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As a result of microbiological activity it is possible to find dimethylselenium (DMSe) and dimethyldiselenium (DMDSe) in a wide type of environmental samples, such as soils, sediments, sewage sludges and plants where methylation can take place. Selenium determination by hydride-generation (HG) techniques requires its presence as Se(IV). Consequently, inorganic speciation by hydride generation techniques is done by first determining Se(IV) and then, after reduction of Se (VI) to Se(IV), the total selenium. Therefore, the concentration of Se (VI) is evaluated as the difference between total inorganic selenium and Se(IV). In the present work it could be demonstrated that DMSe and DMDSe are forming other volatile species by reaction with sodium borohydride, applying the same reduction condition as for inorganic selenium. These species are subsequently detected by several atomic techniques (atomic absorption AAS, atomic fluorescence AFS and inductively coupled plasma-mass spectrometry ICP-MS). The error that their presence can cause in determination of inorganic selenium has been evaluated. The magnitude of this error depends on the specific analytical detector used.The coupling of pervaporation-atomic fluorescence is proposed for the identification of these species and pervaporation-gas chromatography-atomic fluorescence for their individual quantification.

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This paper reports an improvement in the efficiency and selectivity of stibine generation and therefore an improvement in the analytical characteristics for antimony determination in environmental matrices by atomic fluorescence. The sensitized method is achieved by generating the stibine at 70 °C and using additional hydrogen flow to sustain the atomization flame, which makes it possible to reduce the acid and borohydride concentration and therefore to economize the process and reduce the inherent pollution risks due to the high concentrations used. Furthermore, a new phase separator in which temperature is controlled and dead time significantly reduced has been designed and incorporated in the hydride generation system. Selectivity is increased by working in an organized medium, Triton X-100 being the surfactant chosen as the most appropriate. Under the optimized conditions, a limit of detection of 0.3 mg l−1 of Sb was achieved, with a precision of 1.4% for 8 mg l−1, and the calibration graph was linear from 0.3 to 2.7×103 mg l−1. The sensitized method performed satisfactorily when evaluated by the determination of Sb in standard reference material (SRM 1648) of atmospheric urban particulate matter and by recovery studies in sea-water, tap water and in air samples collected on silica filters. The recovery in the enriched samples was 99±1% in all cases. The proposed method was successfully applied to the determination of Sb in samples of Bilbao urban air, being 13.2±0.3 ng m−3, the antimony concentration found.