In the present study, different substances were investigated as chemical modifiers in the direct determination of cadmium in human serum and urine without previous digestion of the samples. The preparation of the sample was made directly in autosampler cups by dilution 1+4 of serum and 1+1 of urine with nitric acid 1 % v/v containing 0.02 % v/v of cetiltrimethyl ammonium chloride. The optimum determination conditions through pyrolysis and atomization curves in the presence of the matrix and analyte taking into account the form of the absorption pulses, low atomization temperatures, background correction and sensitivity were investigated. Tests were carried out without chemical modifier, with the universal mixture of Pd and Mg (10 and 15 µg, respectively), with ruthenium (500 µg) and iridium (500 µg) permanent modifiers. For permanent Ir, the m o was 0.8 pg for serum and 0.7 pg for urine (recommended of 2 pg). Upon the investigation of the use of Ir permanent, it was observed that the peak was symmetrical, returned to the baseline in 3s and that the background was fully corrected with optimum values for pyrolysis and atomization at 300 and 1000°C for serum and 300 and 1000ºC for urine. Calibration was made by matrix matching method, and presented r² (coefficient of correlation of linear regression) higher than 0.999. Analyses of spiked serum and urine samples yielded recoveries varying between 99.3 and 103.2 with a relative standard deviation (RSD, n=3) lower than 12% for serum and between 93.1 and 102.2 % with an RSD lower than 3% for urine. The detection limit (k=3, n=10) were 8 and 9 pg for serum and urine, respectively.
electrothermal atomic absorption spectrometry; cadmium; serum; urine; permanent iridium
