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 mu g/l in the analytical solution for Cr and Ni, respectively. At 1.0 mu g/l and 0.5 mu g/l 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 Cr-52 isotope the presence of (ArC)-Ar-40-C-12, 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., (CaO)-Ca-44-O-16 and (ClNa)-Cl-37-Na-23.