Flow on-line sorption preconcentration in a knotted reactor coupled with electrothermal atomic absorption spectrometry for selective As(iii) determination in sea-water samples

Abstract

A flow injection on-line sorption preconcentration system using a polytetrafluoroethylene (PTFE) knotted reactor was coupled with electrothermal atomic absorption spectrometry (ETAAS) to determine selectively As(III) in sea-water samples. Separation of arsenic inorganic species was achieved by the on-line formation of As(III)–pyrrolidine dithiocarbamate (PDC) complex in an acid medium, its sorption onto the inner walls of the knotted reactor (KR) and elution with 40 μl of ethanol. An enhancement factor (EF) of 44 was obtained compared with the slope of the linear portion of the calibration curve before and after preconcentration The detection limit (3 s) was 0.008 μg l⁻¹ As(III). The precision (RSD n = 11) was 4.5% at 0.1 μg l⁻¹ As(III). The accuracy was demonstrated by total arsenic determination in certificed reference material, NASS-4, after pre-reduction of As(V) with L-cysteine 0.25% (m/v).