DETERMINATION OF SELENITE, SELENATE AND SELENOMETHIONINE BY ION CHROMATOGRAPHY, MICROWAVE DIGESTION AND HGAAS

An on-line system for the simultaneous determination of Se(IV), Se(VI) and selenomethionine (Se-Met) in aqueous samples was developed, consi sting of separation by ion chromatography, microwave digestion and det ection by hydride generation atomic absorption spectrometry. 8.3 mmol/ l Na2HPO4 (pH 9.2) was used as mobile phase for the ion siloxane phase s (C18, SE 52, SE 54, OV 1701) normally used for the separation of the se compounds. Varying the cyclodextrin- and sugar-derivative content i n the investigated procentual range allows a simple way of tuning a ca pillary for a specific application. As shown in Figs. 1 and 2, a 10% c ontent of permethylated beta-cyclodextrin in OV 1701 increases particu larly the retention of the 3.3'4,4'-substituted PCB congeners 77, 105, 126 and 128. Similar results have been achieved by using 16 m of the commercially available Cyclodex B from J & W. The changed selectivity by adding 5% dodecyl-beta-D-maltoside to SE 52 is demonstrated in Figs . 3 and 4 (the other PCB-compounds of the standard mixture show no sig nificant difference).