Electron Capture Gas-liquid Research Articles

Quantitative analysis of vitamin K1 and vitamin K1 2,3-epoxide in plasma by electron-capture gas—liquid chromatography

Quantitative analysis of vitamin K1 and vitamin K1 2,3-epoxide in plasma by electron-capture gas—liquid chromatography

Gas-Liquid Chromatographic Determination of Thiabendazole and Methyl 2-Benzimidazole Carbamate in Fruits and Crops

A method is described for the electron capture gas-liquid chromatographic determination of thiabendazole and methyl 2-benzimidazole carbamate (MBC) after derivatization with pentafluorobenzyl bromide (PFB-Br). The samples are extracted with ethyl acetate, and the residual thiabendazole, benomyl, and MBC are isolated by liquid-liquid extraction into dilute HCl. After neutralization and re-extraction with ethyl acetate, thiabendazole and MBC are reacted with PFB-Br to form the PFB derivatives. Alumina column chromatography was used to clean up extracts, and the derivatives could be detected as low as 5-10 pg. Recoveries were 95-98% from fruits fortified with 0.3-2.0 ppm thiabenzadole; recoveries were 91-97% when 0.05-1.0 ppm benomyl/MBC were added to fruits/crops. The PFB derivatives were identified by gas-liquid chromatography-mass spectrometry.

Identification and quantification of insect juvenile hormones as their 10-heptafluorobutyryloxy-11-methoxy derivatives by combination of high-performance liquid chromatography and electron capture gas-liquid chromatography

A convenient procedure is described for the isolation and quantitative determination of juvenile hormones from biological material by their conversion into the 10-heptafluorobutyryloxy-11-methoxy derivatives. After precipitation at low temperature, the lipid is separated by thin-layer chromatography (TLC), and the isolated hormone fraction is converted into the 10-hydroxy-11-methoxy derivatives which are purified by high-performance liquid chromatography (HPLC). These derivatives are treated with heptafluorobutyrylimidazole and the resulting derivatives are finally separated and quantified by electron capture gas-liquid chromatography. Overall yields are 20–50% with 1–4 g insects extracted. Marker substances used are triphenylmethanol for HPLC, and bis(ethylhexyl) phthalate and dibutyl phthalate for TLC and HPLC.

Sensitive electron-capture gas-liquid chromatographic assay for the DE-ethylated metabolite of metoclopramide

A procedure is described for determining 4-amino-5-chloro-2-methoxy-N-(2-ethylaminoethyl)benzamide, a metbaolite formed by de-ethylation of metoclopramide, in urine from rats. The sample is extracted (at pH ≈ 13) with chloroform and, after treatment with heptafluorobutyric anhydride, derivatives of the extracted compounds are analyzed by gas-liquid chromatography, with electron-capture detection and diazepam as internal standard. The drug and its metabolite are separated, and the latter can be determined in the range 0.4 to 1.85 μg/ml in the sample. The behaviour of the metabolite during chemical-ionization and electron-impact mass spectrometry is discussed.

Electron-capture gas-liquid chromatographic determination of ethosuximide and desmethylmethsuximide in plasma or serum.

We describe the determination of ethosuximide and desmethylmethsuximide, simultaneously or separately, in 50 to 100 microliter of plasma or serum. Derivatives of ethosuximide and desmethylmethsuximide formed by reaction with pentafluorobenzoyl chloride are extremely sensitive to the electron-capture detector of a gas-liquid chromatograph. The sample, with added internal standard and ammonium sulfate as a pH-adjusting and salting-out agent, is extracted with ethyl acetate/benzene (20/80 by vol). The extract is evaporated and the derivatives are formed. Analytical recoveries of ethosuximide and desmethylmethsuximide exceed 99%, and the relative standard deviation (CV) between analyses is usually less than 4.0%. alpha-Methyl-alpha-propylsuccinimide is used as the internal standard for ethosuximide, 2-phenylsuccinimide as the internal standard for desmethylmethsuximide.

Electron capture gas-liquid chromatographic-mass spectral identification of acids produced by Neisseria meningitidis in a defined medium.

The acid metabolites and the cellular fatty acids of three strains of Neisseria meningitidis grown in a chemically defined liquid medium were determined with computerized frequency-pulsed electron capture gas-liquid chromatography. Five acids not previously reported were subsequently identified: isobutyric, octanoic, decenoic (C10:1), dodecenoic (C12:1), and tetradecenoic (C14:1). These acids were produced during active metabolism and were not detected as cellular constituents. The frequency-pulsed electron capture gas-liquid chromatography methods which we used provide a rapid, reliable, sensitive means of detecting both these and other metabolic and cellular acids in spent culture medium.

Temperature Dependence of Electron Capture Detector Responses in the Analysis of Chlorpromazine, Diazepam, and Clonazepam

The temperature dependence of the responses of a pulsed 63 Ni electron capture detector to chlorpromazine, clomipramine, diazepam, flurazepam, and the N-ethyl derivatives of clonazepam and N-desmethylflunitrazepam were determined. The response to chlorpromazine and clomlpramine increases with temperature, while that to diazepam and flurazepom decreases with temperature. The response to N-ethylclonazepam and N-ethyldesmethylflunitrazepam exhibits very little temperature dependence. These results have been used to optimize the analysis of r dlazepam, and clonazepam in plasma by electron capture gas-liquid chromatography.

Extraction and liquid—solid chromatography cleanup procedures for the direct analysis of four pyrethroid insecticides in crops by gas—liquid chromatography

The extraction of four pyrethroid insectidides, fenpropanate (WL 41706, S-3206), permethrin (WL 43479, FMC-33297, PP 557, NRDC-143), cypermethrin (WL 43467, NRDC 149), and fenvalerate (WL 43775, S-5602) from carrots, tomatoes celery, and onions with acetone followed by extraction of the resulting acetone—water mixture with hexane, was investigated and found suitable for residue anaylysis. The elution of the four materials from two types of silica and alumina adsorbents with mixtures of organic solvents of varying polarity was examined. The elution patterns and recoveries from silica gel, aluminum oxide, and water deactivate Florisil indicated potential utility in cleanup. Florisil was found to provide cleanup for asparagus, carrots, tomatoes, tobacco, and onions permitting analyses to 0.01 ppm for most of the insecticides by electron capture gas—liquid chromatography, at extract concentrations of 1 g/ml. The other adsorbents, singly or in combination, were found to provide the cleanup required for radished and those cases involving other crops where Florisil cleanup was insufficient.

Dieldrin-14C elimination from turkeys.

A series of experiments were conducted to find ways of removing dieldrin2 residues from tissues of broiler-type turkeys (Meleagris gallopavo). The turkeys were contaminated with dieldrin and dieldrin-14C by oral dosing. Elimination was measured by assaying for 14C in the droppings. Carcass retention was measured by assaying the tissue for 14C, and in one experiment, dieldrin residues were measured by electron capture gas-liquid chromatography. Charcoal, Colestipol, and cholestyramine at dosages approximately equal to an intake of 5% of the diet were ineffective gastrointestinal adsorbants for removing dieldrin residues from the turkeys. Starvation accelerated the elimination of dieldrin from the turkeys, but only if the body lipids were reduced to approximately 10% or less of the carcass dry matter.

Determination of indicine n-oxide and indicine in plasma and urine by electron-capture gas—liquid chromatography

A sensitive and specific method is described for the quantitative analysis of indicine N-oxide and indicine in plasma and urine. Indicine N-oxide is reduced to the tertiary amine with zinc—acetic acid (plasma) or zinc—ammonium chloride (urine). The indicine is derivatized with pentafluoropropionic anhydride to provide electron-capture detection. Assay of rabbit and human plasma and urine samples can detect 100 ng/ml (plasma) and 200 ng/ml (urine), and the method was applied to the analysis of indicine N-oxide and indicine in rabbits and one patient following administration of indicine N-oxide.

Gas-Liquid Chromatographic Determination of Sodium 5- [2-Chloro-4- (trifluoromethyl) phenoxy] -2-nitrobenzoate Residues on Soybeans and Foliage, Soil, Milk, and Liver

Residues of sodium 5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoate and its free acid are determined by treating a sample extract with diazomethane to convert the residues to methyl 5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoate. This compound is purified by chromatography on Florisil and measured by electron capture gas-liquid chromatography. The method has been used on soybeans, soybean foliage, soil, milk, and liver. It can detect 0.01 ppm with recoveries of 70--75%.

Electron capture gas-liquid chromatographic study of metabolites produced by some arthritic transudate-associated organisms in vitro and in vivo in rabbit models.

Computerized, frequency-pulsed, modulated electron capture gas-liquid chromatography was used to study the acid metabolites produced in vitro in fetal calf serum and in vivo in an animal chamber model. Several strains of Diplostreptococcus agalactiae, Propionibacterium acnes, Staphylococcus aureus, and Streptococcus serogroups A, B, and G were studied. All of these organisms have been reported to be associated with arthritic transudates in humans. Metabolites were detected by this method from derivatized extracts of both spent fetal calf serum and chamber fluids. Since there was little host response to the organisms cultured in the chambers, it is highly probable that the products detected represent metabolites produced in an in vivo type of environment. The metabolic patterns were reproducible and exhibited many similarities in vitro and in vivo. Production of the acids detected was reproducible, and these acids were useful identification markers. The data support published reports (J. B. Brooks, C. C. Alley, and J. A. Liddle, Anal. Chem. 46: 1930-1934, 1974; J. B. Brooks, G. Choudhary, R. B. Craven, D. Edman, C. C. Alley, and J. A. Liddle, J. Clin. Microbiol. 5:625-628, 1977; J. B. Brooks, R. B. Craven, A. R. Melton, and C. C. Alley, in H. H. Johnson and W. B. Newson, ed., Second International Symposium on Rapid Methods and Automation on Microbiology, 1976; J. B. Brooks, R. B. Craven, D. Schlossberg, C. C. Alley, and F. M. Pitts, J. Clin. Microbiol. 8:203-208, 1978; J. B. Brooks, D. S. Kellogg, C. C. Alley, H. B. Short, and H. H. Handsfield, J. Infect. Dis. 129:660-668, 1974) that bacterial metabolites might be detectable in diseased body fluids. The growth characteristics of the organisms in the animal model and fetal calf serum are discussed, and a moderately priced computer for performing data manipulations is evaluated.

Analysis of A, B, E, and F prostaglandins as pentafluorobenzyl esters by electron-capture gas-liquid chromatography

A new and sensitive method is described for the simultaneous analysis of a mixture containing PGE 1, PGE 2, PGF 1α, and PGF 2α by electron-capture gas-liquid chromatography. During derivatization of the mixture, PGE 1 and PGE 2 were converted to PGB 1 and PGB 2, respectively, yielding a mixture of PGB 1, PGB 2, PGF 1α, and PGF 2α trimethylsilyl ether pentafluorobenzyl esters. Gas chromatographic resolution of all four derivatives is sufficient for quantitation of each prostaglandin. The A prostaglandins were analyzed by similar conversion to the respective B prostaglandin derivatives. Minimum detection limits for the B and F prostaglandin derivatives were 10 pg and 1 pg, respectively. Samples of rabbit kidney medulla were incubated and analyzed for A, B, E, and F prostaglandins. The results indicate that the method is capable of high recovery and reproducibility.

Abscission of Flowers and Fruits in Phaseolus vulgaris L. II. The Relationship between Pod Abscission and Endogenous Abscisic, Phaseic, and Dihydrophaseic Acids in Pedicels and Pods1

Abstract In each of 2 cultivars of dry bean, populations of fruits having either low or high abscission potentials were established by removing early opening flowers from half the plants and leaving all flowers on the remainder. Fruits were harvested 4 to 5 days after anthesis and separated according to length, which was negatively correlated with abscission potential. Abscisic acid (ABA), phaseic acid (PA), and dihydrophaseic acid (DPA) contents were determined in methanol extracts of both pods and pedicels, using electron capture gas liquid chromatography. The content of these 3 compounds in pedicels was not significantly affected by cultivar, fruit size or flower removal. ABA content of pods was positively correlated with fruit load but was not related to fruit size. Phaseic acid content increased with fruit size and with fruit load but was not affected by cultivar. Content of DPA was unaffected by pod size or fruit load. We conclude that levels of extractable ABA, PA, and DPA do not regulate fruit abscission in dry bean.

Analysis of lorazepam and its glucoronide metabolite by electron-capture gas—liquid chromatography : Use in pharmacokinetic studies of lorazepam

This paper describes a rapid and sensitive method for analysis of lorazepam and its glucuronide metabolite in plasma and urine following therapeutic doses of lorazepam in humans. After addition of the structurally related benzodiazepine derivative, oxazepam, as the internal standard, 1-ml samples of plasma or urine are extracted twice at neutral pH with benzene (containing 1.5% isoamyl alcohol). The combined extracts are evaporated to dryness, reconstituted, and subjected to gas chromatographic analysis using a 3% OV-17 column and an electron-capture detector. Lorazepam glucuronide in urine is similarly analyzed following enzymatic cleavage with Glusulase. The sensitivity limits are 1–3 ng of lorazepam per ml of original sample, and the variability of identical samples is 5% or less. The applicability of the method to pharmacokinetic studies of lorazepam is demonstrated.

Time-course of interaction between carbamazepine and clonazepam in normal man.

The applicability of a pharmacokinetic model for drug interactions by enzyme induction was tested by chronic dosing situation using carbamazepine (Tegretol) as the inducer and clonazepam (Clonopin) as the drug affected. Seven healthy subjects received one 1.0 mg clonazepam tablet once a day for 29 days and one 200 mg carbamazepine tablet once a day from days 8 to 29. Plasma levels of clonazepam were measured by electron-capture gas-liquid chromatography and those of carbamazepine and its epoxide metabolite by gas chromatographic-chemical ionization-mass spectrometry. Clonazepam plasma levels reached an initial steady-state by day 7 and declined to a lower steady-state over 5 to 15 days after additions of carbamazepine. The decrease in clonazepam levels ranged between 19% and 37%. Autoinduction of carbamazepine metabolism was also evident. Urinary excretion of D-glucaric acid increased 2- to 4-fold following carbamazepine administration (p less than 0.005). This increase provided additional evidence that the present interaction was due to enzyme induction. Experimental clonazepam levels were fitted to an induction pharmacokinetic model for multiple dosing with an exponentially increasing clearance. Induced half-lives of clonazepam (mean = 22.5 +/- 11.5 hr) were shorter (p less than 0.005) than control values (32.1 +/- 16.6 hr). Apparent enzyme(s) turnover half-lives ranged between 1 and 6 days.

Possible use of frequency-pulse-modulated electron capture gas-liquid chromatography to identify septic and aseptic causes of pleural effusions.

Frequency-pulse-modulated electron capture gas-liquid chromatography was used in conjunction with appropriate derivatization procedures to obtain chromatograms from extracts of pleural effusions. These chromatograms were used to rapidly classify the various types of pleural effusions. With this method we have been able to distinguish among a limited number of effusions caused by congestive heart failure, Mycobacterium tuberculosis, and some other types of bacterial empyemas and pleural effusions.

Spontaneous hydrolysis of heroin in buffered solution.

Electron-capture gas-liquid chromatography was used to study the spontaneous hydrolysis of heroin in phosphate buffer (pH 6.4 and pH 7.4) at 23 degrees C. Aliquots of solution were taken over a 24-h period. After extraction at pH 8.9 into propan-2-ol (10%)-ethyl acetate, deacetylated products were made into hepafluorobutyrate derivatives which were analyzed quantitatively using nalorphine as the internal standard. Heroin decomposes to 06-monoacetylmorphine (06-MAM) under these conditions. Further decomposition to morphine was not observed. Spontaneous hydrolysis was faster at pH 7.4 (first-order rate constant, 9.6 x 10-5 min-1) than at pH 6.4 (first-order rate constant, 3.0 x 10-5 min-1). In 24 h, the decomposition to 06-MAM was 13 and 4%, respectively.

Gas-Liquid Chromatographic Determination of Pydrin, a Synthetic Pyrethroid, in Cabbage and Lettuce

Pydrin, alpha-cyano-3-phenoxybenzyl 2-(4-chlorophenyl)-3-methylbutyrate, a synthetic pyrethroid ester, is extracted from vegetables with acetonitrile, partitioned into petroleum ether before cleanup on a Florisil column, and analyzed by electron capture gas-liquid chromatography. Recoveries of 88-102% at 0.01 ppm, 99-102% at 0.1 ppm, and 98-104% at 1.0 ppm were obtained from fortified cabbage and lettuce samples. The method appears applicable to detection of the residues of Pydrin in the foliage of many types of crops.

Gas-Liquid Chromatographic Determination of Kepone Residues in Finfish, Shellfish, and Crustaceans

Finfish, shellfish, and crustacean samples are extracted with isopropanol and benzene; the extract is filtered and then concentrated. The extract, dissolved in hexane, is treated with oleum and extracted with aqueous alkali. The aqueous phase is acidified and extracted with petroleum ether-ethyl ether (1 + 1). The Kepone residue is determined by electron capture gas-liquid chromatography (GLC). Recoveries obtained by 8 laboratories from 15 species of finfish fortified at 0.02-0.23 ppm ranged from 37 to 107% with a mean +/- relative standard deviation of 79.4 +/- 14.5%. For oysters fortified at 0.01-0.10 ppm, recoveries range from 63 to 129% with a mean of 78.8 +/- 20.8%. For crustaceans fortified at 0.05-0.26 ppm, recoveries ranged from 52 to 110% with a mean of 78 +/- 16.4%. The approximate limits of quantitation for finfish and for shellfish and crustaceans are 0.02 and 0.05 ppm, respectively, under the GLC conditions used in this study.