On-line bidirectional electrostacking of chromium(III) and chromium(VI) for flame atomic absorption spectrometry determination

An on-line bidirectional electrostacking-flow injection-flame atomic absorption spectrometry method has been developed for the simultaneous separation, pre-concentration and determination of Cr(III) and Cr(VI). The electrostacking-flow injection unit was established, the pH and components of the support buffer and sample medium were investigated. Results indicated that the ionic mobility, electric field strength and sample area cross-section are the main influence factors on the electrostacking. The calibration range for both, Cr(III) and Cr(VI), was from 20 to 400 mu g l(-1). The limit of detection was 7 mu g l(-1) for three-times the standard deviation of blank values using a electrostacking time of 350 s. The recovery percentages of 100 mu g l(-1) Cr(III) and 25 mu g l(-1) Cr(VI) added to samples were 100 and 94% with variation coefficients of 7 and 10%, respectively. (C) 2000 Elsevier Science B.V. All rights reserved.