Enantiomeric fraction of selected chiral polychlorinated biphenyls in cow, goat, and ewe milk and dairy products by heart-cut multidimensional gas chromatography: First results

The concentration of the most relevant polychlorinated biphenyl (PCB) congeners has been determined in milk and dairy products (i.e., cheese and yogurt, from cow, goat, and ewe). In addition, the enantiomeric composition of 11 atropisomeric PCB has been determined for the first time in this type of product, using heart-cut multidimensional gas chromatography and 2 enantioselective columns for the unambiguous determination of both enantiomers. Results showed a deviation from the racemic composition for PCB 135, 136, 176, 171, and 183 in the samples analyzed. Whereas PCB 135, 136, and 176 showed an enrichment of the first eluted enantiomer, congeners 171 and 183 showed an enrichment of the first or second eluted enantiomer depending on the dairy product and species. The remaining congeners analyzed (PCB 84, 91, 95, 132, 149, and 174) did not present a clear enrichment of any of the enantiomers. Therefore, differences in the enantiomeric composition of some of the target atropisomeric PCB have been found among the 3 species and among the milk samples and the related dairy products analyzed. Enantioselective species-dependent processes, as well as enantioselective processes carried on by microorganisms during the fermentation and ripening in the latter could be possible explanations for the differences observed. However, changes in the enantiomeric composition are still not well understood, and further investigation in this direction is recommended.The authors thank Comunidad Autónoma de Madrid (CAM) for project 07G/0057/2000.Peer reviewe

Feasibility of multidimensional GC techniques (heart-cut MDGC and GC x GC) for the analysis of the enantiomers of chiral toxaphenes

Presentado como póster en el 36th International Symposium on Halogenated Persistent Organic Pollutants (DIOXIN2016).The enantioselective analysis of complex mixtures of chiral pollutants is still a challenge. Besides the difficulties in finding appropriate enantioselective stationary phases able to resolve each chiral compound into its constituent enantiomers, there is an increased risk of co-elution due to the higher number of peaks in real samples. In the case of the pesticide toxaphene, one of the most heavily used chlorinated pesticides world-wide distributed; most of the congeners found in real samples are chiral. In order to provide a more comprehensive understanding of their metabolism and the toxicity associated with their presence, the enantioselective analysis has become a relevant tool in the environmental and food fields.Financial support was acquired from project S-AGR-000312-0505 CM and AGL 2004-02072/ALI-CICYT.Peer reviewe

Determination of toxaphene enantiomers by comprehensive two-dimensional gas chromatography with electron-capture detection

Comprehensive two-dimensional gas chromatography with micro electron-capture detection (GC × GC–μECD) has been evaluated for the enantioseparation of five chiral toxaphenes typically found in real-life samples (Parlar 26, 32, 40, 44 and 50). From the two enantioselective β-cyclodextrin-based columns evaluated as first dimension column, BGB-176SE and BGB-172, the latter provided the best results and was further combined with three non-enantioselective columns in the second dimension: HT-8, BPX-50 and Supelcowax-10. The combination BGB-172 × BPX-50 was finally selected because it provided a complete separation among all enantiomers. A satisfactory repeatability and reproducibility of the retention times in both the first and the second dimension were observed for all target compounds (RSDs below 0.8%, n = 4). Linear responses in the tested range of 10–200 pg/μl and limits of detection in the range of 2–6 pg/μl were obtained. The repeatability and reproducibility at a concentration of 100 pg/μl, evaluated as the RSDs calculated for the enantiomeric fraction (EF), was better than 11% (n = 4) in all instances. The feasibility of the method developed for real-life analyses was illustrated by the determination of the enantiomeric ratios and concentration levels of the test compounds in four commercial fish oil samples. These results were compared to those obtained by heart-cut multidimensional gas chromatography using the same enantioselective column.Financial support was acquired from project 07G/0038/2003 CAM and AGL 2004-02072/ALI-CICYT. L.R.B. thanks CAM for financial support.Peer reviewe

Chiral comprehensive two-dimensional gas chromatography with electron-capture detection applied to the analysis of chiral polychlorinated biphenyls in food samples

The feasibility of comprehensive two-dimensional gas chromatography with electron-capture detection (GC x GC-ECD) for the enantioseparation of chiral PCBs from other possible interfering compounds has been evaluated. Three commercially available enantioselective beta-cyclodextrin-based capillary columns (Chirasil-Dex, BGB-172 and BGB-176SE) have been tested as first-dimension columns. Three non-enantioselective stationary phases (HT-8, BPX-50 and Supelcowax-10) were combined with the enantioselective columns to allow the unambiguous determination of the enantiomers of the target chiral PCBs. Each enantioselective first-dimension column tested was able to separate into enantiomers different PCB congeners, but in all cases, the use of Supelcowax-10 as second-dimension column provided the most satisfactory results. The Chirasil-Dex x Supelcowax-10 column combination allowed the determination of the enantiomeric fraction (EF) of PCBs 84, 91, 95, 132, 136, 149, 174 and 176 in the working standard solution, while that of congener 135 was hindered. The BGB-172 x Supelcowax-10 column set allowed a proper EF determination of congeners 45, 84, 131, 132, 135, 171, 174 and 183, while that of PCB 91 was interfered with co-elutants. The column combination BGB-176SE x Supelcowax-10 allowed the determination of all congeners that this enantioselective stationary phase was able to separate into enantiomers, i.e. PCBs 45, 91, 95, 136, 149 and 176. These column combinations have also been evaluated for the simultaneous determination of the 12 congeners with a toxic equivalency factor assigned by the WHO (PCBs 77, 81, 105, 114, 118, 123, 126, 156, 157, 167, 169, 189) and the seven indicator congeners (PCBs 28, 52, 101, 118, 138, 153 and 180), and evaluated for the analysis of food samples.L.R.B. thanks CAM for a Ph.D. grant. Financial support was acquired from project 07G/0038/2003 CAM and AGL-2003-08216.Peer reviewe

Occurrence of PCBs, PCDD/Fs, PBDEs and DDTs in Spanish breast milk: Enantiomeric fraction of chiral PCBs

Concentrations and congener specific profile of DDTs, PCBs and PCDD/Fs have been determined in a number of Spanish breast milk samples. The concentrations found indicate a decreasing tendency compared to previous data from the 1990s. Mean concentrations of 238 ng/g fat weight, 111 ng/g fat weight and 82.1 pg/g fat weight were found for DDTs, PCBs and 2,3,7,8-PCDD/Fs, respectively. When the WHO-TEQs were calculated, PCDD/Fs was the family contributing with the highest percentage to the total (62–84%), followed by the non-ortho PCBs (10–25%) and the mono-ortho PCBs (5–24%). The congener specific accumulation patterns found were comparable to those reported in other studies in industrialised countries. In addition, the levels of 9 PBDEs congeners have been also determined in the breast milk samples. The concentrations ranged from 0.04 to 1.38 ng/g fat weight. The enantiomeric enrichment of a number of chiral PCBs in the breast milk samples, including congeners 84, 91, 95, 132, 135, 149, 171, 174, 176 and 183, has also been studied, for some of them for the first time in this matrix.The authors thank all participant mothers. CAM is acknowledged for Projects 07G/0057/2000 and S-0505/AGR-0312, and CICyT for Project AGL 2004-02072/AL. L.R. Bordajandi thank CAM for PhD Grant.Peer reviewe

Enantioselective separation of separation of chiral PCBs by multidimensional gas chromatography techniques. Application to real samples

CSIC, CM, INIA, CICYT (Spanish institutions) for financial support.Peer reviewe

Evaluation of organochlorine compounds in peregrine falcon (Falco peregrinus) and their main prey (Columba livia) inhabiting central Spain

6 pages, 3 figures, 1 table.-- PMID: 16152983 [PubMed].The population of peregrine falcon (Falco peregrinus sbs. brookei) inhabiting the Regional Park of southeastern Madrid (RPSM), Spain, has experienced an increase of unsuccessful pairs (from 15% among a total of 20 pairs in 1995 to 55% among a total of 18 pairs in 2001). Traditionally, this area has been known to be contaminated with organochlorine compounds and toxic metals, which are known to be deleterious to the reproductive system of birds. During the breeding seasons of 2000 and 2001, contaminant residues were measured in unhatched eggs of peregrine falcons and liver of their main prey, to determine if they could be affecting the survival of the population. The most abundant contaminants were ortho–polychlorinated biphenyls (ortho-PCBs), ranging from 202.56 to 3,335.16 ng/g (wet wt) in falcon eggs and from 10.25 to 53.51 ng/g (wet wt) in pigeon livers. In all samples, the 2,3,7,8-substituted polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) were detected, although these levels never exceeded 20 pg/g (wet wt). The major contributor to total toxic equivalent quantities (TEQs) were non– ortho-PCBs. Organochlorine levels found in this study may contribute to the entire suite of stressors that are negatively affecting the peregrine population.Financial support for this research was provided by the project 186/RN-38 Consejería de Agricultura y Medio Ambiente de la Junta de Comunidades de Castilla-La Mancha. Sociedad Española de Ornitología Birdlife helped to finance this research.Peer reviewe

Comprehensive two-dimensional gas chromatography in the screening of persistent organohalogenated pollutants in environmental samples

Separations of eight persistent organohalogenated classes of pollutants, organochlorinated pesticides (OCPs), polychlorinated biphenyls (PCBs), polychlorinated diphenyl ethers (PBDEs), polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), polychlorinated naphthalenes (PCNs), polychlorinated terphenyls (PCTs) and toxaphene (CTT) by comprehensive two-dimensional gas chromatography (GC × GC) were evaluated. Columns with different polarity and selectivity, including ZB-5, HT-8, DB-17 and BP-10, were selected as first dimension and combined with columns of increasing polarity in the second dimension, i.e. HT-8, BPX-50 and Carbowax (or Supelcowax-10). In total nine column combinations were tested. Because the main interest of the study was fast screening of the test xenobiotic families in complex matrices, in all cases, attention was primarily focussed on group-type separation. Nevertheless, within-group separation was also considered, especially for those classes containing particularly toxic congeners, such as PCBs and PCDD/Fs. Although none of the assayed column sets allowed the simultaneous and complete separation of all pollutants classes, some column combinations provided satisfactory separations among selected families and the rest of pollutants investigated. That was, for instance, the case of HT-8 × BPX-50 for PBDEs and PCDD/Fs, DB-17 × HT-8 for PCNs and OCPs and BP-10 × BPX-50 for CTT, PCDD/Fs and PBDEs. The feasibility of the proposed approach for the fast screening of the target classes of pollutants in complex samples was illustrated by the analysis of food and marine fat samples prepared using simplified miniaturised sample treatment methods.The authors thank MEC (project CTQ2006-14993/BQU) and CM (projects GR/AMB/0691/2004 and S-2005/AGR-0312) for financial support.Peer reviewe

GCxGC-uECD combined with fast sample preparation methods for the simultaneous screening of selected POP families in food samples

Comprehensive two-dimensional gas chromatography (GC×GC) is a powerful separation technique in which two GC columns with different separation mechanism are coupled via an interface called modulator. This modulator is used to focus and efficiently transfer (i.e. re-inject) the entire effluent from the first column into the second one as consecutive narrow chromatographic bands. Parameters affecting the modulation step such as the cold and hot jet temperatures and the modulation frequency should be carefully optimised to preserve the separation achieved in the first column through the entire separation run. The fast GC separation that takes place in the second column depends on the nature of this stationary phase, its length and the offset of temperature between this column and the main oven. The main features of GC×GC, the influence of the experimental parameters in the final peak capacity and separation power as well as the main advantages of GC×GC as compared to other multidimensional chromatographic separation techniques have been discussed in a number of reviews.Authors thank MEC and CAM for projects BQU2002-04530-C02-02, AGL2004-02072/ALI and GR/AMB/0691/2004, respectively.Peer reviewe