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Titel (primär) A false positive finding in liquid chromatography/triple quadrupole mass spectrometry analysis by a non-isobaric matrix component: the case of benzotriazole in urine for human biomonitoring
Autor Schlittenbauer, L.; Seiwert, B.; Reemtsma, T.;
Journal / Serie Rapid Communications in Mass Spectrometry
Erscheinungsjahr 2016
Department ANA;
Band/Volume 30
Heft 13
Sprache englisch;
POF III (gesamt) T42;
UFZ Querschnittsthemen RU3;
Abstract

Rationale

Multi-residual methods employing liquid chromatography coupled to triple quadrupole mass spectrometry (LC/MS/MS) with selected reaction monitoring (SRM) are attractive also for human biomonitoring (HBM). A new process is determined that can lead to false positive findings by matrix components that are not isobaric to the analyte of interest.

Methods

Benzotriazole (1H-BT) was false positively detected in 87 human urine samples analyzed by ultra-high-performance-(UHP)-LC/MS/MS. The quantifier/qualifier ratio (Q/q ratio) did not match. This was further confirmed by negative results with an optimized gradient. Investigations were performed by UHPLC/high-resolution (HR)MS and model compounds to reveal the identity of the disturbing matrix compound and the way that it interfered with 1H-BT detection.

Results

A formula of C7H5NO (m/z 120.0444) was found at the retention time of 1H-BT (m/z 120.0556) belonging to an in-source product ion of a heavier co-eluting compound. Product ion spectra and Q/q ratios of model compounds indicated a benzene sub-structure with a carbonyl and amine functional group in the ortho- or para-position. Finally, folic acid was confirmed as the disturbing urine component, exhibiting an in-source fragment with the nominal mass of 1H-BT and the same product ions as used in the SRM mode for UHPLC/MS/MS monitoring.

Conclusions

Interferences in SRM detection need not be due to co-eluting isobaric matrix compounds, but can originate from in-source fragmentation of heavier ions. Rigid quality control measures are recommended for LC/MS/MS analysis, especially for small molecules in complex sample matrices to overcome the selectivity limits of SRM.

ID 17727
dauerhafte UFZ-Verlinkung https://www.ufz.de/index.php?en=20939&ufzPublicationIdentifier=17727
Schlittenbauer, L., Seiwert, B., Reemtsma, T. (2016):
A false positive finding in liquid chromatography/triple quadrupole mass spectrometry analysis by a non-isobaric matrix component: the case of benzotriazole in urine for human biomonitoring
Rapid Commun. Mass Spectrom. 30 (13), 1560 - 1566