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 pro posed by graphite furnace atomic absorption spectrometry. The pyrolytic int egrated platform of the THGA tube was coated with 250 jig W+200 mug Rh to i ncrease 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 t he W-Rh coating was decisive for increasing the maximum pyrolysis temperatu re of blood and urine bismuth up to 1100 degreesC. With this approach the t ube lifetime increased by 80% and re-calibrations were minimised when compa red 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 th e proposed method was verified by comparing the results with the decomposed sample solutions. No statistical differences were found by the paired t-te st at the 99% confidence level.