Analysis of undigested honey samples by isotope dilution inductively coupled plasma mass spectrometry with direct injection nebulization (ID-ICP-MS)

Undigested honey samples were analyzed by inductively coupled plasma mass spectrometry (ICP-MS) using direct injection nebulization (DIN). Samples were diluted 25-fold using dilute HNO3 to which Triton X-100 was added. Isotope dilution (ID) was used to quantify Ba, Cu, Pb and Zn in these natural matrix samples. DIN parameters were optimized to obtain a stable transient signal enough to determine multiple isotope ratios. The Ba, Cu and Zn isotope ratios were measured in a single sample injection of 50 μl diluted honey and the Pb isotopes in a separate injection. The analysis was characterized by precisions given by R.S.D. values from 0.20 to 1.24% for Ba, 0.49–1.23% for Cu, 0.61–2.28% for Pb and 0.50–1.51% for Zn. The results were in agreement, at the 95% confidence level, with those obtained by analyzing digested samples using external calibration. Using this direct method, 30 real honey samples per hour could be analyzed.