Detection of phosphorus tagged carboxylic acids using HPLC-SF-ICP-MS

High performance liquid chromatography (HPLC) has been coupled with sector field inductively coupled plasma mass spectrometry (SF-ICP-MS) for the determination of maleic, sorbic and fumaric acids after derivatisation with the phosphorus containing reagent tris(2,4,6-trimethoxyphenyl)phosphonium propylamine (TMPP). This allowed 31P+ selective detection to be performed for these compounds, which are normally invisible to detection by ICP-MS at low concentrations. Optimal reagent conditions for the derivatisation of 0.1 mM maleic acid were: 1 mM TMPP; 10 mM 2-chloro-1-methylpyridinium iodide (CMPI); 11 mM triethylamine. The efficiency of the derivatisation reaction was estimated to be between 10–20% and detection limits, estimated as 3 times baseline noise, were 0.046 nmol for TMPP and 0.25 nmol for derivatised maleic acid, for a 5 μl injection.