Tris(2,4,6-trimethoxyphenyl)phosphonium propylamine bromide (TMPP) has been used for the derivatisation of maleic, fumaric, sorbic and salicylic acids to facilitate determination using liquid chromatography/electrospray ionisation tandem mass spectrometry (LC/ESI-MS/MS) in positive ion mode. Detection limits, achieved using multiple reaction monitoring mode, were 2, 4, 0.4 and 540 fmol (5 muL injection) for derivatised fumaric, sorbic, maleic and salicylic acids, respectively. In comparison, detection limits achieved in negative ion mode for the underivatised acids were 24, 51, 2, and 117 fmol, respectively. The method was successfully used for the determination of sorbic acid in a sample of Panadol. The derivatisation of salicylic acid was not as successful, probably due to poor reaction efficiency.

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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 31 P 1 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 ml injection.