Method and proficiency test for analysis of toxic metals in livestock products by ICP/MS

Abstract

The analytical method of trace toxic metals in livestock products was confirmed and validated through certified reference material (CRM) and the international proficiency tests. There are some difficulties to determine low levels of toxic metals in livestock products because of interferences due to the matrix. The recoveries of CRM (NIST 1577c) ranged from 73.9 to 119% for lead and from 86.4 to 111% for cadmium in bovine liver. The international proficiency tests were carried out with the milk powder and cocoa powder samples including metals provided by Food Analysis Performance Assessment Scheme (FAPAS®, UK). The test samples were prepared by microwave digestion using solution of HNO3 : H2O2 : H2O (v/v/v = 5 : 2 : 4) and analyzed by ICP/MS. The analytical result of cadmium in milk powder was 121 μg/kg with -0.3 of the z-score compared to the assigned value of 131 μg/kg by FAPAS®. The analytical results of lead and cadmium in cocoa powder were 29.2 μg/kg and 97.6 μg/kg, respectively, which satisfied the assigned values of 34.2 μg/kg for lead and 126 μg/kg for cadmium by FAPAS®. It is verified that the analytical method is accurate and reliable to determine trace lead and cadmium in livestock products by microwave digestion and ICP/MS.