Highly Sensitive Determination of Arsenic and Antimony Based on an Interrupted Gas Flow Atmospheric Pressure Glow...

A novel interrupted gas flow (IF) technique has been proposed for highly sensitive determination of ultratrace levels of arsenic and antimony in water samples by atmospheric pressure glow discharge (APGD) excitation source coupled with HCl-KBH₄ hydride generation (HG). It is demonstrated that the gas flow interruption technique provides a dramatic and reproducible enhancement of emission signals of 1-2 orders of magnitude for As and Sb over conventional continuous gas flow (CF) in APGD. The enhanced analyte emission sensitivities in IF-APGD were investigated from the viewpoint of changes in plasma excitation temperature and analyte density. With eight As lines as the thermometric probe, no measurable change in excitation temperature was found, suggesting that the enhancement is caused by an increase in analyte number density in the plasma immediately following the gas flow interruption. Furthermore, the enhancement factor was found to increase with the time interval in between the gas interruption, supporting an analyte adsorption (or trap)-release mechanism hypothesis. Under optimized conditions, the detection limits (DLs) of IF-APGD mode for As and Sb were calculated to be 0.02 and 0.003 μg L^-1, which are, respectively, about 27- and 120-fold improved compared to CF-APGD mode. The linearity of calibration for both As and Sb reached R² > 0.999 in the 0.1-5 μg L^-1 range. The accuracy of the proposed method was validated by the determination of certified reference materials (CRMs), and the results agreed well with the certified values.