APPLICATION OF HYDRIDE GENERATION ATOMIC-ABSORPTION SPECTROMETRY TO THE DETERMINATION OF LEAD COLLECTED ON AIR FILTERS AND SPHAGNUM MOSS

A commercial continuous-flow hydride generation system combined with a tomic absorption spectrometry (HGAAS) was applied to the determination of lead in the urban atmosphere of Oporto. he procedure was used for both atmospheric aerosols collected on cellulose filters and extracell ular aqueous extract of the MOSS Sphagnum auriculatum. Under optimized conditions, which were 0.75% HNO3, 6% (NH4)2S2O8 and 2% sodium citrat e for the sample solution (flow rate 6 ml min-1), and 7% NaBH4 for the reducing solution (flow rate 3 ml min-1), the characteristic concentr ation (0.0044 absorbance) was 0.3 ng ml-1 of lead and the response was linear up to 40 ng ml-1. No interferences occur up to 60 ng ml-1 (Ni) , 30 ng ml-1 (Cu) and 1.0 mug ml-1 (Fe, Mn and Zn), with these metals together in the sample. The ruggedness of the procedure towards either small uncontrolled fluctuations of the experimental parameters or the major interferent heavy metals was ascertained by Youden ruggedness t ests. Direct comparison of HGAAS with AAS with electrothermal atomizat ion (both type of samples) and differential-pulse anodic stripping vol tammetry (moss extracts) was used for validation of the method. A prec ision study performed on real samples showed that the standard deviati on associated with the over-all procedure (sample pre-treatment and su bsequent determination) was mainly due to both lack of sample homogene ity and its treatment, the proposed analytical method having sufficien t recision for the type of environmental applications under considerat ion.