Comparison of effects of four acid oxidant mixtures in the determination of lead in foods and beverages by hydride generation-ICP-OES

摘要

A comparative study was undertaken to evaluate the effects of acetic, citric, nitric, and tartaric acids on the continuous hydride generation of lead using ammonium persulfate as oxidant agent. Inductively coupled plasma optical emission spectrometry (ICP-OES) was used for detection. The operating conditions (chemical and physical parameters) and the concentrations of the acids studied were optimized for the generation of PbH4 (plumbane). Analytical figures of merit including detection limit, precision, and linear dynamic range are given for the four systems employed. The detection limits for Pb ranged between 4.4 and 6.8 mug L-1 depending on the acid used to generate plumbane. Compared to conventional continuous nebulization on a radial ICP, the present coupling gives a sensitivity increase of a factor of approximately two orders of magnitude. The interferent effect of transition metals (Al, Cd, Co, Cu, Cr, Fe, Mn, Mo, Ni, V, and Zn), other hydride-forming elements (As, Bi, Ge, Sb, Se, Sn, and Te,) and Hg upon the Pb signal using the different acids studied were evaluated. Nickel, Se, and Te are the elements that more severely affect plumbane generation in the four systems tested. Plumbane was produced with 85% efficiency in tartaric acid; also a better control of interferences was observed. Method validation was achieved using two certified reference materials, MURST-ISS-A2 (Antarctic Krill) and CRM 063R (Skim Milk Powder), for which reasonable agreement between certified and measured values for lead content was obtained. The proposed method was applied to the determination of Pb at mug g(-1) and mug L-1 levels in foods and beverages, respectively. The determination of Pb in these kinds of samples is of high toxicological relevance. [References: 20]