Derivatization and Gas Chromatography– Low-resolution Mass Spectrometry of Bisphenol A

Gas chromatography–mass spectrometry (GC–MS) has been investigated for identification of bisphenol A (BPA) at ppb levels in biological samples. Initially a limit of detection (LOD) of 600 ppb BPA was established by direct selected-ion monitoring (SIM) GC–MS. Next, standard solutions of BPA and extracts of powdered milk were derivatized with two different reagents – N,O-bis-(trimethylsilyl)trifluoroacetamide (BSTFA) containing 1% trimethylchlorosilane (TMCS), and bromoacetonitrile (BAN). Compounds were separated on a 30 m × 0.25 mm i.d. fused-silica capillary column coated with a 0.25 μm film of 5% diphenyl 95% dimethylpolysiloxane. LOD of BPA and the derivatization products were calculated from the signal-to-noise ratio. Detection limits for BPA were very dependent on the derivatization agent used – 57 ppb for BSTFA + 1% TMCS and 367 ppb for BAN. The procedure was used to confirm the presence of BPA in extracts of powdered milk. Identification of BPA was based on comparison of retention times and peak-intensity ratios of selected ions from mass spectra of BPA derivatization products obtained by GC–MS of standard solutions and milk extracts.