Importance of REP values when comparing the CALUX bioassay results with chemoanalyses results Example with spiked vegetable oils

Differences between chemical activated luciferase gene expression (CALUX) bioassay and chemoanalyses results are observed.This paper shows that calculations of the TEQ values using REP values instead of WHO TEF values give different results. The REP values do affect the results obtained by the CALUX technique. These differences are more marked for the dioxin like PCB compounds (CALUX TEQ values are lower than WHO TEQ values) than for the dioxin compounds (CALUX TEQ values are higher than WHO TEQ values).The CALUX results were compared with the concentrations of the congeners’ spiked into the oil.     

Validation of the CALUX bioassay for PCDD/F analyses in human blood plasma and comparison with GC-HRMS

Following the dioxin crisis of 1999, several studies were conducted to assess the impact of this crisis on the dioxin body burden in the Belgian population. The Scientific Institute of Public Health identified a population from whom plasma samples were available and from whom, during the follow up survey, plasma samples were obtained in 2000. In total, 496 samples were collected for GC-HRMS and CALUX analyses to verify statistical assessment conclusions. This study was seen as an opportunity to validate the CALUX bioassay for biological sample analysis and to compare toxic equivalency (TEQ) values obtained by the reference GC-HRMS technique and by the screening method. This article focuses on the validation results of the CALUX bioassay for the analyses of the dioxin fractions of blood plasma. The sample preparation is based on a liquid–liquid extraction, followed by an acid silica in series with an activated carbon clean-up. A good recovery (82%) and reproducibility (coefficient of variation less than 25%) were found for this method. Based on 341 plasma samples, a significant correlation was established between the bioassay and chemical method (R = 0.64). However, a proportional systematic error was observed when the results obtained with the CALUX bioassay were regressed with the results from the GC-HRMS analyses. The limit of quantification (LOQ) used to calculate TEQ values from the GC-HRMS determinations, the use of the relative potency values instead of the toxic equivalent factor and the potential of CALUX bioassay to measure all compounds with affinity for the AhR may partly explain this proportional systematic error. Nevertheless, the present results suggest that the CALUX bioassay could be a promising valid screening method for human blood plasma analyses.     

Study of the interference problems of dioxin-like chemicals with the bio-analytical method CALUX

The reporter gene expression method CALUX has proven to be a very valuable screening technique for assessing toxic equivalents of dioxins and dioxin-like compounds, because it detects all AhR ligands in a variety of sample matrices. However, the exact meaning of the CALUX response is difficult to evaluate for complex mixtures mainly since not all AhR ligands are known and since antagonistic or synergistic effects occurs.

In this paper, non-additive effects on the CALUX response of dioxins were investigated for a limited number of dioxin-like compounds in concentration ranges that are 10²–10⁸ times higher than that of 2,3,7,8-TCDD. Antagonistic effects are detected for three Aroclors (1242, 1254, 1260), Halowax 1014 (PCN), HCB and PBB 169. The ratios, Aroclor/dioxin, Halowax/dioxin and HCB/dioxin, needed to observe an antagonistic effect are 10 000, 5000 and 50 000, respectively. No significant deviation from additivity was observed for Aroclor 5442 (PCT) and PBB 77 in the concentration range investigated.

Two clean-up procedures have also been tested: in some cases the non-additive effects disappeared or were strongly reduced. Using only an acidic silica column, the classical dioxin-like compounds investigated here (PCB, PCT, PBB, PCN, HCB) as well as the dioxins are collected and analyzed altogether in one fraction. Consequently, no major alteration of the non-additive effects is expected. An acidic silica column combined with an activated carbon column allows the separation of PCDD/F and dioxin-like PCB in two different fractions, PBB 169 is completely eluted in the dioxin fraction and PBB 77 is distributed between the PCB and dioxin fraction. HCB is completely separated from the PCDD/F fraction.     

Importance of clean-up for comparison of TEQ-values obtained by CALUX and chemo-analysis

This paper presents Chemically Activated LUciferine gene eXpression (CALUX) TEQ-values obtained for nine plasma samples following two different purification procedures, one of them involving fractionation. CALUX results obtained for the dioxin (DX) and dioxin + PCB (DX + PCB) fractions were then compared to the GC-HRMS TEQ-values calculated for the 17 polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (17 PCDD/F) and 17 PCDD/F + 4 cPCB congeners, respectively. The overestimation of the CALUX (DX fraction) TEQ-values in comparison with the chemo-analyses of the 17 PCDD/F is mainly explained by the presence of other AhR agonists, like brominated compounds. Otherwise, the constancy of the CALUX (DX + PCB fraction) TEQ-value which compares to increasing the GC-HRMS (17 PCDD/F + 4 cPCB) TEQ results raises questions concerning (1) the significance of CALUX results obtained without fractionation as well as (2) the toxicological effect of a cocktail of contaminants on the human health.     

Interpretation of CALUX results in view of the EU maximal TEQ level in milk

Analyses of dioxins in food have become increasingly important since the European Commission has enforced maximal toxic equivalent concentration (TEQ) levels in various food and feed products. Screening methodologies are usually used to exempt those samples that are below the maximum permitted limit and that can, therefore, be released to the market. In addition, one needs to select those samples that require confirmation of their dioxin TEQ level. When bioassays are used as screening tools, the interpretation of the obtained results should consider the higher variability and uncertainty associated with them. This paper explores the use of CALUX data as quantitative screening results. The validation of the method for the polychlorinated dibenzo-p-dioxins (PCDD)/F TEQ determination in milk samples is described with emphasis on the decision limit (CC) and the precision of the method. The decision limit amounts to 4.53 pg TEQ/g fat. Repeatability and within-lab reproducibility coefficients of variation are below 30%. The newly introduced parameter CC^* of 1.47 pg TEQ/g fat delimits with CC a range of suspicious results. These data are not significantly different from the maximum limit of 3 pg TEQ/g fat and should be confirmed by a confirmatory analytical method such as HRGC–HRMS.     

The international validation of bio- and chemical-analytical screening methods for dioxins and dioxin-like PCBs: the DIFFERENCE project rounds 1 and 2

The European research project DIFFERENCE is focussed on the development, optimisation and validation of screening methods for dioxin analysis, including bio-analytical and chemical techniques (CALUX, GC-LRMS/MS, GC×GC-ECD) and on the optimisation and validation of new extraction and clean-up procedures. The performance of these techniques is assessed in an international validation study and the results are compared with the reference technique GC-HRMS. This study is set up in three rounds and is in accordance with the International Harmonized Protocol for Proficiency Studies and the ISO 5725 standard. The results of the first two rounds are very promising in particular for GC-LRMS/MS. The results obtained with this technique were as accurate as the results reported by the labs using the GC-HRMS. The initial results reported for GC×GC-ECD overestimate the dioxin concentration in the samples. The results reported by the labs using the CALUX technique underestimate the total TEQ concentrations in the samples, compared to the GC-HRMS reference method. The repeatability of the CALUX is significantly higher than the other screening techniques. It was shown that accelerated solvent extraction (ASE) is a valid alternative extraction and clean-up procedure for fish oil and vegetable oil. The results obtained with CALUX and GC-HRMS after ASE are equivalent to the results obtained with the classical extraction and purification procedures.     

DR-CALUX((R)) screening of food samples: evaluation of the quantitative approach to measure dioxin, furans and dioxin-like PCBs

European legislation laid down maximum tolerable levels of dioxin in feed and food as well as analytical method requirements. In order to face with large monitoring programs, it was foreseen in the EU strategy to integrate screening methods, using either a qualitative (screening) approach, or a quantitative approach. In this study, dioxin results obtained using the Dioxin Responsive Chemical-Activated LUciferase gene eXpression (DR-CALUX^®) cell-based assay (quantitative approach), were compared with gas chromatography–high resolution mass spectrometry (GC–HRMS) analyses data. Instead of using World Health Organization–toxic equivalent factor (WHO–TEF), the comparison was based on the assessment of relative effective potencies (REPs) for each congener of the 17 toxic 2,3,7,8-polychlorodibenzo-p-dioxins/furans (PCDD/Fs) and 12 dioxin-like polychlorobiphenyls (DL-PCBs). According to published data, DR-CALUX^®-REP evaluated here appear similar to WHO–TEF for PCDD/Fs while lower values were observed for DL-PCBs.

We analyzed two “home made” contaminated fat samples, displaying both the same WHO–toxic equivalent quantities (WHO–TEQ) concentration (12 pg WHO–TEQ g⁻¹). They were spiked with either a low or a high amount of DL-PCBs. In both cases, the DR-CALUX^® measured concentration (picogram 2,3,7,8 tetrachlorodibenzo-p-dioxin (TCDD) eq. g⁻¹) corresponded to the PCDD/Fs WHO–TEQ concentration only. A good agreement was nevertheless found between the DR-CALUX^® measurements and the recalculated DR-CALUX^®-TEQ contents (using DR-CALUX^®-REP instead of WHO–TEF), demonstrating that the observed response was due, in both cases, to the addition of the responses of the standards added to the fat. By contrast, in real contaminated samples (feed or cod liver samples), DR-CALUX^® measured concentrations were similar to WHO–TEQ GC–HRMS measured concentrations. But, depending on the PCDD/Fs and DL-PCBs congener content, the DR-CALUX^® measured concentrations were either lower or higher than calculated DR-CALUX^®-TEQ contents, demonstrating that possible co-extracted contaminants contributed to the CALUX response.

Owing to these divergences, the quantitative determination of dioxin-like content in food and feed using CALUX as screening method is questionable, except for samples displaying constant congener patterns, in which cases, correction factors could be applied.     

Characterization of AhR agonist compounds in roadside snow

Aryl hydrocarbon receptor (AhR) agonistic contaminants were identified in roadside snow samples. Snow was collected in Oslo, Norway, and compared to a background sample collected from a mountain area. The water and particulate fractions were analysed for AhR agonists using a dioxin-responsive, chemically activated luciferase expression (CALUX) cell assay and by gas chromatography coupled to high-resolution time-of-flight mass spectrometry with targeted analysis for polycyclic aromatic hydrocarbons (PAHs) and broad-spectrum non-target analysis. The AhR agonist levels in the dissolved fractions in the roadside samples were between 15 and 387 pg/L CALUX toxic equivalents (TEQ(CALUX)). An elevated AhR activity of 221 pg TEQ(CALUX) per litre was detected in the mountain sample. In the particle-bound fractions, the TEQ(CALUX) was between 1,350 and 7,390 pg/L. One possible explanation for the elevated levels in the dissolved fraction of the mountain sample could be the presence of black carbon in the roadside samples, potentially adsorbing dioxin-like compounds and rendering them unavailable for AhR interaction. No polychlorinated dibenzodioxins and dibenzofurans or polychlorinated biphenyls were detected in the samples; the occurrence of PAHs, however, explained up to 9 % of the AhR agonist activity in the samples, whilst comprehensive two-dimensional gas chromatography coupled to mass spectrometry GCxGC-ToF-Ms identified PAH derivatives such as polycyclic aromatic ketones and alkylated, nitrogen sulphur and oxygen PAHs in the particle fractions. The (large) discrepancy between the total and explained activity highlights the fact that there are other as yet unidentified AhR agonists present in the environment.     

TEQ-value determinations of animal feed; emphasis on the CALUX bioassay validation

Polyhalogenated aromatic hydrocarbons, such as polychlorinated dibenzo-p-dioxins are a large and diverse group of environmental pollutants. Their tendency to accumulate in the food chain and their toxicity make monitoring necessary. The reference analysis method is laborious and very expensive, therefore cheap and rapid bioassays have been developed. The chemical-activated luciferase bioassay (CALUX) bioassay uses a recombinant cell line, which responds to dioxins and dioxin-like molecules with Ah receptor (AhR)-dependent induction of firefly luciferase in a dose related response. The CALUX was tested for its use in the screening of feed. Aliquots of 20 g of enriched feed were extracted with a toluene:methanol mixture (20:4 v/v) and extracts were defatted on 33% H₂SO₄ silica columns and purified on carbon columns. Only the dioxin and furan fraction was analysed, the PCB fraction was discarded. The precision of the method is acceptable and in compliance with an R.S.D. <30% as suggested for cell-based bioassays in the Commission Directive 2002/70/EC of July 2002. The results evidence good agreement between TEQ-values obtained by either CALUX or GC–HRMS. The method is now routinely in use for a feed screening programme designed by the Federal Agency for the Safety of the Food chain. Approximately, 25 samples are analysed weekly. From the obtained results approximately 10% was confirmed by GC–HRMS. The false positive ratio is 1% and no false negatives were found, making the use of the CALUX technology advantageous.     

The CALUX bio-assay: analytical comparison between mouse hepatoma cell lines with a low (H1L6.1c3) and high (H1L7.5c1) number of dioxin response elements

Dioxins, furans and polychlorinated biphenyls are contaminants of high concern and as such, sensitive tools are needed to detect these persistent organic compounds in a variety of matrices. Due to the large amount of samples that need to be investigated for example for food and feed control, the CALUX bioassay (H1L6.1 clone) was developed allowing rapid and cost-efficient analysis of biological and environmental samples. Recently, a new and more sensitive clone (H1L7.5) was constructed as the third generation CALUX bioassay. This new cell line was subject of an amplification of dioxin response elements (DREs), allowing lower concentrations of target compound to be analyzed. A comparison is made between the previous, well-defined H1L6.1c3 cell line and the new H1L7.5c1 cell line: it appears that the bioassay making use of the higher number of DREs is more stable and robust, shows better repeatability and reproducibility and is; on average, 3 times more sensitive.     

The German bakery waste incident; use of a combined approach of screening and confirmation for dioxins in feed and food

During the last six years several incidents have occurred with dioxins in feed, stressing the need for rapid screening methods for these compounds. The most recent incident was the contamination of bakery waste used for animal feed due to the use of waste wood for drying of the material. In addition to Germany, the material was also shipped to the Netherlands. Levels up to 12 ng TEQ/kg have been detected, being about 15 times over the current limit of 0.75 ng TEQ/kg. In the Netherlands a combined strategy of screening with the CALUX-bioassay and the HRGC/HRMS confirmatory method was used to rapidly control the incident. Pigs were contaminated by the incident but only to a very limited extent. Despite the rather low limits for pig meat, the CALUX bioassay showed excellent performance, once again confirming the value of this assay.     

Performances and limitations of the HRMS method for dioxins, furans and dioxin-like PCBs analysis in animal feedingstuffs: Part I: Results of an inter-laboratory study

The European strategy for dioxin monitoring of the food chain has defined high-resolution gas chromatography coupled to high-resolution mass spectrometry (HRGC/HRMS) method as the confirmatory method that can provide reliable and comparable results at sub-parts per trillion (ppt) level. This paper describes the first inter-laboratory study on dioxins, furans and dioxin-like PCBs by HRGC/HRMS method in animal feedingstuffs. Two different statistical approaches (ISO 5725 and Cofino’s statistics) were used for the statistical evaluation. For this particular study, the performances of the HRGC/HRMS method seem to be congener-independent in repeatability and reproducibility conditions over a concentration range covering more than four orders of magnitude. Results clearly show the effect of precision loss below 0.1 ppt level per congener in repeatability conditions and below 0.2 ppt level per congener in reproducibility conditions. LODs reported by the laboratories give median values of 0.02 ng/kg for most of the toxic congeners. Relative standard deviation between the laboratories’ mean values using upper-bound approach for TEQ calculation is 6.2%, more than twice the maximum level set at 0.75 ng TEQ/kg of product.     

Immunochemical determination of dioxins in sediment and serum samples

Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) are considered highly toxic contaminants and the environmental and biological monitoring of these compounds is of great concern. Immunoassays may be used as screening methods to satisfy the growing demand for rapid and low cost analysis. In this work, we describe the application of an immunoassay that uses 2,3,7-trichloro-8-methyldibenzo-p-dioxin (TMDD) as a surrogate standard for 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) to sediment and human serum samples. Sample extraction and preparation methods were developed with the aim to establish the simplest, cost-effective and efficient removal of the matrix interferences in the enzyme-linked immunosorbent assay (ELISA). The overall method for sediments is based on a hexane extraction; clean up by a multilayered silica gel column and an activated carbon column; an organic solvent exchange with DMSO–Triton X-100 and ELISA measurement. The gas chromatography–high resolution mass spectrometry (GC–HRMS) validation studies (n = 13) revealed that the method is suitable for the toxic equivalents (TEQ) screening of dioxin in sediments with a method detection limit of about 100 pg g⁻¹ dry sediment with a precision of 13–33% R.S.D. The analysis of a large number of samples originating from different sources would be required to establish more precisely the screening level, as well as the number of false positives and negatives of dioxin TEQ by the immunoassay for sediments. The immunoassay method for sediment analysis offers improvement in speed, sample throughput, and cost in comparison to GC–HRMS. Dioxins were determined in serum samples after a simple liquid–liquid extraction and solvent exchange into DMSO–Triton X-100 without further dilution. The current method (approximate method LOQ of 200 pg ml⁻¹ serum) is not sufficiently sensitive for the determination of dioxins in serum to measure acceptable exposure limit.     

Trace analysis of polychlorinated dibenzo-p-dioxins, dibenzofurans and WHO polychlorinated biphenyls in food using comprehensive two-dimensional gas chromatography with electron-capture detection

Trace analysis of 2,3,7,8-polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and the 12 WHO-PCBs (four non-ortho and eight mono-ortho congeners that have been assigned toxic equivalence factors, TEFs, by the World Health Organisation) was conducted by comprehensive two-dimensional gas chromatography with a micro electron-capture detector (GC x GC-microECD). Four food matrices (fish oil from herring, spiked cows' milk, vegetable oil and an eel extract) were analysed by two GC x GC laboratories, and four GC-HRMS laboratories generated reference values. The two GC x GC laboratories used different column combinations for separating the target analytes. For the first dimension, non-polar DB-XLB and VF-1 columns were used, and for the second dimension, an LC-50 liquid crystalline column with unique selectivity for planar compounds. The congener-specific and total toxic equivalence (TEQ) data obtained using DB-XLB x LC-50 were in good agreement with results obtained by the GC-HRMS laboratories. The WHO-PCB data obtained with the VF-1 x LC-50 combination was also good, but the PCDD/F concentrations were sometimes overestimated due to matrix interferences. GC x GC-microECD using DB-XLB x LC-50 seems to fulfil the European Community requirements of a screening method for PCDD/F and WHO-PCB TEQ in food.     

Characteristics of major dioxin/furan congeners in melted slag of ash from municipal solid waste incinerators

Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in slag of fly ash from three municipal solid waste (MSW) incinerators were analyzed to observe any changes in characteristics and distribution of their congeners by melting process. Actual concentration and Toxic Equivalent (TEQ) concentration profiles of 17 major congeners of PCDDs/PCDFs for gas, fly ash and melted slag were compared. The distributions of PCDDs/PCDFs in different streams macroscopically showed similarities with the generally known profiles for emission gas from a municipal waste incinerator. The total concentrations of PCDDs/PCDFs in off-gas and fly ash have been known to be a function of incineration conditions and of air pollution control device utilization; however, their normalized distributions were independent of such conditions. The concentrations of PCDDs/PCDFs in the melted slag of fly ash were not related to the concentrations of PCDDs/PCDFs congeners in fly ash but were rather a function of the melting furnace type and operation. The total amount of PCDDs/PCDFs in the melted slag of fly ash contained almost 150–27,000 times less dioxin than that in fly ash, however, the TEQ of dioxin in the slag was reduced by 435–43,500 times, which could enable them to be utilized as recycled construction materials. In normalized TEQ concentration profiles of 17 congeners of PCDDs/PCDFs, the ratio of PCDFs to PCDDs changed from 1.32 to 2.19 by melting, which showed relatively higher portion of furans left in melted slag than those in fly ash. By comparing reduction ratios of different congeners, PCDDs (dioxins) were relatively easier to destruct than PCDFs (furans) during melting process. The most difficult congener to destruct could be octa-chlorinated dibenzofuran (OCDF) among major congeners. For slag cooling methods, dioxin concentration in TEQ of slow cooled slag by air was four times higher than that of fast cooled slag by water. Thus cooling by water is more appropriate with the added beneficial effect of producing granules/particles, which can be utilized as roadbed materials.     

胆固醇基键合相-反相高效液相色谱法测定正辛醇/水分配系数

通过反相高效液相色谱法系统地考察了中性和弱酸性化合物在新型胆固醇基键合相色谱柱（Cholester柱）上的保留行为。以甲醇和乙腈为有机调节剂,建立了保留因子（k）与有机调节剂比例（φ）间的关系,并外推获取100%水相为流动相时的log k_w;同时进一步建立并验证了不同流动相下正辛醇/水分配系数的对数（log K_ow）和log k_φ（log k_w）间的模型,并预测了部分化合物的log K_ow。结果表明,使用Cholester柱测定log K_ow时,甲醇比乙腈更适合作为有机调节剂;对中性化合物和中性状态的酸性化合物,可以用任意甲醇比例下获取的log k_φ预测log K_ow;对存在离解的酸性化合物,依然用外推方式获取的log k_w预测log K_ow。将采用Cholester柱与文献中采用C₁₈柱、C₈柱建立的log K_ow-log k_φ模型进行对比,结果表明化合物与胆固醇基键合相存在特别的作用。     

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.     

PCDD, PCDF, AND DL-PCB analysis in food: performance evaluation of the high-resolution gas chromatography/low-resolution tandem mass spectrometry technique using consensus-based samples

Due to safety concerns regarding dietary exposure to POPs, regulatory bodies are issuing detailed guidelines for testing for polychlorodibenzodioxins (PCDDs) and polychlorodibenzofurans (PCDFs) ('dioxins') and dioxin‐like (DL)‐PCBs in foods of animal origin. Determination of the aforesaid chemicals at regulatory levels requires highly selective and sensitive testing techniques. The new generation of low‐resolution mass spectrometers (triple quadrupoles) allows very low levels of quantification to be reached (in the order of tens of femtograms), thus suggesting a potential for their application in food and feed analysis. The performance of the low‐resolution tandem mass spectrometry (LRMS/MS) approach with triple quadrupoles was assessed on a qualified set of food samples from proficiency tests (PTs) and defense analysis. Accuracy was tested comparing the results with data from high‐resolution mass spectrometry (HRMS) and with consensus values from PTs. The cumulative TEQ results were characterized by deviations not exceeding 15% of PCDD + PCDF, DL‐PCB, and PCDD + PCDF + DL‐PCB (TEQ_TOT) reference consensus values (sample TEQ_TOT range, 2.29–25.1 pgWHO‐TEQ₉₇/g fat). Congener analytical variabilities did not influence significantly the WHO‐TEQ₉₇ outcome of the corresponding sample. This preliminary performance evaluation highlights the potential of LRMS/MS as a routine technique for quantitative analysis of PCDDs, PCDFs, and DL‐PCBs in food. Copyright © 2011 John Wiley & Sons, Ltd.     

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.     

11种吸附剂上二噁英的热吸附/脱附性能评价

筛选在低温下高效捕集并在一定的高温下可以快速完全脱附二噁英的吸附/脱附材料是二噁英在线热捕集的关键.该研究以1,2,3,4-四氯代二苯并-对-二噁英(1,2,3,4-TCDD)和1,2,3,8,9-五氯代二苯并呋喃(1,2,3,8,9-PCDF)为二噁英模型物,以电子捕获检测器(ECD)作为检测器,利用填充柱气相色谱系...