The use of a W-Rh permanent modifier for direct determination of bismuth in urine and whole blood by electrothermal atomic absorption spectrometry

The direct determination of bismuth in urine and whole blood samples is proposed by graphite furnace atomic absorption spectrometry. The pyrolytic integrated platform of the THGA tube was coated with 250 jig W+200 mug Rh to increase the tube lifetime. Urine samples were diluted (1 + 1 v/v) and blood samples (1 + 4 v/v) in a solution containing 1.0% v/v HNO3 + 0.2% Triton X-100, and 20 mul of the resulting dilute samples were delivered into the W-Rh modified platform together with 10 mul of 10 mg l(-1) Rh solution. After 350 firings a new coating was made. The combined use of Rh solution with the W-Rh coating was decisive for increasing the maximum pyrolysis temperature of blood and urine bismuth up to 1100 degreesC. With this approach the tube lifetime increased by 80% and re-calibrations were minimised when compared to a Pd+Mg conventional modifier. The detection limits (n = 20) were 3.3 mug l(-1) and 8.4 mug l(-1) for urine and whole blood, respectively, and the characteristic mass was 49.0 pg using standard THGA. The accuracy of the proposed method was verified by comparing the results with the decomposed sample solutions. No statistical differences were found by the paired t-test at the 99% confidence level.