DETERMINATION OF SULFATE IN WATER – EVALUATION AND INTERCALIBRATION OF METHODS
In connection with the inter-Nordic standardization (INSTA) of methods in water chemistry, some methods for the determination of sulfate have been evaluated. Two manual spectro-photometric methods were tested, one based on the reagent thorin and the other on methyl thymol blue (MTB), but neither of them were acceptable; the thorin method had a too narrow working range and too low precision, while the MTB method was too sensitive to interference from humic substances. A titrimetric method using thorin as the indicator was however advantageous in these respects.
An intercalibration on sulfate was arranged between four laboratories, concerning seven determination methods: turbidimetric, nephelometric, colorimetric with thorin (manual or automatic), titrimetric with thorin (manual or photometric) and potentiometric titration with a lead electrode. “Complete abstract not presented.”