tert-Butyldimethylsilyl as an alternative for Trimethylsilyl derivatisation during organic acid analysis : a comparison

MSc (Biochemistry), North-West University, Potchefstroom Campus

One of the prevailing fundamental analyses for diagnosing patients with presumable inherited metabolic diseases is organic acid analysis which has the ability to diagnose a number of various diseases within a single run. TMS (Trimethylsilyl) derivatisation remains the most widespread method of derivatisation during organic acid analysis. Ion fragment intensities of TMS derivatives remain small, however, causing quantification to be restricted by MS (mass spectra). An alternative derivatisation method is tBDMS (tert-butyldimethylsilyl) derivatisation which works with the same principle as TMS derivatives. The derivatising reagent tBDMS has advantages over agents that generate TMS derivatives in that tBDMS has higher reactivity and generates moisture stable derivatives with larger [M-57] ions that confer higher detection sensitivity by MS. In this study, TMS derivatives and tBDMS derivatives were compared to one-another using a number of representative organic acid standards. These representative organic acid standards were derivatised with both TMS and tBDMS respectively and run on a GC-MS (Gas Chromatography-Mass Spectrometry) to investigate whether there is a difference in their mass spectra, on-column stability, and precision. Furthermore, after dervatisation, second phase separation was performed with tBDMS dervatisation to investigate whether tBDMS derivatisation will diminish other non-organic acid compounds more efficiently. Literature suggests that tBDMS derivatives tend to be superior to TMS derivatives. This study concurs with the above-mentioned declaration as tBDMS proved to be the predominant derivative in organic acids analysis. Furthermore, tBDMS derivatisation with second-phase separation did to some extent reduce the background noise, but further investigation is recommended for future studies.

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