Examination of separation efficiencies of mercury vapour for different gas–liquid separators in flow injection cold vapour atomic absorption spectrometry with amalgam preconcentration

A comparison has been made of the separation efficiency of three designs of gas–liquid separator when used in a flow injection (Fl) manifold for the determination of Hg by cold vapour atomic absorption spectrometry. The manifold used with each device was separately optimized for maximum sensitivity. This involved studies of the effects of reagent flow rates, argon purge gas flow rate, injection time and post-injection purge time. A significant difference, with respect to both peak height and integrated signal sensitivity (by a factor of approximately 3) between the performance of a miniature design and that of two larger volume designs was obtained. No significant differences in precisions were observed. For the miniature design, the use of either tetrahydroborate or tin(II) reductant was investigated. No difference in peak height sensitivity was found, but the integrated signal sensitivity for the tetrahydroborate was 36% lower. The efficiency of separation was measured by comparison of the signal obtained from a known mass of Hg vapour, introduced via an amalgam preconcentration unit, and the signal obtained from a known mass of Hg in solution, introduced via the Fl manifold and amalgam preconcentration unit. The efficiencies were found to be 101 ± 4% and 103 ± 6% for peak height and integrated signal, respectively.