Flow injection system with flame photometric detection for the measurement of the dimethylsulphide precursor β-dimethylsulphoniopropionate Original Research Article

A flow injection analysis system has been developed for the routine measurement of β-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 measured by sulphur-specific flame photometric detection. This combination of chemical, physical and spectroscopic steps results in a system which is highly selective to DMSP. The system was evaluated for its ability to distinguish 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 1×10−7 mol dm−3 and a working range 1×10−3–1×10−6 mol dm−3, the system is ideally suited to the routine measurement of DMSP in marine macroalgae and phytoplankton.