Determination of selenium species in infant formulas and dietetic supplements using liquid chromatography-hydride generation atomic fluorescence spectrometry

The combination of liquid chromatography with hydride generation atomic fluorescence spectrometry was used as a technique for the speciation of selenite, selenate, selenocystine and selenomethionine. Two chromatographic techniques were used by connecting reversed-phase C18 and ion-exchange columns in series, the mobile phase being a gradient from water to phosphate buffer. Se-compounds were extracted from the samples by a sequential technique which discriminated between water soluble and non-soluble selenium fractions. When the method was applied to the speciation of selenium in fortified foods, as infant formulas and dietetic supplements, selenite was the only species detected in the former while both selenite and selenoamino acids were detected in the latter. The reliability of the procedure was checked by analyzing the total selenium content of the samples by atomic fluorescence spectrometry and with a certified reference material, whole milk powder (CRM 8435). The method can be used for routine quality control applications.