US EPA: SOP for the determination of As and Se in soils, sediments ans solids by GFAAS
STANDARD OPERATING PROCEDURE FOR THE ANALYSIS OF ARSENIC AND SELENIUM IN SEDIMENTS AND SOILS BY GFAA
1. SCOPE AND APPLICATION
1.1 The method is applicable to the determination of arsenic and selenium in soils and sediments as requested for all programs. Without dilution, the working range is from 0.4 to 8 mg/kg, while the estimated detection limits are 0.4 mg/kg for both elements.
2. SAFETY AND WASTE HANDLING
2.1 Unused portions of concentrated stock (1000 ug/L) solutions must be poured into a red labeled (acidic metals) waste container.
2.2 Intermediate solutions must be poured into the red labeled waste containers.
2.3 Concentrated nitric acid must be handled with caution. Gloves and lab coat must be worn during all phases of the sample preparation.
3. SUMMARY OF METHOD
3.1 Solid samples are air dried overnight and weighed to correct for moisture. The sample is pulverized in a plastic vial in a ball mill. If there are many rocks, the procedure in Appendix A and the Calculations section should be followed. About one half gram of sample is weighed into the teflon digestion vessel. Nitric acid is added and the sample heated in the microwave oven. The digest is diluted and filtered into a volumetric flask. The volumetrics are filled to volume, then poured into unused polyethylene bottles. The samples are converted to weight basis results at the time of analysis.
3.2 The samples are analyzed by graphite furnace atomic absorption using Zeeman background correction. The samples are to be analyzed by stabilized temperature platform graphite furnace using the standard curve methodology given in the corresponding water methods (references 13.1 and 13.2), and to proceed with standard additions if the stated criteria are not met (references 13.3 and 13.4).