DETERMINATION OF SELENIUM BY GAS-CHROMATOGRAPHY AND COMPARISON WITH GRAPHITE-FURNACE ATOMIC-ABSORPTION SPECTROMETRY

Selenium(IV) reacts with 3-bromo-5-trifluoromethyl-1,2-diaminobenzene to form 4-bromo-6-trifluoromethylpiazselenol, which is detected by means of a gas Chromatograph equipped with an electron-capture detector. A rapid and sensitive method for the determination of total selenium in plant samples thus developed, is described. A comparison of gas - liquid chromatography with electron-capture detection and graphite furnace atomic absorption spectrometry for the determination of selenium in plant samples, showed no difference between the two methods at the 99% level of confidence. The synthesis and characterisation of substituted 1,2-diaminobenzenes used as reagents for selenium determination is also reported. These reagents, namely 3-chloro-5-trifluoromethyl-1,2- diaminobenzene and 4-chloro-5-fluoro-1,2-diaminobenzene, are very sensitive and have short retention times. Their applicability to the determination of total selenium in National Institute of Standards and Technology Standard Reference Materials was therefore evaluated. The detection limit was 2.2 ng ml-1 and the minimum detectable amount was about 5 pg of selenium. The detection limits were evaluated using statistical methods.