Sulphate measurement in organic-rich solutions: Carbonate fusion pretreatment to remove colour interference

Abstract

Sulphate measurement using a barium sulphate turbidimetric method in solutions with high concentrations of organic mate rial is shown to be problematic. The organics give background colour, which introduces a positive error to the measured absorption, and inhibit the barium sulphate precipitate, which results in a negative error. A carbonate fusion pretreatment of the sample results in the removal of the organic matter and associated interferences. With this pretreatment, excellent sulphate re coveries were obtained (100%). Rigorous testing of the method shows that reproducible and accurate results are obtainable.

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