SEDL / STP / STP573-EB / STP38997S

Automated Method for Sulfate Determination in Lake Water

Santiago, MA
Assistant research chemist, research assistant, and research limnologist, The University of Michigan, Ann Arbor, Mich.

Fielek, S
Assistant research chemist, research assistant, and research limnologist, The University of Michigan, Ann Arbor, Mich.

Schelske, CL
Assistant research chemist, research assistant, and research limnologist, The University of Michigan, Ann Arbor, Mich.

Pages: 12    Published: Jan 1975

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Abstract

An automated turbidimetric method is presented for the determination of sulfate in lake water. Turbidity of samples filtered with 0.45 µm HA Millipore filters is measured at 420 mµm with a Technicon AutoAnalyzer after sulfate is reacted with BaCl² in HCl reagent. A NH⁴OH-EDTA rinse prevents coating of the BaSO⁴ precipitate on the flowcell walls, glass coils, and plastic tubing of the manifold system, eliminating excessive baseline drift. There are no interference effects of seven ions most likely to occur in lake water. Recovery in tests and replicate analyses shows an accuracy better than ±2 percent and a precision of ±2 percent. The method is used to determine 5 to 40 ppm sulfate. Results are compared with those obtained from other automated turbidimetric methods.