A conventional absorption-cell system for vacuum UV atomic absorption spectrometry of mercury

Abstract

Atomic absorption spectrometry of mercury utilizing the Hg I 184.9 nm atomic line which is in the vacuum UV region has been investigated, and compared with that utilizing the atomic line at 253.7 nm. The atomic line at 184.9 nm is a resonance line, and has a larger oscillator strength (about 45 times) than that of the atomic line at 253.7 nm. Therefore, it can be expected that better sensitivity is obtained by utilizing the atomic line at 184.9 nm than at 253.7 nm. In order to realize the measurement of mercury atomic absorption at 184.9 nm, a conventional absorption-cell system was constructed. The cell is fixed inside a large Pyrex glass tube which includes an electrode-less discharge lamp of mercury, two quartz lenses and nitrogen gas inlets. The absorption-cell system was positioned in front of the entrance slit of a monochromator. The monochromator was purged with argon gas. A cold vapor generation method using a tin(II) chloride (3%) solution was used for the atomization of mercury from the sample solution. By using the conventional system mentioned above, the sensitivity (1% absorption) of mercury atomic absorption at 184.9 nm was 0.23 ng (or 0.23 ng/ml), while that at 253.7 nm was 1.2 ng (or 1.2 ng/ml). The relative standard deviation for 8 measurements at 184.9 nm was about 4%, when a 10 ng/ml Hg solution was used.