Determination of PCDD/Fs and dioxin-like PCBs in food and feed using gas chromatography-triple quadrupole mass spectrometry

A method was developed on a gas chromatograph coupled to a triple quadrupole mass spectrometer(GC-MS/MS) for trace level determination of polychlorinated dibenzo-p-dioxins/dibenzofurans(PCDD/Fs) and dioxin-like polychlorinated biphenyls(DL-PCBs) in food and feed. The results demonstrated good sensitivity and repeatability for PCDD/Fs and DL-PCBs at an extremely low level(10 pg mL~(-1) for 2,3,7,8-TCDD/F), as well as wide linear response of over 3 or 4 orders of magnitude in concentration ranges; 0.5–200 ng mL~(-1) for PeCDD/F and 0.2–2000 ng mL~(-1) for DL-PCBs. The method detection limits for PCDD/Fs and DL-PCBs were in the range from 0.018–0.17 pg g~(-1) to 0.13–0.36 pg g~(-1), respectively. The performance of the GC-MS/MS for food and feed sample analysis showed high precision and accuracy compared to the high resolution gas chromatograph/high resolution mass spectrometer. The results indicated the feasibility of GC-MS/MS as a confirmatory method for the measurement of PCDD/Fs and DL-PCBs in food and feed as required by European Union legislation.     

Simultaneous analysis of polychlorinated biphenyls and polychlorinated naphthalenes by isotope dilution comprehensive two-dimensional gas chromatography high-resolution time-of-flight mass spectrometry

Polychlorinated biphenyls (PCBs) and polychlorinated naphthalenes (PCNs) are listed as persistent organic pollutants (POPs) under the Stockholm Convention. Because they have similar physical and chemical properties, they are coeluted and are usually analyzed separately by different gas chromatography high-resolution mass spectrometry (GC-HRMS) methods. In this study, a novel method was developed for simultaneous analysis of six indicator PCBs, 12 dioxin-like PCBs, and 16 PCNs using isotope dilution comprehensive two-dimensional gas chromatography with high-resolution time-of-flight mass spectrometry (GC × GC-HRTOF-MS). The method parameters, including the type of GC column, oven temperature program, and modulation period, were systematically optimized. Complete separation of all target analytes and the matrix was achieved with a DB-XLB column in the first dimension and a BPX-70 column in the second dimension. The isotope dilution method was used for quantification of the PCBs and PCNs by GC × GC-HRTOF-MS. The method showed good linearity from 5 to 500 pg μL⁻¹ for all the target compounds. The instrumental limit of detection ranged from 0.03 to 0.3 pg μL⁻¹ for the 18 PCB congeners and from 0.09 to 0.6 pg μL⁻¹ for the 16 PCN congeners. Repeatability for triplicate injections was always lower than 20%. The method was successfully applied to the determination of 18 PCBs present at 0.9–2054 pg g⁻¹ and 16 PCNs present at 0.2–15.7 pg g⁻¹ in three species of fish. The GC × GC-HRTOF-MS results agreed with those obtained by GC-HRMS. The GC × GC-HRTOF-MS method proved to be a sensitive and accurate technique for simultaneous analysis of the selected PCBs and PCNs. With the excellent chromatographic separation offered by GC × GC and accurate mass measurements offered by HRTOF-MS, this method allowed identification of non-target contaminants in the fish samples, including organochlorine pesticides and polycyclic aromatic hydrocarbons.     

杭州市冬季大气气溶胶PM2.5中二恶英和多氯联苯的污染特征

2014年1月在杭州市选择5个点位采集大气颗粒物PM_2.5样品,采用同位素稀释高分辨气相色谱/高分辨质谱测定PM_2.5中的二恶英（PCDD/Fs）和多氯联苯（PCBs）,对PM_2.5的污染状况以及PM_2.5中PCDD/Fs和PCBs的污染水平及分布特征进行了研究。PM_2.5的质量浓度范围为85~168 μg/m³,PM_2.5污染较重,但与2004年同期相比明显降低。PM_2.5中PCDD/Fs的毒性当量（TEQ）为0.277~0.488 pg I-TEQ/m³,明显高于2004年同期采集样品。颗粒物中PCDD/Fs以八氯代二苯并-对-二恶英（OCDD）为主,毒性当量主要贡献者为2,3,4,7,8-五氯代二苯并呋喃（2,3,4,7,8-PeCDF）。PM_2.5中PCBs的质量浓度范围为2.9~8.1 pg/m³,二恶英类多氯联苯（DL-PCBs）的毒性当量范围为2.6~6.1 fg WHO-TEQ/m³,污染较低。PCBs在颗粒物中分布以PCB-28为主,但对毒性当量贡献最大的为PCB-126。PCDD/Fs和PCBs的气-固分配特征表现为PCDD/Fs主要分布于颗粒物中,而PCBs主要分布于气相中。     

Separation of polychlorinated dibenzo-p-dioxins/furans,non-ortho/mono/di/tri/tetra-ortho-polychlorinated biphenyls,and polybrominated diphenyl ethers groups of compounds prior to their determination with large volume injection gas chromatography—Quadrupole ion storage tandem mass spectrometry

Polychlorinated dibenzo-p-dioxins/furans (PCDD/Fs), polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) are important environmental contaminants. Their maximum legally allowable levels in food and environment are in the low pg g⁻¹ range. Therefore some highly selective and sensitive analytical methods must be used to determine them. Prior to final determination by GC/MS the cleaned-up samples have to be split into some fractions in view of large differences in concentrations of various analytes and existence of numerous chromatographic co-elutions (which in any case cannot be fully avoided). The aim of this study was to: (i) develop a robust, time-saving analytical method to isolate, clean-up and fractionate PCBs, PBDEs and PCDD/Fs prior to their determination with gas chromatography/ion trap mass spectrometry; (ii) assess method performance using laboratory validation data and some certified reference materials; (iii) use the developed method to assess PCB/PBDE/PCDD/F levels in samples of commercially available food. A combination of alumina, florisil, modified silica gel and two carbon columns were used for sample cleanup and fractionation. Separate fractions containing dioxins/furans, PBDE, non-ortho, mono-ortho and di-/tri-/tetra-ortho PCBs were obtained. The method statistical parameters were compatible with 1883/2006 EC Regulation (80–120%, RSD below 15%). The method performance was successfully used to evaluation of some real life food samples.     

Quantification of PCDD/Fs and dioxin-like PCBs in small amounts of human serum using the sensitive H1L7.5c1 mouse hepatoma cell line: optimization and analysis of human serum samples from adolescents of the Flemish human biomonitoring program FLEHS II

Since the CALUX (Chemically Activated LUciferase gene eXpression) bioassay is a fast and inexpensive tool for the throughput analysis of dioxin-like compounds in a large number of samples and requires only small sample volumes, the use of this technique in human biomonitoring programs provides a good alternative to GC-HRMS. In this study, a method for the separate analysis of PCDD/Fs and dioxin-like PCBs (dl-PCBs) in human serum with the new sensitive H1L7.5c1 mouse hepatoma cell line was optimized.Sample dilution factors of 5 and 2.4 were selected for routine analysis of respectively the PCDD/Fs and dl-PCBs. The validation studies showed that repeatability and within-lab reproducibility for the quality control (QC) standard were within the in-house criteria. A long-term within-lab reproducibility of 25% for the PCDD/F fraction and 41% for the dl-PCB fraction for the analysis of pooled serum samples, expressed as pg BEQ/g fat, was determined. CALUX recoveries of the spiked procedural blanks were within the acceptable in-house limits of 80-120% for both fractions and the LOQ was 30.3 pg BEQ/g fat for the PCDD/Fs and 14.5 pg BEQ/g fat for the dl-PCBs. The GC-HRMS recovery of a C13-spiked pooled serum sample was between 60 and 90% for all PCDD/F congeners and between 67 and 82% for the non-ortho PCBs. An adequate separation between both fractions was found. The CALUX/GC-HRMS ratio for a pooled serum sample was respectively 2.0 and 1.4 for the PCDD/Fs and the dl-PCBs, indicating the presence of additional AhR active compounds. As expected, a correlation was found between human serum samples analyzed with both the new H1L7.5c1 cell line and the more established H1L6.1c3 cell line. The geometric mean CALUX-BEQ values, reported for the adolescents of the second Flemish Environment and Health Study (FLEHS II) recruited in 2009-2010, were 108 (95% CI: 101-114) pg CALUX-BEQ/g fat for the PCDD/Fs and 32.1 (30.1-34.2) pg CALUX-BEQ/g fat for the dioxin-like PCBs.     

Analysis of polychlorinated dibenzo-p-dioxins, dibenzofurans and dioxin-like polychlorinated biphenyls in vegetable oil samples by gas chromatography-ion trap tandem mass spectrometry

Gas chromatography coupled to ion trap tandem mass spectrometry (CG-MS-MS) has been evaluated for the analysis of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) and dioxin-like polychlorinated biphenyls (dl-PCBs) in vegetable oil samples containing different concentration levels (0.2-6 pg WHO-TEQ g(-1) for both PCDD/Fs and dl-PCBs) of the 29 toxic congeners of PCDD/F and dioxin-like PCBs. The effect of potential interfering compounds such as polychlorinated naphthalenes (PCNs), polychlorinated biphenyls (PCBs) and polychlorinated diphenylethers (PCDEs) on the quantification of mono-ortho PCBs has been investigated. In addition, the influence of the clean-up procedure on the final determination by CG-MS-MS was studied, showing that the quality of the results depends to a great extent on this analytical step. Quality parameters have been established and good precisions (CV: 3-19%) and low limits of detection for PCDD/Fs (0.04-0.20 pg g(-1) oil) and dl-PCBs (0.08-0.64 pg g(-1) oil) were obtained. The method was validated by a comparison of the CG-MS-MS results with those obtained by GC-HRMS.     

Development of new cleanup method of polychlorinated dibenzo-p-dioxins/dibenzofurans in fish by freezing-lipid filtration

Freezing-lipid filtration as a new method has been developed for the rapid determination of polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDDs/Fs) in biological samples. This method can effectively reduce the time of sample pretreatment, labor and amount of solvents compared with conventional methods. By freezing-lipid filtration procedure, about 90% of lipids in extract could be removed without any significant loss of PCDD/Fs. For further cleanup of extracts after freezing-lipid filtration, automatic parallel LC columns including silica gel, alumina and carbon columns were applied. During automatic parallel LC columns cleanup, most of co-extracted interferences such as residue lipids and fatty acids could be eliminated and dioxins could be separated from many other dioxin-like congeners such as polychlorinated biphenyls by this procedure. The extracts after cleanup were analyzed by high-resolution gas chromatography (HRGC)/high-resolution mass spectrometry (HRMS) using an isotope dilution method. The average recoveries and relative standard deviation (R.S.D.) of 17 native congeners in the spiked fish samples at 8-80 pg/g (n = 3) were ranged between 85.3 and 117.2% and 5.7-20.3%, respectively.     

Quantification of the neurotransmitters melatonin and N-acetyl-serotonin in human serum by supercritical fluid chromatography coupled with tandem mass spectrometry

The aim of this study was developing a supercritical fluid chromatography tandem mass spectrometry (SFC-MS/MS) method and an ultra-high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) method, for the analysis of N-acetyl-serotonin (NAS) and melatonin (Mel) in human serum, and to compare the performance of these methods. Deuterated isotopologues of the neurotransmitters were synthesized and evaluated for suitability as internal standards in sample preparation. Liquid-liquid extraction was selected as sample preparation procedure. With chloroform, the best extraction solvent tested, an extraction yield of 48 ± 2% for N-acetyl-serotonin and 101 ± 10% for melatonin was achieved. SFC separation was accomplished within 3 min on a BEH stationary phase, employing isocratic elution with 90% carbon dioxide and 0.1% formic acid as well as 0.05% ammonium formate in methanol. For the 4 min UHPLC gradient separation with 0.1% formic acid in water and methanol, respectively, a Kinetex XB-C18 was used as stationary phase. Both chromatographic techniques were optimized regarding mobile phase composition, additives to the mobile phase and column temperature. Multiple reaction monitoring (MRM) analysis was used for quantification of the metabolites. Both methods were validated regarding retention time stability, LOD, LOQ, repeatability and reproducibility of quantification, process efficiency, extraction recovery and matrix effects. LOD and LOQ were 0.017 and 0.05 pg μL⁻¹ for NAS and 0.006 and 0.018 pg μL⁻¹ for Mel in SFC-MS/MS compared to 0.028 and 0.1 pg μL⁻¹ for NAS and 0.006 and 0.017 pg μL⁻¹ for Mel in UHPLC-MS/MS.     

Analysis of trace levels of domoic acid in seawater and plankton by liquid chromatography without derivatization,using UV or mass spectrometry detection

Quantitation of trace levels of domoic acid (DA) in seawater samples usually requires labour-intensive protocols involving chemical derivatization with 9-fluorenylmethylchloroformate and liquid chromatography with fluorescence detection (FMOC–LC–FLD). Procedures based on LC–MS have been published, but time-consuming and costly solid-phase extraction pre-concentration steps are required to achieve suitable detection limits. This paper describes an alternative, simple and inexpensive LC method with ultraviolet detection (LC–UVD) for the routine analysis of trace levels of DA in seawater without the use of sample pre-concentration or derivatization steps. Qualitative confirmation of DA identity in dubious samples can be achieved by mass spectrometry (LC–MS) using the same chromatographic conditions. Addition of an ion-pairing/acidifying agent (0.15% trifluoroacetic acid) to sample extracts and the use of a gradient elution permitted the direct analysis of large sample volumes (100 μl), resulting in both high selectivity and sensitivity (limit of detection = 42 pg ml⁻¹ by LC–UVD and 15 pg ml⁻¹ by LC–MS). Same-day precision varied between 0.4 and 5%, depending on the detection method and DA concentration. Mean recoveries of spiked DA in seawater by LC–UVD were 98.8% at 0.1–10 ng ml⁻¹ and 99.8% at 50–1000 ng ml⁻¹. LC–UVD exhibited strong correlation with FMOC–LC–FLD during inter-laboratory analysis of Pseudo-nitzschia multiseries cultures containing 60–2000 ng DA ml⁻¹ (r² > 0.99), but more variable results were obtained by LC–MS (r² = 0.85). This new technique was used to confirm the presence of trace DA levels in low-toxicity Pseudo-nitzschia spp. isolates (0.2–1.6 ng ml⁻¹) and in whole-water field samples (0.3–5.8 ng ml⁻¹), even in the absence of detectable Pseudo-nitzschia spp. cells in the water column.     

Rapid aryl hydrocarbon receptor based polymerase chain reaction screening assay for polychlorinated dibenzo-p-dioxins and furans in soil and sediment

A method for the estimation of polychlorinated dibenzo-p-dioxin and furan (PCCD/F) toxicity equivalent quotient (TEQ) of soil and sediment matrices is described. The method includes extraction, isolation of the PCDD/Fs from interfering compounds, such as polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs), and measurement of PCDD/F using the PROCEPT aryl hydrocarbon (AhR) receptor based polymerase chain reaction (PCR) assay. The values obtained using the PROCEPT assay correlate well with reference TEQ values generated from gas chromatography-high resolution mass spectrometry (GC-HRMS), with a linearity coefficient (R(2)) of 0.94. Applied in a screening mode at 50pg/g PCDD/F TEQ, the PROCEPT assay yielded five false positive results (2.6%) and no false negative results for 196 analyses of spiked soils and environmental samples obtained from US EPA Superfund sites.     

Uncertainty assessment of polychlorinated dibenzo-p-dioxins and dibenzofuran and dioxin-like polychlorinated biphenyl analysis in stationary source sample emissions in accordance with the impending European standard EN-1948 using fly ashes

The analysis of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (dl-PCBs) present in stack gas emissions and solid residues from incinerators will be mandatory in the foreseeable future. European standard EN-1948 is in the process of being updated through the addition of a new Part 4 related to the analysis of the 12 dl-PCBs. Therefore, either a comprehensive and reliable method capable of analyzing all of these 29 compounds (12 dl-PCBs and 17 2,3,7,8-PCDD/Fs) needs to be developed, or the existing PCDD/F analytical procedure must be adapted to include the dl-PCBs. This study has taken the latter approach of modifying PCDD/F methodology and in particular the fractionation step, by isolating dioxins and dl-PCBs into separate fractions ready for high resolution gas chromatography coupled to high resolution mass spectrometry (HRGC/HRMS) analysis. Results obtained from the analysis of Certified Reference Materials (CRM-490 and CRM-615) and fly ashes from the European Committee for Standardization (CEN) intercalibration study demonstrated that the proposed methodology is appropriate to determine the dl-PCBs in accordance with the impending European standard EN-1948. Uncertainty values obtained during the validation of the analytical methodology were 13% total I-TEQ (International Toxic Equivalent) for PCDD/Fs and 31% total WHO-TEQ (World Health Organization Toxic Equivalent) in the case of dl-PCBs. In addition, ‘real’ samples such as emissions and fly ashes were successfully analyzed following the proposed analytical method.     

Suitability of selective pressurized liquid extraction combined with gas chromatography-ion-trap tandem mass spectrometry for the analysis of polybrominated diphenyl ethers

A one-step extraction and clean-up method using pressurized liquid extraction (PLE) (selective PLE) combined with gas chromatography-ion-trap tandem mass spectrometry (GC-ITMS-MS) was evaluated for the analysis of polybrominated diphenyl ethers (from tri- to hepta-PBDEs) at low concentrations in fish and shellfish samples. To this end, the performance of an on-line PLE extraction/clean-up method and of a classical Soxhlet extraction and clean-up method using a multi-layer modified silica column were compared. The two sample treatment methods provided similar results, although an important reduction in the sample treatment time (40 min per sample) was achieved using the selective PLE method. In addition, the suitability of the PLE combined with GC-ITMS-MS method was evaluated by comparing the results obtained in the analysis of fish samples with those obtained by gas chromatography-high resolution mass spectrometry (GC-HRMS). Good agreement between both techniques was obtained with differences between the mean values of less than 16%. The selective PLE method coupled to GC-ITMS-MS produced accurate results for PBDE determination with low limits of detection (1.0-16.8 pg g⁻¹ wet weight) and quantification (3.1-51 pg g⁻¹ wet weight) as well as good precision (RSD < 16%). This method has been applied to the analysis of PBDEs in fish and shellfish samples collected at fish markets in Catalonia (NE Spain).     

Aromatic amines from polyurethane adhesives in food packaging: The challenge of identification and pattern recognition using Quadrupole-Time of Flight-Mass Spectrometry

Toxic primary aromatic amines (PAAs) are reaction products from residual isocyanates in polyurethane adhesives. The maximum migration level of the total sum of PAAs is 10 ng g⁻¹ of food. This paper reports on a method for quantification of 18 PAAs by UHPLC–MS/MS that was optimised and applied to a series of industrial laminates prepared from polyurethane adhesives. Non-intentionally added substances (NIAS), impurities and other migrants were identified by Q-TOF/MS^E. A comparison of the quantitative values obtained by the colorimetric method using NEDA and by UHPLC–MS/MS confirmed that the first method can overestimate the quantification of PAAs. This could be attributed to the impurities and other NIAS present in the plastic laminate. Values of R² in the analytical characteristics of UHPLC–MS/MS were obtained, the best value being 0.9964 and the most unfavourable 0.7626. The detection limit (LOD) and the quantification limit (LOQ) were 2 pg g⁻¹ and 7 pg g⁻¹, respectively. The stability of the PAAs over time in the acidic simulant in contact with the plastic laminate is also reported.     

Analysis of heterocyclic amines in hair by on-line in-tube solid-phase microextraction coupled with liquid chromatography−tandem mass spectrometry

Mutagenic and carcinogenic heterocyclic amines (HCAs) are formed during heating of various proteinaceous foods, but human exposure to HCAs has not yet been elucidated in detail. To assess long-term exposure to HCAs, we developed a simple and sensitive method for measuring HCAs in hair by automated on-line in-tube solid-phase microextraction (SPME) coupled with liquid chromatography–tandem mass spectrometry (LC–MS/MS). Using a Zorbax Eclipse XDB-C8 column, 16 HCAs were analyzed within 15 min. The optimum in-tube SPME conditions were 20 draw/eject cycles of 40 μL sample at a flow rate of 200 μL min⁻¹ using a Supel-Q PLOT capillary column as an extraction device. The extracted HCAs were easily desorbed from the column by passage of the mobile phase, with no carryover observed. This in-tube SPME LC–MS/MS method showed good linearity for HCAs in the range of 10–2000 pg mL⁻¹, with correlation coefficients above 0.9989 (n = 18), using stable isotope-labeled HCA internal standards. The detection limits (S/N = 3) of 14 HCAs except for MeAαC and Glu-P-1 were 0.10–0.79 pg mL⁻¹. This method was successfully utilized to analyze 14 HCAs in hair samples without any interference peaks, with quantitative limits (S/N = 10) of about 0.17–1.32 pg mg⁻¹ hair. Using this method, we evaluated the exposure to HCAs in cigarette smoke and the suitability of using hair HCAs as exposure biomarkers.     

Method development for the analysis of polybrominated diphenyl ethers, polychlorinated biphenyls, polychlorinated dibenzo-p-dioxins and dibenzo-furans in single extract of sediment samples

A comprehensive method was developed for quantitative analysis of polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCBs) and polychlorinated dibenzo-p-dioxins and dibenzo-furans (PCDD/Fs) in one single extract of environmental samples. The sample preparation procedure included two fractionation steps using silver nitrate silica chromatography to separate PBDEs from PCBs and PCDD/Fs and florisil column to separate PCBs from PCDD/Fs. Acidic silica, acidic alumina and gel permeation chromatography (GPC, for PCBs) or activated carbon column (for PCDD/Fs) were used for further clean-up. The sample extracts were analyzed by using high-resolution gas chromatography/high-resolution mass spectrometry. The entire method was validated from the analysis of mixed standards of PBDEs, PCBs and PCDD/Fs (n = 3); the analysis of certified reference biota (WMF-01). The method was applied for the analysis of 10 sediment samples collected from Haihe River and Dagu Drainage River in Tianjin City. No significant PBDEs pollution was found in the areas.     

Determination of polybrominated diphenyl ethers in water and soil samples by cloud point extraction-ultrasound-assisted back-extraction-gas chromatography–mass spectrometry

A novel and efficient analytical methodology is proposed for extracting and preconcentrating polybrominated diphenyl ethers (PBDEs) from samples of environmental interest prior gas chromatography–mass spectrometry (GC–MS) analysis. It is based on the induction of micellar organized medium by using a non-ionic surfactant (Triton X-114) to extract the target PBDEs. To enable coupling the efficient extracting technique with GC analysis, ultrasound-assisted back-extraction (UABE) into an organic solvent was required. Several factors, including surfactant type and concentration, equilibration temperature and time, ionic strength, pH and buffers nature and concentration were studied and optimized over the extraction efficiency of the proposed technique. Under optimal experimental conditions, the target analytes were quantitatively extracted achieving an enrichment factor of 250 when 10 mL aliquot of ultrapure water spiked with PBDE-standard mixture (10 pg mL⁻¹ each PBDE) was extracted. Method detection limits (MDLs) calculated with aqueous PBDEs solutions as three times the signal-to-noise ratio (S/N), ranged from 1 to 2 pg mL⁻¹ with RSDs values ≤8.5% (n = 5). The coefficients of estimation of the calibration curves obtained following the proposed methodology were ≥0.9987 and linear range of all PBDEs was 4–150 pg mL⁻¹. The proposed methodology was validated by carrying out a recovery study by spiking the samples at two different concentration levels of PBDEs (10 and 50 pg mL⁻¹ for waters samples). Recoveries values in the range of 96–106% for water samples were obtained showing satisfactory robustness of the method for analyzing PBDEs in water samples. The proposed methodology was applied for the analysis of PBDEs: 2,2′,4,4′-tetraBDE (BDE-47), 2,2′,4,4,5-pentaBDE (BDE-99), 2,2′,4,4,6-pentaBDE (BDE-100) and 2,2,4,4′,5,5′-hexaBDE (BDE-153) in water samples, including drinking, lake, river water and soil samples. Significant quantities of PBDEs were not found in the analyzed samples.     

A new cleanup method of dioxins in sediment using large volume injection gas chromatography online coupled with liquid chromatography

A new cleanup method was developed and validated for the determination of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) in sediment. The sample extract was first treated with sulfuric acid and then cleaned up by a large volume injection gas chromatography online coupled with liquid chromatography (LVI-GC-LC) system. PCDD/Fs in the extract were separated by a GC column (DB-5), selected cut, cool trapped and transferred to a LC column (alumina). The fraction of PCDD/Fs eluted from the alumina column was collected and concentrated for the instrumental analysis. Under the optimized conditions, LVI-GC-LC method achieved the recoveries of 57–102% for 2,3,7,8-substituted PCDD/Fs, which met the requirements of US Environmental Protection Agency (EPA) Method 1613 and were better than those obtained using the conventional multistep column cleanup method. Meanwhile, compared with the conventional method, the limit of detection (LOD) values of 2,3,7,8-substituted PCDD/Fs cleaned up by LVI-GC-LC method were decreased due to the high-efficiency removal of interferents. These results suggested that the LVI-GC-LC cleanup method was a promising alternative to the multistep cleanup procedure for the determination of dioxins in environmental samples.     

Gas chromatography–ion trap tandem mass spectrometry method for the analysis of methoxylated polybrominated diphenyl ethers in fish

Gas chromatography coupled to ion trap tandem mass spectrometry (GC–ITMS-MS) is proposed for the analysis of methoxylated polybrominated diphenyl ethers (MeO-PBDEs) in fish and shellfish. MS–MS operating parameters related to the isolation and fragmentation of the precursor ions were optimized to achieve maximum sensitivity and selectivity. This new method allows the determination of both MeO-PBDEs and PBDEs in a single run. Low limits of detection (0.4–2.5 pg injected) and high precision (RSD < 13%) were achieved. A sample treatment based on a selective pressurized liquid extraction (PLE) using Florisil as fat retainer was applied for the analysis of these compounds in fish samples. Method limits of quantification ranged from 0.11 to 0.95 ng g⁻¹ lipid weight for MeO-PBDEs and between 0.18 and 0.50 ng g⁻¹ lipid weight for PBDEs. In addition, good repeatability of the whole method was achieved (RSD < 15%). The suitability of the method was evaluated by analyzing a certified reference material (SRM 1945, whale blubber) with satisfactory results. The developed method was applied to the simultaneous analysis of MeO-PBDEs and PBDEs in fish and shellfish samples from the Mediterranean Sea.     

Multi-residue analysis of 30 currently used pesticides in fine airborne particulate matter (PM 2.5) by microwave-assisted extraction and liquid chromatography–tandem mass spectrometry

A confirmatory and rapid procedure has been developed for the determination of 30 currently used pesticides (CUP) in fine airborne particulate matter (PM 2.5) at trace level. The proposed method includes extraction of PM 2.5-bound pesticides by microwave-assisted extraction (MAE) followed by a direct injection into LC–MS/MS. The main parameters affecting the MAE extraction (time, temperature and volume of solvent) were optimised using statistical design of experiments (DoE). The matrix effect was also evaluated. Recoveries ranged from 72 to 109% and the limit of quantification (LoQ) was 32.5 pg m⁻³ for chlorpyrifos, 13.5 pg m⁻³ for fenhexamid, imazalil and prochloraz, and 6.5 pg m⁻³ for the rest of pesticides, when air volumes of 760 m³ were collected. The method was applied to 54 samples collected from three stations of the atmospheric monitoring network of the Regional Valencia Government (Spain) during April–July 2009. Nineteen out of 30 pesticides investigated were found in at least one sample: omethoate, carbendazim, acetamiprid, thiabendazole, malathion, flusilazole, metalaxyl, azoxystrobin, iprovalicarb, myclobutanil, tebuconazole, triflumizole, cyprodinil, tebufenpyrad, buprofezin, pyriproxyfen, hexythiazox, flufenoxuron and fenazaquin. The measured concentrations ranged from 6.5 to 1208 pg m⁻³. To our knowledge, 11 of the pesticides detected have been reported for the first time in ambient air.     

Optimization of a heart-cutting multidimensional gas chromatography-based method for the assessment of enantiomeric fractions of o,p′-DDT in environmental samples

The enantiomeric fractions present in soil samples may provide information useful in distinguishing recent inputs of DDT from past DDT pollution. In this study, a chromatographic procedure for the determination of the enantiomeric fractions of o,p′-DDT based on heart-cutting multidimensional gas chromatography was developed. The optimization carried out achieved low ratios of DDT degradation (<15%) in the chromatographic system. High selectivity and sensitivity in the detection of the target compounds, with a limit of detection as low as 2.1 pg μL⁻¹, was reached. In addition, high degrees of repeatability (RSD < 2.0%) and reproducibility (RSD < 3.2%) were obtained for the enantiomeric fractions measured in analytical standards and soil samples.