APCI as an innovative ionization mode compared with EI and CI for the analysis of a large range of organophosphate esters using GC-MS/MS.

Organophosphate esters (OPEs) are chemical compounds incorporated into materials as flame-proof and/or plasticizing agents. In this work, 13 non-halogenated and 5 halogenated OPEs were studied. Their mass spectra were interpreted and compared in terms of fragmentation patterns and dominant ions via various ionization techniques [electron ionization (EI) and chemical ionization (CI) under vacuum and corona discharge atmospheric pressure chemical ionization (APCI)] on gas chromatography coupled to mass spectrometry (GC-MS). The novelty of this paper relies on the investigation of APCI technique for the analysis of OPEs via favored protonation mechanism, where the mass spectra were mostly dominated by the quasi-molecular ion [M + H]+ . The EI mass spectra were dominated by ions such as [H4 PO4 ]+ , [M-R]+ , [M-Cl]+ , and [M-Br]+ , and for some non-halogenated aryl OPEs, [M]+● was also observed. The CI mass spectra in positive mode were dominated by [M + H]+ and sometimes by [M-R]+ , while in negative mode, [M-R]- and more particularly [X]- and [X2 ]-● were mainly observed for the halogenated OPEs. Both EI and APCI techniques showed promising results for further development of instrumental method operating in selective reaction monitoring mode. Instrumental detection limits by using APCI mode were 2.5 to 25 times lower than using EI mode for the non-brominated OPEs, while they were determined at 50-100 times lower by the APCI mode than by the EI mode, for the two brominated OPEs. The method was applied to fish samples, and monitored transitions by using APCI mode showed higher specificity but lower stability compared with EI mode. The sensitivity in terms of signal-to-noise ratio varying from one compound to another.