Determination of chromium and nickel in human blood by means of inductively coupled plasma mass spectrometry

The suitability of inductively coupled plasma mass spectrometry (ICP-MS) for the determination Cr and Ni in human whole blood was investigated. Strict criteria for blood sampling and sample treatment were set to avoid contamination or loss of analytes. A wide concentration interval of analytes was obtained by collecting specimens from subjects with a history of exposure to one of the two elements or both. A dynamic range of more than three orders of magnitude was achieved with operative detection limits of 0.03 and 0.04 μg/1 in the analytical solution for Cr and Ni, respectively. At 1.0 μg/1 and 0.5 μg/1 concentration levels for Cr and Ni, respectively, the instrumental precision, as relative standard deviation (R.S.D.), was 2.6% and 3.8%, while for reproducibility of the entire analytical cycle of analysis, including sample pretreatment, values of 4.8% and 5.5% were obtained. The accuracy of the method was verified by using the serum NIST 909 reference material for Cr and an in-house standard for Ni with mean recovery percentages of 95.0% and 105%, respectively. These performance characteristics were obtained by careful evaluation and correction of the interferences at the masses used for determination. For the 52Cr isotope the presence of 40Ar12C, due to the high concentration of C in the organic matter, exerted a dramatic influence. This was overcome only by reduction of the C content of the sample performing a full digestion cycle in a microwave oven and by a suitable correction equation. For Ni measurements, mass 60 gave satisfactory results because of very scarce influence of the main potential interferent ions, i.e., 44Ca16O and 37Cl23Na.