[Show abstract][Hide abstract] ABSTRACT: We describe an ultrasensitive and reliable method for determining vanadium in human serum by electrothermal atomic absorption spectrometry. After lyophilization, the serum is digested in acid at high pressure, and the digests are evaporated to a small volume. Vanadium in the digests is complexed with cupferron, extracted, and dried. The residue is redissolved in formic acid, where it is 15-fold more concentrated than in the original serum sample. To enhance the furnace sensitivity, we injected six 40-microL aliquots (total, 240 microL) of the concentrated extract. The median concentration of vanadium in 108 persons was 50 ng/L, in good agreement with previously reported results by neutron activation analysis. The characteristic mass obtained (the mass required to give a signal of 0.0044A. s) was 28 pg, the limit of detection 11 ng/L, the limit of quantification 17 ng/L, and the total imprecision (CV) 5.5% at 1.54 micrograms/L. In two assays of Standard Reference Material 1577a (certified vanadium content 99 +/- 8 ng/g), we obtained values of 94.1 and 97 ng/g.
[Show abstract][Hide abstract] ABSTRACT: We made sensitive and accurate electrothermal atomic absorption spectrometric measurements of vanadium in small volumes of serum. The wet-digested sample was extracted into an organic solvent, with N-benzoyl-N-(o-tolyl)hydroxylamine (BTA) as the chelating reagent. After evaporating the solvent, we dissolved the residue in acetic acid, and injected a 60-microL aliquot into a graphite furnace. In this way we could measure vanadium concentrations as low as 80 ng/L in 4 mL of serum. The within-run CV was 3.3% for serum, 7.7% for urine. Analytical recoveries of vanadium added to serum and urine were 90.3% and 90.8%, respectively. We measured vanadium concentrations in sera from 64 healthy persons (group 1), 15 nondialyzed uremic patients (group 2), and 11 hemodialyzed patients (group 3). The highest concentration of vanadium in group 1 was 240 ng/L; about 60% of the values for this group were less than 80 ng/L. In group 3, the vanadium concentrations were extremely high (15 +/- 14.2 micrograms/L, mean +/- SD), less so (but still above normal) in group 2 (1.58 +/- 3.16 micrograms/L).
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