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Biomedical subjects

J Van Bocxlaer

Publications and source records attributed to J Van Bocxlaer.

12 recordsLinked to original sources
PubMed2006

Class identity assignment for amphetamines using neural networks and GC-FTIR data.

An exploratory analysis was performed in order to evaluate the feasibility of building of neural network (NN) systems automating the identification of amphetamines necessary in the investigation of drugs of abuse for epidemiological, clinical and forensic purposes. A first neural network system was built to distinguish between amphetamines and nonamphetamines. A second, more refined system, aimed to the recognition of amphetamines according to their toxicological activity (stimulant amphetamines, hallucinogenic amphetamines, nonamphetamines). Both systems proved that discrimination between amphetamines and nonamphetamines, as well as between stimulants, hallucinogens and nonamphetamines is possible (83.44% and 85.71% correct classification rate, respectively). The spectroscopic interpretation of the 40 most important input variables (GC-FTIR absorption intensities) shows that the modeling power of an input variable seems to be correlated with the stability and not with the intensity of the spectral interaction. Thus, discarding variables only because they correspond to spectral windows with weak absorptions does not seem be not advisable.

Amphetamines↗
PubMed2002

Chemometric detection of thermally degraded samples in the analysis of drugs of abuse with gas chromatography-Fourier-transform infrared spectroscopy.

We present a chemometric procedure for the identification of the reference standard chromatographic peak in cases where the GC-FTIR analysis of commercial standards results in the appearance of more than one peak in the GC chromatogram. The procedure has been designed for phenethylamines, which represent the class with the largest number of individual molecules on the illicit drug market, and which are abused for their stimulant and/or hallucinogenic effects. The similarity between their vapor-phase FTIR spectra was modeled using principal component analysis (PCA), and class identity was assigned on the basis of soft independent modeling of class analogy (SIMCA). Additional peaks could be assigned to impurities in the standards, but most often they were artifacts formed during the GC-FTIR analysis of thermolabile or chemically unstable compounds. The latter case is illustrated by the identification of the reference standard chromatographic peak and FTIR spectrum of the potent psychotropic amphetamine derivative N-methyl-1-(3,4-methylenedioxyphenyl)-2-butanamine (MBDB), and by the elucidation of the chemical changes that occur in the molecule of MBDB due to thermal degradation.

Chromatography, Gas↗
PubMed2001

Compound A production from sevoflurane is not less when KOH-free absorbent is used in a closed-circuit lung model system.

In an in vitro study, less compound A was formed when a KOH-free carbon dioxide absorbent was used. To confirm this observation we used a lung model in which carbon dioxide was fed in at 160 ml min(-1) and sampling gas was taken out for analysis at 200 ml min(-1); ventilation aimed for a PE'CO2 of 5.4 kPa. The soda lime canister temperatures in the inflow and outflow ports (Tin and Tout) were recorded. In six runs of 240 min each, a standard soda lime, Sodasorb (Grace, Epernon, France) was used and in eight runs KOH-free Sofnolime (Molecular Products, Thaxted, UK) was used. Liquid sevoflurane was injected using a syringe pump to obtain 2.1% E'. Compound A was measured by capillary gas chromatography combined with mass spectrometry. Median (range) compound Ainsp increased to a maximum of 22.7 (7.9) ppm for Sodasorb and 33.1 (20) for Sofnolime at 60 min and decreased thereafter; the difference between groups was significant (P<0.05) at each time of analysis up to 240 min. The canister temperatures were similar in both groups and increased to approximately 40 degrees C at 240 min. Contrary to expectation, compound A concentrations were greater with the KOH-free absorbent despite similar canister temperatures with both absorbents.

Absorption↗
PubMed2000

Quantitative determination of paraquat in a fatal intoxication by HPLC-DAD following chemical reduction with sodium borohydride.

A fatality due to a massive ingestion of paraquat is presented. Screening by enzyme-multiplied immunoassay of postmortem blood and urine disclosed the presence of tricyclic antidepressants (in urine only), benzodiazepines, cotinine, and caffeine. Further analysis of blood, urine, and stomach contents with thin-layer chromatography, high-performance liquid chromatography (HPLC), and gas chromatography confirmed the results found in the preliminary routine screening. It also revealed the presence of paraquat in blood, urine, and stomach contents, of diethyl parathion in urine and stomach contents, and of mevinphos in blood and stomach contents. Quantitation of paraquat was performed using HPLC with diode-array detection. Sample preparation involved a protein-precipitation step using trichloroacetic acid (necessary only for blood and tissue homogenate), followed by a chemical reduction with sodium borohydride of the fully ionized paraquat to a diene, which is amenable to solvent extraction. Quantitative results were obtained for all postmortem matrices available: blood, 5.05 mg/L; urine, 6.00 mg/l; stomach contents, 17.2 g/L; liver, 4.86 mg/kg; and kidney, 80.6 mg/kg. The paraquat distribution in this case is compared with analytical findings reported in the literature. As would be expected, concentrations found in fatal paraquat intoxications display large differences. The data presented illustrate the outspoken lethal nature of the herbicide paraquat and the ongoing appearance of this compound in deadly accidental and suicidal poisonings.

Borohydrides↗
PubMed1994

Determination of embutramide in biological matrices by gas chromatography with nitrogen-phosphorus detection.

Embutramide is a general anesthetic having a strong narcotic effect on the central nervous system where it paralyzes the brain center that controls respiration. It is a constituent of T61, a veterinary euthanasia drug. This paper describes a gas chromatographic procedure using nitrogen-phosphorus detection for the determination of embutramide in biological matrices. The drug and the internal standard (ambucetamide) are extracted with dichloromethane under alkaline conditions. The method is linear from 100 to 3000 ng/ml. The within-day and day-to-day coefficients of variation range from 5.1 to 5.7% and from 9.1 to 10.0%, respectively. The recovery is above 80% while the minimum detectable level under the conditions described is 40 ng/ml analyzing a 1-ml or a 1-g aliquot of a sample (blood or tissue). The method is also applied to different samples from dogs euthanized with T61.

Amides↗
PubMedDate not supplied

A fatal case of trazodone and dothiepin poisoning: toxicological findings.

A fatal case of trazodone and dothiepin self-poisoning is presented. A multi-technique approach (EMIT, TLC, HPLC/DAD, and GC/MS) allowed the unequivocal identification of trazodone and dothiepin as toxicologically relevant substances. Both compounds were quantitatively determined in a number of postmortem samples. Blood and urinary trazodone concentrations (28.7 and 90.5 micrograms/mL, respectively) and dothiepin concentrations (2.1 and 9.7 micrograms/mL, respectively) were far above therapeutic concentrations (i.e., 1.5 and 0.05 microgram/mL for trazodone and dothiepin, respectively, in blood) and were clearly the cause of death in this particular case. These data confirm the high toxicity and the high mortality rate in trazodone intoxications, especially when co-ingestion of other substances is involved.

Adult↗
PubMedDate not supplied

Analysis of zopiclone (Imovane) in postmortem specimens by GC-MS and HPLC with diode-array detection.

A 26-year-old black female was found dead at home. Her mouth was covered with a fluid containing chalky particles. Empty strips of Imovane (zopiclone) and an empty bottle of Fortal (pentazocine) were also found. No urine was available at autopsy. Screening of postmortem blood and stomach contents with enzyme-multiplied immunoassay technique (EMIT) detected only caffeine. Further screening using routine high-performance liquid chromatography (HPLC) with diode-array detection and gas chromatography (GC) with mass spectrometric detection revealed the presence of large amounts of pentazocine in the blood and stomach contents. In the HPLC chromatogram, a second peak that was only partially resolved from the solvent front was observed. Thin-layer chromatography demonstrated the presence of zopiclone, but optimized HPLC and GC conditions had to be used for proper identification and quantitation. This case illustrates the fact that zopiclone can be easily overlooked during routine forensic screening.

Adult↗
PubMedDate not supplied

Fatal 4-MTA intoxication: development of a liquid chromatographic-tandem mass spectrometric assay for multiple matrices.

The case history and toxicological findings of an overdose fatality involving 4-methylthioamphetamine (4-MTA) and 3,4-methylenedioxymethamphetamine (MDMA) are reported along with a description of the analytical method. Detection and quantitation of 4-MTA and MDMA were performed by liquid chromatography-tandem mass spectrometry using phentermine as internal standard. Application of this technique to a variety of matrices allowed an insight in the distribution of 4-MTA. Several blood samples including femoral vein blood (5.23 mg/L), urine (95.5 mg/L), vitreous humor (1.31 mg/L), bile (36.4 mg/L), and numerous tissue samples such as liver (30.8 mg/kg), spleen (4.10 mg/kg), and frontal lobe (31.7 mg/kg) were assayed. These values indicated that 4-MTA could be identified as the cause of this fatality, whereas the concentrations of MDMA, also described, are less important because the concentrations found are lower. This case reports, for the first time, an extensive toxicological analysis of 4-MTA, by which the data presented may shed some light on the distribution of 4-MTA.

Adult↗
PubMedDate not supplied

The determination of cocaine, benzoylecgonine, and cocaethylene in small-volume oral fluid samples by liquid chromatography-quadrupole-time-of-flight mass spectrometry.

A quantitative analysis was developed for the determination of cocaine, benzoylecgonine, and cocaethylene in oral fluid using liquid chromatography-tandem mass spectrometry. After internal standardization and solid-phase extraction, chromatographic separation was achieved on a reversed-phase column by gradient elution. The reconstructed mass chromatograms of the collision-induced dissociation transitions of m/z 290 --> m/z 168 (benzoylecgonine), m/z 304 --> m/z 168+119 (2'-methylbenzoylecgonine), m/z 304 --> m/z 182 (cocaine), m/z 318 --> m/z 196 (cocaethylene), and m/z 318 --> m/z 182+119 (2'-methylcocaine) were used for quantitation. The developed method was adequately validated. Good linearity was obtained from 10 to 1000 microg/L. Extraction recoveries exceeded 85% for all compounds. Excellent total and within-run reproducibilities (CV% < 20%) and accuracy figures were obtained. The limit of detection (signal-to-noise ratio >/= 3) was 1 microg/L for all three compounds. As such, a method for drug abuse confirmation analysis in oral fluid, compatible with the present day saliva collecting devices, is obtained. The method was applied to real samples (n = 15) obtained from suspected drug users, of which seven proved positive. The concentrations found in the positive samples were between 10.2 and 200.6 microg/L for cocaine, < limit of quantification (LOQ) and 10.5 microg/L for cocaethylene, and < LOQ and 59.2 microg/L for benzoylecgonine.

Chromatography, Liquid↗