Abstract

A new, rapid and simple procedure based on dispersive liquid-liquid microextraction (DLLME) of the Cr(VI) chelate with ammonium pyrrolidine dithiocarbamate (APDC) and subsequent ICP-MS analysis of the extracts by using dried-droplet laser ablation (LA) sample introduction was developed for the determination of ultratrace amounts of Cr(VI). DLLME was performed using 1 mL of methanol containing 50 μL of CCl4 as extraction mixture. Several factors influencing the DLLME performance of Cr(VI), such as sample pH, concentration of APDC and effect of potential interferents were established. Dried microdroplets (7 μL) of the obtained extracts were ablated from a polystyrene substrate and quantitated by ICP-MS. External calibration was used in combination with platinum (195Pt) as an internal standard. No matrix-matched standards are required to perform quantitative analysis. Proposed methodology yields sufficiently low detection limits (0.11 and 0.31 μg L-1 for 52Cr and 53Cr, respectively) with precision between 4 and 8%. The method was applied to determine Cr(VI) in tap and river samples. The spike recoveries showed acceptable performance of the method, with all of the recoveries within 7% of the nominal spike values.

Keywords: Dispersive liquid-liquid microextraction, Cr(VI), Dried-droplet laser ablation, ICP-MS, Water analysis.