Electron impact, electron capture negative ionization and positive chemical ionization mass spectra of organophosphorus flame retardants and plasticizers

Abstract

Phosphate esters are important commercial products that have been used both as flame retardants and as plasticizers. To analyze these compounds by gas chromatographic mass spectrometry, it is important to understand the mass spectra of these compounds using various ionization modes. This paper is a systematic overview of the electron impact (EI), electron capture negative ionization (ECNI) and positive chemical ionization (PCI) mass spectra of 13 organophosphate esters. These data are useful for developing and optimizing analytical measurements. The EI spectra of these 13 compounds are dominated by ions such as H4 PO4 (+) , (M - Cl)(+) , (M - CH2 Cl)(+) or (M)(+) depending on specific chemical structures. The ECNI spectra are generally dominated by (M - R)(-) . The PCI spectra are mainly dominated by the protonated molecular ion (M + H)(+) . The branching of the alkyl substituents, the halogenation of the substituents and, for aromatic phosphate esters, ortho alkylation of the ring are all significant factors controlling the details of the fragmentation processes. EI provides the best sensitivity for the quantitative measurement of these compounds, but PCI and ECNI both have considerable qualitative selectivity.

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

“…Nine OPEs representative from groups A, B, and C were selected for both PCI and NCI. Observations were in accordance with previous work from Ma and Hites for both modes as well as with Quintana et al for PCI. Additionally, the two brominated OPEs from group D were subjected to NCI.…”

“…Regarding the three chlorinated phosphates (group C) and in accordance with the previous work, the presence of electronegative atoms appeared to change the profile of the mass spectra. The base peaks were [M–Cl] + for TCEP, [M–2R–CH 2 Cl + 2H] + for TCPP, or [C 3 H 4 Cl] + for TCDIPP.…”

“…Regarding the two brominated phosphates (group D) and in accordance with the previous work available for TDBPP only, [M] +● was not detected. These compounds are considered as special members of OPEs due to their high molecular masses (697.6 and 1017.3 g mol ‐1 ) along with log partitioning coefficient values ( k ow ) of 3.71 and 9.03, respectively.…”

“…Regarding the seven alkyl phosphates (group A) and in accordance with previous work, these undergo three successive McLafferty rearrangements, the base peak being mostly represented by the protonated phosphoric acid [H 4 PO 4 ] + at m / z 99. Exceptions were observed with TBEP, exhibiting a base peak at m/z 85 for [C 5 H 9 O] + , due to the presence of an ether group creating a β cleavage and with TEHP for which the first ion appeared at m/z 113 for [C 8 H 17 ] + from the side chain.…”

“…Regarding the seven aryl phosphates (group B) and in accordance with the previous work on four compounds, the base peak was not always the same, in some case quasi‐molecular ion [M] +● (TPP, m‐TCP, and p‐TCP), [M–R] + (EHDP), [M–2R] + (DBPhP), the phenol radical cation [C 6 H 5 OH] +● (DPhBP), or [(C 6 H 4 ) 2 CH] + (o‐TCP).…”