Non-target and suspect characterisation of organic contaminants in ambient air – Part 1: Combining a novel sample clean-up method with comprehensive two-dimensional gas chromatography
Authors: Röhler Laura , Bohlin-Nizzetto Pernilla , Rostkowski Pawel , Kallenborn Roland , Schlabach Martin 
Published: February 2021

Abstract. Long-term monitoring of regulated organic chemicals, such
as legacy persistent organic pollutants (POPs) and polycyclic aromatic
hydrocarbons (PAHs), in ambient air provides valuable information about the
compounds' environmental fate as well as temporal and spatial trends. This
is the foundation to evaluate the effectiveness of national and
international regulations for priority pollutants. Extracts of high-volume
air samples, collected on glass fibre filters (GFF for particle phase) and
polyurethane foam plugs (PUF for gaseous phase), for targeted analyses of
legacy POPs are commonly cleaned by treatment with concentrated sulfuric
acid, resulting in extracts clean from most interfering compounds and
matrices that are suitable for multi-quantitative trace analysis. Such
standardised methods, however, severely restrict the number of analytes for
quantification and are not applicable when targeting new and emerging
compounds as some may be less stable under acid treatment. Recently developed
suspect and non-target screening analytical strategies (SUS and NTS,
respectively) are shown to be effective evaluation tools aimed at
identifying a high number of compounds of emerging concern. These
strategies, combining highly sophisticated analytical technology with
extensive data interpretation and statistics, are already widely accepted in
environmental sciences for investigations of various environmental matrices,
but their application to air samples is still very limited. In order to apply
SUS and NTS for the identification of organic contaminants in air samples,
an adapted and more wide-scope sample clean-up method is needed compared to
the traditional method, which uses concentrated sulfuric acid. Analysis
of raw air sample extracts without clean-up would generate extensive
contamination of the analytical system, especially with PUF matrix-based
compounds, and thus highly interfered mass spectra and detection limits
which are unacceptable high for trace analysis in air samples. In this study, a novel wide-scope sample clean-up method for high-volume air
samples has been developed and applied to real high-volume air samples,
which facilitates simultaneous target, suspect and non-target analyses. The
scope and efficiency of the method were quantitatively evaluated with organic
compounds covering a wide range of polarities (logP 2–11), including legacy
POPs, brominated flame retardants (BFRs), chlorinated pesticides and
currently used pesticides (CUPs). In addition, data reduction and selection
strategies for SUS and NTS were developed for comprehensive two-dimensional
gas chromatography separation with low-resolution time-of-flight mass
spectrometric detection (GC × GC-LRMS) data and applied to real
high-volume air samples. Combination of the newly developed clean-up
procedure and data treatment strategy enabled the prioritisation of over 600
compounds of interest in the particle phase (on GFF) and over 850 compounds
in the gas phase (on PUF) out of over 25 000 chemical features detected in
the raw dataset. Of these, 50 individual compounds were identified and
confirmed with reference standards, 80 compounds were identified with a
probable structure, and 774 compounds were assigned to various compound
classes. In the dataset available here, 11 hitherto unknown halogenated
compounds were detected. These unknown compounds were not yet listed in the
available mass spectral libraries.