Application of rapid air sampling and non-targeted analysis using thermal desorption comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry to accidental fire.

To be able to gauge the health risks and biological effects of e-waste fires, it is of key importance to know what types and amounts of chemicals are released when they occur. In this case study, we pumped 6-24 L of air from an accidental fire at a recycling depot through a Tenax-TA tube and conducted comprehensive (non-targeted) analysis by thermal desorption/comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry (TD/GC × GC/ToFMS). A special focus was placed on the search for halogenated compounds. More than 5000 components were detected in the atmosphere around the fire; however, component separation was insufficient, even when using GC × GC. The number of organohalogen compounds retrieved was increased about 1.8-fold by the refinement process of the exact mass spectrum using mass defect filtering (MDF) software. After processed by MDF, 386 peaks were concluded to be halogenated compounds. The major retrieved substances included chlorinated (or chlorinated-brominated) dioxins, chlorinated (or brominated) phenols, benzene, and various other halogenated aromatic compounds. Direct comparison of mass spectra was carried out to investigate the potential for qualitative and quantitative comparison of detected peaks without specific identification. The approximate quantitative values are summarized for each compound in the estimated substance group. Their ratios were estimated to be halogenated phenols: 13%, benzenes: 9.6%, dibenzo-p-dioxins: 9.6%, dibenzofurans: 8.4%, biphenyls; 7.4% and toluenes: 6.4%.

Application of inert gas-mediated ionization for qualitative screening of chlorinated aromatics in house dust by comprehensive two-dimensional gas chromatography-high-resolution time-of-flight mass spectrometry.

The development of highly selective and sensitive analytical methods for the nontarget screening of persistent organic pollutants such as halogenated compounds in environmental samples is a challenging task. Soft ionization mass spectrometry has emerged as a powerful technique for obtaining essential molecular information, and it is expected to reveal compounds that remain hidden with conventional fragmentation techniques such as electron ionization (EI). In this study, a soft ionization method based on electron capture negative ionization using an inert gas was developed for the nontarget screening of chlorinated aromatics in environmental samples and was applied to comprehensive two-dimensional gas chromatography-high-resolution time-of-flight mass spectrometry (GC × GC-HRToFMS). In particular, argon (Ar) and helium (He) were evaluated as inert moderating gases, and were compared against the conventional methane (CH4). The optimal ionization conditions, including the flow rate and ion source temperature, were investigated based on the molecular ion intensities of highly chlorinated aromatics decachlorobiphenyl and octachlorodibenzofuran. Ar-mediated soft ionization provided the best sensitivity to molecular ions among the three gases at a low flow rate (0.1 mL min-1) and low ion source temperature, and more selective detection of molecular ions (i.e., less fragmentation) was obtained with the inert gases than with CH4. This method is also applicable to other chlorinated aromatics such as tetra- to nonachlorobiphenyls, tetra- to heptachlorinated dibenzofurans, pentachlorobenzene, and hexachlorobenzene. To demonstrate the applicability of the proposed method to a wide range of chlorinated aromatics in environmental samples, both Ar-mediated soft ionization and conventional EI were applied to GC × GC-HRToFMS for analysis of a crude extract of house dust. Soft ionization enabled the selective and sensitive detection of molecular ions for minor amounts of chlorinated aromatics, even in complex matrices. Furthermore, the extracted ion chromatograms of halide anions (Cl- or Br-) were useful for screening other chlorinated or brominated compounds in the environmental samples. The results suggest that combining information on halide anions obtained by soft ionization and the structural information provided by EI would constitute a powerful approach for the comprehensive identification of chlorinated aromatics.

Comprehensive screening of polybromochlorodibenzo-p-dioxins, dibenzofurans as mixed halogenated compounds in wastewater samples from industrial facilities by GC×GC/ToFMS and post-data processing.

An enormous number of pollutants must be investigated to be able to understand which types threaten human health and environmental biota. In this study, we propose a workflow for screening polybromochlorodibenzo-p-dioxins and dibenzofurans (PBCDD/Fs), which are compounds that have thousands of isomers and congeners, by combining measurement of a sample without any in-laboratory-cleanup with the results of comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry and post-data processing. This process can be regarded as "in silico sample cleanup." The post-data processing stage comprises two methods in which the extracted mass spectra are matched to exact mass and isotopic ratios specified as formulae and filtering via mass deficiency. We applied this workflow to wastewater samples from industrial facilities to identify mixtures of halogenated dioxins. As a result, it was estimated that dioxins in an absolute quantity of 10-500 pg could be detected with sufficient accuracy by recovery testing of a standard mixture against sample crude extracts. Tri- to octa-halogenated dioxins were detected in 8 of 13 samples. Leachate from an industrial landfill was found to contain relatively large numbers of PBCDD/Fs, and several congeners were found in wastewater from an industrial fabric facility that handles decabromodiphenyl ether. The workflow, including the post-data processing method developed and applied in this study, has the advantage that additional identifications can be performed at any time from a single set of measurement data. This also enables the screening of substances that have thousands of homologous isomers, such as chlorinated and brominated dioxins, as well as other non-halogenated compounds.

Evaluation of a data-processing method for target and non-target screening using comprehensive two-dimensional gas chromatography coupled with high-resolution time-of-flight mass spectrometry for environmental samples.

We evaluated the possibility of semi-automatic target and non-target screening by comprehensive two-dimensional gas chromatography coupled with high-resolution time-of-flight mass spectrometry (GC×GC-HRToFMS) by using estuarine sediment samples. Two-way screening consisting of compound-based (target screening) and data-based (non-target screening) analyses was performed by using two original software programs, including mass-spectral deconvolution software based on non-negative matrix factorization, the NIST Mass Spectral Library, and an in-house accurate mass spectral library with a retention index (RI) for the 1st column. Target screening detected 47 organohalogen compounds, including polychlorinated biphenyls, polybrominated diphenyl ethers and organochlorine pesticides, in the sediment sample. Among about 54,000 peaks detected in the non-target screening, 53.6% showed match factors (MF) of ≥ 700 in an automatic mass spectral library search using the peak-top mass spectra. Both mass error of molecular ions and RI error were calculated automatically for the first-hit compounds in the library search; 0.03% of peaks passed all criteria, namely MF ≥ 700, mass error ≤±â€¯20 ppm, RI error ≤ ±â€¯20, and intensity of molecular ion ≥ 10,000. Two compounds-a phosphorus flame retardant and a brominated phenol-were tentatively identified in the non-target screening process. The advantages of semi-automatic GC×GC-HRToFMS data processing with the two original software programs is its simplicity, high reproducibility, and shortened time for processing a large volume data. The results suggest that an In-source HiRes search-i.e. library matching using accurate mass spectra-is useful and could be applied for non-target screening using high-resolution MS in the future.

Biodegradation of the aromatic fraction from petroleum diesel fuel by Oerskovia sp. followed by comprehensive GC×GC-TOF MS.

Polycyclic aromatic hydrocarbons (PAHs) from petroleum and fossil fuels are one of the most dominant pollutants in the environment. Since aromatic fraction from petroleum diesel fuel is mainly composed of PAHs, it is important to discover new microorganisms that can biodegrade these compounds. This article describes the biodegradation of the aromatic fraction separated from petroleum diesel fuel using the strain Oerskovia sp. CHP-ZH25 isolated from petroleum oil-contaminated soil. The biodegradation was monitored by gravimetry and GC × GC-TOF MS. An innovative method was applied to visualize degraded compounds in the data provided by a GC × GC-TOF MS. It was shown that Oerskovia sp. CHP-ZH25 degraded 77.4% based on gravimetric analysis within 30 days. Average rate of degradation was 14.4 mg/L/day, 10.5 mg/l/day and 4.0 mg/l/day from 0 to 10 day, 10-20 and 20-30 day, respectively. The order of PAH degradation based on decrease in peak volume after 30 days of incubation was as follows: dibenzothiophene derivatives > benzo[b]thiophene derivatives > naphthalene derivatives > acenaphthene derivatives > acenaphthylene/biphenyl derivatives > fluorene derivatives > phenanthrene/anthracene derivatives. Here we demonstrated that Oerskovia sp. CHP-ZH25 could potentially be a suitable candidate for use in bioremediation of environments polluted with different PAHs.

Selective and comprehensive analysis of organohalogen compounds by GC × GC-HRTofMS and MS/MS.

Thousands of organohalogen compounds, including hazardous chemicals such as polychlorinated biphenyls (PCBs) and other persistent organic pollutants (POPs), were selectively and simultaneously detected and identified with simple, or no, purification from environmental sample extracts by using several advanced methods. The methods used were software extraction from two-dimensional gas chromatography-high-resolution time-of-flight mass spectrometry (GC × GC-HRTofMS) data, measurement by negative chemical ionization with HRTofMS, and neutral loss scanning (NLS) with GC × GC-MS/MS. Global and selective detection of organochlorines and bromines in environmental samples such as sediments and fly ash was achieved by NLS using GC × GC-MS/MS (QQQ), with the expected losses of 35Cl and 79Br. We confirmed that negative chemical ionization was effective for sensitive and selective ionization of organohalogens, even using GC × GC-HRTofMS. The 2D total ion chromatograms obtained by using negative chemical ionization and selective extraction of organohalogens using original software from data measured by electron impact ionization were very similar; the software thus functioned well to extract organohalogens. Combining measurements made by using these different methods will help to detect organohalogens selectively and globally. However, to compare the data obtained by individual measurements, the retention times of the peaks on the 2D chromatograms need to match.

Multi-stir bar sorptive extraction for analysis of odor compounds in aqueous samples.

As reproducible coating of stir bars with more polar phases was found to be very difficult, a supporting grid was used in the development of an ethyleneglycol-modified Silicone (EG Silicone) coated stir bar. This new polar coating showed good performance for the extraction of polar solutes, but long term use also showed degradation of the coating due to friction while stirring. In order to address the lower robustness of the EG Silicone stir bar which has a much softer coating compared to a conventional polydimethylsiloxane (PDMS) stir bar, a novel SBSE procedure termed multi-SBSE ((m)SBSE) was developed. (m)SBSE consists of the robust PDMS stir bar stirring at the bottom of the vial and the EG Silicone stir bar attached on the inner side wall of the vial (a magnetic clip is used for the set-up). After extraction, the two stir bars are placed in a single glass desorption liner and are simultaneously thermally desorbed. The desorbed compounds were analyzed by thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS). Compared to conventional SBSE, (m)SBSE provides more uniform enrichment of a wide range of odor compounds in aqueous sample since both stir bars can complement each other, while eliminating the damage of the EG Silicone phase during the extraction. The robustness of the EG Silicone stir bar was dramatically increased and more than 30 extraction and desorption cycles were possible without loss in performance. The recoveries for polar solutes such as 2-acetyl pyrrole (logKow: 0.55), benzyl alcohol (logKow: 1.08), guaiacol (logKow: 1.34), and indole (logKow: 2.05) were increased by a factor of about 2-7. The (m)SBSE-TD-GC-MS method showed good linearity (r(2)>0.9913) and high sensitivity (limit of detection: 0.011-0.071 ng mL(-1)) for the test compounds spiked in water. The feasibility and benefit of the method was demonstrated with analysis of odor compounds in roasted green tea. The normalized areas obtained from (m)SBSE showed the best enrichment for most of the selected compounds compared to conventional SBSE using the PDMS stir bar or the EG Silicone stir bar. Fifteen compounds were determined in the range of 0.15-210 ng mL(-1) (RSD<14%, n=6).

Thermal desorption - comprehensive two-dimensional gas chromatography coupled with tandem mass spectrometry for determination of trace polycyclic aromatic hydrocarbons and their derivatives.

We developed a highly sensitive method for determination of polycyclic aromatic hydrocarbons (PAHs) and their derivatives (oxygenated, nitrated, and methylated PAHs) in trace particulate samples by using thermal desorption followed by comprehensive two-dimensional gas chromatography coupled with tandem mass spectrometry (TD-GC×GC-MS/MS) with a selected reaction monitoring mode. The sensitivity of TD-GC×GC-MS/MS was greater than that of TD-GC-HRMS and TD-GC×GC-QMS by one or two orders of magnitude. The instrumental detection limits were 0.03-0.3pg (PAHs), 0.04-0.2pg (oxygenated PAHs), 0.03-0.1pg (nitrated PAHs), and 0.01-0.08pg (methylated PAHs). For small amounts (10-20µg) of standard reference materials (SRMs 1649a and 1650b, urban dust and diesel exhaust particles, respectively), the values measured by using TD-GC×GC-MS/MS agreed with the certified or reference values within a factor of two. Major analytes were quantified successfully by TD-GC×GC-MS/MS from diesel exhaust nanoparticles (18-32nm) and accumulation-mode particles (100-180nm) from an 8-L diesel engine with no exhaust after-treatment system. The PAH profiles differed among driving conditions but they did not differ markedly among the particle sizes.

Stir bar sorptive extraction and comprehensive two-dimensional gas chromatography coupled to high-resolution time-of-flight mass spectrometry for ultra-trace analysis of organochlorine pesticides in river water.

A method for the determination of ultra-trace amounts of organochlorine pesticides (OCPs) in river water was developed by using stir bar sorptive extraction (SBSE) followed by thermal desorption and comprehensive two-dimensional gas chromatography coupled to high-resolution time-of-flight mass spectrometry (SBSE-TD-GC×GC-HRTOF-MS). SBSE conditions such as extraction time profiles, phase ratio (ß: sample volume/polydimethylsiloxane (PDMS) volume), and modifier addition, were examined. Fifty milli-liter sample including 10% acetone was extracted for 3 h using stir bars with a length of 20 mm and coated with a 0.5 mm layer of PDMS (PDMS volume, 47 µL). The stir bar was thermally desorbed and subsequently analyzed by GC×GC-HRTOF-MS. The method showed good linearity over the concentration range from 50 to 1000 pg L(-1) or 2000 pg L(-1) for all analytes, and the correlation coefficients (r(2)) were greater than 0.9903 (except for ß-HCH, r(2)=0.9870). The limit of detection (LOD) ranged from 10 to 44 pg L(-1). The method was successfully applied to the determination of 16 OCPs at pg L(-1) to ng L(-1) in river water. The results agree fairly well with the values obtained by a conventional liquid-liquid extraction (LLE)-GC-HRMS (selected ion monitoring: SIM) method using large sample volume (20 L). The method also allows screening of non-target compounds, e.g. pesticides and their degradation products, polyaromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and pharmaceuticals and personal care products (PPCPs) and metabolites in the same river water sample, by using full spectrum acquisition with accurate mass in GC×GC.

Global and selective detection of organohalogens in environmental samples by comprehensive two-dimensional gas chromatography-tandem mass spectrometry and high-resolution time-of-flight mass spectrometry.

We successfully detected halogenated compounds from several kinds of environmental samples by using a comprehensive two-dimensional gas chromatograph coupled with a tandem mass spectrometer (GC×GC-MS/MS). For the global detection of organohalogens, fly ash sample extracts were directly measured without any cleanup process. The global and selective detection of halogenated compounds was achieved by neutral loss scans of chlorine, bromine and/or fluorine using an MS/MS. It was also possible to search for and identify compounds using two-dimensional mass chromatograms and mass profiles obtained from measurements of the same sample with a GC×GC-high resolution time-of-flight mass spectrometer (HRTofMS) under the same conditions as those used for the GC×GC-MS/MS. In this study, novel software tools were also developed to help find target (halogenated) compounds in the data provided by a GC×GC-HRTofMS. As a result, many dioxin and polychlorinated biphenyl congeners and many other halogenated compounds were found in fly ash extract and sediment samples. By extracting the desired information, which concerned organohalogens in this study, from huge quantities of data with the GC×GC-HRTofMS, we reveal the possibility of realizing the total global detection of compounds with one GC measurement of a sample without any pre-treatment.

Environmental analysis of chlorinated and brominated polycyclic aromatic hydrocarbons by comprehensive two-dimensional gas chromatography coupled to high-resolution time-of-flight mass spectrometry.

A method for the analysis of chlorinated and brominated polycyclic aromatic hydrocarbon (Cl-/Br-PAHs) congeners in environmental samples, such as a soil extract, by comprehensive two-dimensional gas chromatography coupled to a high resolution time-of-flight mass spectrometry (GC×GC-HRTOF-MS) is described. The GC×GC-HRTOF-MS method allowed highly selective group type analysis in the two-dimensional (2D) mass chromatograms with a very narrow mass window (e.g. 0.02Da), accurate mass measurements for the full mass range (m/z 35-600) in GC×GC mode, and the calculation of the elemental composition for the detected Cl-/Br-PAH congeners in the real-world sample. Thirty Cl-/Br-PAHs including higher chlorinated 10 PAHs (e.g. penta, hexa and hepta substitution) and ClBr-PAHs (without analytical standards) were identified with high probability in the soil extract. To our knowledge, highly chlorinated PAHs, such as C(14)H(3)Cl(7) and C(16)H(3)Cl(7), and ClBr-PAHs, such as C(14)H(7)Cl(2)Br and C(16)H(8)ClBr, were found in the environmental samples for the first time. Other organohalogen compounds; e.g. polychlorinated biphenyls (PCBs), polychlorinated naphthalenes (PCNs), and polychlorinated dibenzofurans (PCDFs) were also detected. This technique provides exhaustive analysis and powerful identification for the unknown and unconfirmed Cl-/Br-PAH congeners in environmental samples.

Comprehensive two-dimensional gas chromatography coupled to high-resolution time-of-flight mass spectrometry and simultaneous nitrogen phosphorous and mass spectrometric detection for characterization of nanoparticles in roadside atmosphere.

A method is described for characterization of size-resolved particles including the nanoparticles fraction with a diameter of 29-58 nm in roadside atmosphere. The method is based on thermal desorption (TD) of a sample followed by comprehensive two-dimensional gas chromatography (GC x GC) with novel detection capabilities, including high resolution time-of-flight mass spectrometry (HRTOF-MS) and simultaneous detection with a nitrogen phosphorous detector (NPD) and a quadrupole mass spectrometer (qMS). Increased selectivity with the GC x GC-HRTOF-MS allows a group type separation of a selected chemical class, e.g. oxygenated polycyclic aromatic hydrocarbons (oxy-PAHs), using mass chromatography with a 0.05 Da wide window in the complex sample matrix. Also, exact mass measurements provide candidate elemental compositions as well as NIST library search results for tentative identifications of 50 compounds. Moreover, the simultaneous detection with the NPD and the qMS elucidate the presence of 15 nitrogen-containing compounds. Quantitative analysis of selected PAHs in several size-resolved particles was also performed by use of the TD-GC x GC-qMS with limited scan range. The method showed good linearity (r2>0.988) and high sensitivity (limit of quantification: <10 pg) for most of the target PAHs. The concentration of PAHs per particulate matter (PM) mass in nanoparticles was considerably higher than those of larger size of particles with a diameter of >102 nm.

Analysis of nonylphenol isomers in a technical mixture and in water by comprehensive two-dimensional gas chromatography-mass spectrometry.

Nonylphenol (NP) is a degradation product of nonylphenol polyethoxylate surfactants and has been reported to occur in water and sediments from urban areas. Technical NP is composed of several structural isomers, and conventional gas chromatography-mass spectrometry techniques have tentatively identified up to 22 components. Isolation and characterization of individual isomers in a technical NP mixture is important, because of the differences in estrogenic and bioaccumulation potential among the isomers. In this study, comprehensive two-dimensional gas chromatography (GC x GC) combined with mass spectrometry (MS) enabled tentative identification of 102 components of NP from a technical mixture. GC x GC-MS was also used to quantify two NP isomers in river water samples. This is the first study to use GC x GC-MS to characterize NP isomers in technical mixtures and for quantitative analysis of NP in river waters.