Biosynthesis of sulfur-34 labelled yeast and its characterisation by multicollector-ICP-MS†
Yeast labelled with 34S (92.82% enriched) has been prepared by yeast growth on a 34S-enriched, specially prepared, culture medium in the absence of natural abundance sulfur. The final product has been characterised both with reference to isotope enrichment and total sulfur concentration by isotope dilution analysis and isotope pattern deconvolution using a MC-ICP-MS instrument. Additionally, two different sulfur spike solutions of 33S (99.70% enrichment) and 34S (99.37% enrichment) were characterised by MC-ICP-MS with reference to a natural abundance sulfur standard solution. Spectral interferences on the determination of the isotopic composition of all sulfur solutions were also evaluated using a double focusing, single collector ICP-MS instrument. The more serious interferences observed were the presence of 32SH+ and 33SH+, which could be important for the natural abundance sulfur (interference on 33S) and the 33S-enriched sulfur (interference on 34S), respectively. Fortunately, those interferences could be eliminated using the pseudo-high resolution mode of the multicollector instrument. The analytical procedure used was validated by the analysis of a blood serum reference material, which contained a certified concentration of sulfur, both using the 34S and the 33S spikes either separated or in combination using isotope pattern deconvolution. The results found were in agreement with the certified values.
- This article is part of the themed collection: 2007 European Winter Conference on Plasma Spectrochemistry, Taormina, Italy