Method 9036

Sulfate (Colorimetric, Automated, Methylthymol Blue, AAII)


This method is for the determination of sulfates from ground water, drinking and surface waters, and domestic and industrial wastes.  The 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 a pH of 2.5-3.0 to form barium sulfate.  The combined solution is raised to a pH of 12.5-13.0 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 30 mg sulfate /liter; thus the amount of uncomplexed MTB is equal to the sulfate present.  Analysis is performed using an automated colorimeter.

Samples in the range of 0.5 to 300 mg sulfate/liter can be analyzed. 


(EPA SW-846)

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Method Data

Hold Times, Preservatives, Preps, Collection, Analytical & Documentation
Holding Time:   28 days from sample collection to analysis.
Preservatives:   Store samples at 4°C.
Required Preps:   250 mL HDPE or amber glass bottle
Collection Method:   Grab sampling
Analytical Methodology:   IC/Colorimeter
Documentation:   9036

Analyte List*

Analyte Formula CAS Number Detection Limit
Sulfate
SO4
14808-79-8
0.5
 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.