Combined target and post-run target strategy for a comprehensive analysis of pesticides in ambient air using liquid chromatography-Orbitrap high resolution mass spectrometry

• A comprehensive strategy for analysis of airborne pesticides have been developed.
• The methodology developed combine target and post-target accurate mass spectrometry.
• The LOQ was 6.5 pg m−3 for the majority of target pesticides.
• The fragmentation was optimised for target pesticides.
• A design of experiments was used for mass analyzer optimisation.

A comprehensive strategy for the analysis of current airborne pesticides has been developed using liquid chromatography coupled to high resolution mass spectrometry. The methodology includes both quantitative target analysis and post-run target screening analysis. The quantitative method was validated after a previous statistical optimisation of the main factors governing the ion source ionization and a study of the single-stage Orbitrap fragmentation through the HCD cell. The quantitative method presented recoveries ranging from 73 to 116%, with precision (RSD) lower than 20%, for the 35 substances in the scope of the target method. The full-scan accurate mass data were acquired with a resolving power of 50000 FWHM (scan speed, 2 Hz), and alternating two acquisition events, ESI+ without fragmentation and ESI+ with fragmentation. The method-LOQ was 6.5 pg m−3 for most of the target pesticides. For post-target screening a customized theoretical database, that included pesticides, metabolites and other substances such as emerging flame retardants was built up. For identification, accurate exact mass with less than 5 ppm, and some diagnostic ions including isotopes and/or fragments were used.The strategy was applied to ten samples collected in a rural area of Valencia (Spain). Four pesticides, namely carbendazim, metalaxyl, myclobutanil and terbuthylazine, were detected in concentrations from 16 pg m−3 to 174 pg m−3. Some pesticides and metabolites (endothal, fenfuram, terbuthylazine-2-OH), in addition to two flame retardants were tentatively identified in the post-run target screening analysis.