DETERMINATION OF TRACE LEVELS OF SULFATE IN WATER USING FLOW-INJECTION AND IN-LINE PRECONCENTRATION

Sulphate is preconcentrated on a strong anion-exchange resin and determined using the effect of sulphate ions on the complexation of methylthymol blue and barium. A computer-controlled flow-injection analyser is used to automate the whole procedure. The resin has two functions: it preconcentrates sulphate and also separates sulphate from divalent cations that may interfere in the determination step. The system can handle 30 samples per hour and has a working range from 25 to 1000-mu-g 1(-1) of sulphate. Lower detection limits can be obtained by changing the preconcentration conditions. The effect of both anionic and cationic interferents was studied.