Important developments in methods and techniques for the determination of dioxins and PCBs in foodstuffs and human tissues

Immunofluorescence detection and localization of B[a]P and TCDD in earthworm tissues

An immunohistochemical method using antibodies against polycyclic aromatic hydrocarbons (PAHs) and dioxins was developed on frozen tissue sections of the earthworm Eisenia andrei exposed to environmentally relevant concentrations of benzo[a]pyrene (B[a]P) (0.1, 10, 50 ppm) and 2,3,7,8-tetrachloro-dibenzo-para-dioxin (TCDD) (0.01, 0.1, 2 ppb) in spiked standard soils. The concentrations of B[a]P and TCDD in E. andrei exposed to the same conditions were also measured using analytical chemical procedures. The results demonstrated that tissues of worms exposed to even minimal amount of B[a]P and TCDD reacted positively and specifically to anti-PAHs and -dioxins antibody. Immunofluorescence revealed a much more intense staining for the gut compared to the body wall; moreover, positively immunoreactive amoeboid coelomocytes were also observed, i.e. cells in which we have previously demonstrated the occurrence of genotoxic damage. The double immunolabelling with antibodies against B[a]P/TCDD and the lysosomal enzyme cathepsin D demonstrated the lysosomal accumulation of the organic xenobiotic compounds, in particular in the cells of the chloragogenous tissue as well as in coelomocytes, involved into detoxification and protection of animals against toxic chemicals. The method described is timesaving, not expensive and easily applicable.

Considerations for potency equivalent calculations in the Ah receptor-based CALUX bioassay: normalization of superinduction results for improved sample potency estimation

The chemically activated luciferase expression (CALUX) system is a mechanistically based recombinant luciferase reporter gene cell bioassay used in combination with chemical extraction and clean-up methods for the detection and relative quantitation of 2,3,7,8-tetrachlorodibenzo-p-dioxin and related dioxin-like halogenated aromatic hydrocarbons in a wide variety of sample matrices. While sample extracts containing complex mixtures of chemicals can produce a variety of distinct concentration-dependent luciferase induction responses in CALUX cells, these effects are produced through a common mechanism of action (i.e. the Ah receptor (AhR)) allowing normalization of results and sample potency determination. Here we describe the diversity in CALUX response to PCDD/Fs from sediment and soil extracts and not only report the occurrence of superinduction of the CALUX bioassay, but we describe a mechanistically based approach for normalization of superinduction data that results in a more accurate estimation of the relative potency of such sample extracts.

Dietary intake of PCDD/Fs and dioxin-like PCBs of the Belgian population

The World Health Organization recommends assessing human exposure to contaminants on a regular basis. In order to assess the current dietary exposure of the Belgian adult population to PCDD/Fs and dioxin-like PCBs and to update exposure estimates of 2000-2001, a total diet study was designed. The mean dietary intake of PCDD/Fs and dioxin-like PCBs in the Belgian adult population in 2008 was estimated to be 0.72pgTEQkgbw(-1)d(-1) (middle bound concentrations, TEF of 1998) based on occurrence data of 2008 and national food consumption data of 2004. This value is clearly below the Tolerable Weekly Intake (TWI) of 14pgTEQkgbw(-1)week(-1) set by the Scientific Committee on Food of the European Commission and below the provisional tolerable monthly intake of 70pgTEQkgbw(-1)month(-1) set by the Joint FAO/WHO Expert Committee on Food Additives. Considering the cumulative distribution, the intake was less than 1pgTEQkgbw(-1)d(-1) for more than 80% of the population, and less than 2pgTEQkgbw(-1)d(-1) for the entire population. When using the 2005 TEF instead of the 1998 TEF, the mean dietary intake in the Belgian adult population was estimated to be 0.61pgTEQkgbw(-1)d(-1).

Comparison of levels of polychlorinated biphenyls in edible oils and oil-based products--possible link to environmental factors

Food consumption has been widely reported to be the main source of human exposure to PCBs. A total of 47 samples of food products on sale in supermarkets in the United Kingdom were thus analyzed for PCBs to determine residual levels in oil and oil-based products. The objective was to compare the measured levels of total PCBs (Sigma PCBs) in food products to those reported in various environmental compartments. Combined extraction and online clean up was achieved using Accelerated Solvent Extraction (ASE) to recover target analytes for analysis by GC-MSD (gas chromatography mass spectrometry). Sigma PCBs (ng/g) in each product were in the ranges of 4.73-44.38 edible oil; 1.40-6.18 mayonnaise; 1.21-6.25 salad cream; 1.28-5.64 seafood sauce, and 0.97-15.08 exotic dressing. The level of human exposure to PCBs in all products was < 1 microg/kg body weight/day when considering a 70 kg male or 57 kg female, possibly reflecting the reported decline of PCBs in the environment.

Evaluation of GC-ion trap-MS/MS methodology for monitoring PCDD/Fs in infant formulas

The application of high resolution gas chromatography in combination with low resolution mass spectrometry with electron ionization and MS/MS detection (HRGC-MS/MS) is tested for its use in the analysis of PCDD/Fs in infant formulas. Development of the analytical method was based upon EPA directrices and international recommendations. Calibration linearity was tested and average relative response for any native and labelled compound over the five-point calibration range below 14% was found. The precision and accuracy of the proposed analytical procedure are also presented. Results obtained are in agreement with EPA criteria. The method is applied to the analysis of a number of initial and follow-on milk based infant formulas. In general, HRGC-MS/MS constitutes an interesting method for the analysis of dioxins in such matrices.

Comprehensive two-dimensional gas chromatography (GC×GC) in environmental analysis and monitoring

Compared to conventional one-dimensional gas chromatography (1D-GC), comprehensive two-dimensional gas chromatography (GC x GC) offers increased peak capacity, improved resolution and enhanced mass sensitivity. In addition, it generates structured two-dimensional (2-D) chromatograms, which aids in the identification of compound classes. Sample preparation procedures can often be minimized, or even eliminated in some cases, due to the superior separating power offered by the technique. All of these advantages make GC x GC a very powerful tool in environmental analysis involving the determination of trace levels of toxic compounds in complex matrices. This review paper summarizes and examines the historical and recent GC x GC applications in environmental analysis and monitoring.

Comprehensive two-dimensional gas chromatography with isotope dilution time-of-flight mass spectrometry for the measurement of dioxins and polychlorinated biphenyls in foodstuffs

A comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (GC x GC-TOF-MS) experimental setup was tested for the measurement of seven 2,3,7,8-substituted polychlorinated dibenzo-p-dioxins (PCDDs), ten 2,3,7,8-substituted polychlorinated dibenzofurans (PCDFs), four non-ortho-polychlorinated biphenyls (PCBs), eight mono-ortho-PCBs, and six indicator PCBs (Aroclor 1260) in foodstuff samples. A 40m RTX-500 (0.18mm I.D., 0.10 microm df) was used as the first dimension (1D) and a 1.5 m BPX-50 (0.10mm I.D., 0.10 microm df) as the second dimension (2D). The GC x GC chromatographic separation was completed in 45 min. Quantification was performed using 13C-label isotope dilution (ID). Isotope ratios of the selected quantification ions were checked against theoretical values prior to peak assignment and quantification. The dynamic working range spanned three orders of magnitude. The lowest detectable amount of 2,3,7,8-TCDD was 0.2 pg. Fish, pork, and milk samples were considered. On a congener basis, the GC x GC-ID-TOF-MS method was compared to the reference GC-ID high resolution mass spectrometry (HRMS) method and to the alternative GC-ID tandem-in-time quadrupole ion storage mass spectrometry (QIST-MS/MS). PCB levels ranged from low picogram (pg) to low nanogram (ng) per gram of sample and data compared very well between the different methods. For all matrices, PCDD/Fs were at a low pg level (0.05-3 pg) on a fresh weight basis. Although congener profiles were accurately described, RSDs of GC x GC-ID-TOF-MS and GC-QIST-MS/MS were much higher than for GC-ID-HRMS, especially for low level pork and milk. On a toxic equivalent (TEQ) basis, all methods, including the dioxin-responsive chemically activated luciferase gene expression (DR-CALUX) assay, produced similar responses. A cost comparison is also presented.

Recent advances in mass spectrometric measurement of dioxins

Past years, many efforts have been dedicated to the development of alternative analytical methods for the measurement of dioxins in various types of matrices. Polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and polychlorinated biphenyls (PCBs) are compounds that are present in samples at part-per-billion (ppb) or part-per-trillion (ppt) level. Their measurement requires the use of very sensitive analytical methods. Gas chromatography (GC) coupled to quadrupole ion storage mass spectrometry (QISTMS), fast GC (FGC) coupled to time-of-flight mass spectrometry (TOFMS) and comprehensive two-dimensional gas chromatography (GC x GC) coupled to TOFMS are the more promising tools challenging the reference GC high resolution mass spectrometry (HRMS) based on sector instruments. We report herein some of the advances we achieved in the past years in our laboratory on the development of alternative measurement methods for those compounds.

Analysis of polychlorodibenzo-p-dioxins and dibenzofurans (PCDDs/PCDFs) in baked-salt food additives in Korea

Thirty-one samples of baked-salt products used in commercial food additives were analyzed for the presence of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs). Dioxins were highly detected in 12 samples of baked salts. The amount of dioxins found in the samples ranged from 12.47 pg/g to 406.56 pg/g (0.71 pg TEQ/g to 23.51 pg TEQ/g, respectively). The most abundant congeners, as TEQ values, were 2,3,4,7,8-PeCDF; 1,2,3,7,8-PeCDF; and 1,2,3,4,7,8-HxCDF in PCDF congeners and 1,2,3,7,8-PeCDD; 1,2,3,6,7,8-HxCDD; and 1,2,3,7,8,9-HxCDD in PCDD congeners. Meanwhile, PCDDs/PCDFs were analyzed in high-temperature-treated samples of natural sea salt alone and natural sea salt to which di-(2-ethylhexyl)phthalate (DEHP) had been added. In the former case, PCDD/PCDF formation was most evident at temperatures near 450 degrees C, the total amount of dioxins was 90.07 pg/g (6.07 pg TEQ/g), and PCDD congeners comprised less than 50% of the total PCDDs/PCDFs. However, when the latter samples were heated, the total PCDD/PCDF concentration was 512.30 pg/g (21.53 pg TEQ/g), with PCDD congeners comprising over 87% of the total PCDDs/PCDFs.

Determination of dioxin and dioxin-like compounds in sediments from UK estuaries using a bio-analytical approach: chemical-activated luciferase expression (CALUX) assay

The DR-CALUX assay has been utilised for the bio-analytical screening of a number of estuarine sediments for dioxin-like activity. Total sediment extracts (samples containing all extracted compounds) and cleaned-up extracts (samples with the most stable compounds isolated from the total extracts) were screened. The concentration of the stable dioxin-like compounds in the cleaned-up sediment extracts was between 1.0 and 106 pgTEQCALUX g(-1) dry weight. The majority of sediments contained levels of dioxin-like compounds that were above concentrations that are considered to be a low risk to aquatic organisms. The CALUX bio-analytical approach showed some disparity with the traditional analytical approach. The reasons for these differences have been identified tentatively: firstly, the DR-CALUX assay responds to all dioxin-like compounds, and secondly, it measures non-additive effects. The dioxin-like activity of compounds in sediment total extracts, which contain both labile and stable compounds, were also assessed and were six orders of magnitude higher than the cleaned-up samples. This suggests the vast majority of the total dioxin-like activity is attributable to labile compounds. Overall, the DR-CALUX assay is shown to be a useful tool in the assessment of dioxin-like activity in estuarine sediments.

Accelerated solvent extraction and confirmatory analysis of sulfonamide residues in raw meat and infant foods by liquid chromatography electrospray tandem mass spectrometry

This paper describes a new method for the rapid extraction and unequivocal confirmation of 13 sulfonamides (SAs) in raw meat and infant foods. The highly automated extraction procedure is based on accelerated solvent extraction followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) as a confirmatory analysis. After 1 g of food matrix was blended with 2 g of C18 as a solid support material, the mixture was packed into the extraction cell and the SAs were extracted with 10 mL of hot water at 160 degrees C and 100 atm; 100 microL of the extract was directly injected into the LC-MS system. The analytes were ionized in an electrospray interface operating in the positive ion mode and were identified by selecting two multireaction monitoring transitions, which guaranteed method specificity. Typical recoveries from crude meat and baby food samples ranged from 70 to 101% at a fortification level of 100 ppb, corresponding to the maximum residue limits established by the European Union and the U.S. Food and Drug Administration. The interday method precision was less than 8.5%, and the limits of detection were below 2.6 ppb. This study has taken matrix-induced suppression of ionization into account, by comparing standard and matrix-matched calibration curves. Four of the 13 monitored SAs have been detected in some baby foods and raw meat samples, bought from Roman supermarkets and butchers' shops, using the described methodology.

Miniaturised sample preparation of fatty foodstuffs for the determination of polychlorinated biphenyls

A miniaturised analytical method allowing the exhaustive extraction of environmentally relevant polychlorinated biphenyls (PCBs) from fatty foodstuffs and the purification of the extracts in a single step has been developed. After dispersion of the freeze dried sample on silica modified with 44% (w/w) of sulphuric acid, the mixture was packed in a glass column on top of a multilayer silica column used for removal of the lipids and biogenic co-extracted material. Using this arrangement, a complete sample preparation can be accomplished by two successive 10 min static extractions with hexane followed by a brief dynamic step to ensure purging of the sample and sorbents. The analytical method showed a satisfactory performance, with recoveries of the endogenous PCBs studied in the 81-134% range of those found using a more conventional off-line procedure, even though as small an amount of sample as 0.1 g was used. Detection limits by gas chromatography with micro-electron capture detection (GC-ECD) were in all cases lower than 0.3 ng/g sample (freeze dried basis) and the repeatability of the complete analytical procedure better than 14% (except for PCB 167). When combined with GC and ion trap detection in the tandem mass spectrometry mode, the miniaturised method has been proved to be a valuable alternative to the more expensive high resolution mass spectrometry for fast screening of PCBs 77, 126, and 169, even if these congeners were not isolated from the bulk of PCBs.

A review of environmental toxicant analysis by using multidimensional gas chromatography and comprehensive GC

The purpose of this review is to highlight the developments in coupled-column gas chromatography methods for qualitative analysis of selected environmental toxicants such as dioxin, polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), etc. In particular, the new technique of GC x GC will be introduced, and its role, and the promise it offers to this field is discussed. The benefits of enhanced separation to quantitative analysis will be considered. In order to perform an accurate risk assessment, both the dose and biological effects of environmental toxicants have to be determined with a high degree of certainty. This is most often achieved by using chromatographic methods. Given the complexity of most environmental sample extracts, single-column gas chromatography is unable to fully resolve all the components of interest frequently leading to a positive bias in the reported concentrations. Advanced separation tools, such as multidimensional gas chromatography (MDGC), were investigated quite early and demonstrated improvements in separation. However, limitations in the number of target analytes that could be analyzed in a single run as well as insufficient robustness lead to a continued interest in alternative solutions. The parallel development of mass spectrometric identification and quantification strategies proved useful in many cases, although it frequently failed to provide positive identification of chromatographically unresolved isomeric compounds. More recently, comprehensive two-dimensional gas chromatography (GC x GC) may offer a solution to that problem, especially because it offers enhanced resolution for complex mixtures containing trace level environmental toxicants.

Recent applications of sample preparation techniques in food analysis

Even with the emergence of advanced techniques of separation and identification, it is rarely possible to analyse food without manipulation. The traditional techniques for sample preparation are time consuming and require large amount of reagents, which are expensive, generate considerable waste, contaminate the sample and can enrich it for analytes. The more analytical techniques have become highly developed, the more has sample clean-up become important in order to fully take advantage of them. Due to the multiplicity of food matrices, it is not possible to use one sample preparation technique, so many methods have been proposed for meeting all the requirements. The newest variations of wet digestion, solvent and sorbent extraction and membrane separation are summarised and their most recent applications to food analysis are provided.

Determination of polychlorinated biphenyl congeners in human milk by gas chromatography-negative chemical ionization mass spectrometry after sample clean-up by solid-phase extraction

This paper describes a simple and efficient procedure for measuring 25 congeners of polychlorinated biphenyls in human milk. The limit of quantitation was 0.1 ng/ml for five less chlorinated congeners (PCB 70, 74, 87, 99,101), and 0.01 ng/ml for the remaining 20 congeners (PCB 77, 105, 118, 126, 128, 138, 151, 153, 156, 169, 170, 180, 183, 187, 191, 194, 205, 206, 208 and 209). Solid phase extraction technology was applied to extract the analytes from the matrix and to remove lipids. Three columns were used sequentially, and they were a Bond Elut C(18), a Sep-Pak Plus NH2 and a Bond Elut PCB cartridge. The instrumental method was gas chromatography-mass spectrometry with negative chemical ionization, and selected ion monitoring mode was used.

Fast automated extraction and clean-up of biological fluids for polychlorinated dibenzo-p-dioxins, dibenzofurans and coplanar polychlorinated biphenyls analysis

A fast automated extraction and clean-up procedure for low-level analysis of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and coplanar polychlorinated biphenyls (cPCBs) in biological fluids is presented. Online extraction of prepared fluids is carried out using disposable octadecyl bonded (C(18)) solid-phase extraction columns. Extracts are then cleaned up through disposable multi-layer silica (acidic, basic and neutral) and dispersed PX-21 carbon columns. This new methodology is compared with classical Soxhlet extraction and manual solid-phase extraction in terms of repeatability, reproducibility, accuracy and recovery rates for reference and certified materials. Robustness is evaluated on different matrices, such as cow's milk, breast milk and human serum. As a consequence of the reduced number of reusable glassware used, as well as lowering of solvent consumption, recorded blank levels are decreased in favor of limits of detection (LODs). Total analysis time and cost are further reduced using simultaneous sample preparation units and the sample throughput is increased compared to classical methods. As a result, this new approach appears to be suitable for the fast sample preparation often required for such fluids in case of emergency foodstuffs analysis or during large epidemiological studies.

Study of an accelerated solvent extraction procedure for the determination of acaricide residues in honey by high-performance liquid chromatography-diode array detector

An accelerated solvent extraction (ASE) procedure has been optimized for the determination of synthetic acaricides (amitraz, bromopropylate, cymiazole, coumaphos, T-fluvalinate, and flumethrin) and their residues in honey by reversed-phase high-performance liquid chromatography. The effects of experimental variables such as solvent composition, temperature, static extraction time, and solvent flush volume on the ASE efficiency have been studied. The acaricides were extracted by hexane-propanol (1/3, vol/vol) at 95 degrees C and 2.000 psi for 8 min. Recovery values of between 53 and 108% were achieved with the different substances, with coefficients of variation between 2 and 13% and limits of detection from 0.01 to 0.2 microg/g.

Combinatorial bio/chemical analysis of dioxin and dioxin-like compounds in waste recycling, feed/food, humans/wildlife and the environment

The present review describes international activities using bioassays/biomarkers in combination with chemical analysis to measure the effects of dioxin and dioxin-like compounds (DLCs) in the environment. The above authors reviewed already the state-of-art bioanalytical detection methods (BDMs) for dioxins and DLCs [Environ Int (2001)]. The aim of this study will be to review applications of these bioassays/biomarkers to evaluate potential dioxins and DLCs. The present literature study lists relative potencies (REPs) of polyhalogenated dibenzo-p-dioxins and -furans (PXDD/Fs; X = Cl, Br, F), their thio analogues polychlorinated dibenzothiophenes (PCDTs) and thianthrens (PCTAs), polyhalogenated biphenyls (PXBs), polychlorinated naphthalenes (PCNs) and other Ah receptor agonists measured by several biodetectors (Tier 3 screening). The authors will discuss some examples of the applications of some of these biodetectors in biomonitoring programmes and recently occurred dioxin crisis in feed/food. The diagnosis of the biopotency of these pollutants in technical processes like thermally treated waste, waste water treatment, landfill leachate treatment, commercial PCB-mixtures, the release into the environment (soil, air and water) and the final intake into wildlife and humans will be reviewed.

Bioanalytical screening methods for dioxins and dioxin-like compounds a review of bioassay/biomarker technology

Determination of environmental pollutants utilizing biodetectors such as bioassays, biomarkers, enzyme immunoassays (EIAs), or other bioanalytical tools is a continuously growing area. The present literature review describes the principles and advantages/limitations of several bioanalytical detection methods (BDMs) for the screening and diagnosis of dioxin and dioxin-like compounds. This study characterizes briefly the family of dioxin and dioxin-like compounds, discusses potential Ah receptor (AhR) ligands and cytochrome P-450 (CYP) 1A1-enzyme-inducing compounds. 'Milestones' in the development of BDMs are summarized and explained in detail for a number of bioanalytical tools that can be used to detect these classes of dioxin-like persistent bioaccumulative toxicants (PBTs). The design of a screening profile with a battery of bioassays/biomarkers coupled with the chemical analysis is evaluated. The relative potencies (REPs) to 2,3,7,8-TCDD for dioxin-like compounds are reviewed for various BDMs and the differences are noted.