| Inductively coupled plasma mass spectrometry (ICP-MS) is a powerful tool for elemental analysis and has been used to find the composition of many materials in recent years. This thesis deals with the analytical utility of ICP-MS for the determination of endogenous levels of Li in serum Factors such as the scanned mass range and the dwell time were found to significantly affect the instrument response. Under optimum conditions for Li the serum matrix was found to cause limited non-spectroscopic interferences. Elemental recombinations of the major electrolytes in the matrix did not affect Li determination. However, several biologically important elements e.g. Cr, V, and As were significantly affected by these interferences which limited the usability of the multi-element capabilities of the technique. The feasibility of the analysis of dilute serum was investigated. The results showed that the high levels of proteins in serum caused a rapid deterioration of the magnitude and the stability of the signal. Therefore, a wet digestion technique using HNO3 was devised. The method proved to be accurate and precise not only for Li but also for B, Mg, Co, Cu, Zn, Se, Br, Rb and Cs. International standard reference materials (SRM) were used in order to test the accuracy of the overall procedures. Comparable results to the certified values were obtained for all the elements studied. In addition, this work provided the first data for Li and B in two SRMs, namely, NIST bovine serum and Versieck's second generation serum. The levels of Li in the serum of healthy subjects were evaluated based on the analysis of 196 samples. The data showed that the reference value for Li in serum approximates to 0.9 ng.ml-1. To demonstrate the applicability of this work for biological studies, the levels of Li, B, Mg, Co, Cu, Zn, Se, Br, Rb and Cs were determined in the serum of patients with skin disorders. Several changes in trace element levels e.g. the elevation of Li in polymorphic light eruption were observed. Overall, this study demonstrates the suitability of ICP-MS for routine multi-element analysis of several trace elements in serum. Although matrix dependent problems can be a limiting factor, ICP-MS is likely to become the instrument of choice for routine analysis of biological materials. |
