Effects of selenate supplemented fertilisation on the selenium level of cereals - identification and quantification of selenium compounds by HPLC-ICP-MS

Laboratory experiments were carried out to investigate whether the selenium content of different kinds of cereals grown on Austrian soil could be raised by the application of compound fertilisers containing selenium as selenate. An anion exchange chromatographic system coupled to an HP 4500 inductively coupled plasma mass spectrometer (ICP-MS) was used for the identification and quantification of selenium compounds in cereal samples. The HPLC-ICP-MS system was optimized for the separation of selenite, selenate, selenocystine, and selenomethionine using a Hamilton PRP-X100 column. Separation was obtained, with a 10 mM citrate buffer (pH 5), 2% methanol as mobile phase and a flow rate of 1.5 ml min(-1). Four baseline separated chromatographic peaks were obtained within 6 min. The retention behavior of a further five selenium [selenohomocystine (Sehcys), selenocystathionine (Secysta), selenoethionine (Seet), trimethylselenonium iodide (TmSe), and dimethyl(3-amino-3-carboxy-1-propyl)selenonium iodide (DmpSe)] compounds was investigated. Aqueous extraction and enzymatic hydrolysis of the biological materials were also compared with respect to the amount of selenium extracted. In the aqueous extracts only 3-9% of the total concentration of selenium was found. When the cereal samples were exposed to an enzymatic hydrolysis, recovery rates ranging from 80 to 95% were obtained. A major part of the selenate, which had been taken up by the cereals was converted to selenomethionine. (C) 2001 Elsevier Science Ltd. All rights reserved.