MT-100 system for automated titration analysis

MT Series of Automated Environmental Titration and Multi-Parameter Analyzers

Rugged & Reliable

Whether your laboratory requires a simple pH system or a system with eight parameters, MANTECH will deliver. We realize each laboratory is unique and as a result, our systems are tailor configured with off-the-shelf modules to meet your requirements for sample volume, parameters and sample size. Each system is fully automated by easy to use software and robust robotics.

 

Benefits

  • Automates 26-400 samples in a single batch
  • Customizable user interface for simplified operation
  • IntelliRinse™ prevents cross contamination between samples
  • Eliminates potential for human error with automated pipetting using MANTECH’s Titrasip™
  • Non-destructive sample preparation allows for up to 5 parameters on a single sample

Applications

  • Water
  • Soil
  • Food & Beverage

Parameters

MANTECH is a leading manufacturer of automated titration and multi-parameter analysis systems. We can deliver analysis systems that perform the following functions: (click the links to view method abstracts)

We have purchased a MANTECH system to automate our suite of pH, Conductivity and Turbidity analysis. From industry feedback we knew that this suite is notoriously difficult to automate and the MANTECH system presented a new and viable solution to the problem. Camlab, the UK representatives have helped us from the very outset with the financial justification and there on with the development of our methods and engineering support. The staff, from product specialist to the engineers at Camlab have understood the constraints of our methodologies and have worked with us as a partnership to deliver the high performance we need.
I worked with three multi-parameter systems running applications such as pH, conductivity and alkalinity. It was wonderful being able to set up my run and then move on to other tasks around the lab. One of the systems often ran for ten hours straight (approximately 750 samples). The MANTECH systems were easy to use and very durable.
MANTECH instruments used by ALS have proven to be robust analytical solutions, generating accurate and precise results with a low per sample operating cost.
The support was excellent from all vendors but the software and hardware support teams for the MANTECH PC-Titrate system were local and are marketed and supported by the same company. The precision was superior on the PC-Titrate system as was the multi-valve cleaning system, which included more titrants, and purging of titrant lines. In conclusion the PC-Titrate system met our needs most closely and was the best long-term choice for our solutions analysis.

Models & Specifications

Model
MT-10
MT-30
MT-100
MT-30 Automated titration system for pH analysis
Capacity
26-400
28-400
30-400
DualProbe*
IntelliRinse™
Static and Dip Multiple Stations
Dynamic
Dynamic
SampleProtect™*
Temperature Compensation
Automated with Manual Temperature entry
Automated with Thermistor
Automated with Thermistor
PeCOD® COD Analyzer Add-on (15min COD and NOM)
BOD5 Day DUO Add-on
Food Applications, Total Acidity, Sulfite, Chloride
2 or more titration methods
In different sample cups
In different sample cups
From a single sample cup
125ml cups
50ml tubes
 ✓
 ✓
15ml tubes
 ✓
IntelliVOL™**
 ✓
 ✓
Automated Pipetting
RapidDuo™ e.g. alkalinity & hardness in 2 different vessels

*Available with AM122, AM197 and AM354 Autosamplers
**Aspiration of sample to a known volume via extraction pump. Accurate sample volume allows for titration directly in 125 mL cup or 50 mL tube

All of our systems can be customized to suit your needs. Contact us for more information.

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Frequently Asked Questions

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.

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.

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.

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.

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.

‘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.

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.

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.

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.

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.

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.

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 out technical bulletin here.

The standard method for measuring temperature is with a glass thermistor, and for certain specified applications, a stainless steel thermistor is used. Alternatively, when measuring conductivity, one can measure the temperature directly from the conductivity probe.

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.

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.

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.

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.

The minimum total volume can be as small as 6 ml using the TitraPro3 pH electrode.  This is due to the lower immersion depth of this electrode and precise autosampler coordinate specifications.

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.

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.

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.

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.

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