Determination of arsenic(III) by flow injection solid phase extraction coupled with on-line hydride generation atomic absorption spectrometry using a PTFE turnings-packed micro-column.

A novel flow injection (FI) solid phase extraction method for the determination of arsenic(III) at trace levels was developed, using on-line hydride generation atomic absorption spectrometry (HG-AAS). Selective determination of As(III) was achieved by on-line formation and retention of the pyrrolidine dithiocarbamate arsenic complex As(III)-PDC on the PTFE turnings which are packed in the preconcentration micro-column. The retained complex was eluted by 2 ml 2 mol l(-1) HCl and subsequently introduced on-line into the integrated reaction chamber/gas-liquid separator (RC-GLS). A 1.5% (m/v) NaBH4 solution was used for arsine generation, while a gas stream of N2 was employed for flash release and transportation towards the atomic absorption flow through cell (AAC) for atomization and measurement. The excellent performance of PTFE turnings as sorbent material and the compact design of the RC-GLS result to high sensitivity, selectivity and sampling frequency. For 60s preconcentration time and sample consumption 10.4 ml a sampling frequency of 25 h(-1) and a detection limit of c(L)=0.02 microg l(-1) were obtained. The repeatability, expressed as relative standard deviation (R.S.D.), at 1.0 microg l(-1) As(III), was s(r)=2.8%. The proposed method was successfully applied to the selective determination of As(III) in natural waters and total arsenic determination in certified reference material.