Effect of Absorption-Tube Shape on Hydride Generation for Trace Selenium Determination in Flame-in-Tube Atomic Absorption Spectrometry

Abstract

Effect of absorption-tube shape in flame-in-tube atomic absorption spectrometry of selenium was investigated. About ten quartz tubes with various hydrogen and air introduction systems were designed and compared for selenium sensitivity. From the examination of the tube size ranging 6 to 50cm in length and 1 to 7mm in id., the following conclusion was found. At relatively large i.d. (-7mm), no sensitivity increase is observed by tube elongation. However, at i.d. of 1mm, elongation of the tube length from 30 to 50cm increases the sensitivity in proportion to the tube length. At i.d.′s between 1 and 7mm, sensitivity increase is certainly observed for tube elongation, but the increase is not so much as expected if it would be in proportion to the tube length. This would be due to the difference of the atomic population in a tube in this medium i.d. range. The best sensitivity and detection limit obtained with a tube of 50cm long and 1mm id. were 0.021ng (1% absorption) and 0.047ng, respectively. The method was successfully applied to the analyses of NBS SRM′s.