Sulfate EPA 375.2

Analytes

Sulfate CAS 14808-79-8


Summary

Brief Method Summary A sample is first passed through a sodium form cation-exchange column to remove multivalent metal ions. The sample containing sulfate is then reacted with an alcohol solution of barium chloride and methylthymol blue (MTB) at an acidic pH to form barium sulfate. The combined solution is raised to a basic pH so that excess barium reacts with MTB. The uncomplexed MTB color is gray; if it is all chelated with barium, the color is blue. Initially, the barium and MTB are equimolar and equivalent to 300-mg SO4/L; thus the amount of uncomplexed MTB is equal to the sulfate present. The amount of sulfate in the sample is measured by measuring the absorbance of uncomplexed MTB using a spectrophotometer.


Published Method

method_375-2_1993.pdf

Matrix

Water


Instrumentation

Lachat Flow Injection Analyzer (FIA)


Analytical Category

Conventional