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Biomedical subjects

P Schepens

Publications and source records attributed to P Schepens.

At least 37 records · Page 2Linked to original sources
PubMed2001

Comparison of CALUX-TEQ values with PCB and PCDD/F measurements in human serum of the Flanders Environmental and Health Study (FLEHS).

In 1999, a campaign of the Flemish Ministry of Health, Belgium was set up to assess pollutant concentrations and related health effect biomarkers in humans living in two regions of Flanders. The study was called the 'Flemish Environment and Health Study' (FLEHS). Concentrations of selected organochiorine pesticides, polychlorinated biphenyls (PCB) and polychlorinated dibenzo-p-dioxins (PCDD) and flirans (PCDF) were measured by gas chromatography-mass spectrometry in 47 pooled human serum samples originating from 200 individual women between 50 and 65 years living in two Flemish regions. The CALUX (Chemical-Activated Luciferase gene eXpression) bioassay was assessed on the same pools. The correlation between CALUX-TEQ and total TEQ (sum of PCDD/PCDF, non- and mono-ortho PCBs) varied from 0.43 to 0.73 for the rural and urban region, respectively. The mean value for the total TBQ (75 pg WHO-TEQ/g fat) was two times higher than the mean TEQ value determined with the CALUX bioassay (36 pg TEQ/g fat). This shows that the assessment of dioxin-like exposure by these two measurements was different. However, regional differences in concentrations were observed for neither total TEQs, nor CALUX-TEQs. It was concluded that the CALUX can be an alternative screening tool for biomonitoring purposes, especially when the objective is to compare different groups of people (e.g. living in different regions).

Adult↗
PubMed2001

Mass spectrometric detection in narrow-bore (0.10 mm i.d.) capillary chromatography fast, sensitive and selective analysis of polychlorinated biphenyls.

The combination of narrow-bore capillary gas chromatography with bench-top quadrupole mass spectrometric detection was evaluated for the determination of polychlorinated biphenyls (PCBs). The qualitative and quantitative performances of the system are illustrated by several analyses (PCB standards and human milk extracts). Capillary columns with different internal diameters (0.10, 0.18 and 0.22 mm, respectively) were compared for their ability to separate PCB congeners and the analysis time. Short run times (less than 7 min) were sufficient for complete separation of PCB congeners on a 0.10-mm internal diameter (I.D.) capillary column without any loss of resolution when compared with a 0.22 mm I.D. column. Good qualitative and quantitative data acquisition was possible with quadrupole mass spectrometer for run times of 8 min, but incomplete peak reading was observed when run times were reduced to 3-4 min. Selected ion monitoring and dwell times of 10 ms are necessary to obtain detection limits for individual PCB congeners as low as 0.4 pg microl(-1) for standard solutions and 0.2 ng g(-1) fat for milk extracts. By using cold splitless injection, relatively high volumes (1 microl) for narrow-bore capillaries could be injected without any peak distortion.

Gas Chromatography-Mass Spectrometry↗
PubMed2001

The Belgian PCB and dioxin incident of January-June 1999: exposure data and potential impact on health.

In January 1999, 500 tons of feed contaminated with approximately 50 kg of polychlorinated biphenyls (PCBs) and 1 g of dioxins were distributed to animal farms in Belgium, and to a lesser extent in the Netherlands, France, and Germany. This study was based on 20,491 samples collected in the database of the Belgian federal ministries from animal feed, cattle, pork, poultry, eggs, milk, and various fat-containing food items analyzed for their PCB and/or dioxin content. Dioxin measurements showed a clear predominance of polychlorinated dibenzofuran over polychlorinated dibenzodioxin congeners, a dioxin/PCB ratio of approximately 1:50,000 and a PCB fingerprint resembling that of an Aroclor mixture, thus confirming contamination by transformer oil rather than by other environmental sources. In this case the PCBs contribute significantly more to toxic equivalents (TEQ) than dioxins. The respective means +/- SDs and the maximum concentrations of dioxin (expressed in TEQ) and PCB observed per gram of fat in contaminated food were 170.3 +/- 487.7 pg, 2613.4 pg, 240.7 +/- 2036.9 ng, and 51059.0 ng in chicken; 1.9 +/- 0.8 pg, 4.3 pg, 34.2 +/- 30.5 ng, and 314.0 ng in milk; and 32.0 +/- 104.4 pg, 713.3 pg, 392.7 +/- 2883.5 ng, and 46000.0 ng in eggs. Assuming that as a consequence of this incident between 10 and 15 kg PCBs and from 200 to 300 mg dioxins were ingested by 10 million Belgians, the mean intake per kilogram of body weight is calculated to maximally 25,000 ng PCBs and 500 pg international TEQ dioxins. Estimates of the total number of cancers resulting from this incident range between 40 and 8,000. Neurotoxic and behavioral effects in neonates are also to be expected but cannot be quantified. Because food items differed widely (more than 50-fold) in the ratio of PCBs to dioxins, other significant sources of contamination and a high background contamination are likely to contribute substantially to the exposure of the Belgian population.

Animals↗
PubMed1999

Determination of melatonin in pharmaceutical formulations and human plasma by gas chromatography-electron impact mass spectrometry.

A simple and reliable method for gas chromatography-mass spectrometry (GC-MS) has been developed for the determination of melatonin in commercially available tablet formulations and human plasma. The dissolution of the tablets in ethyl acetate was simply obtained by sonication. The filtrate of the resultant solution, after concentration, was derivatized with pentafluoropropionic anhydride (PFPA) and analysed by GC-MS using splitless injection. The linear response range for melatonin was 5-250 ng on column. The same method can be used, with minor modifications, for the determination of melatonin in spiked human plasma in the range 50-1000 pg/mL plasma.

Calibration↗
PubMed1986

Skin lesions as a sign of subacute pentachlorophenol intoxication.

Pentachlorophenol (PCP) and its sodium salt are frequently used in wood preservatives. Little is known about the effects on man when being chronically exposed. Only vague skin symptoms, such as rashes, acne and cutaneous infections were described. We present two cases of pemphigus vulgaris with a known non-occupational chronic PCP exposure. The clinical course and the titer of pemphigus antibodies roughly correlate with the PCP levels in serum. In one case of chronic urticaria the exacerbations also run parallel to the PCP serum levels and increased anti-skin antibodies, without any manifestation of pemphigus vulgaris. The role of PCP as one of the causes provoking pemphigus vulgaris and chronic urticaria with raised anti-skin antibodies is discussed.

Adult↗
PubMed1978

GLC determination of pemoline in biological fluids.

A specific GLC method for the determination of microgram quantities of the central stimulant pemoline in biological fluids is described. Extraction problems due to the low solubility of pemoline are avoided by acid hydrolysis of the drug to 5-phenyl-2,4-oxazolidinedione, which then can be easily isolated by two-phase extraction with dichloromethane, ether, or chloroform. Amide-imide tautomerism enables a cleanup of the extract. Quantitative determination at the microgram level is done on a methylated fraction of the dichloromethane extract by GLC using a suitable internal standard. For supporting evidence of the GLC method's specificity, the compound is also identified by examining an aliquot of the final dichloromethane extract by TLC.

Chromatography, Gas↗
PubMedDate not supplied

Simplified method for determination of organochlorine pollutants in human serum by solid-phase disk extraction and gas chromatography.

Solid-phase disk extraction (SPDE) was developed as an improved method for isolation of selected organochlorine pollutants from human serum. An Empore C18 bonded silica extraction disk cartridge was used for the initial extraction and enrichment of the analytes. Subsequent clean-up was done by adsorption chromatography on concentrated sulphuric acid:silica gel (1:1, w/w). Analysis was achieved by gas chromatography-mass spectrometry or electron capture detection on two different capillary columns. Recoveries for selected organochlorines range from 62% to 74% (RSD < 14%). The method was validated through successful participation to several interlaboratory tests and by analysis of human serum with different organochlorine loading.

Chemistry Techniques, Analytical↗