Chlorinated organic compounds in concrete as specific markers for chlorine gas exposure.

The formation of chlorinated organic compounds in concrete debris exposed to reactive chlorine was studied to search for markers specific to chlorine gas exposure. Concrete materials of different origins were exposed to a range of species of reactive chlorine including bleach, humid and dry chlorine gas at different concentrations. Chlorinated organic compounds in concrete extracts were analysed by targeted gas and liquid chromatography-tandem mass spectrometry (GC-MS/MS and LC-MS/MS) and by non-targeted screening using the corresponding high-resolution techniques (GC-HRMS and LC-HRMS). Overall, different levels and species of chlorinated organic compounds namely chlorophenols, chlorobenzenes, chloromethoxyphenols, chloromethylbenzenes and chloral hydrate were identified in these chlorinated concrete extracts; two examples of diagnostic markers for neat chlorine exposure were trichloromethylbenzene and tetrachlorophenol. The old concrete samples from the 1930s and 1950s had the most chlorinated organic compounds after exposure to neat chlorine gas. Lignin or lignin degradation products were identified as probable candidates for phenolic precursor molecules in the concrete samples. Multivariate data analysis (OPLS-DA) shows distinct patterns for bleach and chlorine exposure. The chlorinated chemicals and specific markers for chlorine gas discovered in our research assist other laboratories in forensic investigations of chlorine gas attacks.

Disposable Polypropylene Face Masks: A Potential Source of Micro/Nanoparticles and Organic Contaminates in Humans.

We have been effectively protected by disposable propylene face masks during the COVID-19 pandemic; however, they may pose health risks due to the release of fine particles and chemicals. We measured micro/nanoparticles and organic chemicals in disposable medical masks, surgical masks, and (K)N95 respirators. In the breathing-simulation experiment, no notable differences were found in the total number of particles among mask types or between breathing intensities. However, when considering subranges, <2.5 µm particles accounted for ∼90% of the total number of micro/nanoparticles. GC-HRMS-based suspect screening tentatively revealed 79 (semi)volatile organic compounds in masks, with 18 being detected in ≥80% of samples and 44 in ≤20% of samples. Three synthetic phenolic antioxidants were quantified, and AO168 reached a median concentration of 2968 ng/g. By screening particles collected from bulk mask fabrics, we detected 18 chemicals, including four commonly detected in masks, suggesting chemical partition between the particles and the fabric fibers and chemical exposure via particle inhalation. These particles and chemicals are believed to originate from raw materials, intentionally and nonintentionally added substances in mask production, and their transformation products. This study highlights the need to study the long-term health risks associated with mask wearing and raises concerns over mask quality control.

Differences in mirex [dechlorane] and dechlorane plus [syn- and anti-] concentrations observed in Canadian human milk.

As part of the pan-Canadian Maternal-Infant Research on Environmental Chemicals (MIREC) study, human milk samples were collected between 2008 and 2011, and analyzed for mirex, an organochlorine insecticide and flame retardant, in addition to dechlorane plus (syn- and anti-DDC-CO), the flame retardant replacement for mirex. Mirex was analyzed separately, using a method for the analysis of existing organochlorine insecticides, while the presence of DDC-CO isomers was determined using a method developed for the detection of emerging flame retardants. Mirex was detected in all samples analyzed (n = 298), while syn- and anti-DDC-CO were present in 61.0% and 79.5% of the samples, respectively (n = 541). Mirex concentrations have declined in human milk since the 1990s. Since this is the first pan-Canadian dataset reporting DDC-CO concentrations in human milk, no temporal comparisons can be made. Maternal age was correlated with concentrations of both compounds although parity did not impact concentrations of either analyte. Given the presence of this relatively recently identified flame retardant (DDC-CO) in human milk from women across Canada, studies to identify dominant sources of this compound are critical. Despite low concentrations of environmental chemicals in human milk from Canadian women, Health Canada supports breastfeeding of infants because of the important health benefits to both the mothers and their infants.

Development of a headspace-solid phase microextraction gas chromatography-high resolution mass spectrometry method for analyzing volatile organic compounds in urine: Application in breast cancer biomarker discovery.

BACKGROUND AND AIM: Breast cancer (BC) is the leading cause of cancer-related death in females. The development of non-invasive methods for the early diagnosis of BC still remains challenge. Here, we aimed to discover the urinary volatile organic compounds (VOCs) pattern of BC patients and identify potential VOC biomarkers for BC diagnosis. METHODS: Urine samples were analyzed by headspace-solid phase microextraction (HS-SPME) combined with gas chromatography-high resolution mass spectrometry (GC-HRMS). To assure reliable analysis, the factors influencing HS-SPME extraction efficiency were comprehensively investigated and optimized by combing the Plackett-Burman design (PBD) with the central composite design (CCD). The established HS-SPME/GC-HRMS method was validated and applied to analyze urine samples from BC patients (n = 80) and healthy controls (n = 88). RESULTS: A total number of 134 VOCs belonging to distinct chemical classes were identified by GC-HRMS. BC patients demonstrated unique urinary VOCs pattern. Orthogonal partial least squares-discriminant analysis (OPLS-DA) showed a clear separation between BC patients and healthy controls. Eight potential VOC biomarkers were identified using multivariate and univariate statistical analysis. The predictive ability of candidate VOC biomarkers was further investigated by the random forest (RF) algorithm. The candidate VOC biomarkers yielded 76.3% sensitivity and 85.4% specificity on the training set, and achieved 76.0% sensitivity and 92.3% specificity on the validation set. CONCLUSIONS: Overall, this work not only established a standardized HS-SPME/GC-HRMS approach for urinary VOCs analysis, but also highlighted the value of urinary VOCs for BC diagnosis. The knowledge gained from this study paves the way for early diagnosis of BC using urine in a non-invasive manner.

Metabolic profiling of the fluorinated liquid-crystal monomer 1-ethoxy-2,3-difluoro-4-(trans-4-propylcyclohexyl)benzene.

1-Ethoxy-2,3-difluoro-4-(trans-4-propylcyclohexyl)benzene (EDPrB) is a typical fluorinated liquid-crystal monomer (LCM). LCMs contaminants are becoming increasingly concerning due to their potential persistence, bioaccumulation, toxicity, and broad prevalence in environmental and human samples. However, LCM metabolism is poorly understood. Herein, by introducing selected EDPrB into the appropriate liver microsomes in vitro, we examined the metabolic pathways of LCM in humans, rats, pigs, Cyprinus carpio, crucian carp, and Channa argus. A total of 20 species-dependent metabolites were identified and structurally elucidated by gas and liquid chromatography-high resolution mass spectrometry for the first time. Dealkylation, H-abstraction, and hydroxylation reactions are the primary metabolic pathways. Half of these in vitro metabolites were found in the urine, serum, and fecal samples of Sprague-Dawley rats exposed to EDPrB. Toxicity predictions indicate that 17 metabolites can be classified as toxic. According to the Ecological Structure Activity Relationships (ECOSAR), a number of metabolites exhibit equivalent or greater aquatic toxicity to that of EDPrB. Toxicity Estimation Software Tool (T.E.S.T.) predicts that some metabolites exhibit developmental toxicity and mutagenicity in rats. These findings suggest that biotransformation should be particularly emphasized, and more toxicological and monitoring studies should be performed to assess the ecological and human safety of LCMs.

Nontarget analysis and comprehensive characterization of halogenated organic pollutants by GC-Q-Orbitrap-HRMS in association with chromatogram segmentation and Cl/Br-specific screening algorithms.

Nontarget analysis enables high-efficiency screening and identification of halogenated organic pollutants (HOPs) in complex matrices irrespective of lacking authentic standards, particularly for novel and emerging species, thereby realizing comprehensive component characterization of HOPs. Notwithstanding, nontarget analysis and comprehensive characterization of HOPs remain on the way to improvement. In this study, we implemented nontarget analysis of HOPs in fly ash, egg and sediment using gas chromatography quadrupole-orbitrap high-resolution mass spectrometry with the aid of chromatogram segmentation and Cl/Br-specific screening algorithms, and further performed comprehensive characterization of components and distribution of HOPs. In total, 122 HOP formulas were identified and tentatively assigned with structures, of which 28 were found in ≥ two matrices. Taking isomers into account, in total 1059 HOP congeners were found. Based on the identification and semiquantification results, the chemical components and concentration profiles of HOPs were preliminarily clarified, and accordingly the overall pollution signatures of HOPs were sketched. The total concentrations of HOPs in the fly ash, egg and sediment were 4.7, 41.2 and 750.8 µg g-1, respectively. Organochlorines were the most abundant among the categories classified by halogen types, and halogenated benzenes, halogenated dioxins, halogenated biphenyls/terphenyls and halogenated polycyclic aromatic hydrocarbons (H-PAHs) were the predominant of the structurally classified categories. Moreover, dozens of formulas of novel/little-known HOPs such as mix-chlorinated/brominated PAHs with ≥4 aromatic rings and polychlorinated terphenyls were identified. This study presents an accurate and high-performance nontarget analysis method for HOPs in complex matrices, and yields new cognitions on the pollution status of HOPs from an overall perspective.

[Determination of 82 polychlorinated biphenyls in biological samples using accelerated solvent extraction-isotope dilution-high resolution gas chromatography-high resolution mass spectrometry].

In China, the detection methods for polychlorinated biphenyls (PCBs) in aquatic products are mainly effective for 6 indicative PCBs and 12 coplanar dioxin-like PCBs, which only account for a limited proportion of PCBs in organisms. In this study, to obtain the detailed concentration levels of PCBs in organisms, elucidate the metabolism and enrichment characteristics of PCBs in organisms, and accurately evaluate the exposure level and risks of PCBs to humans, an improved method for the simultaneous determination of 82 PCBs in fish and shellfish samples was developed using isotope dilution-high resolution gas chromatography-high resolution mass spectrometry (ID-HRGC-HRMS). The recovery and reproducibility of two extraction methods, i. e., oscillatory extraction and accelerated solvent extraction (ASE), were compared. Finally, ASE was chosen for subsequent experiments. Specifically, after adding 1 ng13C-labeled extraction internal standards, the samples were extracted under pressure by ASE using a mixture of n-hexane-dichloromethane (1∶1, v/v). The experimental conditions employed for this were a pressure of 10.3 MPa, heating temperature of 100 ℃, heating time of 5 min, static time of 8 min, flush volume of 60%, purging time of 120 s, and 34 mL cells. Subsequently, the extracts were loaded on an 8 g acid silica gel (44%) column (inner diameter: 15 mm) and eluted with 90 mL of n-hexane. After purification and concentration, the analytes were determined by HRGC-HRMS with a fused-silica capillary column (DB-5MS, 60 m×0.25 mm×0.25 µm). The temperature program was optimized to separate the most target compounds at the baseline. Specifically, the initial oven temperature was 120 ℃, which was held for 1 min, following by heating to 180 ℃ at 30 ℃/min, heating to 210 ℃ at 2 ℃/min and holding for 1 min, and further heating to 310 ℃ at 2.5 ℃/min and holding for 1 min. The injector and ion source temperatures were 270 ℃ and 280 ℃, respectively. With a static resolution of 10000, the HRMS instrument was operated in the selected-ion monitoring mode at an electron energy of 35 eV. The 82 PCBs were qualified by their retention time and two characteristic ions, and thereafter quantified using the mean relative corresponding factor (RRF). The results showed that the relative standard deviation (RSD) of the RRF obtained from six-point calibration standard solutions was less than 20%. The linearity ranges were from 0.1 to 200 µg/L, and the correlation coefficients (r2) were greater than 0.99. Under optimum conditions, the method detection limits (MDLs) for the PCBs of biological samples were in the range of 0.02-3 pg/g. To validate the method, the fish and shellfish samples were spiked with a low level (0.4 ng) and high level (3.6 ng) of native PCB standards. The spiked recoveries using low-concentration native PCBs were 71.3%-139% in fish and 76.9%-143% in shellfish, and the RSDs (n=7) were 2.1%-14% and 4.5%-14%, respectively. The spiked recoveries using high-concentration native PCBs were 77.6%-141% and 82.2%-131%, respectively, and the RSDs (n=7) were 1.4%-9.4% and 1.7%-11%, respectively. An analysis of fresh fish and shellfish samples showed that the contents of a single PCB ranged from "not detected" to 54.1 pg/g, where 12 coplanar dioxin-like PCBs were detected in the range of 12.6 pg/g to 74.5 pg/g, six indicative PCBs in the range of 30.9 pg/g to 62.1 pg/g, and 82 PCBs in the range of 174 pg/g to 672 pg/g. It was concluded that this method could be successfully applied for the determination of PCBs in biological samples with good accuracy and precision. This comprehensive analytical method of PCBs in aquatic products provides effective technical support for biological monitoring; it will also aid in ecological and environmental management and the implementation of the Stockholm Convention policies.

Halogen substitution reactions of halobenzenes during water disinfection.

Although being successfully applied all over the world for more than 100 years water disinfection by means of chlorination possesses certain drawbacks, first of all formation of hazardous disinfection by-products (DBP). Aromatic halogenated DBPs significantly contribute to the total organic halogen and developmental toxicity of chlorinated water. The present study deals with investigation of possible substitution of one halogen for another in aromatic substrates in conditions of aqueous chlorination/bromination. The reaction showed high yields especially in case of substrates with proper position of an activating group in the aromatic ring. Thus, ipso-substitution of iodine by chlorine is the main process of aqueous chlorination of para-iodoanisole. Oxidation of the eliminating I+ ions into non-reactive IO3- species facilitates the substitution. Oxidation of eliminating Br+ is not so easy while being highly reactive it attacks initial substrates forming polybrominated products. Substitution of iodine and bromine by chlorine may also involve migration of electrophilic species inside the aromatic ring resulting in larger number of isomeric DBPs. Substitution of chlorine by bromine in aromatic substrates during aqueous bromination is not so pronounced as substitution of bromine by chlorine in aqueous chlorination due to higher electronegativity of chlorine atom. However, formation of some chlorine-free polybrominated products proves possibility of that process.

[Determination of atmospheric organochlorine pesticides using isotope dilution high-resolution gas chromatography/high-resolution mass spectrometry].

A method for the determination of 25 organochlorine pesticides (OCPs) in the atmosphere using isotope dilution high-resolution gas chromatography/high-resolution mass spectrometry (ID-HRGC/HRMS) was developed. Sample extraction was performed using an accelerated solvent extractor (ASE). The extraction parameters were as follows: the extraction solvent was 50% (v/v) hexane in dichloromethane, the extraction temperature was 100 ℃, the static time was 8 min, the cell was rinsed with 60% cell volume using the aforementioned extraction solvent, the purging time was 180 s with N2 gas, and the extraction proceeded through three cycles. The eluting solutions of common cartridges such as florisil, graphitized carbon black, alumina, and silica were determined via cartridge elution tests. Use of the aforementioned cartridges alone cannot remove the pigments in the air sample solution. Subsequently, all possible pairwise combinations of the four cartridges were used for sample cleaning, and only the combination of florisil and graphitized carbon black was found to completely remove the pigments. Thus, the combination of florisil and graphitized carbon black cartridges using 10 mL toluene for elution was determined as the final cleaning method in this study. A high-resolution mass spectrometer equipped with a gas chromatograph was used for quantification. A fused-silica capillary column (Rtx-CL Pesticides2, 30 m×0.25 mm×0.2 µm) was used to separate the target compounds. Injection was performed in the splitless mode at 250 ℃. The flow rate of nitrogen gas was maintained constant at 1 mL/min. The oven temperature was 110 ℃ (1 min), 20 ℃/min up to 210 ℃, 1.5 ℃/min up to 218 ℃ (1 min), and 2 ℃/min up to 260 ℃ (1 min). HRMS was conducted at >8000 resolution, the source temperature was 280 ℃ in the electron impact mode using ionization energy of 35 eV, and measurements were performed in the selective ion monitoring (SIM) mode. Twenty-five OCPs were identified by comparing their GC retention times with those of the corresponding labeled compounds, and the actual ion abundance ratios of two exact m/z values with the corresponding theoretical values. The 25 OCPs were quantified by average relative response factors (RRFs), and the relative standard deviations (RSDs) of the RRFs with six calibration solutions were no more than 20%. The linear range of this method was 0.4 to 800 µg/L, and the correlation coefficients (R2) were higher than 0.992. To validate the method, clean materials (one quartz fiber filter (QFF) and two polyurethane foam (PUF) plugs) were spiked with 100 pg, 400 pg, and 15 ng native OCP standards, respectively; the RSDs of the 25 OCPs for each spiked level ranged from 0.64% to 16%. The spiking recoveries of the native OCPs ranged from 67.2% to 135%. Penetration experiments were conducted by sampling various volumes of air (15-1000 m3) using a filter-PUF/PUF high-volume active sampler. The breakthrough volume was sampled when the amount of OCPs collected in the PUF of the non-sampling end reached 5% of the total amount collected by both PUFs. When a high-volume active sampler with filter-PUF/PUF was used as an adsorbent for sampling atmospheric OCPs, a serious breakthrough of pentachlorobenzene (PeCB) occurred. The effective sampling volume of hexachlorobenzene (HCB) was very low, and was no more than 30 m3 under the standard conditions (101.325 kPa, 273 K). The effective sampling volumes of other OCP compounds should be no more than 1200 m3. This will necessitate the use of high-adsorption-capacity adsorbents such as the PUF-XAD (a styrene-divinylbenzene copolymer) sandwich used for sampling air PeCB and HCB. Calculation with the effective sampling volumes from the penetration experiment revealed that the limits of detection of the 25 OCPs were in the range of 0.002 to 0.7 pg/m3. Thus, the detection levels of OCPs in this study were reduced to at least 2% of the current monitoring standards. Analysis of air samples in Beijing showed that all the target compounds except for trans-heptachlor epoxide, endrin, cis-nonachlor and 4,4'-DDD were 100% detected in the air samples. The concentrations of HCB (in volumes of 15-30 m3) ranged from 514 to 563 pg/m3, while those of the other OCPs (in a volume of 600 m3) ranged from 0.01 to 18.9 pg/m3. The recoveries of surrogate standards in this sample analysis were in the range of 33.9% to 155%, which satisfied the requirements of EPA Method 1699. Because of the very high detection limits, the current related monitoring standards cannot meet the requirements of atmospheric OCP analysis, especially at the ultra-trace level. In addition, highly sensitive monitoring standard methods are urgently needed. This method is suitable for analyzing most atmospheric OCPs, even at the ultra-trace level. It also lays the foundation for a new standard method formulation and provides strong support for the implementation of relevant international conventions.

Chlorine isotope analysis of polychlorinated organic pollutants using gas chromatography-high resolution mass spectrometry and evaluation of isotope ratio calculation schemes by experiment and numerical simulation.

Compound-specific isotope analysis of chlorine (CSIA-Cl) is a practicable and high-performance approach for revelation of transformation processes and source identification of chlorinated organic pollutants. This study conducted CSIA-Cl for typical polychlorinated organic pollutants using gas chromatography-high resolution mass spectrometry (GCHRMS) with an alternate injection mode using perchloroethylene (PCE) and trichloroethylene (TCE) as model analytes. PCE and TCE standards from two manufacturers were employed for method development, and chlorine isotope ratio calculation schemes were evaluated by experiment and numerical simulation. The achieved precision (standard deviation of isotope ratios) was up to 0.21‰ for PCE and 0.43‰ for TCE. The limits of detection for CSIA-Cl of were 0.05 µg/mL (0.05 ng on column), and the linearities were 0.05-1 µg/mL. Two isotope ratio calculation schemes, i.e., one using complete molecular isotopologues and another using the first pair of neighboring chlorine isotopologues of each analyte, were evaluated in terms of accuracy and precision. The complete-isotopologue scheme showed evidently higher precision and was more competent to reflect trueness than the isotopologue-pair scheme and the two schemes could present completely different outcomes. The method has been successfully applied to PCE and TCE reagents from different suppliers, a trichloromethane reagent, and a plastic material. The relative isotope ratio variations (Δ37Cl) of PCE and TCE in the reagents and plastic material were from -1.84±0.7‰ to 15.12±0.85‰. The analytes from different sources could mostly be discerned from each other by chlorine isotope ratios. This study will be conducive to transformation process elucidation and source identification of for PCE and TCE, and facilitate CSIA-Cl using GC-MS for more polychlorinated organic pollutants, particularly in selection and optimization of isotope ratio calculation schemes.

Analysis of Dechlorane Plus and related compounds in gull eggs by GC-HRMS using a novel atmospheric pressure photoionization source.

Here, a new gas chromatography-atmospheric pressure photoionization-high-resolution mass spectrometry (GC-APPI-HRMS) method combined with selective pressurized liquid extraction (sPLE) has been developed for the selective determination of Dechlorane Plus (DP) and its related compounds in gull egg samples used as a bioindicator of contamination. To the best of our knowledge, this is the first time these compounds have been analyzed by GC-MS using atmospheric pressure photoionization (APPI). Negative ion dopant-assisted APPI using vapors of diethyl ether and a source temperature of 250 °C provided high ionization efficiencies and mass spectra characterized by intense in-source fragment ions as well as the presence of molecular ion and characteristic cluster ions containing oxygen atoms in their chemical structure. This made it possible to improve the selectivity in the determination of these compounds compared to that obtained with traditional GC-MS ion sources. Under optimized conditions, the sPLE GC-APPI-HRMS (Orbitrap) method provided high recoveries (> 91%), good precisions (RSD% < 12%), and low method limits of detection (0.1-3.5 pg g-1 wet weight). The developed methodology has been applied to the determination of DP and related compounds in eggs of two gull species (L. michahellis and L. audouinii) from several Spanish protected areas. The results obtained showed significant differences in the DP concentration profiles in eggs from different gull breeding locations and between gull species of the same protected area. These results demonstrated the good performance of the GC-APPI-HRMS system to achieve a selective and sensitive determination of DP and related compounds in complex environmental samples.

Atmospheric pressure ionization for gas chromatography-high resolution mass spectrometry determination of polychlorinated naphthalenes in marine sediments.

In this work, the performance of the atmospheric pressure chemical ionization (APCI) and photoionization (APPI) was assessed to develop a new selective and sensitive gas chromatography-high resolution mass spectrometry (GC-HRMS) method for the determination of polychlorinated naphthalenes (PCNs) in sediment samples. The capability of both APCI and APPI sources for the ionization of PCNs was investigated, showing the formation of the molecular ion and the [M‒Cl+O]‒ ion in positive and negative ion modes, respectively. Positive ion APCI provided high responses using high corona ion current, while the use of high vapour pressure dopant-solvents, such as toluene in positive mode and diethyl ether in the negative mode, was required to achieve high ionization efficiencies in APPI. The performance of the two API sources in the PCN determination by GC-HRMS were compared and the best results were achieved using the GC-APPI(+)-HRMS (Orbitrap) system. The GC-APPI(+)-HRMS (Orbitrap) method was applied to the characterization of Halowax mixtures and the analysis of marine sediments collected near to the coastal area of Barcelona (NE, Spain), demonstrating a great detection capability with low method limits of detection (0.2-1.6 pg g-1 dry weight), good precision (RSD <15%) and trueness (relative error <13%). Total PCN concentrations ranged from 0.35 to 5.0 ng g-1 dry weight and the presence of related compounds, such as polychlorinated biphenyls (PCBs), was also detected by combining positive and negative ion modes, providing complementary information to better monitor of all PCN congener groups. The results presented here show the feasibility of the GC-APPI-HRMS method for the suitable determination of PCNs.

Determination of volatile compounds during deterioration of African opaque beer using a stir bar sorptive extraction technique and gas chromatography-high resolution mass spectrometry.

Opaque beer traditional to African communities undergoes quick deterioration and is consumed within 7 days of its production. The current study has utilized a stir bar sorptive extraction technique followed by GC-HRT determination to trace variations of 84 volatile compounds in four opaque beers commonly brewed in South Africa over the 7-day shelf life period. The major fruity esters were observed to increase up to Day 4 and eventually decreasing until Day 7 where their levels were finally lower than Day 1. Aldehydes reduced drastically and were less than 50% on Day 2 and becoming almost undetectable at Day 7. The common beer alcohols (phenylethyl alcohol and 3-methyl-1-butanol) decreased during beer shelf life while phenolics with undesirable medicinal tastes (creosol and p-cresol) increased up to 24-fold by Day 7. This study might open future research perspectives around opaque beer traditional to African rural communities.

Feasibility of gas chromatography-atmospheric pressure photoionization-high-resolution mass spectrometry for the analysis of polychlorinated dibenzo-p-dioxins, dibenzofurans, and dioxin-like polychlorinated biphenyls in environmental and feed samples.

In this work, the suitability of atmospheric pressure photoionization (APPI) has been assessed for the determination of polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (dl-PCBs) by gas chromatography-high-resolution mass spectrometry (GC-HRMS). The APPI of target compounds has been tested in both positive and negative ion modes. Under positive ion mode, the analytes generated the molecular ion, which was favoured using dopants that promote charge exchange gas-phase reactions (i.e., benzene), while in negative ion mode, the ion [M-Cl+O]- for PCDFs and dl-PCBs were mainly formed, providing the best results using benzene and diethyl ether as dopants, respectively. Concerning PCDDs, highly chlorinated congeners were mainly ionized by means of the [M-Cl]- ion, whereas [M-Cl+O2]- was the base peak for tetraCDD and [M-Cl+O]- for penta- and hexaCDDs. Method quality parameters, in accordance with the current EU Regulation guidelines for food and feed analysis, showed the good performance of the two GC-APPI-HRMS (Orbitrap) methods since they provided high detection capability (low fg levels), good linearity, and satisfactory precision (RSD% < 9%). In addition, the GC-APPI-HRMS (Orbitrap) methods were validated by analysing selected environmental and feed samples and the results were compared to those obtained using conventional GC-EI-HRMS, demonstrating the good performance in the analysis of the target compounds. Hence, the GC-APPI-HRMS technique can be proposed as alternative to the conventional methods for the determination of PCDD/Fs and dl-PCBs in environmental and feed matrices.

[Determination of 32 polychlorinated biphenyls in aquatic products by gas chromatography-high-resolution mass spectrometry with accelerated solvent extraction-purification simultaneously coupled to isotope internal standard method].

Gas chromatography (GC)-high-resolution mass spectrometry (HRMS) with accelerated solvent extraction (ASE)-purification simultaneously coupled to the isotope internal standard method is proposed for the determination of 32 polychlorinated biphenyls (PCBs) in aquatic products. Synchronous purification was achieved by adding 2 g of anhydrous sodium sulfate, 1 g of Cleanert Florisil, and 50 g of neutral alumina as the adsorbent to the ASE system. The PCBs were extracted from aquatic product samples using a dichloromethane-n-hexane (1:1, v/v) mixture at 100 ℃ with two extraction cycles. The extracting solution was purified twice with 0.5 mL concentrated sulfuric acid. After concentration to a constant volume, the target compounds were detected by GC-HRMS and quantified by the isotope internal standard method. Under the optimized conditions, the relative standard deviations (RSDs) of the mean relative response factor (RRF) for the 32 PCBs in the range of 0.1-20 µg/L were less than 15%. The limits of quantification were 0.3-1.9 ng/kg. At three spiked levels (5, 20, and 50 ng/kg) in grass carp and sea bass, the recoveries of the 32 PCBs were between 71.9% and 119.0%, with the RSDs varying from 3.5% to 19.6%. This method effectively reduces the matrix interference and shows high sensitivity, good reproducibility, and stable recovery, thus proving useful for the detection of PCBs in aquatic products.

[Determination of multiple chloropropanols in soy sauce by dispersive solid phase extraction-gas chromatography-high resolution mass spectrometry].

A method for the rapid screening of 1,3-dichloro-2-propanol, 2,3-dichloro-1-propanol,3-monochloropropane-1,2-diol, and 2-monochloropropane-1,3-diol in soy sauce was developed based on dispersive solid phase extraction-gas chromatography-high resolution mass spectrometry (GC-HRMS). The samples were extracted by ethyl acetate, cleaned up using N-propylethylenediamine and detected by GC-HRMS. The chloropropanols were quantified by the internal standard method. The results demonstrated that the limits of quantitation of the four chloropropanols were in the range of 0.5-10 µg/kg. The recoveries of the four chloropropanols in soy sauce spiked with three levels varied from 78% to 103%, and the relative standard deviations were no more than 8.8%. The proposed method is simple, accurate, sensitive and suitable for the rapid screening of the four chloropropanols in soy sauce.

Quantitative and semiquantitative analyses of hexa-mix-chlorinated/brominated benzenes in fly ash, soil and air using gas chromatography-high resolution mass spectrometry assisted with isotopologue distribution computation.

Hexa-mix-chlorinated/brominated benzenes (HXBs), a group of newly found analogues of hexachlorobenzene (HCB) and hexabromobenzene (HBB), may exhibit similar environmental risks and toxicities as HCB and HBB, and therefore possess high interests in environmental and toxicological research. Yet information regarding HXBs in the environment remains scarce. In this study, we developed an isotope dilution method for quantitative and semiquantitative determination of five HXBs in fly ash, soil and air using gas chromatography high resolution mass spectrometry (GC-HRMS) in multiple ion detection mode. The samples were Soxhlet-extracted and purified with multilayer composite silica gel-alumina columns, followed by GC-HRMS detection. Identification of HXBs was conducted by the comparison between theoretical and detected mass spectra using paired-samples T test and cosine similarity analysis. Two HXBs (C6BrCl5 and C6Br4Cl2) with reference standards were quantitatively determined while the rest three (C6Br2Cl4, C6Br3Cl3 and C6Br5Cl) without reference standards were semiquantitatively analyzed by sharing the calibration curves of C6BrCl5 and C6Br4Cl2 in cooperation with isotopologue distribution computation. The accuracies for C6BrCl5 and C6Br4Cl2 were 87.3-107.8% with relative standard deviations (RSD) of 2.8-5.0%. The method limits of quantification of the HXBs were 0.10 ng/g in fly ash and soil samples and 0.09 pg/m3 in ambient air samples. The recoveries ranged from 42.7% to 102.1% with RSD of 3.7-13.9%. This method has been successfully applied to the analysis of the HXBs in the environmental samples. The total concentrations of HXBs in the fly ash, soil and ambient air samples were 19.48 ng/g, 10.44 ng/g and 5.13 pg/m3, respectively, which accounted for 10.6%, 0.4% and 10.8% of the corresponding total concentrations of HCB and HBB. This study provides a reference method for quantitative and/or semiquantitative analyses of novel mix-halogenated organic compounds, and sheds light on the full picture of HXBs pollution in the environment.

Chlorine and bromine isotope fractionations of halogenated organic compounds in fragmentation by gas chromatography-electron ionization high resolution mass spectrometry.

Revealing fractionations of chlorine and bromine isotope in electron ionization mass spectrometry (EI-MS) is crucial for accurate compound-specific isotope analysis of chlorine/bromine (CSIA-Cl/Br) for halogenated organic compounds (HOCs) using gas chromatography EI-MS (GC-EI-MS). This study investigated chlorine/bromine isotope fractionation of 12 organochlorines and 5 organobromines in EI-MS using gas chromatography-high resolution mass spectrometry. The observed isotope fractionations were evaluated with relative variation of chlorine/bromine isotope ratios (Δ37Cl or Δ81Br) between precursor ions and their product ions. All the 17 HOCs exhibited significant isotope fractionations with varied modes and magnitudes depending on compound and EI energy. The magnitudes of the observed isotope fractionations were extremely large in contrast to those in in-solution dehalogenation reactions, showing the Δ37Cl and Δ81Br values within the ranges of -149.2 to 292.0‰ and -362.2 to 546.2‰, respectively. Inter-ion and intra-ion isotope fractionations counteractively influenced the measured chlorine/bromine isotope ratios of individual dehalogenation product ions, whereas only the former could affect (enhance) the measured isotope ratios of molecular ions. The magnitudes of inter-ion isotope fractionation were generally lower than those of intra-ion isotope fractionation for most HOCs (11/17). Stable EI energy and isotope-ratio calculation using complete chlorine/bromine isotopologues of individual molecular ions help to obtain CSIA-Cl/Br data with high precision and accuracy. The results of this study could facilitate exploration of chlorine and bromine isotope fractionations of HOCs during dehalogenation in such conditions as photoinduced dehalogenation, and further elucidate relevant dehalogenation pathways in light of reaction mechanisms revealed by CSIA data.

Determination of human metabolites of chlorinated phosphorous flame retardants in wastewater by N-tert-butyldimethylsilyl-N-methyltrifluoroacetamide-derivatization and gas chromatography-high resolution mass spectrometry.

The analysis of wastewater for the determination of human biomarkers of exposure (human metabolites) is a non-intrusive, economic and complementary alternative to the analysis of urine in the monitoring of human exposure to chemicals of concern. This study provides the first gas chromatography-based method for the determination of three metabolites of chlorinated organophosphorous flame retardants (OPFRs: bis(2-chloroethyl) phosphate, bis(chloropropyl) phosphate and bis(1,3-dichloro-2-propyl) phosphate) in wastewater. A solid-phase extraction procedure based on the use of mixed-mode reversed-phase weak anion exchange sorbents was optimized including a fractionated elution of OPFRs and their metabolites. Analytes derivatization was investigated by comparing two silylating reagents, N-tert-butyldimethylsilyl-N-methyltrifluoroacetamide and N-methyl-N-(trimethylsilyl)trifluoroacetamide, the first one providing better results. Determination was performed by gas chromatography-high resolution mass spectrometry with a quadrupole-time-of-flight system (GC-QTOF) in order to improve selectivity. Furthermore, the use of GC-QTOF combined with the specific ion obtained from silylated metabolites (m/z 154.9924) can be exploited to screen for other phosphate ester metabolites. Under final conditions, the overall method performance was satisfactory, affording method detection limits ranging from 1.1 to 4.6 ng/L, percentages of recovery from 90% to 110%, and relative standard deviations below 13%. The analysis of composite raw wastewater samples collected over 24 h in the NW of Spain allowed to quantify, for the first time in this matrix, the metabolite bis(chloropropyl) phosphate at levels over 60 ng/L.

Simultaneous observation of concurrent two-dimensional carbon and chlorine/bromine isotope fractionations of halogenated organic compounds on gas chromatography.

It has been reported that isotope fractionation can occur on gas chromatography (GC), yet little is known about concurrent dual-elements isotope fractionations on GC. Revelation of concurrent two-dimensional carbon and chlorine/bromine isotope fractionations of halogenated organic compounds (HOCs) on GC may be of important significance for compound-specific isotope analysis (CSIA). This study presents an in-depth investigation of the two-dimensional C and Cl/Br isotope fractionations of HOCs on GC using GC-double focus magnetic-sector high resolution mass spectrometry (GC-DFS-HRMS). The two-dimensional C and Cl/Br isotope fractionations of four organochlorines and four bromobenzenes on GC were simultaneously measured by GC-DFS-HRMS. The isotope fractionations were evaluated with isotope ratios, relative variations of isotope ratios (△hE) and isotope fractionation extents (ΛhE). All the HOCs exhibited significant inverse C and Cl/Br isotope fractionations, with Λ13C of 38.14‰-307.56‰, Λ37Cl of 59.60‰-146.85‰, and Λ81Br of 25.89‰-142.10‰. The isotope fractionations were significant in both ends of chromatographic peaks, while the isotope ratios in center retention-time segments were the closest to comprehensive isotope ratios in the whole peaks. Significant correlations between C isotope fractionation and Cl/Br isotope fractionation were observed, indicating that the isotope fractionations might have strong relationships and/or be dominated by similar factors. Relevant mechanisms for the two-dimensional C and Cl/Br isotope fractionations were tentatively proposed on basis of a modified two-film model and the theories related to zero point energy. The results of this study gains new insights into concurrent two-dimensional isotope fractionation behaviors of HOCs during physical processes, and are conducive to CSIA studies involving C, Cl and Br for obtaining high-quality data, particularly to dual-elements CSIA of C and Cl/Br.