Comprehensive two-dimensional gas chromatography–time-of-flight mass spectrometry for the identification of organobrominated compounds in bluefin tuna

Non-target analysis of organohalogenated contaminants in deep-sea fishes from the Mediterranean Sea by comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry

The enhanced separation power and identification capabilities make comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry (GC × GC - ToF MS) a valuable instrumental alternative for non-target analysis (NTA). In the present study, GC × GC - ToF MS has been used for the NTA of chlorine- and bromine-containing compounds in composite livers of two scarcely investigated Mediterranean deep-sea fish species, hollowsnout grenadier (Coelorinchus caelorhincus) and roughsnout grenadier (Trachyrhinchus trachyrhinchus). Attention focused on the identification of organohalogenated compounds with structural characteristics similar to those of persistent organic pollutants (POPs). In total, 116 Cl-, Br- and mixed Cl/Br-compounds were either positively or tentatively identified in the analyzed liver samples. Up to 88 of these compounds were legacy POPs, being polychlorinated biphenyls (PCBs) and organochlorinated pesticides (OCPs) the most abundant and frequently detected families. The other 28 identified POP-like compounds were analytes not considered by current regulation and environmental monitoring programs, including, among others, degradation products of specific OCPs, naturally produced organohalogen compounds and several perchlorinated diethyldiphenylmethane-derivatives whose presence in the investigated species is reported here for the first time. The presence of other naturally occurring brominated and mixed halogenated compounds in these fish species is also described for the first time. Our results also showed differences in the accumulation profile of the identified compounds in both species. Thereby, anthropogenic POPs showed higher relative abundances in the livers of roughsnout grenadiers than those in hollowsnout grenadiers, while for naturally occurring compounds the opposite trend or similar levels were found in both species.

Nontarget Screening of Organohalogen Compounds in the Liver of Wild Birds from Osaka, Japan: Specific Accumulation of Highly Chlorinated POP Homologues in Raptors

Nontarget screening studies have recently revealed the accumulation of typically unmonitored organohalogen compounds (OHCs) in various marine animals, but information for terrestrial food chains is still lacking. This study investigated the accumulation profiles of known and unknown OHCs in the liver of representative wild bird specimens from Osaka, Japan using nontarget analysis based on two-dimensional gas chromatography-time-of-flight mass spectrometry. A large number of unmonitored OHCs were identified, including anthropogenic contaminants and marine halogenated natural products (HNPs), and their accumulation profiles were considered to be influenced by terrestrial and brackish water-based diets. Anthropogenic OHCs were highly accumulated in terrestrial predator species (peregrine falcon, hawks, and black kite), and some unmonitored highly chlorinated contaminants reached the levels of microgram per gram lipid in the liver, i.e., C₁₀-/C₁₅-based chlordane related compounds (CHLs) and their epoxides, dichlorodiphenyldichloroethylene (DDE) homologues, and polychlorinated terphenyls (PCTs). In contrast, HNPs were accumulated at higher levels in piscivorous birds (gray heron and common cormorant). Considering the enrichment of the unmonitored C₁₀-/C₁₅-based CHLs, PCTs, and DDE homologues relative to structurally similar persistent organic pollutants (POPs) in high trophic-level species such as raptors, further studies are needed to elucidate their environmental levels, behavior in terrestrial food chains, and ecotoxicological impacts.

Exhaustive characterization of (semi-)volatile organic contaminants in car dust using comprehensive two-dimensional gas chromatography ‒ Time-of-flight mass spectrometry

This work represents the first reported effort to build an extensive database of the organic volatile and semi-volatile contaminants present in car dust as a result of migration from materials used in auto-manufacturing. Untargeted analysis of car dust samples has been performed using comprehensive two-dimensional gas chromatography combined with time-of-fight mass spectrometry (GC×GC ‒ToF MS) after generic sample preparation. The enhanced separation power and structural confirmation capabilities provided by this technique have been used for the either positive or tentative identification of 245 GC-amenable compounds, a number of them being identified for the first time in this type of matrix. Information concerning 5 compounds remaining unidentified has also been provided. Results have been summarised in a searchable database containing chromatographic, mass spectral and normalised abundances calculated for the detected analytes in the ten investigated car dusts used to discuss the main findings of the study. Results are expected to serve other researcher to take decisions concerning priority analytes for further evaluation in this research field and for car manufacturers who might search for safer materials.

Unique ion filter-A data reduction tool for chemometric analysis of raw comprehensive two-dimensional gas chromatography-mass spectrometry data

Comprehensive gas chromatography with time of flight mass spectrometry is a powerful tool in the analysis of complex samples. Chemometric analysis of raw chromatographic data is more useful in one- and two-dimensional separations relative to peak tables. The data volume from such experiments generally necessitates the use of data reduction tools. Such tools often sacrifice some of the multivariate information in the mass to charge ratio dimension. The unique ion filter reduces the over-redundancy in two-dimensional gas chromatography-mass spectrometry data by limiting the data to a few unique/pseudo-unique ions, sub-peaks/slices in the first dimension, and spectra in the second dimension. We explore the performance of this algorithm through careful inspection of two-dimensional gas chromatography-mass spectrometry data before and after application of the filter. A reduction (99%) in the number of variables in a two-dimensional gas chromatography-mass spectrometry chromatogram passed on to subsequent analysis was observed. Feature selection times for model optimization reduced from 229 (±13) to 6.8 (±0.5) min when the filter was applied. An estimate of two unique/pseudo-unique ions, one sub-peak in the first dimension and five spectra in the second dimension were considered to provide a true representation of each chromatogram and provided enough information to achieve 100% model prediction accuracy.

Elevated Concentrations of 4-Bromobiphenyl and 1,3,5-Tribromobenzene Found in Deep Water of Lake Geneva Based on GC×GC-ENCI-TOFMS and GC×GC-μECD

We quantified the concentrations of two little-studied brominated pollutants, 1,3,5-tribromobenzene (TBB) and 4-bromobiphenyl (4BBP), in the deep water column and sediments of Lake Geneva. We found aqueous concentrations of 625 ± 68 pg L^-1 for TBB and 668 ± 86 pg L^-1 for 4BBP over a depth range of 70-191.5 m (near-bottom depth), based on duplicate measurements taken at five depths during three separate 1 month sampling periods at our sampling site near Vidy Bay. These levels of TBB and 4BBP were 1 or 2 orders of magnitude higher than the quantified aqueous concentrations of the components of the pentabrominated biphenyl ether technical mixture, which is a flame retardant product that had a high production volume in Europe before 2001. We observed statistically significant vertical concentration trends for both TBB and 2,2',4,4',6-pentabromobiphenyl ether in the deep water column, which indicates that transport and/or degradation processes affect these compounds. These measurements were enabled by application of a comprehensive two-dimensional gas chromatograph coupled to an electron capture negative chemical ionization time-of-flight mass spectrometer (GC×GC-ENCI-TOFMS) and to a micro-electron capture detector (GC×GC-μECD). GC×GC-ENCI-TOFMS and GC×GC-μECD were found to be >10× more sensitive toward brominated pollutants than conventional GC×GC-EI-TOFMS (with an electron impact (EI) ionization source), the latter of which had insufficient sensitivity to detect these emerging brominated pollutants in the analyzed samples. GC×GC also enabled the estimation of several environmentally relevant partitioning properties of TBB and 4BBP, further confirming previous evidence that these pollutants are bioaccumulative and have long-range transport potential.

Identification of potential novel bioaccumulative and persistent chemicals in sediments from Ontario (Canada) using scripting approaches with GC×GC-TOF MS analysis

This work describes a single and fast approach using a filtering script as a means of prioritizing sample processing of data acquired by GC×GC-TOF MS for the identification of potentially novel persistent and bioaccumulative halogenated chemicals. The proposed script is based on the recognition of a generic halogenated isotope cluster pattern that allows for the simultaneous detection of chlorinated, brominated, or mixed halogen-substituted compounds in a single classification. Once developed, the script was applied to the identification of organohalogens in stream sediments collected across the southern region of Ontario (Canada). Classified peaks were first compared with available analytical standards and reference libraries to confirm the known chemicals. Unknown potential persistent organic pollutants (POPs) were evaluated for occurrence within the samples and high resolution mass spectrometry was used in order to identify some of the most prevalent compounds in the samples and resulting in the identification of three decachlorinated dechlorane analogs (C18H14Cl10), two undecachlorinated dechlorane species (C18H13Cl11), and a novel mixed chloro/bromo-carbazole (C12H5NCl2Br2) in a number of sediments analyzed. Relative peak abundances of these unknown halogenated compounds were in the same order of magnitude or slightly higher than levels observed for conventional POPs detected in the samples.