Pretreatment procedure for selenium speciation in shellfish using high‐performance liquid chromatography–microwave‐assisted digestion–hydride generation‐atomic fluorescence spectrometry

A pretreatment procedure based on an enzymatic hydrolysis extraction followed by a two‐step clean‐up has been performed for selenium speciation in shellfish samples. Bivalve samples were extracted with protease XIV, lipase VII and protease VIII. By using a protease VIII–lipase VII mixture, quantitative recoveries were obtained for all the selenium species, except for selenocystine (59%). Owing to the complexity of the matrix, clean‐up procedures were required to remove interferents that affected the chromatographic separation. The extracts were first partitioned in dichloromethane and then passed through a column with aminopropylsilane. Speciation of selenocystine, selenomethionine, selenoethionine, selenite and selenate was obtained using a high‐performance liquid chromatography–microwave‐assisted digestion–hydride generation‐atomic fluorescence spectrometry coupling. The chromatographic system consisted of an anion exchange and a reversed‐phase column, both connected through a six‐port switching valve. On‐line microwave‐assisted digestion and hydride generation steps were performed prior to atomic fluorescence detection. The method was applied to clam and prawn samples collected from the southwest coast of Spain. Copyright­© 2002 John Wiley & Sons, Ltd.     

硒半胱氨酸和硒胱氨酸的间接气相色谱测定──溴化氰－气相色谱法

将硒半胱氨酸（ＳｅＣｙｓＨ）甲基化，对硒胱氨酸（ＳｅＣｙｓ）需还原后再甲基化。它们生成的甲基硒半胱氨酸（ＣＨ＿３ＳｅＣｙｓＨ）能与溴化氰（ＣＮＢｒ）发生专一性反应，定量生成的硒氰酸甲酯（ＣＨ＿３ＳｅＮ）可用气相色谱法（ＧＣ）测定。此法简称ＣＮＢｒ－ＧＣ法，检测限４×１０￣（－８）克ＳｅＣｙｓ，准确度８９．５％，相对标准差１２．１％，非含硒氨基酸不干扰。此法适于样品中微量硒氨基酸（硒蛋氨酸ＳｅＭｅｔ，ＳｅＣｙｓＨ和Ｓｅｃｙｓ）的测定。     

Novel approaches for selenium speciation in foodstuffs and biological specimens: A review

Selenium is an essential element for human health. It has been recognized as an antioxidant and chemopreventive agent in cancer. Selenium is known to develop its biological activity via selenocysteine residue in the catalytically active centre of selenoproteins. The main source of selenium in human beings is the diet. However, in several regions of the world the content of selenium in diet has been estimated insufficient for a correct expression of the proteins. The beneficial effects of selenium on human health are strongly dependent on its chemical form and concentration. This review critically evaluated the state-of-the art of selenium speciation in biological matrices mainly focused in nutritional and food products. Besides the number of publications related to selenium speciation, isolation and accurate characterization and quantification of selenium species is still a challenge. Hyphenated techniques based on coupling chromatography separation with inductively coupled plasma spectrometry (ICP-MS) and its combination with molecular mass spectrometry (ESI-MS, ESI-MS-MS and MALDI-TOF) and isotopic dilution allow identification, quantification and structural characterization of selenium species. Particular attention is paid in the development of Se-enriched food and nutritional products and how the application of the techniques mentioned above is mandatory to get reliable results on selenium metabolisms in these particular matrices.