A comparison of electrospray ionization, atmospheric pressure chemical ionization, and atmospheric pressure photoionization for the liquid chromatography/tandem mass spectrometric analysis of bisphenols. Application to bisphenols in thermal paper receipts and U.S. currency notes.

Abstract

Human health concerns have arisen for common bisphenols (BPA and BPS) as well as new structural analogs. While native sulfone bisphenols and sulfone-derivatized bisphenols are amenable to electrospray ionization (ESI), alternative ionization methods such as atmospheric pressure chemical ionization (APCI) and APPI were investigated to analyze non-derivatized, non-sulfone-containing bisphenols. Ionization of bisphenols using negative ion APPI was compared to negative ion ESI and negative ion APCI for their relative abilities to produce [M-H]- precursor ions for subsequent collision-induced dissociation (CID) in a triple quadrupole mass analyzer. Multiple reaction monitoring (MRM) transitions were optimized using the most sensitive ion transitions and coupled with high-performance liquid chromatographic (HPLC) separation to detect and quantify BPA, BPB, BPF, BPZ, BPAP, BPS, and BPSIP. APPI provides a more universal sensitivity over ESI toward the classes of bisphenols studied with detection limits of 20-50 pg on-column. The LC/APPI-MS/MS method was used to examine the levels of these seven bisphenols in thermal paper receipts and in U.S. paper currency. In both receipts and currency, BPA and BPS were the dominant bisphenols found in the paper. The measurement of BPA and bisphenol analogs in thermal paper receipts and transfer of bisphenols from receipts to currency notes is of increasing importance to assess human dermal exposure routes to this class of compounds. Equivalent sensitivity between sulfone- and non-sulfone-containing bisphenols is achievable through the use of alternate ionization sources such as APCI and APPI that circumvents tedious and time-consuming derivatization procedures to render analytical sensitivity by ESI.