An automated submicrogram determination of selenium in vegetation by quartz-tube furnace atomic-absorption spectrophotometry

An automated method for the determination of submicrogram amounts of selenium in vegetation is described. A weighed sample of vegetation is digested with a 4:1 nitric-perchloric acid mixture, and made up to a known volume. The digested sample is placed in a Technicon sampler and reacted with sodium borohydride solution. The selenium converted into the gaseous hydride is swept by an argon stream into a gas-liquid separator. The mixed gas stream is passed through a heated quartz cell, positioned in the light-path of an atomic-absorption spectrophotometer. The absorption by the atomized selenium is recorded. The method is capable of analysing 50 samples a day by the use of a calibration curve or 25 a day by the standard addition technique. A relative standard deviation of better than 10% and a detection limit of 0.025 μg g were obtained.