Determination of chromium, iron and selenium in foodstuffs of animal origin by collision cell technology, inductively coupled plasma mass spectrometry (ICP-MS), after closed vessel microwave digestion

Abstract

The determination of chromium ( 52Cr), iron ( 56Fe) and selenium ( 80Se) isotopes in foodstuffs of animal origin has been performed by collision cell technology (CCT) mode using an inductively coupled plasma mass spectrometry (ICP-MS) as detector after closed vessel microwave digestion. To significantly decrease the argon-based interferences at mass to charge ratios ( m/ z): 52 ( 40Ar 12C), 56 ( 40Ar 16O) and 80 ( 40Ar 40Ar), the gas-flow rates of a helium and hydrogen mixture used in the hexapole collision cell were optimised to 1.5 ml min −1 H 2 and 0.5 ml min −1 He and the quadrupole bias was adjusted daily between −2 and −15 mV. Limits of quantification (LOQ) of 0.025, 0.086 and 0.041 mg kg −1 for Cr, Fe and Se, respectively, in 6% HNO 3 were estimated under optimized CCT conditions. These LOQ were improved by a factor of approximately 10 for each element compared to standard mode. Precision under repeatability, intermediate precision reproducibility and trueness have been tested on nine different certified reference materials in foodstuffs of animal origin and on an external proficiency testing scheme. The results obtained for chromium, iron and selenium were in all cases in good agreement with the certified values and trueness was improved, compared to those obtained in standard mode.