Simple hollow fiber liquid membrane based pre-concentration of silver for atomic absorption spectrometry

Abstract

Silver pollution has gained attention in the last few years because silver is being massively used as a bactericide in self-care, medical and textile products. Difficulties of Ag determination are associated with the very low concentrations in which it is normally found (ng L⁻¹) and the nature of the sample matrix. Standard methods such as liquid–liquid extraction (LLE) are regularly used. Alternatively, liquid phase micro-extraction (LPME) appears to be an environmentally friendly tool for sample treatment that offers higher pre-concentration factors. This allows the determination of ultra-trace levels of silver using standard instrumental techniques such as atomic absorption spectrometry. In this work, a hollow fiber LPME is proposed. Silver pre-concentration has been conducted using tri-isobutylphosphine sulphide (TIBPS) as a carrier from the sample to an acceptor solution through a solvent placed in the fiber pores. Accurel-PP 50/280 fibers with an internal volume of 20 μL were used for 50 mL samples. After optimization, 0.1 M KNO₃ in the sample, 0.1 M TIBPS in dihexyl ether as the organic phase and 1 M Na₂S₂O₃ in the acceptor solution were established. The system offers enrichment factors of 1053 times, a limit of detection of 1.16 ng L⁻¹. This method improves the limit of detection of the most recent liquid micro-extraction methods for silver pre-concentration coupled with GFAAS, being in this case comparable to ICP-MS detection based techniques.