This method is for the determination of sulfate in drinking, surface and saline water, domestic and industrial wastes. This method is the most accurate method for sulfate concentrations above 10 mg/L and should be used whenever results of the greatest accuracy are required. Sulfate is precipitated as barium sulfate in a hydrochloric acid medium by the addition of barium chloride. After digestion, the precipitate is filtered, washed with hot water until free of chloride, ignited, and weighed as barium sulfate.
High results may be obtained for samples that contain suspended matter, nitrate, sulfite, and silica. Alkali metal sulfates frequently yield low results, especially alkali hydrogen sulfates. Occlusion of alkali sulfate with barium sulfate causes the substitution of an element of lower atomic weight than barium in the precipitate. Hydrogen sulfate of alkali metal acts similarly and decomposes when heated. Heavy metals such as chromium and iron, cause low results by interfering with complete precipitation and by formation of heavy metal sulfates.
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| Hold Times, Preservatives, Preps, Collection, Analytical & Documentation | |
|---|---|
| Holding Time: | 28 days from sample collection to analysis. |
| Preservatives: | Store samples at 4°C. |
| Required Preps: | 100 mL HDPE or amber glass bottle |
| Collection Method: | Grab sampling |
| Analytical Methodology: | Gravimetric |
| Documentation: | 
375.3
|
| Analyte | Formula | CAS Number | Detection Limit | |
|---|---|---|---|---|
| Sulfate | SO4 |
14808-79-8 |
10 |
mg/L |
* The analytes and detection limits listed for each method represent the typical detection limits and analytes reported for that particular method. Keep in mind that analyte lists may vary from laboratory to laboratory. Detection limits may also vary from lab to lab and are dependent upon the sample size, matrix, and any interferences that may be present in the sample.