCOD® COD/BOD Analyzer calibrated?

    Calibrations are comprised of 6 different stages. The first stage is called the “Normalization Phase” and lasts 100 seconds. During this time, the LED strength is adjusted to maintain a baseline electrical current of 20 mA. This is performed on the blank solution, containing range specific electrolyte and COD free deionized water. Once the LED is set, oxidation of the blank solution will occur. This is comprised of 3 stages, visualized by 3 distinct curves. The stages are known as the Burn-In, Pre-Burn, and Oxidation of port B. The blank acts as a zero reference for the calibration based on the charge generated from the DI and electrolyte mixture. The area under the curve is used to quantify charge. Once the Port B stages have completed, the Port A stages will begin. The calibrant and electrolyte mixture is introduced across the TiO2 sensor, where similar Pre-Burn and Oxidation curves are generated. The concentration of the calibrant is determined based on the sample COD/BOD range. Once the specified number of calibrations have completed, the calibrant solution can be run as a sample (referred to as a QC check). It is expected that the COD result will be + / – 5% of the standard COD/BOD value. To view an example of the stages of a PeCOD® calibration, view our video here.

  • Why does KHP measure high on PeCOD?

    KHP (Potassium Hydrogen Phthalate) has historically been a common reference standard used in a variety of chemistry applications including the traditional dichromate COD test, where it does provide a result close to the theoretical COD result, and for TOC analysis. KHP is not recommended for use in the PeCOD COD analysis as it over reports compared to the theoretical COD amount. This is predominantly due to some pre-concentration of the molecule on the surface of the PeCOD sensor prior to analysis which is a peculiarity of KHP with the PeCOD COD method.

    It is important to note that for all COD methods there are specific molecules whereby the individual analytical result is not well aligned to the theoretical value. For instance, organic compounds such as propionic acid, diethylamine or nicotinic acid could not be used as a COD standard for the dichromate COD method due to poor correlation to theoretical results but could be suitable for the PeCOD COD method. It is therefore important to chose a standard that provides a strong correlation to the theoretical result for the method employed, is a good reflection of the samples to be analysed, is suitable for general laboratory use and is readily available. For details on preparing sorbitol and glucose-based COD standards for the PeCOD COD method, read our technical bulletin 2017-029: PeCOD Standard Recipe.

  • What is the cost per sample using the PeCOD?

    The cost per sample varies depending on the number of samples analyzed, as this affects consumable usage such as calibrant, electrolyte and sensors. In general, the cost per sample decreases with an increase in the number of samples. There are several reasons for this, one being that the sensor should be replace monthly, therefore running more samples per month will yield a better return on sensor usage. In addition, the PeCOD® requires a daily calibration; by running more samples per calibration users save on consumable costs associated with calibrant. There are no disposal costs for the PeCOD, whereas disposal costs accumulate via the traditional dichromate method with every sample vial. Try out our Consumables Calculator today to estimate the cost per sample based on your predicted usage.

  • How do inorganic compounds affect PeCOD® COD determination?

    The following tables summarize the impact of a range of common inorganic anions and cations on the determination of COD using the PeCOD® technique. You can download this FAQ as a pdf document at this link.

    For each inorganic species, solutions containing 0, 20, 50, 100, 250, 500 ppm (by mass) of the anion or cation, 60ppm COD (as sorbitol) and 1M LiNO3 (containing 20ppm COD spike) were prepared and analyzed, unless otherwise stated. Therefore, the below ion concentrations represent the concentration IN THE CELL (i.e. if analyzed in a different range, the interference levels may vary due to different electrolyte dilution effects).

     

    Anions Formula Remark
    Ammonium NH4+ No interference for NH4+ ≤ 500 ppm

    Note: Similar results are obtained for Ammonia

    Carbonate CO32- No interference for CO32- ≤ 500ppm using chloride resistant sensor
    Chlorate ClO3 No interference for ClO3 ≤ 500ppm
    Chloride Cl No interference for Cl < 200 ppm. COD reduced by up to 20% at Cl- levels of 500ppm using Chloride resistant sensor. Other halides (F-, Br-, I-) would be expected to behave in the same manner
    Nitrate NO3 No interference, NO3 can be used as PeCOD electrolyte
    Nitrite NO2 No interference for NO2 ≤ 500ppm
    Perchlorate ClO4 No interference, ClO4 can be used as PeCOD electrolyte
    Phosphate PO43- No interference for PO43- ≤ 500ppm
    Sulfate SO42- No interference for SO42- ≤ 500ppm
    Sulfite SO32- Interference for SO3 ≥ 20 ppm, giving COD high by 90% at 250 ppm SO32-
    Sulfide S2- Interference for S2- > 0 ppm, giving COD high by >100% at 50 ppm S2-

     

    Cations Formula Remark
    Aluminum Al3+ No interference for Al3+ ≤ 500ppm
    Calcium Ca2+ No interference for Ca2+ ≤ 500ppm
    Chromate Cr3+ Interference for Cr3+ > 2 ppm, giving low COD
    Ferric Iron Fe3+ No interference for Fe3+ ≤ 500ppm
    Ferrous Iron Fe2+ Interference for Fe2+ > 100 ppm, giving low COD
    Magnesium Mg2+ No interference for Mg2+ ≤ 500ppm
    Potassium K+ No interference for K+ ≤ 500ppm
    Silver Ag+ Interference for Ag+ > 10 ppm, giving low COD
    Sodium Na+ No interference for Na+ ≤ 500ppm
    Zinc Zn2+ No interference for Zn2+ ≤ 500ppm
  • Do I need to filter my samples for peCOD analysis?

    Samples must be filtered prior to peCOD analysis to ensure that no particulates greater than 50 micron (um) are primed into the peCOD.  Particulates larger than 50um can cause clogging, which can lead to damage of the internal fluidics of the machine.  To prevent clogging and ensure proper sample preparation, MANTECH has a Sample Filtering Guide for PeCOD Analysis.

    For pulp and paper and wastewater applications, MANTECH recommends using a 35um polyethylene (PE) syringe filter.  These filters can contribute trace amounts of organics, which are negligible for wastewater applications.  For drinking and source water applications it’s important to use a filter that does not contribute organics to the filtered sample.  One of MANTECH’s research partners has recommended a 0.45um polyethersulfone (PES) filter; however, other filter types may also be acceptable, if no organics are contributed by the filter.  Since these applications traditionally see less particulates, having a smaller pore size filter hasn’t shown an impact on the peCOD results.

  • What is chemical oxygen demand?

    Chemical Oxygen Demand (COD) analysis is a measurement of the oxygen-depletion capacity of a water sample contaminated with organic waste matter. Specifically, it measures the equivalent amount of oxygen required to chemically oxidize organic compounds in water. COD is used as a general indicator of water quality and is an integral part of all water quality management programs. Additionally, COD is often used to estimate BOD (Biochemical Oxygen Demand) as a strong correlation exists between COD and BOD, however COD is a much faster, more accurate test. Learn more here.