Precision and Bias of Graphite Furnace Analysis of Environmental Samples

Abstract

* Determination of Cr(lIl)+Cr(VI). To 25 mL of sample, add 0.3 mL of 8% PHP, adjust pH to 3.5, and add 3 mL of 10% APDC and 5 mL of PHP-saturated MIBK. Extract for 20 min. Determine Cr(lll)+Cr(VI) in the MIBK layer. * Determination of Cr(VI). Proceed as above except for the addition of 3 mL of 8% PHP and 3 mL of 2% APDC and for the extraction time of 10 mm. * Determination of Cr(III). The value of Cr(III) is obtained as the difference between Cr(Ill) +Cr(VI) and Cr(VI). The concentration of Cr(111) is also determined by the SM-7 ion exchange procedure [1]. In all the above cases, the Cr atomic absorption signal was measured by using the dry/atomize program of 900 'C-30 s (ramp)-30 s (hold)/2500 0 C-O s (ramp)-6 s (hold).