Voltammetric methods for the simultaneous determination of trace metals in foods, plant tissues and soils.

摘要

An analytical procedure for the sequential determination of copper(II), chromium(VI), thallium(I), lead(II), tin(II), antimony(III) and zinc(II) by anodic stripping voltammetry (ASV) in three interdependent matrices involved in foods and food chain as meals, cereal plants and soils is described. The digestion of each matrix was carried out using a mixture of concentrated acids: HCl-HNO3-H2SO4 for meals and cereal plants, and HCl-HNO3 for soils. Dibasic ammonium citrate (0.1 mol L-1; at either pH 6.2 or 8.3) was used as the supporting electrolyte. The voltammetric measurements were carried out using, as working electrode, a stationary hanging mercury drop electrode (HMDE) and a platinum electrode and an Ag|AgCl|KClsat. electrode as auxiliary and reference electrodes, respectively. The analytical procedure was verified by the analyses of the standard reference materials: Wholemeal BCR-CRM 189, Wheat Flour NIST-SRM 1567a, Tomato Leaves NIST-SRM 1573a and Montana Soil Moderately Elevated Traces NIST-SRM 2711. For all the elements in the certified matrix, the precision as repeatability, expressed as relative standard deviation (sr) was of the order of 3-5%. The accuracy, expressed as relative error (e) was of the order of 3-7%, while the detection limits were in the range 0.011-0103 micro g g-1. Once set up on the standard reference materials, the analytical procedure was transferred and applied to commercial meal samples and cereal plants and soil samples taken from sites used for agriculture. A critical comparison with spectroscopic measurements is also discussed..