Determination of selenium in biological samples by solvent extraction-graphite furnace atomic absorption spectrometry

Abstract

Selenium in biological samples was determined by graphite furnace atomic absorption spectrometry coupled with sodium diethyldithiocarbamate(DDTC)-solvent extraction technique. The authors also developed a new, small apparatus equipped with PTFE (Teflon) porous film as a separating medium for rapid and efficient extraction. The procedure is as follows : An aliquot of sample solution digested with nitric acid and hydrogen peroxide is taken into a test tube with a plug, and selenate in it is reduced to selenite with concentrated hydrochloric acid by heating on a boiling water-bath. Then, the pH of the sample solution is adjusted to 4.5 with ammonia water and citrate buffer solution, and EDTA solution and DDTC solution are added to it. Lastly, organic solvent such as carbon tetrachloride or cyclohexane is added, and after shaking for 2 min the organic phase is separated by the apparatus. The extracted solution is introduced into the graphite furnace. The absorbance at the line of 196.0 nm is recorded. The calibration curve was linear over the range 0 to 40 ng/ml in aqueous standard solution. The analyte concentrations corresponding to 1% absorption and S/N=2 were 0.9 ng/ml and 4.0 ng/ml, respectively. The coefficient of variation (10 replicate extractions) was about 9%. Such co-extractable ions as arsenic(III), copper(II) and tellurium(IV) caused negative interferences in the mixture of standard solutions. For the test of accuracy, Bovine Liver (NBS-SRM, 1577) and Oyster Powder (IAEA, Monaco, MA-M-1) were used, and good agreement with the NBS certificate value and with the average of the values from 14 laboratories mainly by neutron activation analysis was obtained. This method was applied to the shark muscle, and the content of selenium was found to be 0.28μg/g (wet weight). © 1977, The Japan Society for Analytical Chemistry. All rights reserved.