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R9 Laboratory SOP 403
Sample Preparation for Graphite Furnace Atomic Absorption, Inductively Coupled Plasma -
Atomic Emission Spectrometry and Inductively Coupled Plasma - Mass Spectrometry Analyses
Summary
This SOP provides sample preparation procedures for the determination of dissolved and total recoverable elements by graphite furnace atomic absorption (GFAA), Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES) and Inductively Coupled Plasma - Mass Spectrometry (ICP-MS) in ground water, surface water, drinking water, storm runoff, industrial and domestic wastewater. The analyses of samples prepared in this SOP are detailed in EPA Region 9 Laboratory SOPs 505, 507 and 511.
Dissolved analytes can be determined in aqueous samples after suitable filtration and acid preservation. Refer to SOPs 505, 507 and 511.
Samples may be analyzed directly without acid digestion if the sample has been properly preserved with acid, has a turbidity of <1 NTU (nephelometric turbidity units) at the time of analysis. This total recoverable determination procedure is referred to as "direct analysis."
For the determination of total recoverable analytes in aqueous samples a digestion is required prior to analysis when the elements are not in solution (e.g., aqueous samples that may contain particulate and suspended solids). Aqueous samples containing suspended or particulate material >1% (w/v) should be digested as a solid type sample (Region 9 Laboratory SOP 405).
Nitric and hydrochloric acids are dispensed into a digestion tube containing an accurately measured, well-mixed, homogeneous aqueous sample. Aqueous samples are first reduced in volume by gentle heating. Then, metals are solubilized from the undissolved portion of the aqueous sample by covering the tube with a watch glass and refluxing the sample in the dilute acid mixture. After digestion, the solubilized analytes are diluted to specified volumes with reagent water, mixed and allowed to settle overnight before analysis. Diluted samples are to be analyzed by GFAA, ICP-AES and ICP-MS as soon as possible after preparation.