Submitted to: Analytical Chemist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 16, 1996
Publication Date: N/A
Interpretive Summary: Selenium is an essential mineral nutrient that is present in only trace quantities in foods and tissues. Many new techniques for measuring selenium have been reported, but they have usually only been tested on one or two types of sample. Research in selenium nutrition requires measurement of widely different selenium concentrations in many types of biological samples (blood, hair, urine, muscle, etc.) and in a variety of foodstuffs. To be really useful, a method for selenium analysis needs to work equally well in any type of sample and must be sensitive enough to measure the very lowest levels encountered. We modified an existing method to increase the sensitivity 26 times. We showed that the new method /is accurate in any typr of biological sample and is a "gold standard" for selenium analysis. We characterized the performance of this new method and showed that it was unsurpassed by any other method available. Laboratories susing this new method can do at least twice as many selenium assays per da because of bigger batch sizes and because samples don't need to be re-tested because they were too big or too small. With this method, ples researchers will be able to make selenium measurements on much smaller h samples and to measure much lower selenium concentrations in fluids. Using this method, the quality of selenium analytical data will be improved because of the complete lack of interferences from other substances.
Technical Abstract: An improved method for the high performance liquid chromatographic determination of selenium in biological materials using the fluorogenic reagent 2,3- diaminonaphthalene has been developed. The mass detection limit was 48 pg selenium (3 sigma) and the concentration detection limits were 48 parts-per-trillion in biological fluids and 120 to 480 parts-per-tillion in dried biological materials. The linear dynamic range of the method extended up to approximately 800 ng. Relative standard deviations of 9.4% to 2.7% were observed in repeated analyses of standards in the range of 0.5 ng to 500 ng. The proposed method was validated with respect to 23 biological reference materials spanning an 1800-fold range of selenium concentrations and was found to be free of significant constant or proportional biases despite greatly different matrix compositions. This method offers an unsurpassed combination of sensitivity, accuracy, linear dynamic range, and freedom from matrix interferences and may be considered a reference method for the reliable determination of selenium in biological materials.