Determination of beryllium and selenium in human urine and of selenium in human serum by graphite-furnace atomic absorption spectrophotometry

For human urine beryllium (Be), each sample (500 mul) was diluted (1+1) wit h Nash reagent (containing 0.2% (v/v) acetylacetone and 2.0 M ammonium acet ate buffer at pH 6.0) and then a 20-mul volume of Triton X-100 (0.4%, v/v) aqueous solution was added. An aliquot (10 mul) of the diluted urine mixtur e was introduced into a graphite cuvette and was atomized according to a te mperature program. The method detection Limit (MDL, 3 sigma) for Be was 0.3 7 mug/l in the undiluted urine sample and the calibration graph was linear up to 65.0 mug/l. Calibration graphs were prepared by the standard addition method. Accuracies of 98.6- 102% were obtained when testing standard refer ence material (SRM 2670) freeze dried human urine samples. Precision (relat ive standard deviation, RSD) for urine Be was less than or equal to2.3% (wi thin-run, n = 5) and was less than or equal to3.0% (between-run, n = 3). Fo r human urine and serum selenium (Se), samples (100 mul) were diluted with HNO3 (0.2%, v/v) to make a (1+1) dilution for urine analysis or a (1+4) dil ution for serum analysis. An additional aliquot (10 mul) of Triton X-100 (0 .1%, v/v) was added to each 200 mul of (1+1) diluted urine (or 20 mul of th e Triton X-100 was added to each 500 mul of (1+4) diluted serum) sample. Af ter the diluted sample mixture (10 mul) was introduced into a graphite cuve tte, the corresponding chemical modifier (10 mul, containing Ni2+ + Pd + NH 4NO3 in HNO3 (0.2%, v/v)) was added to it and the mixture was atomized. The MDL (3 sigma) for Se in urine and in serum was 4.4 and 21.4 mug/l in undil uted sample, respectively, and the calibration graphs were Linear up to 150 and 400 mug/l. Accuracies of urine Se were 98.9 - 99.4% by testing SRM 267 0 (NIST) urine standards with RSD (between-run, n = 3) within 2.9%; and tha t of serum Se was 97.2% when testing a certified second-generation human se rum (No. 29, #664) with RSD (between-run, n = 3) of 1.4%. The proposed meth od can be applied easily, directly, and accurately to the measurement of Be and Se in real samples (including six urine Se and four serum Se from pati ents of Blackfoot Disease in Taiwan).