EPA Method 7742

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EPA Method 7742:

Samples are prepared according to the nitric acid digestion procedure for aqueous and extract samples and the nitric/peroxide/hydrochloric acid digestion procedure for sediments, soils, and sludges. Excess peroxide is removed by evaporating samples to near-dryness at the end of the digestion followed by dilution to volume and degassing the samples upon addition of urea. The selenium is converted to the +4 oxidation state during digestion in HCl. After a 1:10 dilution, selenium is then converted to its volatile hydride using hydrogen produced from the reaction of the acidified sample with sodium borohydride in a continuous-flow hydride generator.

Method 7742 is an atomic absorption procedure for determining 3 ?g/L to 750 ?g/L concentrations of selenium in wastes, mobility procedure extracts, soils, and ground water. Method 7742 is approved for sample matrices that contain a total of up to 1000 mg/L concentrations of cobalt, copper, iron, mercury, and nickel. A solid sample can contain up to 10% by weight of the interferents before exceeding 1000 mg/L in a digested sample. All samples including aqueous matrices must be subjected to an appropriate dissolution step prior to analysis. Spiked samples and relevant standard reference materials are employed to determine the applicability of the method to a given waste.

Test Description:
Selenium - AA, Gaseo

Report Number:
SW-846 Ch 3.3