The use of pseudo‐MRM for a sensitive and selective detection and quantification of polycyclic aromatic compounds by tandem mass spectrometry

Abstract

Rationale: Multiple Reaction Monitoring (MRM) is a sensitive and selective detection mode for target trace-level analysis. However, it requires the fragmentation of labile bonds which are not present in molecules such as Polycyclic Aromatic Hydrocarbons (PAHs) and their heterocyclic derivatives (PANHs, PASHs). Methods:We present the application of an alternative tandem mass spectrometry (MS/MS) mode called "pseudo-MRM" for the GCMS/MS analysis of Polycyclic Aromatic Compounds (PACs). This mode is based on the monitoring of transitions with no mass loss between the precursor and the product ion. Pseudo-MRM peak areas were compared with those of classic MRM on three different mass spectrometers: two triple quadrupoles and an ion trap.Results: For all non-polar PACs studied here (PAHs, PANHs and PASHs), the pseudo-MRM transition was always the most intense. The classic MRM transitions exhibited peak areas 2 to 5 times lower. On the contrary, for the functionalized PACs (oxygenated and nitrated PAHs), classic MRM was favored over pseudo-MRM. These observations were confirmed on two triple quadrupoles (QqQs), and the real-world applicability of pseudo-MRM on QqQs was validated by the successful analysis of Diesel PM. However, a comparison with an ion trap showed that pseudo-MRM was never favored on that instrument, which caused fragmentation of non-polar PACs in MS/MS. Conclusions:The results of this study show an important gain in sensitivity when using pseudo-MRM instead of MRM for non-polar PACs on QqQ instruments. The selectivity of MRM is preserved in pseudo-MRM by applying non-zero collision energies to which only these non-polar PACs are resistant, not the isobaric interferences. No interference issue was observed when analyzing Diesel PM, a complex matrix, with our pseudo-MRM method. Therefore, we advise for a broader use of this MS/MS mode for trace-level determination of non-polar PAHs.

Development of an Online Instrument for Continuous Gaseous PAH Quantification: Laboratory Evaluation and Comparison with The Offline Reference UHPLC-Fluorescence Method

“…When PAH speciation is considered, many studies were carried out on the measurement of PAH in the air [13,23,24,26,[32][33][34] or water [35,36], but the vast majority used offline and non-automatic methods.…”

“…The numerous sample processing steps are complicated procedures that can lead to significant errors in quantification. Gas chromatography (GC) methods coupled with detection using a mass spectrometer (MS) or alternatively other types of detectors are also frequently used and reported in the literature for the analysis of PAHs in the air [3,21,22,26]. All the GC-MS used are sedentary laboratory gas chromatographs, not able to work in online mode with continuous air sampling and analysis.…”

Removal of isobaric interference using pseudo‐multiple reaction monitoring and energy‐resolved mass spectrometry for the isotope dilution quantification of a tryptic peptide

“…Pseudo-MRM corresponds then to a 'no mass loss' transition between MS 1 and MS 2 . 2 It has shown good performances for the analysis of complex samples, due to the reduction of isobaric coelution inside the collision cell.…”

“…Pseudo-MRM corresponds then to a 'no mass loss' transition between MS 1 and MS 2 . 2 It has shown good performances for the analysis of complex samples, due to the reduction of isobaric coelution inside the collision cell. [2][3][4][5][6] However, in pseudo-MRM, there is no clear indication of the optimal collision voltage to be applied in order to confirm the complete removal of isobaric interferences by CID.…”

“…It is based on monitoring, at high collision energy, only the precursor ions instead of the fragment ions. Pseudo‐MRM corresponds then to a ‘no mass loss’ transition between MS 1 and MS 2 2 . It has shown good performances for the analysis of complex samples, due to the reduction of isobaric co‐elution inside the collision cell 2–6 .…”