- Borohydride-coupled HPLC-FPD instrumentation and its use in the determination off dimethylsulffonium compounds
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Novel HPLC instrumentation has been developed which employs an in-line sodium tetrahydroborate (borohydride) reaction step to generate volatile sulfur species from a variety of sulfonium compounds. Transfer of the resulting volatile sulfur-containing products into the gas phase permits them to be monitored using sulfur-specific flame photometric detection. The system has been evaluated for the determination of a collection of dimethylsulfonium compounds, comprising (dimethylsulfonio)propionate, S-methylmethionine (SMM), (dimethylsulfonio)-2-methylpropionate, dimethylsulfocholine, (dimethylsulfonio)-acetate, (dimethylsulfonio)butanoate, and (dimethylsulfonio)pentanoate. Following their separation by either cation- or anion-exchange HPLC, these compounds react in-line with the tetrahydroborate, generating dimethyl sulfide, which is then swept into a flame photometric detector. The development of chromatographic conditions for the resolution of the seven sulfonium compounds is described. In an example application of the instrumentation, the levels of SMM in parsley and cabbage were found to be 16 and 74 mmol kg-1, respectively, on a fresh weight basis.
- Howard,Russell
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p. 2882 - 2887
(2007/10/03)
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- One-electron Reduction of Sulphonium Salts in Aqueous Solution: a Pulse Radiolysis Study
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Absolute rate constants have been measured for the reduction of 1-alkylthiolanium (1a-c), 1-alkylthianium (2a-e), 1-(n-carboxyalkyl)thiolanium (3a,b) and 1-(n-carboxyalkyl)thianium (4a,b) salts, and ω-dimethylsulphonioalkanoic acids (5a,b), including biologically active S-methylmethionine (6) and dimethyl-β-propiothetin (5b), by hydrated electrons in aqueous solutions using the pulse radiolysis method.This reaction was found to occur very rapidly (k in the range 109-1010 dm3mol-1s-1), the individual rate constants being dependent on the electron inductive power of the substituents on the positive sulphur centre.The sulphuranyl radical R3S., a possible reaction intermediate, could not be detected within the 0.1 μs time resolution of the applied technique.No reaction was observed between S-methylmethionine and CO2.- or Me2C.OH under experimental conditions.The one-electron reduction potential of this sulphonium salt has been estimated to be -aq. were characterized by using p-benzoquinone as a radical scavenger.It was found that ring opening is the predominant process rather than the cleavage of methyl or methyl radicals.
- Bonifacic, Marija,Anklam, Elke
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p. 243 - 248
(2007/10/02)
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