electrodes
16 Issue 6 2019
Electrodes for quick and precise measurements M ettler Toledo’s range of InLab electrodes offer outstanding performance in both the laboratory and the field. Electrochemical sensors combine innovative technologies for fast pH, ORP, conductivity and dissolved oxygen measurements. High precision and reliability, as well as low maintenance, make them the ideal choice for a wide range of applications.
pH electrodes Separate pH and reference electrodes are recommended for applications where the lifetime of the pH electrode is significantly shorter than that of the reference electrode. Economy pH electrodes offer outstanding value for money. Routine InLab electrodes are part of any classical laboratory tool and cover the traditional applications in aqueous media.
Increased data security and easy handling The introduction of several unique electrodes with Intelligent Sensor Management (ISM) complete the InLab portfolio. ISM is a sophisticated safety concept that leaves nothing to chance. With this technology, the instrument will automatically detect the connected sensor and will use the most up-to-date calibration data stored on the sensor.
ORP/redox electrodes ORP/redox electrodes are the ideal solution for testing the oxidation/reduction in factory and industrial waste (chromium and cyanide concentration), fish farming and aquariums (water quality), and swimming pools (sanitation levels). Ion-selective and gas electrodes Ion-selective and gas-sensitive electrodes allow quick and easy determination of
Ammonium D Fast and robust determination according to current ISO, EPA, and ASTM standards using direct measurement
etermination of ammonium is one of the most crucial applications for sectors such as water and wastewater analysis, fertilisers, and others. Metrohm Application Bulletin AB-133 describes the determination of ammonium by ion measurement according to ISO 6778, EPA 359.2, EPA 305.3, and ASTM D1426. Tips and tricks on how to deal with possible interferences, sample preparation, and handling of the ammonia ion selective electrode are also covered. While there exist photometric methods for ammonium, they are rather timeconsuming (up to 90 minutes reaction time). Moreover, photometric determination in opaque solutions is always a challenge. Determination by direct measurement using an ion selective
Perfectly designed sensors to measure ion content
W
ith the increased capability of modern automatic titrators, it is possible to measure ion content in a matter of minutes using an ion-selective electrode (ISE). This can be achieved either by direct measurement or by incremental techniques such as standard addition or subtraction. These methods are easily automated using the Mettler Toledo titrators. To support these capabilities, Mettler Toledo offers a wide range of ionselective electrodes and accessories. Depending on the sample, it is often possible to measure from less than one part per million up to a few grams per litre. By using multiple standard addition measuring techniques, it is possible to measure in the nonlinear range of the electrode. With the Excellence Line T90 titrator, it is possible to perform an automatic GRAN evaluation, yielding an even better determination limit.
In addition to the direct measurement or incremental techniques, ISEs can often be used as the indicating electrode in the titration of an ionic species, for example, titration of sulphate using a barium ISE and barium chloride as titrant, or titration of calcium and magnesium with EDTA using a calcium ISE. MICROSEP (PTY) LTD Rudy Maliepaard Tel: (011) 553 2300 Fax: (011) 553 2400 rudy.maliepaard@microsep.co.za www.microsep.co.za
concentration and activity of a variety of dissolved ions and gases. Ion concentration measurement is vital in a wide range of applications. Some common examples are calcium content of milk, chloride in food and fluoride in toothpaste. Conductivity sensors The new range of InLab conductivity sensors show enhanced measuring performance and improved handling for accurate conductivity measurement. Competence in electrochemical measurement has been extended by offering a complete range of electrode accessories and consumables for portable and bench meters. To assist in finding the right sensor for your application, Mettler Toledo offers an Online Sensor Product Guide, as well as a selection of guides to electrochemical analysis.
electrode, on the other hand, is faster and more robust. Hence, measurements can be easily performed in wastewater, liquid fertiliser, urine, as well as in soil extracts. Determination of ammonia in ammonium salts, of the nitric acid content in nitrates, and of the nitrogen content of organic compounds with the ion-selective ammonia electrode is based on the principle that the ammonium ion is released as ammonia gas upon addition of excess caustic soda: NH4+ + OH– → NH3 + H2O
MICROSEP (PTY) LTD Elisha Ramlal Tel: (011) 553 2300 Fax: (011) 553 2400 elisha.ramlal@microsep.co.za www.microsep.co.za
in the form of an ammonium salt, it must first be converted into such a salt. To this end, organic nitrogen compounds, especially amino compounds, are digested according to Kjeldahl by heating with concentrated sulfuric acid. The carbon is oxidised to carbon dioxide in the process, while the organic nitrogen is transformed quantitatively into ammonium sulphate.
METROHM SA (PTY) LTD
The outer membrane of the electrode allows the ammonia to diffuse through. The change in the pH value of the inner electrolyte solution is monitored by a combined glass electrode. If the substance to be measured is not present
Tel: (011) 656 1918 CPT: (021) 852 0213 DBN: (031) 265 0067 Fax: (011) 656 2698 078 643 7113 info@metrohm.co.za www.metrohm.co.za
No wires - unique WTW digital sensor electrodes
H
ave your measurement wirelessly processed with the electrode you are holding while measuring any of the standard parameters of pH, conductivity, dissolved oxygen and turbidity. The WTW IDS (Intelligent, Digital Sensor) is unique: the plug head sensor on the WTW electrode is wireless and will process signals into digital data, store calibration records and provide data for documentation. No cables and no tugging. The sensitive signals from the electrodes are transferred via Bluetooth to the WTW Inolab Multi meters, with a choice of 1-3 channels, in a fail-safe and error-free manner. This outstanding innovation ensures that measurements are processed in the sensor, not the meter. The smart IDS sensors will log on automatically, transfer description, serial number, calibration
record and calibration history, as well as their complete parameters. The same module is used for all parameters. The meter allows for simultaneous measurement and documentation of up to three user-defined parameters, with a memory for 10 000 records. The WTW IDS gives you full flexibility in all areas where cables and wires would disturb, even under laboratory hoods or laminar flow benches. The complete WTW kit is also offered with a wireless module for the sensor and meter, USB charger and universal power supply. LABOTEC (PTY) LTD JHB: (011) 315 5434 CPT: (021) 531 7660 DBN: (031) 566 4870 Fax: (011) 315 5882 sales@labotec.co.za www.labotec.co.za
