Chloride ions are one of the major inorganic anions in water and wastewater. Although high concentrations of chloride in water are not known to be toxic to humans, its regulation is mainly due to taste. It is essential to monitor chloride concentration in boiler systems to prevent damage of metal parts. In high levels, chloride can corrode stainless steel and be toxic to plant life.
Hanna Instruments offers a wide variety of instrumentation for measuring chloride. Products include portable and benchtop pH/ISE meters that can use a solid-state chloride Ion-Selective Electrode (ISE) for direct measurement. In addition, Hanna offers portable photometers, checker colorimeters, and chemical test kits.
The argentometric titration for chloride is a very common measurement when determining the sodium content in food. In this titration sodium chloride reacts with silver nitrate to form silver chloride precipitate. The precipitation of chloride results in less free chloride in the sample which is detected by a chloride ISE. A silver ISE is also used as a detector tol sense the free silver ions once all the chloride has been reacted with. The argentometric titration is used in other industries where sodium concentration can be inferred by the chloride that is present and for ones that are looking to determine the concentration of chloride.
Below are the most common products used for measuring chloride.
Titration systems with precision dosing pumps are available to measure chloride. There are options for titrators with two analog inputs and two dosing pumps. This configuration would allow for a linked titration in which acidity can be measured then chloride. A complete system would include an auto sampler that has additional pumps for the acid reagent to automatically be added when the salt titration is performed.
Benchtop pH/ISE meters
Benchtop pH/ISE meters include a two channel option in which a pH probe can be connected to one channel and the chloride ISE to the other. The benchtop meters have the ion charge and formula weight pre-programmed for use with the chloride ISE. The benchtop meters also have incremental methods pre-programmed including the known addition, known subtraction, analyte addition and analyte subtraction methods.
Portable pH/ISE Meters
Portable pH/ISE allow the flexibility to perform an ISE measurement with a portable. It is a laboratory measurement that requires the addition of the ISA to fix the ion activity in the sample and the use of a magnetic stirrer to keep the sample homogenous. The portable pH/ISE meter has the ion charge and formula weight pre-programmed for concentration measurements. Also availabe multi-parameter portable meters that measure pH, ORP, dissolved oxygen, conductivity, ammonium, chloride, and nitrate. The multi-parameter portables can be ordered with probes that can also measure turbidity and meters that have built-in GPS for data mapping.
The chloride ISE is a solid state sensor that measures free chloride ions in ground water, boiler water, drinking water, and many other applications including in concrete materials testing. This chloride ISE is available as either a single half-cell or combination design with a reference cell. The ISE is a convenient way to measure chloride. The chloride ISE used with the mulitparameter meter does not use ISA. The activity coefficient is based on typical surface water conductivity values.
Solutions for chloride measurement include ISE standards and ISA for calibration and measurement. Other solutions include the CAL Check standards for verifying and, if needed, the calibration of portable photometers. Each CAL Check standard is supplied with a Certificate of Analysis stating the accuracy and traceability of the standard.
Spectrophotometers are available with the chloride method pre-programmed into the meter. The spectrophotometer offers the highest precision due to the quality of the optical system that has a wavelength accuracy of +/- 1.5 nm. The spectrophotometer allows for custom methods.
Benchtop photometers include multiparameter versions for water quality analysis. Each photometer is customized to have the parameters used by a specific industry. All benchtop have a digital pH electrode input allowing it to be used as a traditional pH meter. All benchtop photometers can display results in multiple chemical forms.
Single parameter portable photometers are available and have the Hanna CAL Check feature that allows for performance verification and, if needed, recalibration using the CAL Check standards. The portable meters are available as a meter only option or as a kit. The kit version include a rugged carrying case and CAL Check standards.
Checker HC, like a chemical test kit, is reagent based with a color change based on concentration. The handheld colorimeters, like portable and benchtop instrumentation, use the Beer-Lambert principle to determine the color change. The color change is measured by a photoelectric cell which is more accurate than subjective visual interpretation.
Reagents include the reagents used with Checker HC and photometers.
Accessories include spare cuvettes and caps for photometers, magnetic stirrers to ensure adequate mixing when using an ISE and the spare parts for the chloride ISE.