Detection of more than 50 substituted phenols as their t-butyldimethylsilyl derivatives using gas chromatography-mass spectrometry

Abstract

More than 50 substituted phenols have been derivatized successfully with N-( t-butyldimethylsilyl)- N-methyltrifluoroacetamide (MTBSTFA) by forming their t-butyldimethylsilyl derivatives. The study included 21 chlorinated phenols, 13 nitrophenols, 3 aminophenols, 4 alkylphenols, o-phenylphenol, the non-substituted phenol and some other substituted phenols including six phenolic pesticides. The determination and detection of the derivatives were performed by capillary gas chromatography-mass spectrometry. The mass spectra of all phenol derivatives are dominated by very characteristic ions [M−57] + resulting from the cleavage of the t-butyl moiety during electron ionization in the mass spectrometer. Scanning the major fragment ion [M−57] + and two other prominent ions for each compound, detection limits down to 5 pg could be achieved using electron ionization in the selected ion monitoring (SIM) mode. The gas Chromatographic separation of all phenol derivatives was achieved using two capillary columns of different polarities: a 25 m HP-5 capillary column with 0.20 mm i.d. and 0.33 μm film thickness and a 30 m Rtx-200 capillary column with 0.32 mm i.d. and 0.25 μm film thickness. Thus, the distinction of all isomeric phenols exhibiting similar mass spectra was possible. Applying solid-phase extraction (SPE) with polymeric adsorbents, phenols can be detected at the ng l −1 level, even in environmental samples with high matrix contents.