Desenvolvimento e validação de procedimento analítico para a determinação de elementos potencialmente tóxicos em alimentos infantis por ICP-MS

Abstract

Feeding is one of the pillars of human health and is an extremely important issue, especially when it comes to childhood feeding. During food processing stages, these can be exposed to contaminants, both organic and inorganic. Inorganic contamination can be caused by chemical elements that present potential toxicity to human beings. Taking into account this possible risk and importance, several world organizations establish laws that define the limits to these potentially toxic elements in food. In Brazil, ANVISA published in 2017 a resolution (RDC Nr. 193) that specifically defines limits for As, Cd, Pb and Sn in infant food. Given this context, the purpose of this work was developing and validating a single analytical procedure for the determination of As, Cd, Cr, Cu, Hg, Pb, Ni, Se e Sn in powder milk, infant formulas, child cereals, and transition foods made of fruits, vegetables, and meat. A microwave-assisted sample preparation procedure in closed vessels was developed to digest the studied samples using 3 mL of concentrated distilled HNO3. Such efficiency was evaluated by determining the dissolved carbon in the digests. The choice of using concentrated HNO3 was also based on the risk of contaminations when using H2O2 combined with diluted nitric acid solution. For ICP-MS measurements it was possible to establish a single procedure to determine all analytes. It was necessary to use argon gas as a diluter in AMS (All Matrix Solution) System. This resource minimized positive errors presented for As and Se. The kinetic energy discrimination mode of operation was used for determination. For procedure validation, the LOQ’s were calculated and they complied with the limits established in RDC nr. 193. The linearity of the analytical curves proved to be adequate by statistical studies such as determination of the coefficients r and r2, residue evaluation, homoscedasticity, among others. Selectivity study for the evaluation of matrix effect showed satisfactory results for all samples, elements and concentration levels. Precision evaluation, which was divided into repeatability and intermediate precision, was considered satisfactory, presenting CV values below 15 % for both tests. CV’s values in repeatability ranged from 0.51 % (powdered milk, Pb, high level) to 14.8 % (Cu, infant formula, low level). CV’s for intermediate precision were from 0.8 % (Sn, high level, vitamin supplement) to 14.4 % (Cu, low level, infant formula). Samples recoveries ranged from 77.3 % (Hg, low level, fruit baby food) to 114.7 % (As, medium level, infant formula) proving the accuracy of the developed procedure by providing results between the limit range of 60 to 115 %. Finally, the measurement uncertainty was calculated for all samples and ranged from 7.22 % for Hg in infant formula to 29.67 % for Se in powdered milk, with precision parameter being the major contributor source to the combined uncertainty. The developed procedure will be implemented in routine work and it will make possible to meet the current demand of the Laboratório Exata.