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.

Potential of topological descriptors to model the retention of polychlorinated biphenyls in different gas chromatography stationary phases, including ionic liquid-based columns.

The aim of this study was to develop a statistical model based on a set of intuitive topological descriptors that will help to determine the influence of the polychlorinated biphenyls (PCBs) structural features on the chromatographic behavior of these analytes in a variety of gas chromatographic stationary phases, including the highly polar ionic liquid (IL)-based SLB-IL76 and SLB-IL60 columns. The model was developed using the stepwise multiple linear regression method, and constructed through several levels of increasing complexity to make evident the relative influence of the selected descriptors. The proposed model was easy to implement and provided similar satisfactory results irrespective of the dependent variables used (i.e., retention index or retention time) or the chromatographic conditions applied (i.e., pseudo-isotherm and programmed temperature) for IL-based phases. The model also allowed the correct prediction of the elution order of selected PCBs in these and other less polar phases evaluated (i.e., SW-10, DB-17, ZB-5 and HT-8). To our knowledge, this is the first models based on topological descriptors described in the literature that provided a satisfactory fitting of the PCB behavior in IL-based phases. Our results indicated that the mechanism governing the chromatographic separation of PCBs in these highly polar columns showed significant differences compared with those observed in other less polar stationary phases.

An untargeted evaluation of the volatile and semi-volatile compounds migrating into food simulants from polypropylene food containers by comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry.

This study reports on the potential of comprehensive two-dimensional gas chromatography combined with time-of-flight mass spectrometry (GC×GC-ToF MS) for the exhaustive untargeted characterization of the volatile and semi-volatile analytes migrating from four commercial polypropylene food containers into four simulants (water, 3% acetic acid, 10% ethanol, and isooctane) according to European Regulation 10/2011. Collected extracts were concentrated and directly subjected to GC×GC-ToF MS analysis without any further treatment to preserve migrants integrity. As expected, the nature and total number of compounds detected in the migrates depended on both the brand (i.e., manufacture and/or sterilization procedure) and the simulant applied. In total, 107 analytes, including some less volatile compounds, were either positively or tentatively identified in the investigated simulants, a number of these compounds being reported for the first time as migrants from this type of material. A database containing chromatographic, mass spectral and partition information concerning these compounds, plus 23 remaining unidentified, is provided.

Evaluation of ionic liquid gas chromatography stationary phases for the separation of polychlorinated biphenyls.

The feasibility of six ionic liquid- (IL-) based stationary phases for the analysis of environmentally important polychlorinated biphenyls (PCBs) by gas chromatography combined with either electron capture micro-detector (GC-micro-ECD) or quadrupole mass spectrometry (GC-MS, for confirmation) have been evaluated. These IL-based columns showed a separation mechanism different from that observed for other commercial phases, such a low bleed high temperature 8% phenyl (equiv.) polycarborane-siloxane suggested shape-selective phase for non-ortho and mono-ortho-CBs, HT-8, or a polar poly(ethylene glycol), resulting in a different elution order of the 69 investigated PCBs. However, no all phases provided equality satisfactory resolutions for the most environmentally relevant congeners, the 12 toxic and the 7 priority PCBs. From this point of view, the best results were obtained with the SLB-IL76 and SLB-IL59 phases, which showed a number of coelutions for these specific congeners only slightly higher to that observed on HT-8. Interestingly, the SLB-IL59 phase was the only one among the evaluated phases allowing a complete resolution of the most toxic non-ortho substituted congeners # 77, 126 and 169 from all other PCBs investigated. SLB-IL76 and SLB-IL59 also demonstrated a superior chromatographic performance concerning peak symetry, retention time stability and column bleeding, compared to the other four IL-based columns evaluated. Altogether, results obtained for the analysis of pure standards illustrated the potential of, in particular, SLB-IL 59 as an alternative phase for confirmation of the identity of PCBs typically detected in environmental matrices that coeluted on conventional non-polar phases in use for this type of determination. However, the long-term stability and quantitative behaviour of these stationary phases during the analysis of real samples still need to be addressed.

Characterization of organic aromatic compounds in soils affected by an uncontrolled tire landfill fire through the use of comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry.

Discarded vehicle tires have become an increasing concern worldwide due to the enormous amount of wastes generated and the increasing evidence of health problems associated to their disposal and accidental combustion. Previous studies conducted involving either simulated or open uncontrolled tire fires have identified aromatics belonging to two main classes, volatile organic compounds and polycyclic aromatic compounds (PAHs), as the most relevant chemicals generated in these burning processes. As a consequence, and due to their recognized toxicity, most studies reported up to now have mainly focused on these two categories of compounds being information concerning the possible occurrence of other aromatic classes rather limited. In this study, the enhanced separation power and structural confirmation capabilities provided by comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry (GC×GC-ToF MS) has been used, for the first time, for the non-targeted analysis of soils impacted by a tire fire and an ash collected at the scene of the fire. In total, 118 volatile and semi-volatile aromatic compounds have been differentiated. Among them, 104 compounds have been either positively or tentatively identified. PAHs with 3-5 rings and their alkyl-derivatives were the most numerous and relevant classes in the investigated samples. A significant number of sulfur, oxygen- and nitrogen-containing PAHs were also detected in the samples. The application of a script function to the raw GC×GC-ToF MS data allowed the fast filtering and automatic recognition of compounds containing halogens in their structure. This part of the study evidenced that only a limited number of regulated persistent organic pollutants were present in the investigated samples. However, it also revealed the presence of emerging organophosphorous flame retardants, whose levels in tire fire impacted soils are reported for the first time.