Cryogenic trapping with a packed cold finger trap for the determination and speciation of arsenic by flow injection/hydride generation/atomic absorption spectrometry

Abstract

An innovative analytical system based on the combination of cryogenic trapping and unambiguous gas chromatographic separation performed within a packed cold finger trap (PCFT) has been developed here. In this hydride generation-packed cold finger trap-atomic absorption spectrometric (HG-PCFT-AAS) system, the carrier gas (He) and heating voltage were optimized from a complete factorial experiment and in accordance with a base-line resolution (RS > 1.4) between monomethylarsonic acid (MMA) and dimethylarsenic acid (DMA); the sheath gas argon (Ar) flow rate, on the other hand, was optimized from a single factorial experiment to obtain the highest signal-to-noise (S/N) ratio. Here, for MMA and DMA analysis, compromised levels of the parameters for hydride generation were determined from an L16(4)5 orthogonal array experimental design following the principle of the larger-is-better S/N ratio. The hydride evolution after the addition of a citrate buffer was employed to selectively measure arsenite (AsIII). With an atomic absorption spectrometer (AAS) serving as the detector, the limits of detection were 0.9, 0.8, 0.5, and 0.6 ng for AsIII, AsV (arsenate), MMA and DMA, respectively. The results of the application of the method in freshwater and seawater showed spike recovery ranges from 82∼113% and relative standard deviation of triplicate analysis ranges from 3∼10%, depending on the arsenic species. Accuracy of the established method was also validated by analyzing two standard reference materials, NASS-5 and SLEW-3, in which two arsenic species, AsIII and AsV, are detected.