Simple fluorimetric determination of selenium in food and biological materials. A validation study.

A method for the determination of selenium in food and biological materials has been developed. The method involves sample decomposition in a closed system at 150 degrees C with nitric acid, perchloric acid treatment of the digest, reduction of selenium to the tetravalent state with hydrochloric acid followed by Se-2,3-diaminonaphthalene (DAN) complex formation and extraction in a single-step operation. Performance characteristics of the method (accuracy and repeatability) were extensively tested for eleven reference materials and ten practice samples covering both a wide variety of matrices and a wide range of selenium content. Almost all results for reference materials were within the 95% confidence range of the certified value or the best estimate thereof. The coefficient of variation for all samples ranged from 2.3 to 10.1%, average value 4.7%. Average recovery for spiking experiments-levels 0.060, 0.075 and 0.150 micrograms/g was 102%; range 84-114%.