Flow injection system with flame photometric detection for the measurementof the dimethylsulphide precursor beta-dimethylsulphoniopropionate

A flow injection analysis system has been developed for the routine measure ment of beta-dimethylsulphoniopropionate (DMSP), an algal osmoregulator and cryoprotectant which plays a crucial role in the cycling of sulphur in the environment. The analysis system combines an in-line base hydrolysis step with transport of generated dimethylsulphide to the gas phase where it is m easured by sulphur-specific flame photometric detection. This combination o f chemical, physical and spectroscopic steps results in a system which is h ighly selective to DMSP. The system was evaluated for its ability to distin guish DMSP from other dimethylsulphonium compounds. S-methyl methionine was not detected by the system. Only with very closely related compounds, such as the 2-methyl derivative of DMSP, were false responses generated. With a detection limit (twice background) of 1x10(-7) mol dm(-3) and a working ra nge 1x10(-3)-1x10(-6) mol dm(-3), the system is ideally suited to the routi ne measurement of DMSP in marine macroalgae and phytoplankton. (C) 1998 Els evier Science B.V. All rights reserved.