| Abstrakt: |
In this work, a group of chemical modifiers used in solution or as permanent modifiers were studied for the determination of chromium in human serum by ETAAS. The serum samples were diluted in the autosampler in the ratio 1 + 4 with 1% v/v nitric acid containing 0.02% v/v of cetyltrimethylammonium choride (CTAC). Formation of crusts in all the modifiers was prevented by addition of an optimized concentration of CTAC. Pyrolysis and atomization temperature curves were constructed for each modifier in the serum sample. For all the studied permanent modifiers (Ir, Ru, Zr and a mixture of Ir plus Rh) a plateau was obtained rather than peak formation, which, even for a 10 s atomization, did not return to the base line. With Pd + Mg, the peak was irregular and noisy and had a sensitivity about 4 times lower than that without modifier. The best results were obtained without a modifier, and with pyrolysis and atomization temperatures of 1000 and 2200 °C, respectively (characteristic mass of 0.6 ± 0.01 pg, recommended 8.0 pg without modifier for aqueous solutions). Calibration curves were similar using standard additions and aqueous solutions (with coefficients of 0.030 and 0.031, respectively). Three replicates of spiked serum samples were analyzed on three different days and the results were always close to 100%. The limit of detection (n = 10, k = 3) was 0.04 µg L−1. It was possible to run more than 300 cycles of atomization with a tube, without alteration in the signal and without the formation of crusts. |
