Gas chromatography–ion trap tandem mass spectrometry versus GC–high-resolution mass spectrometry for the determination of non-ortho-polychlorinated biphenyls in fish

Chicken Egg Yolk Antibody (IgY) Protects Mice Against Enterotoxigenic Escherichia coli Infection Through Improving Intestinal Health and Immune Response

Chicken egg yolk antibody (IgY), considered as a potential substitute for antibiotics, has been used for preventing pathogens infection in food, human and animals. This study investigated effects of IgY on growth, adhesion inhibitory and morphology of enterotoxigenic Escherichia coli (ETEC) K88 in vitro, and evaluated the protective effects of IgY on intestinal health and immune response of mice infected with ETEC in vivo. Sixty pathogen-free C57BL/6J (4-6 weeks of age) mice were divided into six treatments: control (neither IgY nor ETEC infection), ETEC infection, ETEC-infected mice treated with 250 μL of high-dose (32 mg/mL), medium-dose (16 mg/mL) or low-dose (8 mg/mL) anti-ETEC IgY, or ETEC-infected mice treated with 250 μL of non-specific IgY (16 mg/mL). Anti-ETEC IgY inhibited ETEC growth, reduced adherence of ETEC to intestinal epithelial cells J2 and damaged the morphology and integrity of ETEC cell. Oral administration of anti-ETEC IgY effectively ameliorated ETEC-induced clinical signs, reduced ETEC colonization and intestinal permeability, alleviated inflammatory response through reducing the production and expression of proinflammatory cytokines, improved intestinal morphology, and inhibited excessive activation of the mucosal immune response of challenged mice. The overall protective effects of high-dose and medium-dose anti-ETEC IgY against ETEC infection were more effective. These results suggest that anti-ETEC IgY may function as a promising novel prophylactic agent against enteric pathogens infection.

Design of a simple and novel photoelectrochemical aptasensor for detection of 3,3',4,4'-tetrachlorobiphenyl

In view of the urgent need of determining polychlorinated biphenyls in the environment, we developed a highly sensitive and selective photoelectrochemical (PEC) aptasensor for determination of 3,3',4,4'-tetrachlorobiphenyl (PCB77) by immobilizing aptamer on N-doped TiO₂ nanotubes (N-doped TiO₂ NTs). To improve analytical performance of the PEC sensor, the complementary DNA functionalized CdS quantum dots (DNA-CdS QDs) were introduced onto N-doped TiO₂ NTs by hybridization. In addition of PCB77, owing to high affinity of aptamer to PCB77, PCB77-aptamer complexes were formed by being bound of PCB77 whilst DNA-CdS QDs were released from the sensing surface. The complexes with poor conductivity hindered the interfacial electron transfer, leading to the photocurrent decrease. The more important is the release of DNA-CdS QDs enhanced the photocurrent decrease, playing the role of signal amplification. The photocurrent change was utilized to detect PCB77 quantitatively. The PEC aptasensor exhibited excellent analytical performance for detection of PCB77 with wide linear range of 0.1-100 ng/L and a low detection limit of 0.1 ng/L. It manifested outstanding selectivity for PCB77 in control experiments by employing six interferents which had similar structure or coexisted with PCB77. Besides, the PEC aptasensor was used to detect the content of PBC77 in the environment.

Meeting the European Commission performance criteria for the use of triple quadrupole GC-MS/MS as a confirmatory method for PCDD/Fs and dl-PCBs in food and feed samples

Until recently, European Union (EU) legislation required the use of high-resolution gas chromatography coupled to high-resolution mass spectrometry (HRGC-HRMS) based on magnetic sector analyzers as a standard approach for confirmatory analysis of dioxins (PCDDs) and furans (PCDFs) in feed and food. However, recent technological advances in MS instruments enabled other alternative analytical techniques to meet the same analytical criteria as those requested for HRGC-HRMS. In this sense, triple quadrupoles (GC-MS/MS) can be a realistic alternative for the analysis of dioxins. In this work, the performance of GC-MS/MS technology was evaluated against the criteria demanded by the EU for confirmatory analysis of dioxins and PCBs in food and feed. Thus, the study comprises a number of parameters including chromatographic separation, limit of quantification, linearity, repeatability, and ion ratio precision. Analyses of solvent standards as well as sample extracts (inter-calibration extracts and certified reference materials) were also considered within the scope of this study. Additionally, direct comparisons of the results obtained by GC-MS/MS with those from GC-HRMS were made. The results of this work suggested that GC-MS/MS was highly sensitive and selective for confirmatory analysis of PCDD/Fs and related compounds in food and feed samples and meets all the criteria requested by the European Commission.

Non-dioxin-like and dioxin-like polychlorinated biphenyls in butter sampled from the Polish retail market

The aim was to investigate levels of polychlorinated biphenyls (PCBs) in butter available on the Polish retail market. A gas chromatography-based method was developed for the purpose of this study. An ion-trap mass spectrometer was used as a detection system with high-resolution chromatography. Recoveries of individual PCBs from spiked samples varied from 58% to 105% with a recovery relative standard deviation in the range 3-16%. Levels of eight non-dioxin-like and twelve dioxin-like congeners were determined. Toxic equivalent factors (TEQs) were calculated using World Health Organization (WHO) TEQs. The average concentration of the sum of six PCBs (28, 52, 101, 138, 153, and 180) was found to be 1561±728 pg g(-1) (fat) and the upper-bound concentrations of dioxin-like congeners were (1 standard deviation uncertainty) 0.441±0.384 pg PCB-TEQ g(-1) (fat).

Gas chromatography-triple quadrupole mass spectrometry for the determination of atmospheric polychlorinated naphthalenes

Atmospheric polychlorinated naphthalenes (PCNs) ranging from mono-CNs to octa-CNs were detected using isotope-dilution gas chromatography coupled with triple quadrupole mass spectrometry (GC-MS/MS). The developed instrumental method was successfully applied to the determination of PCNs in technical products. It was observed that there were significant differences in concentrations, homologue profiles, chlorinated contents and total toxic equivalents (∑TEQs) of PCNs for four Halowax products. Subsequently, the validation of the analytical method was evaluated for the determination of PCNs in air samples in terms of method detection limit (MDL), recovery and matrix effect. The results demonstrated that this method could provide satisfactory sensitivity and adequate selectivity with lower cost. It was conducted to comprehensively evaluate the levels, composition patterns, ∑TEQs, and daily intake exposure of PCNs in indoor and outdoor air samples. Concentrations and ∑TEQs of PCNs in air samples ranged 47.7-832.7 pg m(-3) and 1.31-5.99 fg m(-3), respectively, and the predominant homologues were di- and tri-CNs in the gas phase. The results indicated that this analytical method was useful for the accurate and specific evaluation of dioxin-like toxicity and human exposure levels of PCNs in the atmosphere.

The analysis of dioxins and related compounds

The analysis of polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, polychlorinated biphenyls, and other related compounds requires complex sample preparation and analytical procedures using highly sensitive and selective state-of-the-art instrumentation to meet very stringent data quality objectives. The analytical procedures (extraction, sample preparation), instrumentation (chromatographic separation and detection by mass spectrometry) and screening techniques for the determination of dioxins, furans, dioxin-like polychlorinated biphenyls and related compounds with a focus on new approaches and alternate techniques to standard regulatory methods are reviewed.

Occurrence of polychlorinated naphthalenes, polychlorinated biphenyls and short-chain chlorinated paraffins in marine sediments from Barcelona (Spain)

Polychlorinated naphthalenes (PCNs), short-chain chlorinated paraffins (SCCPs) and polychlorinated biphenyls (PCBs) were analysed in marine sediment samples collected from the coastal area of Barcelona (Spain) and near of a submarine emissary coming from a waste water treatment plant located at the mouth of the Besòs River (Barcelona). An integrated sample treatment based on Soxhlet extraction followed by a simple clean-up with Florisil and graphitized carbon cartridge was employed. Gas chromatography coupled to ion-trap tandem mass spectrometry (GC-MS/MS) and gas chromatography-mass spectrometry in electron capture negative ionization mode, were used for PCN and SCCP determinations, respectively, while for PCB analysis gas chromatography with electron capture detection (GC-ECD) was used. The method developed provided low limits of detection (0.001-0.003 ng g(-1) dry weight (dw) for PCNs, 1.8 ng g(-1) for SCCPs and 0.006-0.014 ng g(-1)dw for PCBs) and good run-to-run precisions (lower than RSD 8%) for the analysis of sediment samples. Concentration levels ranging from 0.17 to 3.27 ng g(-1)dw for PCNs, between 0.21 and 1.17 microg g(-1)dw for SCCPs, and from 2.33 to 44.00 ng g(-1) (dw) for PCBs, were found in the coastal sediments, while for samples collected near to the submarine emissary higher levels (from 2.02 to 6.56 ng g(-1)dw for PCNs, between 1.25 and 2.09 microg g(-1)dw for SCCPs and from 22.34 to 37.74 ng g(-1)dw for PCBs) were obtained. The results obtained provide new data about the occurrence of PCN and SCCP in the coastal area of Barcelona.

Ion-trap tandem mass spectrometry for the analysis of polychlorinated dibenzo-p-dioxins, dibenzofurans, and dioxin-like polychlorinated biphenyls in food

This paper reports on the applicability of gas chromatography coupled to ion-trap tandem mass spectrometry (GC/ITMS/MS) for the analysis of polychlorinated dibenzo- p-dioxins (PCDDs), dibenzofurans (PCDFs), and dioxin-like polychlorinated biphenyls (dl-PCBs) in food. MS/MS parameters were selected to achieve the high sensitivity and selectivity required for food analysis. Good precision (RSD=5-18% for PCDD/Fs and 6-14% for dl-PCBs) and low limits of detection for PCDD/Fs (0.1-0.93 pg/g of fat) and dl-PCBs (0.1-0.89 pg/g of fat) were obtained. A comparative study of the congener-specific determination using both GC/ITMS/MS and GC-high resolution mass spectrometry (GC/HRMS) was performed by analyzing several matrices such as milk, fish oil, chicken, pork, fish, eggs, and a chicken compound feed, at low pg/g levels. The results using GC/ITMS/MS were in good agreement with those obtained by GC/HRMS. Consequently, GC/ITMS/MS is proposed for the analysis of PCDD/Fs and dl-PCBs in food and feed samples.

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.

Sample handling strategies for the determination of persistent trace organic contaminants from biota samples

Even after emergence of most advanced instrumental techniques for the final separation, detection, identification and determination of analytes, sample handling continues to play a basic role in environmental analysis of complex matrices. In fact, sample preparation steps are often the bottleneck for combined time and efficiency in many overall analytical procedures. Thus, it is not surprising that, in the last two decades, a lot of effort has been devoted to the development of faster, safer, and more environment friendly techniques for sample extraction and extract clean up, prior to actual instrumental analysis. This article focuses on the state of the art in sample preparation of environmental solid biological samples dedicated to persistent organic pollutants (POPs) analysis. Extraction techniques such as Soxhlet extraction, sonication-assisted extraction, supercritical fluid extraction (SFE), microwave-assisted extraction (MAE), pressurised liquid extraction (PLE) and matrix solid-phase dispersion (MSPD) are reviewed and their most recent applications to the determination of POPs in biota samples are provided. Additionally, classical as well as promising novel extraction/clean-up techniques such as solid phase microextraction (SPME) are also summarized. Finally, emerging trends in sample preparation able to integrate analytes extraction and their adequate clean-up are presented.

Challenges in the application of conventional PCB quantitation methods to studies of "invasive" freshwater organisms

We describe significant and unexpected errors in application of a conventional method for the quantitative determination of polychlorinated biphenyls (PCBs) in unusual biological tissue samples. A standard method based upon microwave-assisted extraction (MAE) and gas chromatography tandem mass spectrometry (GC-MS/MS) was applied to a variety of "invasive" freshwater organisms, representing a variety of genera. The 12 "co-planar" PCBs (co-PCBs) were determined at ng g(-1) levels in small samples (ca. 750-1000 mg) of eight freshwater species (n = 172). We found that the conventional method could lead to random and relatively large changes in retention times. A nearly five-fold increase in retention variability was observed for "lower" organisms compared to that observed in the analysis of predatory fish tissue. These unexpected retention time changes would result in misidentifications, and become problematic not only for non-selective detectors such as electron capture but also for MS-based approaches. That is, for electron impact (EI) ionization methods, molecular ions (M(+)) are produced by loss of Cl not only for congeners in the same homolog class but also for fragments of higher homologs (e.g. M - 35 and M - 37), thereby yielding false positive measurement of the target congener when the retention time windows overlap.

Ion-trap tandem mass spectrometry-based analytical methodology for the determination of polychlorinated biphenyls in fish and shellfish

Optimization of the Varian Saturn 2200 ion-trap tandem mass spectrometry (IT-MS/MS) system and comparison of its data quality with two other detection methods [electron-capture detection (ECD) and high-resolution mass spectrometry (HRMS)] was pursued by measuring polychlorinated biphenyls (PCBs) levels in fish and shellfish samples. IT-MS/MS methodology provided limits of detection (LOD) comparable to those obtained by ECD but superior specificity for the detection of a selected number of 39 PCB native congeners and 9 (13)C-labelled PCB standards. The method detection limits (MDLs) established for IT-MS/MS ranged between 1.0 and 5.0 pg/g on a wet weight basis while those obtained by ECD and HRMS were 1.0-4.0 pg/g and 0.1-2.0 pg/g, respectively. Overall, the results obtained in the study demonstrate that gas chromatography (GC) combined with IT-MS/MS provide higher data quality than those achievable by GC-ECD. For this particular set of target analytes the specificity achievable with IT-MS/MS was comparable to that obtained by HRMS and both techniques provided comparable data in terms of accuracy and precision.

Advances in the environmental analysis of polychlorinated naphthalenes and toxaphene

Recent advances in the analysis of the chlorinated environmental pollutants polychlorinated naphthalenes (PCNs) and toxaphene are highlighted in this review. Method improvements have been realized for PCNs over the past decade in isomer-specific quantification, peak resolution, and the availability of mass-labeled standards. Toxaphene method advancements include the application of new capillary gas chromatographic (GC) stationary phases, mass spectrometry (MS), especially ion trap MS, and the availability of Standard Reference Materials that are value-assigned for total toxaphene and selected congener concentrations. An area of promise for the separation of complex mixtures such as PCNs and toxaphene is the development of multidimensional GC techniques. The need for continued advancements and efficiencies in the analysis of contaminants such as PCNs and toxaphene remains as monitoring requirements for these compound classes are established under international agreements.

Sample pretreatment method for the determination of polychlorinated biphenyls in bird livers using ultrasonic extraction followed by headspace solid-phase microextraction and gas chromatography–mass spectrometry

A simple and reliable sample methodology based on simultaneous ultrasonic extraction, sulfuric acid clean-up and headspace solid-phase microextraction (SPME)-gas chromatography-mass spectrometry has been developed as an advantageous analytical tool for the determination of seven polychlorinated biphenyl congeners in bird livers at low levels. The influence of several parameters on the efficiency of the proposed method was systematically investigated. The clean-up efficiency of sulfuric acid treatment was tested and compared with those of column chromatography (Flosiril, silica gel and alumina) and solid-phase extraction (SPE) (Supelclean ENVI-Carb cartridge) procedures. The use of sulfuric acid in the clean-up step prior to headspace solid-phase microextraction analysis allows the removal of interfering matrix compounds present in the liver extracts that would otherwise cause severe ionization suppression of the polychlorinated biphenyls (PCBs) during the ionization process. The optimized method had good linearity (R2>0.99) over the range studied (5-500 ng/g wet weight) and showed satisfactory level of precision, with RSD values lower than 10.6%. The obtained relative recoveries ranged between 63 and 94%. The limits of detection (0.06-0.63 ng/g wet weight) were low enough to check for harmful levels of polychlorinated biphenyls in biological samples, and were well below most of the restrictive limits established by European Union regulations. The method was found to be reliable under the operational conditions proposed and was applied successfully to the analysis of individual polychlorinated biphenyls in liver tissues. The results obtained from five bird species from Greece revealed the presence of the target compounds in all samples analyzed, at levels ranging between 0.54 and 39.45 ng/g wet weight.

Two-dimensional gas chromatography coupled to triple quadrupole mass spectrometry for the unambiguous determination of atropisomeric polychlorinated biphenyls in environmental samples

Two-dimensional gas chromatography coupled to triple quadrupole mass spectrometry (GC-GC-MS-MS) is presented as a robust, selective and sensitive method for the accurate quantification of enantiomeric fractions (EFs) of atropisomeric polychlorinated biphenyls (PCBs) in a range of environmental matrices. The method was subjected to a set of quality control and validation experiments. EF precision of the atropisomers 95, 149, 132, and 174 ranged from 0.7 to 1.4% in soil samples. Quantified amounts of these congeners in soil and compost samples (59<n<100) were on average within 3-26% of the numbers gathered with conventional (achiral) bench top GC-MS. However, significant deviations were observed between EFs obtained by GC-GC-MS-MS and those by GC-GC-MS, GC-MS-MS, and GC-MS. The method was successfully applied to a variety of sample types, such as soil, air, herring, human milk, and, for the first time, compost. EFs in soils are shown to vary with land use and correlations with soil pH were observed. EFs in compost samples were mostly close to, or racemic.

Feasibility of gas chromatography - ion trap tandem mass spectrometry for the determination of polychlorinated biphenyls in food

The different parameters affecting the ionisation and fragmentation of selected polychlorinated biphenyls (PCBs) in an IT detector working in the MS/MS mode, ITD(MS/MS), have been optimised for maximum selectivity and sensibility. The low LODs (in the range 0.03-0.3 microg/L), the satisfactory repeatability (RSDs in general below 11%) and reproducibility (RSDs below 17%) obtained when analysing standard solutions ensured proper determination of the PCBs studied at the concentrations typically found in food samples. Foodstuffs naturally contaminated with varying levels of PCBs have been analysed using the optimised GC-ITD(MS/MS) method. The results obtained compared favourably with those found using more conventional detectors, such as (micro-)electron capture detection (for ortho-PCBs) and high-resolution MS (for non-ortho-PCBs), as well as with the consensus PCB levels established for these particular samples via an international interlaboratory exercise. The relative merits of these three detectors have been discussed.