Abstract: | Speciation analysis of four selenium species (selenite, selenate, selenocystine, and selenomethionine) has been performed
by on-line coupling of liquid chromatography (LC), UV decomposition, hydride generation (HG), and atomic-fluorescence spectrometry
(AFS). Because only selenite (SeIV) can generate hydrides, on-line conversion of organic and inorganic selenium species is discussed. Preliminary study showed
that the use of only UV light was not sufficient to reduce selenate, because no absorption is observed for this compound at
the main wavelength of the low-pressure mercury lamp (253.7 nm). Thus, new conditions based on addition of a reducing reagent
(I−) were developed. Mechanisms of action are proposed to explain selenium species conversions. Because of their compatibility
with on-line treatment, phosphate buffers were used for chromatographic separation on an anion exchange column (Hamilton PRP-X100).
Detection limits (19–60 pg Se) and repeatability of the technique were close to those obtained by conventional quadrupole
ICPMS. Applications to real samples such as water and oysters are presented and emphasize the robustness of the system. |