DETERMINATION OF TRIMETHYLSELENONIUM ION AND ITS BEHAVIOR IN SOIL

Trimethylselenonium ion (TMSe+) is a major urinary metabolite of selenium, and a small amount of TMSe+ contained in animal urine has been spilled onto soils. Then, a method for the determination of TMSe+ in soils was developed and the method was applied to the study of the behavior of TMSe in soils. (1) TMSe+ in soils was quantitatively recovered by repeated extractions with 0.2 mol L-1 hydrochloric acid. To separate the TMSe+ in the extract from other selenium compounds, such as inorganic selenium and seleno-amino acids, cation-exchange chromatography was carried out. After seleno-amino acids adsorbed together with TMSe+ onto the cation-exchange column were eluted with 0.5 mol L-1 ammonium hydroxide solution, the TMSe+ remaining on the column could be recovered by elution with 1 mol L-1 sodium hydroxide solution. The amount of TMSe+ was determined from the amount of the selenium contained in the sodium hydroxide solution. (2) TMSe+ was estimated to be a minor component in the forms of organically-bound selenium in air-dried soils, because only a small amount of TMSe+ was detected in the soils. (3) TMSe+ added to soils was rapidly decomposed by soil microbes and the major part of the TMSe+ was directly transformed to gaseous selenium compounds, such as dimethylselenide, probably due to demethylation. The existence of TMSe+ as one of the stable organically-bound selenium compounds in soil was not confirmed.