THE DETERMINATION OF CHLORATE AND CHLORITE IN DRINKING WATER
Report No FR0390

P R Smith and L Harding

Jul 1993

SUMMARY

I BENEFITS

A method of determining chlorate and chlorite, capable of detecting low levels, would be of use to those responsible for monitoring drinking water and the operators of treatment works.

II OBJECTIVES

The aim of the work was to develop a reliable method capable of achieving detection limits of about 20 µgl^-1 for chlorite and chlorate in drinking water.

III REASONS

Chlorate and chlorite occur as disinfection by-products during water treatment and so can be present in drinking water. There is concern over these substances in relation to potential health effects and possible future drinking water standards. A sufficiently sensitive method for their analysis is required.

IV CONCLUSIONS

An automated method based on ion chromatography has been developed which has limits of detection of 10 µgl^-1 for chlorite and 21 µgl^-1 for chlorate.

Nitrate is an interference on chlorate due to its close elution and high levels of nitrate can raise the limit of detection for chlorate.

V RECOMMENDATIONS

The method described in the report has lower limits of detection and interference effects than other current published methods. Further work is required on testing the method with different types of waters and possibly on overcoming the effect of nitrate.

Vl RESUME OF CONTENTS

The development of a method for measuring chlorate and chlorite in drinking water is described along with the method testing that was carried out. The method is detailed in an appendix together with instrument details.

Further method testing is recommended.

Copies of the Report are available from FWR, price £15.00 less 20% to FWR Members