Cyanide in Water Measurement

This describes the method for the determination of cyanide in water samples when metals which form cyanide complexes are not present.

CAUTION: Cyanide solutions are extremely dangerous. Always use bulb or automatic pipettes, wear protective gloves, eyewear and a lab coat and do not mouth pipette. Follow good laboratory practice. 

Image showing a combination Ion Selective Electrode.
An image showing a portable ion meter.


Equipment Required

1. QP459 Portable Ion Meter

2. 3291 Cyanide Combination ISE

3. 1000ppm Cyanide Standard Solution

4. 30304 Cyanide Ionic Strength Adjustment Buffer

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

6. Deionised water.


Standard Preparation:                      

In a 1 litre volumetric flask, dissolve exactly 2.505g of analytical grade Potassium Cyanide in distilled water and dilute to the mark (make up fresh before each analysis). This is 1000ppm Cyanide Solution.

Prepare standards of 10 and 100ppm Cyanide by serial dilution of the 1000ppm standard. This is 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.  Prepare other standards as necessary. 



Wear protective gloves and Safety Glasses at all times

To 100ml of each of the standards and samples add 5ml of 30304 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 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 3291 Cyanide Combination electrode in each of the standards in increasing concentration steps in the calibration mode of the Ion Meter, rinsing the electrodes with distilled water and dabbing off the excess water between standards. Dispose of Tissues immediately.

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



As both standards and sample have been diluted by the same amount the result obtained from the QP459 Ion Meter relates to the concentration of the original sample.