Many ionic substances are easily measured by means of potentiometry using ion-selective electrodes (ISE). The potential between the ISE and a suitable reference electrode depends on the concentration of the ion-species to be measured. The most common ion-specific electrode is the pH-electrode.
This versatile measuring principle is used in the ISE-Analyser/Titrator to measure a variety of different parameters like:
- Ammonia - NH4+
- Bromide – Br-
- Chloride - Cl-
- Cyanide - CN-
- Fluoride - F-
- Iodide – I-
- Nitrate – NO32-
- Potassium – K+
- Sulphide – S2-
- Sulphate – SO42-
- Alkalinity, acidity (m/p-value)
Depending on matrix interferences, measuring range, detection limit etc. three different analytical methods can be applied:
The simplest mode is to measure the difference of the potential between an ion-selective electrode “ISE” and a suitable reference electrode and calculate the concentration based on the Nernst-equation. This method can be applied in samples where interferences from other ions or compounds like complexing agents are absent.
The method of standard addition is applied in samples where an excess of an interfering compound is present that reacts with the analyte to be measured. Since the interference reacts with the sample in the same manner as on the standard-additions the real concentration is calculated be means of linear regression.
In this analytical method the change of the potential of a suitable electrode is used to detect the inflection point during titrations. For some applications a photometer is used to detect the change in absorbance at a suitable wavelength during titrations.
Depending on the users requirements the following options are available:
- Automatic cell and line cleaning
- Automatic filtration and filter cleaning
- Automatic calibration and/or validation
- Up to 8-channel multiplexer
Analytical method:Potentiometry, Photometry; Standard Addition; Titration
Meas. interval:5 - 30 Min. (typical)
Max. num. channels:Up to 8
Measurement system:Ion-selective electrode; pH-electrode; Redox-electrode; Photometer (depending on application)
Alarms:Threshold, system fault, potential free, NC/NO
Status signal:For remote start/stop (potential free, optional)
Outputs:Max. 8; (0)4 – 20mA, max. 500 Ohms
Digital input: Start/stop, others
Dimensions:Width: ±400 mm x depth: ±270 mm x highth: ±910 mm
Weight:Approx. 30 kg