UV-photochemical vapor generation of selenium for atomic absorption spectrometry: Optimization and Se-75 radiotracer efficiency study
Abstrakt
Volatile selenium compounds were generated UV-photochemically in the continuous flow mode using four UV-photoreactors differing in the material of the reaction coil; Teflon tubing and quartz tubes with various inner diameters and wall thicknesses were tested. Atomic absorption spectrometry with an externally heated quartz furnace atomizer was employed as the detector.
The relevant experimental generation parameters were optimized and the basic analytical characteristics were determined. Using formic acid as the photochemical agent, limits of detection achieved for selenium were in the range 46-102 ng L-1 in dependence on the type of UV-photoreactor employed.
When nitric acid was also added to the photochemical agent, the limits of detection were reduced to 27-44 ng L-1. The repeatability did not exceed 2.4% (5 mu g L-1 Se(IV), n = 10).
Experiments with Se-75 radiotracer have been performed for the first time to quantify the efficiency of UV-photochemical vapor generation (UV-PVG) of selenium. The highest efficiency of 67 +/- 1% was obtained for a UV-photoreactor containing a quartz reaction coil (2.0 mm i.d., 4.0 mm o.d.).
The generation efficiency of 61 1% was obtained fora Teflon reaction coil (1.0 mm i.d., 1.4 mm o.d.). Mapping of the radiotracer distribution in the individual parts of the apparatus did not reveal substantial transport losses of the analyte in the UV-PVG system.