Chloride in Water Measurement

The Chloride concentration in natural water can vary considerably and have implications for plant life and organisms as well as its effect on the corrosion of any immersed metal structures. Fortunately the accurate measurement of Chloride in water is simple and can be carried out in the field or on collected samples in the laboratory.


A method for the measurement of Chloride ion concentration in drinking water, ground water and waste water for samples containing 1 to 1000 ppm chloride. This range may be extended by dilution with deionised water to the appropriate level. This can be desirable in waste or contaminated water.

Equipment Required

1.   The Model QP459 Portable Ion Meter

2.  The 3261 Chloride Combination ISE

3.   21301 Chloride 1000ppm Standard Solution

4.   30301 Chloride Ionic Strength Adjustment Buffer

5.   Glassware. Beakers 250ml, Volumetric Flask 100ml. 10ml Graduated pipette

6.   Deionised water.

 Standard Preparation

Prepare standards of 100, 10ppm by serial dilution of the 21301 1000 ppm Standard solution.

This is best achieved by pipetting 10ml of the standard into a 100ml volumetric flask and diluting to the mark with deionized water. This is now a 100ppm Standard solution.

 Sample Preparation

If the sample is clean no preparation is necessary. Filtration may be necessary if there is a high solid content. .


To 100ml of each of the standards and samples add 2ml of 30301 ISAB and mix the contents. Be sure the beakers are clean and make sure not to touch the inside of the beakers with bare hands as Chloride contamination from sweat etc. is common. Beakers that have been washed with softened water or tap water will be contaminated. In these cases rinse the beakers with deionised water.

Immerse the electrode in each of the standards in increasing concentration steps following the calibration routine on the Ion Meter, rinsing the electrodes with distilled water and dabbing off the excess water between standards. 

Using the QP459 Ion meter will allow the result to be read directly on the display. It also allows for up to a 3 point calibration if required.

If you do not have an ION meter you can read the mV values using a pH/mV meter such as an EDT model QP451. Record the mV response and plot a graph of mV vs. log of Concentration.


There are no interference from up to 500 ppm S=, 1000 ppm Br- or I- a 100:1 excess of CN over Cl-, or from 1000 ppm NH4+