Analysis of silyl derivatives of methylphosphonic acid esters by gas chromatography-mass spectrometry with atmospheric pressure photoionization

Abstract

Using trimethylsilyl (TMS) and tert-butyldimethylsilyl (TBDMS) derivatives of methylphosphonic acid and methylphosphonic acid esters, a comparative study of two ionization methods, namely, atmospheric pressure photoionization (APPhI) and photochemical ionization (APCPhI), in gas chromatography/mass spectrometry has been performed. It has been shown that, in the case of APPhI, the mass spectra of TMS and TBDMS derivatives contained only peaks corresponding to [M + 73]+ and [M + 115]+ (or [M + Si(Me)3]+ and [M + Si(tBu)(Me)2]+ ions, respectively, where M is the molecular mass of a respective TMS or TBDMS derivative of methylphosphonic ester). APCPhI mass spectra recorded in the presence of acetone as a reagent substance consisted of only peaks of [M + H]+ and [M + MA + H]+ ions (MA is acetone molecule). The corresponding detection limits for silylated derivatives in APPhI and APCPhI were 30–125 pg and 1.1–23 pg, respectively (depending on the analyte).