Capillary Gas Chromatography-electron Capture Detection Research Articles

Clearance and disposition of indometacin in chronically instrumented fetal lambs following a 3-day continuous intravenous infusion.

Indometacin is used in pregnancy for the treatment of premature labour, but there are limited data on the disposition of the drug in the fetus. In order to elucidate fetal indometacin pharmacokinetics at plasma levels and duration comparable with those occurring with use of the drug for tocolysis in humans, indometacin was administered at doses of 1.9 (low dose, LD; n = 5) or 7.5 (high dose, HD; n = 9) microg min(-1) to steady state over a 3-day period in chronically instrumented fetal lambs. Indometacin concentrations in biological fluid samples were analysed by a sensitive capillary gas chromatography-electron capture detection method. The mean steady-state fetal arterial plasma indometacin concentrations were 68.6+/-16.5 ng mL(-1) in the LD infusion and 230.3+/-28.8 ng mL(-1) in the HD infusion. Indometacin concentrations in amniotic fluid were approximately 10% of those in fetal plasma, and below assay detection limits in tracheal fluid. Total body clearance (TBC) in the LD and HD infusions were not different and the overall mean was 11.3+/-1.2 mL min(-1) kg(-1). In the 11 experiments where paired fetal arterial and umbilical venous samples were collected, the extraction of indometacin across the placenta averaged only 5.2+/-1.1%, indicating low placental permeability to the drug in sheep. However, fetal placental clearance (CLpl) of indometacin (10.0+/-2.5 mL min(-1) kg(-1), n = 10) averaged 115.1+/-41.2% of TBC in these animals and the calculated value for fetal non-placental clearance (0.6+/-2.8 mL min(-1) kg(-1)) was not significantly different from zero. Fetal renal clearance of intact indometacin (3.8+/-1.1 microL min(-1) kg(-1); n = 12) was also very low. However, treatment of fetal urine with glucuronidase indicated the presence of glucuronide conjugates and these comprised 69.9+/-8.2% of the total drug concentration (i.e. intact+conjugated) in urine. Thus, the fetal lamb appears to be able to glucuronidate indometacin, but the contribution of this and other non-placental routes to overall fetal elimination of the drug appear minimal. CLpl of the drug is also low owing to the physicochemical properties of indometacin (high polarity) and the permeability characteristics of the sheep placenta.

Determination of Organochlorine Pesticides Residue in Ginseng Root by Orthogonal Array Design Soxhlet Extraction and Gas Chromatography

Organochlorine pesticides are known to enter plant products from contamination via spillage and volatilization of the residues from pesticide-treated soils or storage. A method involving four-factor-three-level orthogonal array design including extracting solvent component, particle size, solvent overflow recycle and time needed for the optimization of extracting nine organochlorine pesticides from ginseng root was developed using Soxhlet extraction followed by capillary gas chromatography–electron capture detection and mass spectrometric confirmation. The extraction conditions were optimized from the experimental data. Relationship between the bioaccumulation of benzenehexachloride isomers and their polarity is discussed based on experimental results.

Fluvalinate residues in honey by capillary gas chromatography—Electron capture detection—Mass spectrometry

A fast, simple and accurate analytical method for determination of residual Fluvalinate in honey is described. Honey sample was dissolved in methanol-water and Fluvalinate extracted with ethyl acetate. The organic phase was evaporated and the residue dissolved in ethyl acetate. After clean-up on a C18 Sep-Pak cartridge Fluvalinate was eluted withn-hexane, concentrated under a stream of nitrogen and analysed by capillary GC-ECD-MS in selected-ion monitoring mode. Recoveries from honey samples spiked at 7 fortification levels (0.01–50 ng g−1) range from 93.8–100.2%, RSD≤5.0%. The limit of detection was 8 ng g−1 in GC-ECD and 18 ng g−1 in GC-MS (SIM) with RSDs of 7.2 and 6.8% respectively. The method was used to analyse several types of honey (60 samples) from different Italian regions. Fluvalinate residues were detected in these samples and concentrations ranged from LOD to 0.09 ng g−1.

Automated Gel Permeation Chromatographic Clean-up of Human Adipose Tissue for Multiresidue Analysis of Organochlorine Compounds

Human adipose tissue samples have been analysed for organochlorine pesticides and polychlorinated biphenyls (PCBs). Following a micro liquid-solid extraction, clean-up is performed by automated gel permeation chromatography. The GPC separation provides clean extracts, allowing subsequential analysis by capillary gas chromatography-electron capture detection without additional clean-up.

Matrix solid-phase dispersion extraction of organophosphorus and synthetic pyrethroid pesticides in cashew nut and passion fruit

A multiresidue extraction method based on matrix solid-phase dispersion (MSPD) and capillary gas chromatography–electron capture detection for quantification of five widely used organophosphorus insecticides (diazinon, malathion, parathion, methidathion, and pyrazophos) and one synthetic pyrethroid (permethrin) in Brazilian fruits is described. Cashew nut and passion fruit are plants native to South America. Capillary gas chromatography with mass selective detection was also utilized to confirm the pesticides through mass spectra. Different parameters were optimized, such as the solid phase and dispersant used, amounts, type of eluant and volume, and sample amount. The best results were obtained using a silica gel cartridge column and Florisil as dispersant. The eluant was ethyl acetate. Analysis of fortified fruit (n=3) shows an average recovery of 101.4% for cashew nut and 97.8% for passion fruit at 0.3–1.0-mg/kg levels. Detection limits ranged from 0.2 to 0.4 pg for the compounds studied using 1-g samples. The linearity, repeatability, and recoveries of the method are presented. This MSPD method was compared with solid-phase extraction (SPE) for cleanup, using an alumina–silica gel (1 : 1) cartridge column and ethyl acetate as eluant. Analysis of fortified fruit (n=3) shows an average recovery of 104.9% for cashew nut and 106.8% for passion fruit at 0.1–0.6-mg/kg levels. Detection limits ranged from 0.2 to 0.6 pg for the compounds studied using 25-g samples. The combined use of C18 and silica (or Florisil) makes this extraction system unsuitable for these fruits matrixes. The cleanest extracts are obtained using two polar (Florisil and silica) solid phases. In conclusion, the proposed MSPD method described here can be applied to extract five organophosphorus pesticides and permethrin in 1 g of fruit. It is advantageous because it uses ethyl acetate as the only solvent, is faster and uses less solvent than SPE methods, and requires only small sample sizes. ©1999 John Wiley & Sons, Inc. J Micro Sep 11: 367–375, 1999

Comparative determination of total isomeric truxillines in illicit, refined, South American cocaine hydrochloride using capillary gas chromatography-electron capture detection

The isomeric truxillines and their hydrolysis products are present as manufacturing impurities in most illicit, refined cocaine samples. Methodology is described for the comparative gas chromatographic determination of total isomeric truxilline manufacturing impurities/by-products, i.e., intact truxillines and their hydrolysis products, in illicit, refined cocaine samples seized in South America. These isomers, namely, alpha-, beta-, delta-, epsilon-, gamma-, omega-, zeta-, peri-+neo- and epi-truxilline, were all quantified relative to mu-truxillic acid, a structurally-related internal standard. In this method, the cocaine samples were first subjected to treatment with boron trifluoride-methanol, followed by lithium aluminum hydride reduction and then acylation with heptafluorobutyric anhydride. The resultant di-heptafluorobutyryl derivatives of the truxillyl and truxinyl diols exhibited excellent chromatography and low-picogram on-column detection when using a moderately polar fused-silica capillary column interfaced with an electron-capture detector. This methodology demonstrated good reproducibility, as determined by the repetitive analysis of a selected illicit cocaine exhibit. The analysis of 117 unadulterated, illicit, refined cocaine samples revealed that total truxilline levels ranged from 0.2–12.3% (w/w relative to cocaine), with the two most abundant truxillines being the alpha- and beta- isomers. Truxilline data for the total individual truxilline isomers in cocaine hydrochloride exhibits from five South American countries are presented.

Hygrine, bona fide alkaloid or artifact: its chemical reduction, novel di-heptafluorobutyrylation and sensitive detection in South American coca leaves using capillary gas chromatography-electron capture detection

Methodology is described for the isolation of hygrine, along with the related compound-cuscohygrine, from South Americancoca leaf and its major tropane alkaloids. The isolated hygrine was reduced with lithium aluminum hydride to yield diastereomeric alcohols, which were subsequently derivatized with heptafluorobutyric anhydride in the presence of 4-dimethylaminopyridine. The resultant diastereomeric di-heptafluorobutyryl derivatives could be detected on-column at femtogram levels when using a polar fused-silica capillary column interfaced with 63Ni electron-capture detector. The artifactual formation of hygrine, resulting from the degradation of cuscohygrine, is discussed. Quantitative data are provided for hygrine and cuscohygrine levels in South American coca.

Quantitation of the fatty acid composition of phosphatidic acid by capillary gas chromatography electron-capture detection with picomole sensitivity.

We describe a relatively simple and sensitive method to measure femtomole amounts of phosphatidic acid in cells. Phosphatidic acid was extracted from cells in the presence of 1-heptadecanoyl-2-heptadecanoyl-sn-glycero-3-phosphate as an internal standard, purified by two-dimensional thin-layer chromatography, and hydrolyzed to its constituent free fatty acids which were then derivatized to the corresponding pentafluorobenzyl esters. Pentafluorobenzyl esters of fatty acids were analyzed by gas chromatography with electron-capture detection. Long-chain fatty acids were resolved with excellent signal-to-noise ratios. Using heptadecanoic acid as an internal standard for quantitation, as little as 1 fmol of pentafluorobenzyl ester of stearic acid was detected with a linear response up to 10 pmol. Linear detector responses were obtained for all major classes of fatty acids. For phosphatidic acid measurement, the detection limit was at least 50 fmol thus achieving a 1000-fold increase in sensitivity compared to the most sensitive of the previously described methods. An example is provided of quantitating phosphatidic acid from minute amounts of biological samples such as islets of Langerhans.

The Application of Capillary Gas Chromatography-Electron Capture Detection in the Comparative Analyses of Illicit Cocaine Samples

The gas chromatographic detection of manufacturing impurities in illicit cocaine can be enhanced by chemical derivatization and the use of an electron-capture detector. After derivatization of illicit cocaine hydrochloride samples with heptafluorobutyric anhydride, the isolated heptafluorobutyryl derivatives of the cocaine impurities were subjected to capillary gas chromatography-electron capture detection analysis. The on-column detection of cocaine impurities at low picogram levels was possible for compounds such as N-norcocaine and other N-demethylated impurities, amidic by-products, including N-benzoylnorecgonine methyl ester and tertiary amines possessing hydroxy functions. The latter compounds include the so-called hydroxycocaine impurities, believed to be new coca leaf alkaloids. This methodology is especially suited for sample comparison analyses.

Miniaturisation of size-exclusion chromatography as a powerful clean-up tool in residue analysis

A miniaturised size-exclusion chromatography (SEC) column with a 2 mm I.D. was developed and compared to a routinely used SEC column with a 10 mm I.D. for the determination of organochlorine pesticides. The flow-rate and sample size were decreased in proportion with the decrease in diameter and the column was tested for recovery of pesticides and for clean-up of animal fat and vegetable samples. Analysis was performed with capillary gas chromatography—electron-capture detection. The miniaturised column proved to be better than the standard SEC column with regard to the removal of the matrix in vegetables samples, while comparable results were obtained with regard to recoveries obtained and results of analysis. Sample size and solvent consumption for the miniaturised SEC column as well as the volume of the collected fraction are dramatically decreased. This facilitates evaporation of solvent which may be necessary to achieve the needed limit of detection.

Determination of patulin by capillary gas chromatography of the heptafluorobutyrate derivative

Formation and capillary gas chromatography of patulin heptafluorobutyrate is reported for the first time. The derivative was identified by gas chromatography—mass spectrometry (M + = 350). Electron-capture detector response for patulin heptafluorobutyrate was linear in the range 0.05 to 0.5 ng. This sensitive and reproducible derivatization technique was applied to the determination of patulin in apple juice by capillary gas chromatography—electron-capture detection. The overall method recovery averaged 84% and ⪕10 μg/l could be detected.

Trace Analysis of Chloramphenicol Residues in Egg Powders by Capillary Gas Chromatography-Electron Capture Detection

Chloramphenicol (CAP) in egg powder samples was extracted with acetonitrile by sonication. After centrifugation, the supernatant was diluted with water and defatted with n-hexane, and cleanup was performed on a microcolumn of graphitized carbon black (GCB). Different silylation methods were compared for the derivatization of the analytes. Trimethylsilyl N,N-dimethylcarbamate produced stable di-TMS derivatives which were analyzed by capillary gas chromatography-electron capture detection (CGC-ECD) after splitless injection. The meta isomer of the chloramphenicol served as the internal standard for quantitation, and 80% + mean recovery was obtained in the 0.1-10 micrograms/kg (ppb) concentration range.

Quantitative determination of nitroglycerin by capillary gas chromatography—electron capture detection

A rapid and sensitive capillary gas chromatographic method based on the one described by Noonan et al. [1] was used to evaluate the nitroglycerin content in serum samples of healthy volunteers, who had orally received a special preparation of the drug (Nisconitrine 6.5®, Bio-Therabel). Concentrations were monitored up to 12 h after administration. In accordance with other literature data [2], no detectable amounts of the mother compound were found (limit of detection: 50 pg ml −1). Yet, significant amounts of the active metabolites, 1,2- and 1,3-dinitroglycerin could be demonstrated. Due to the low mass spectrometric response (electron impact ionization) of the different nitroglycerins, positive confirmation of the results with GC—MS was not possible. However, the concentrations reported here do agree with literature data [2], i.e. the ng ml −1 level.

Analysis of N- n-propylnorapomorphine in plasma and tissue by capillary gas chromatography—electron-capture detection

Capillary gas chromatography combined with electron-capture detection (GC—ECD) was applied to the detection and quantitation of N- n-propylnorapomorphine (NPA) and related compounds in serum and tissue using trifluoroacetyl (TFA) derivatives. The detection limits for NPA using GC—ECD of TFA derivative extend into the subpicogram level, but quantitation in serum was limited to levels of 100 ng/ml due to matrix interferences. The method was applied to the analysis of NPA in rat serum after administration of a moderate dose of the drug and was applied to the detection of NPA in rat brain after the peripheral administration of (—)10,11-methylenedioxy-N- n-propylnoraporphine (MDO-NPA). These results support previous proposals that MDO-NPA is a prodrug of NPA, which acts at cerebral dopamine-receptors.