Determination of lead in paper for food contact by inductively coupled plasma mass spectrometry

Abstract

This study aimed at the method validation for determination of lead contamination in paper for food contact materials (FCMs). They were digested with acid and using the microwave digestion. Then the amount of lead in the solution was determined by inductively coupled plasma mass spectrometer and the performance characteristics which are linearity, limit of determination (LOD), limit of quantitation (LOQ), bias, precision and matrix effect were studied. The target uncertainty associated with the quantification of lead in paper, should be no bigger than ±15%. From the study, it was found that LOD and LOQ are 0.043 mg/kg and 0.40 mg/kg, respectively, while working range of this method was 0.40–4.0 mg/kg. The method bias was evaluated from the recoveries of the standard substance added to the lead-free paper at 3 concentration levels (low, medium and high) of the working range under repeatability conditions. It showed that the recoveries were 97.0–103.2%. The precision study, the same concentration of the bias study was added to the samples showed that the relative standard deviation was less than 10% and the matrix effect was investigated by considering the relationship between the concentration and the amount of lead in the paper sample solution. It was found that the coefficient of determination, R² approached 1. This indicates that there is no matrix effect. The information obtained from the bias and precision can be used to estimate measurement uncertainty. It was found that the expanded uncertainties of this method at the confidence level of 95% was ±15%. Therefore, the proposed method for determination of lead in paper is accurate, precise, reliable, and fit for the intended use.