Evaluation of automated direct sample introduction with comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry for the screening analysis of dioxins in fish oil

Authentication of fish oil (omega-3) supplements using class-oriented chemometrics and comprehensive two-dimensional gas chromatography coupled to mass spectrometry

Food supplement authentication is an important concern worldwide due to the ascending consumption related to health benefits and its lack of effective regulation in underdeveloped countries, making it a target of fraudulent activities. In this context, this study evaluated fish oil supplements by comprehensive two-dimensional gas chromatography coupled to mass spectrometry (GC×GC-MS) to obtain fingerprints, which were used to build predictive models for automated authentication of the most popular products sold in Brazil. The authentication process relied on a one-class classifier model using data-driven soft independent modeling of class analogy (DD-SIMCA). The output of the model was a binary classifier: certified IFOS fish oils and non-certified ones - regardless of the source of adulteration. The compositional analysis showed a significant variation in the samples, which validated the need for reliable statistical models. The DD-SIMCA algorithm is still incipient in GC×GC studies, but it proved to be an excellent tool for authenticity purposes, achieving a chemometric model with a sensitivity of 100%, specificity of 98.6%, and accuracy of 99.0% for fish oil authentication. Finally, orthogonalized partial least square discriminant analysis (OPLS-DA) was used to identify the features that distinguished the groups, which ascertained the results of the DD-SIMCA model that IFOS-certified oils are positively correlated to omega-3 fatty acids, including eicosapentaenoic acid (EPA, C20:5 n-3) and docosahexaenoic acid (DHA, C22:6 n-3).

New approach for removing co-extracted lipids before mass spectrometry measurement of persistent of organic pollutants (POPs) in foods

Persistent organic pollutants (POPs) methods for foods and animal feeds require sufficient sample intake followed by an extensive removal of interfering matrix components and concentration before a gas chromatographic mass spectrometry (GC-MS) method can be applied. The extraction dissolves associated lipids in animal foods or feeds. Methods must eliminate all co-extracted lipids before determination by GC-MS. A new approach for removing lipids is presented using basic silica gel or metal ion immobilized silica gel (Ag+) in a single step. Absorbent order, adsorbent amounts, and flow rates were found to be essential for consistent results. KOH/silica gel or Ag⁺ ion (AgNO₃) silica gel were both shown to retain 75-85% of the co-extracted lipids without using sulfuric acid. KOH/silica gel method applied to butter fortified at 7.3 pg TEQ/g lipid with polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs) produced accurate results for all fortified congeners with 20% of predicted (n = 6). Ag⁺ silica gel incorporated into the Miura GO-EHT automated system produced similar results fortified at 3 pg TEQ/g lipid. During PCDD/F fortifications of butter with PCDD/Fs (n = 6), labeled standard recoveries for PCDD/Fs and planar polychlorinated biphenyls (PCBs) were all acceptable (52-99%) averaging 77% using the Miura system. A reduction in the amounts of sulfuric acid silica gel needed was possible in the completion of co-extractant removal. PCDD/F spikes into butter and for a spiked sunflower oil (PCDD/Fs and coplanar PCBs) were within ± 20% of the predicted using the Miura system; suitable for current methods criteria for foods including criteria in EU legislation.

Two-Dimensional Gas Chromatography Coupled With Mass Spectrometry in Food Analysis

The development of instrumental analytical techniques provided the opportunity for in-depth characterization of many food matrices. In particular, the use of gas chromatography coupled with mass spectrometry gives impressive results in terms of quality and authenticity testing, conducting food freshness evaluations and contamination assessments. A new variant of gas chromatography, namely two-dimensional gas chromatography (GC × GC), and various versions of mass spectrometry have been developed since last 15 years, and they still remain at the time of their renaissance. The present critical review is focused on the use of GC × GC coupled with mass spectrometry for qualitative and quantitative reasons in food analysis. It is explained how powerful analytical tool is above-mentioned technical solution. Special attention is devoted to the issues related to the development of this technique during last years in terms of key construction elements, such as modulators and MS detectors. Finally, the critical discussion on many various aspects including advantages and more important disadvantages, caused probable moderate interest of this solution, in food analytics is concerned.

Distribution of 2,3,7,8-substituted polychlorinated dibenzo-p-dioxin and polychlorinated dibenzofurans in the Jukskei and Klip/Vaal catchment areas in South Africa

Comprehensive two dimensional gas chromatography (GCxGC)-μECD analysis was used to determine 2,3,7,8-substituted dibenzo-p-dioxin (PCDD) and polychlorinated dibenzofuran (PCDF) distribution in the Jukskei and Klip/Vaal catchment areas from ten sites previously identified as persistent organic pollutant hotspots in major rivers in the Gauteng province of South Africa. Five sediment samples from the Jukskei River catchment area and five sediment samples from the Kilp/Vaal River catchment area were collected for analysis. The extracts were screened for dioxin-like activity using the DR-Luc bioassay prior to GCxGC-μECD analysis. All sediment samples tested positive for dioxin-like activity with total activity ranging from 16 to 37 pg toxic equivalents (TEQ) g(-1) dry weight (dw) for the Jukskei River catchment and 1.5-22 pg TEQ g(-1) dw for the Klip/Vaal River catchment, indicating that the Jukskei River catchment area had higher concentrations of total dioxin-like compounds. Confirmatory tests for the presence of the most potent seven PCDDs and ten PCDFs conducted using GCxGC-μECD revealed presence of 11 PCDD/Fs and 6 PCDD/Fs in the Jukskei and Klip/Vaal River catchments respectively. Total organic carbon (TOC) and particle size distribution analysis were conducted to understand the distribution of PCDD/Fs within the Jukskei and Klip/Vaal catchments.

Triple quadrupole tandem mass spectrometry: A real alternative to high resolution magnetic sector instrument for the analysis of polychlorinated dibenzo-p-dioxins, furans and dioxin-like polychlorinated biphenyls

This paper reports on the optimisation, characterisation, validation and applicability of gas chromatography coupled to triple quadrupole mass spectrometry in its tandem operation mode (GC-QqQ(MS/MS) for the quantification of polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs, dioxins) and dioxin-like polychlorinated biphenyls (DL-PCBs) in environmental and food matrices. MS/MS parameters were selected to achieve the high sensitivity and selectivity required for the analysis of this type of compounds and samples. Good repeatability for areas (RSD = 1-10%, for PCDD/Fs and DL-PCBs) and for ion transition ratios (RSD = 0.3-10%, for PCDD/Fs, and 0.2-15%, for DL-PCBs) and low instrumental limits of detection, 0.07-0.75 pg μL(-1) (for dioxins) and 0.05-0.63 pg μL(-1) (for DL-PCBs), were obtained. A comparative study of the congener specific determination using both GC-QqQ(MS/MS) and gas chromatography-high resolution mass spectrometry (GC-HRMS) was also performed by analysing several fortified samples and certified reference materials (CRMs) with low (feed and foodstuffs), median (sewage sludge) and high (fly ash) toxic equivalency (TEQ) concentration levels, i.e. 0.60, 1.83, 72.9 and 3609 pg WHO-TEQ(PCDD/Fs) g(-1). The agreement between the results obtained for the total TEQs (dioxins) on GC-QqQ(MS/MS) and GC-HRMS in all the investigated samples were within the range of ±4%, and that of DL-PCBs at concentration levels of 0.84 pg WHO-TEQs (DL-PCBs) g(-1), in the case of feedstuffs, was 0.11%. Both instrumental methods have similar and comparable linearity, precision and accuracy. The GC-QqQ(MS/MS) sensitivity, lower than that of GC-HRMS, is good enough (iLODs in the down to low pg levels) to detect the normal concentrations of these compounds in food and environmental samples. These results make GC-QqQ(MS/MS) suitable for the quantitative analysis of dioxins and DL-PCBs and a real alternative tool to the reference sector HRMS instruments.

Nontargeted comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry method and software for inventorying persistent and bioaccumulative contaminants in marine environments

Analytical methods for contaminant monitoring are generally targeted; i.e., they measure defined lists of compounds. Routine monitoring projects using targeted methods are not usually designed to screen for unrecognized or novel contaminants and therefore miss compounds within the region or population of study that cause, or have the potential to cause, adverse biological impacts. We describe a nontargeted analytical method utilizing direct sample introduction coupled to comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry. To test the capabilities of this instrumental method within the context of marine contaminant surveys, we characterized a broad array of nonpolar, persistent, and bioaccumulative contaminants in Atlantic common dolphin ( Delphinus delphis ) blubber, including compounds that are not typically monitored. Compound identifications were made by searching a standard reference database, by contemporaneously analyzing mass spectra from reference standards, and by de novo interpretation. We identified a total of 271 compounds belonging to 24 classes; all compounds but 1 were halogenated. Anthropogenic contaminants and halogenated natural products were concurrently detected. A total of 86 compounds were anthropogenic contaminants that are not routinely targeted in environmental surveys, and 54 compounds were halogenated natural products. A total of 112 spectra were identified de novo, demonstrating that exclusive reliance on commercially available reference standards and mass spectral libraries may miss a significant fraction of identifiable compounds. We also cataloged 27 halogenated mass spectra that were not able to be identified. Due to the volume and complexity of the identification data, we developed custom software to organize and provide shared access to the identified mass spectra and related information. The nontargeted analytical method and data reporting system, in combination with the analysis of a high-trophic-level sentinel species, demonstrates a framework for creating an inventory of persistent and bioaccumulative contaminants in marine environments, with the future goal of suggesting new compounds for further investigation by targeted monitoring and risk assessment.

Investigation of the binding of dioxin selective pentapeptides to a polyaniline matrix

Polyaniline in form of emeraldine salt and emeraldine base was used as a matrix to attach several labeled and non-labeled dioxin selective pentapeptides both directly to the polymer and using glutaraldehyde as a linker. The peptides have been selected as a model to study the binding process due to their smaller size, lower sensitivity to the environment and potential application as solid state extraction reagents for chlorinated toxins. The composition and the properties of the compounds were investigated by means of elemental analysis, XPS, FTIR, UV/vis, and fluorescence spectroscopy. The results have shown that 3.30-7.76% peptides were attached to the emeraldine base both with and without a linker. Glutaraldehyde and the peptides were connected to the matrix via chemical bond resulting in formation of compounds whit similar composition and stability in a broad pH range. The influence of the linker and the peptides on the electronic properties and composition of the polymer have been investigated by principal component analysis.

Halogenated persistent organic pollutants and polycyclic aromatic hydrocarbons in food

During recent years, mass spectrometry (MS) and hyphenated chromatographic instrumentation and techniques have been a subject of dramatic developments, resulting in the introduction of various useful tools for the analysis of halogenated persistent organic pollutants (POPs) and polycyclic aromatic hydrocarbons (PAHs) in food and environmental matrices. This chapter describes state-of-the-art in the field of MS as a primary detection tool for the halogenated POPs and PAHs previously separated using either gas chromatography (GC) or liquid chromatography (LC). Since sample preparation practice plays a crucial role for obtaining optimal performance characteristics of a particular analytical method, a brief overview of sample extraction and clean-up procedures in the POPs/PAHs analysis is also briefly outlined.

Predicting PCDD/F and dioxin-like PCB contamination levels in bovine edible tissues from in vivo sampling

European Union regulation has defined maximum levels for polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans (PCDD/F) and dioxin-like polychlorinated biphenyls (PCB) in food from animal origin. In case of particular event where livestock is potentially exposed to a specific source of contamination, the possibility of accurate estimation of the PCDD/F and dioxin-like PCB levels in edible tissues of the animals from in vivo and weakly invasive biological matrices (fast animal recovery, no major side effects) may be of clear valuable interest. This study investigated the correlations between contamination levels determined in subcutaneous adipose tissue and blood samples obtained from living animals and those measured after slaughtering in muscle and liver. The obtained results demonstrated very good correlations between these in vivo and ex vivo samples in terms of PCDD/F and PCB contamination levels. Finally, it seems to be demonstrated that a weakly invasive biopsy of subcutaneous adipose tissue performed on living animal (potentially completed by a blood sample) can be used in order to predict contamination levels in muscle and liver destined to human consumption.

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.

Prediction of the PCDD/F and dl-PCB 2005-WHO-TEQ content based on the contribution of six congeners: toward a new screening approach for fish samples?

Current European Union regulation regarding polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (dl-PCBs) in food and feed is based on Toxic Equivalent Quotient (TEQ) concept. For confirmatory purpose, the isotope-dilution method associated to a measurement by gas chromatography coupled with high resolution mass spectrometry is usually the method of choice for precisely measuring the 29 target congeners in three separated fractions. Time and cost related to these analyses are very significant. Various kinds of screening concepts can be considered. In the present study, we elaborated and validated a prediction model for the 2005 World Health Organization TEQ in fish, based on the measurement of 4 PCDD/F and 2 non-ortho dl-PCB congeners, potentially analyzable in a single extracted fraction by gas chromatography coupled with mass spectrometry. Large independent datasets have been used for model elaboration (n=108) and validation (n=363, n=357 and n=6).