ChromatographicAnalysis of Chloramines Using Electrochemical Detection

ReportWSAA No 11

April 1990

SYNOPSIS

Theintroduction of chloramination procedures for the disinfection of potable watersupplies requires the associated development of accurate laboratory techniquesto monitor the levels of these compounds.

Presentmethods used routinely to analyse chloramines are prone to a broad range ofinterferences, are difficult to automate, and require the pH to be altered fromthe natural value of the sample. This gives rise to uncertainty in the accuracyof speciation data.

Wereport here the development and evaluation of a method using HPLC withelectrochemical detection (HPLC/EC). It gives an order of magnitude improvementin sensitivity over existing methods using HPLC with spectropotometricdetection. The working determination limits for real samples were 0.1 mg/L formonochloramine and >0.03 mg/L for dichloramine.

Themajor problems encountered in HPLC/EC determination of chloramines are:

1.       There are noreadily available standards, so the method must be calibrated against anotheraccepted method.

2.       Theelectrochemical cell requires regular disassembly to clean the electrode.

3.       It takes 1-2hours to achieve a stable background current in the electrochemical detectorafter it is first connected.

Theseproblems need to be addressed before the method could be introduced as aroutine laboratory test.

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