DETERMINATION OF TRACE AND ULTRATRACE ELEMENTS IN HUMAN SERUM WITH A DOUBLE FOCUSING MAGNETIC-SECTOR INDUCTIVELY-COUPLED PLASMA-MASS SPECTROMETER

The purpose of this study was to evaluate the potential of ICP-MS with a double focusing instrument for the determination of both spectrally and not spectrally interfered ultratrace elements in human serum afte r minimised sample pre-treatment and without using any separation or p reconcentration techniques, Because of the heavy matrix (6-8% proteins and 1% inorganic compounds) of the material investigated, a higher re solving power than is available with quadrupole instruments was necess ary for the determination of some elements in order to eliminate spect ral interferences, This was achieved by using ICP-MS apparatus equippe d with a double focusing magnetic sector MS, This type of instrument a lso permits lower detection limits when compared with traditional quad rupole ICP-MS instruments, mainly owing to the low instrumental backgr ound values. Determinations were carried out using external calibratio n and, for most of the elements, also single standard additions as cal ibration techniques, Both the non-spectrally interfered (Cd, Sn, Ag an d U) and the spectrally interfered (Al, Si, P, S, Ti, Cr, Mn, Fe, Cu a nd Zn) elements were determined in a Second Generation Human Serum Ref erence Material, Sample preparation consisted in reconstitution of the ; freeze-dried material or in microwave digestion, both followed by di lution, In addition, to continuous nebulization, flow injection was al so applied as an introduction technique for the determination of some elements in reconstituted serum, The results for the certified element s were all within the certified range except for Cr for which a signif icantly higher value was obtained, The results of the remaining elemen ts were compared with literature values where they existed, Very low c oncentrations could tie determined: for instance a concentration as lo w as 98 ng l(-1) was determined for Ag with a standard deviation of le ss than 10%, The major difficulty encountered in this study was to kee p the blank values sufficiently low, which could only be achieved by u sing ultra-pure reagents and by working in a clean environment.