Electron Capture Gas-liquid Chromatography Research Articles

Rapid determination of diazepam and nordiazepam in plasma by electron capture gas—liquid chromatography

A rapid method was developed for the determination of diazepam and nordiazepam (N-desmethyldiazepam) in human plasma using electron capture gas--liquid chromatography (GLC--ECE). The concentration of diazepam and nordiazepam is determined using 0.5 ml of plasma extracted with 1.0 ml of benzene containing 25 ng/ml of methylnitrazepam as the internal standard. The benzene extract is removed and an aliquot is subjected to automated GLC-ECD analysis. The method has a sensitivity limit of 5 ng diazepam and 10ng nordiazepam per milliliter of plasma. The method was used to determine the plasma levels in man following the first 5-mg diazepam dose, as well as during chronic oral administration of 5 mg diazepam three times daily and 15 mg diazepam once a day.

Simplified Micro Perchlorination Method for Polychlorinated Biphenyls in Biological Samples

Simplified methodology is presented for the micro determination of polychlorinated biphenyls (PCBs) in biological samples, by conversion to the decachlorobiphenyl (DCB) derivative. Beef adipose tissue and human milk extracts were fortified with PCB standards at 0.1--5.0 ppm, and perchlorinated with antimony pentachloride (SbCl5). Several Aroclors representing various degrees of chlorine content were investigated to assess the efficiency of conversion to DCB. Samples were cleaned up on a Florisil mini column and the PCBs were quantitated by electron capture GLC. Several chlorinated pesticides which were subjected to the perchlorination procedure did not interfere. As little as 0.1 ppm PCBs in 500 mg tissue extract can be recovered at 79-99%. The background DCB content of several brands of SbCl5 was determined. The levels of PCBs in human milk obtained by the perchlorination technique are compared with data acquired by electron capture gas-liquid chromatography in which the individual chlorobiphenyls in the sample are measured.

An Oxidative Screening Procedure for Nanogram Amounts of Benzodiazepines and Other Drugs in Blood

A method is presented for the sensitive detection of benzodiazepines and some other drugs in blood. The procedure involves the extraction of 0.4 ml blood followed by chromic acid oxidation and analysis of the oxidized extract using electron capture gas-liquid chromatography. The method is suitable for a mass screening of blood samples for therapeutic and overdose levels of benzodiazepines.

Determination of morphine by electron capture gas-liquid chromatography.

We describe a micromethod for determining as little as 0.1 microgram of morphine per liter of human urine. The procedure is about 20-fold more sensitive than are currently used gas-liquid chromatographic methods. It is particularly suitable for use as a confirmatory method for large-scale radioimmunoassay screening tests. The procedure involves extraction of morphine from urine and analysis of its heptafluorobutyryl derivative by gas-liquid chromatography with electron capture detection. Morphine can be determined by this procedure over a range of 0.1-200 microgram/liter of urine, 2 pg of the pure derivative being the lowest amount detectable. Urine samples from patients receiving methadone were analyzed by thin-layer chromatography, radioimmunoassay, and our procedure. The results by our procedure agreed well with those obtained by radioimmunoassay.

Selenium content of mushrooms

The selenium contents of 83 species of wild mushrooms were determined by oxygen combustion of the sample, followed by conversion of selenite to bromopiazselenol and final estimation by electron capture gas-liquid chromatography. Selenium concentration were found to range from 0.012-20.0 mg/kg dry weight. Selenium content was species-dependent. High concentrations were found in Agaricaceae and in certain Boletaceae of the genus Tubiporus, whereas in Russulaceae, Amanitaceae and Cantharellaceae selenium-rich species were absent or rare. Ascomycetes and all mushrooms growing on wood had a very low selenium content. The highest selenium concentrations (up to 20 ppm) were found in Boletus (Tubiporus) edulis, a most popular edible mushroom. Analyses of various parts of carpophores of B. edulis, Suillus luteus and Amanita muscaria indicate that in all three species the stalk contains less selenium than the fleshy part of the cap. In Boletus and Suillus the highest selenium content was found in the tubes.

Determination of Serum and Urine Concentrations of Tranylcypromine by Electron-Capture Gas-Liquid Chromatography

Determination of Serum and Urine Concentrations of Tranylcypromine by Electron-Capture Gas-Liquid Chromatography

Quantitative determination of naltrexone and naltrexone prodrugs by electron-capture gas-liquid chromatography

An electron-capture gas chromatographic method has been applied to the determination of eleven ester and ether derivatives of naltrexone believed to act as prodrugs. Standard analytical curves are presented for all prodrugs and quantitation is shown to be possible from 10 ng to 1.5 μg of each compound. Ester derivatives of naltrexone are hydrolyzed to naltrexone prior to analysis as the perfluoroalkyl esters. Analysis of synthetic mixtures of these with naltrexone demonstrated that quantitation by difference measurements is possible with naltrexone-derivative ratios from 4:1 to 1:10. Ether derivatives are analyzed without hydrolysis. This method is applicable to biological fluids as well as aqueous solutions.

Micromethod for determination of diazepam by electron-capture gas-liquid chromatography.

We used 100 microliters of plasma for the determination of diazepam. After the internal standard, prazepam, is added, the serum is directly extracted with diethyl ether, the extract is evaporated, the residue is dissolved in ethanol, and the drug is measured by gas-liquid chromatography, with use of an electron capture detector. With this procedure, 2.5 ng of diazepam in the sample can be speedily measured with specificity, accuracy, and reproducibility (CV = 4.5%).

A Micromethod for the Determination of Clonazepam in Serum by Electron-Capture Gas-Liquid Chromatography

An electron-capture GLC procedure for clonazepom Is presented using methyl-clonazepam as Internal standard. The method Involves extracting 1001 buffered serum with benzene:ethyl acetate containing the reference compound. Residue from the extract Is reconstituted with 20 I solvent and an aliquot is Injected into the gas chromatograph without derivatlzation. Results from 328 determinations Indicate a need for monitoring this antleplleptlc drug.

Rapid diagnosis of lymphocytic meningitis by frequency-pulsed electron capture gas-liquid chromatography: differentiation of tuberculous, cryptococcal, and viral meningitis.

Cerebrospinal fluid specimens from patients with tuberculous (17 cases), cryptococcal (15 cases), and viral (14 cases) meningitis were analyzed by frequency-pulsed electron capture gas-liquid chromatography and mass spectrometry. Compounds that disappeared after therapy were found to be present in each of these specimens and were not detected in controls. They occurred in repetitive patterns such that these three types of meningitis could be rapidly distinguished. The compound associated with tuberculous meningitis has been tentatively identified. These finding have implications for rapid diagnosis, pathophysiological studies, and possible new therapeutic approaches.

Electron capture gas chromatography detection and mass spectrum identification of 3-(2'-ketohexyl)indoline in spinal fluids of patients with tuberculous meningitis.

A basic, extractable, indolic type of compound, which was derivatized with heptafluorobutyric anhydride and pyridine, was obtained from the cerebrospinal fluids of patients with acute tuberculous meningitis. The compound was detected by frequency-pulsed, modulated electron capture gas-liquid chromatography, and it was tentatively identified by mass spectrometry as 3-(2'-ketohexyl)indoline. The compound was found to be valuable for differentiating between tuberculous, cryptococcal, and aseptic meningitides.

Determination of clorazepate and its major metabolites in blood and urine by electron capture gas-liquid chromatography

A sensitive and specific blood level method employing differential extraction was developed for the determination of clorazepate and its N-desmethyldiazepam metabolite by electron capture gas-liquid chromatography (GLC-ECD). The assay requires the initial extraction of N-desmethyldiazepam, the major metabolite, into benzene-methylene chloride (90:10) from the biological sample made alkaline with 0.1 N NaOH. The sample is then acidified with 2 N HCl to decarboxylate clorazepate to N-desmethyldiazepam, which is then extracted into benzene-methylene chloride (90:10) after adjusting the pH to 12.8 with NaOH. The two extracts are evaporated, and the residues are dissolved in benzene which contains griseofulvin as the reference standard. These solutions are assayed by GLC-ECD. The overall recovery and sensitivity limit of the assay for clorazepate is 60 ± 5% (S.D.) and 4.0 ng/ml blood, respectively, while that for N-desmethyldiazepam is 95 ± 5% (S.D.) and 4.0 ng/ml blood, respectively. The urinary excretion of clorazepate was determined by the measurement of the levels of N-desmethyldiazepam and oxazepam, the major urinary metabolites of clorazepate, both prior to and after enzymatic deconjugation. These methods were applied to the measurement of clorazepate and its metabolites in blood and urine following a single 15-mg dose of clorazepate dipotassium.

Confirming Heptachlor and Heptachlor Epoxide in Food Samples by Gas-Liquid Chromatography of Their Photo derivatives

The food sample extract is cleaned up on a Florisil column and the 6% ethyl ether in petroleum ether cluate is subjected to repeated concentrations, using a micro-Snyder column, to expel volatile materials that absorb ultraviolet (UV) light. The sample and standard solutions of heptachlor and heptachlor epoxide are placed in quartz cells and exposed to UV radiation in the dark. Characteristic photoderivatives of the respective pesticides which form in the sample extract are identified and measured by comparison with those formed in the irradiated standard solutions, using electron capture gas-liquid chromatography. Recoveries of the 2 pesticides from 13 products, fortified at levels from 0.01 to 0.3 ppm and determined after derivatization, ranged from 67 to 110%.

Trace Analysis of Zearalenone and/or Zearalanol in Animal Chow by High Pressure Liquid Chromatography and Gas-Liquid Chromatography

An analytical method is described for determining residues of the estrogens zearalenone and/or zearalanol in animal chow at levels as low as 10 ppb. The chow is extracted with methanol and cleaned up by a 3-step procedure employing a Sephadex LH-20 column, liquid-liquid partitioning at pH 13 and 8.3, and a silica gel column. Residues of the 2 compounds, separated on silica gel, are assayed by using high pressure liquid chromatography with ultraviolet detection. Additional data are also included concerning p-values of the compounds in several solvent systems, Rf values from thin layer chromatography with 9 solvent systems, solubilities in 3 solvents, and a procedure for preparing their pentafluoropropionyl derivatives for analysis by electron capture gas-liquid chromatography.

Clinical pharmacokinetics of lorazepam. II. Intramuscular injection.

A single dose of 4 mg of lorazepam was injected into the deltoid muscles of six healthy male volunteers. Multiple venous blood samples were drawn during 48 hr after the dose and all urine was collected for 24 hr after the dose. Concentrations of lorazepam and its major metabolite, lorazepam glucuronide, were determined by electron-capture gas-liquid chromatography. Lorazepam was rapidly absorbed from the injection site, reaching peak concentrations within 3 hr. Mean pharmacokinetic pamrameters for unchanged lorazepam were: apparent absorption half-life: 21.2 min; elimination half-life: 13.6 hr; volume of distribution: 0.9 L/kg; total clearance: 58.2 ml/min. Lorazepam glucuronide rapidly appeared in plasma, reached peak concentrations within 12 hr of the dose, then was eliminated approximately in parallel with the parent drug. Within 24 hr a mean of 47.6% of the dose was recovered in the urine as lorazepam glucuronide and less than 0.5% was recovered as unchanged lorazepam.

Collaborative Study of the Recovery of Hexachlorobenzene and Mirex in Butterfat and Fish

Abstract A previously published method applicable to the recovery of hexachlorobenzene (HCB) and Mirex (dodecachlorooctahydro-1,3,4-metheno-2H-cyclobuta (cd) pentalene) from fats and oils has been collaboratively studied by 8 laboratories. The method involves distribution of the fat or oil on unactivated Florisil and elution of the HCB and Mirex with acetonitrile. The 2 compounds are then partitioned into petroleum ether and eluted through activated Florisil with methylene chloride-hexane. Electron capture gas-liquid chromatography is utilized as the determinative step. In the collaborative study, samples of sablefish and butterfat were fortified at 2 different levels; each level was determined in duplicate. Average HCB recoveries of 98±7% and 95±13% at respective levels of 0.06 and 0.5 ppm were obtained from the fish sample. Mirex recoveries in the fish sample at the same levels were 85±l4% and 96±10%. The butterfat sample was fortified at a low level of 0.13 ppm for both compounds and at high levels of 0.62 and 0.66 ppm for HCB and Mirex, respectively. The low level HCB recovery was 104±6% and the high level was 99±10%. In the same order, Mirex was recovered at 104±7% and 103±6%. The method has been adopted as official first action for the determination of HCB and Mirex in fish and fatty dairy products.

Determination of thiabendazole by electron-capture gas-liquid chromatography after reaction with pentafluorobenzoyl chloride

Determination of thiabendazole by electron-capture gas-liquid chromatography after reaction with pentafluorobenzoyl chloride

Comparative study on the derivatization of l-α-acetylmethadol metabolites for electron capture gas-liquid chromatography

Six reagents—trichloroacetyl chloride, trichloroacetic anhydride, pentafluorobenzoyl chloride, heptafluorobutyryl chloride, heptafluorobutyric anhydride, and trifluoroacetic anhydride—were evaluated as potential derivatizing reagents for quantitating the metabolites of l-α-acetylmethadol (LAAM)—noracetylmethadol, dinoracetylmethadol, methadol, and normethadol—by electron capture gas-liquid chromatography. All of the reagents studied reacted quantitatively with all of the metabolites except methadol; however, trichloroacetyl chloride was found to be the most satisfactory general reagent for analyzing these metabolites in biological fluids. A gas-liquid chromatographic method is presented which combines both flame ionization and electron capture detection for quantitating plasma and urine levels of methadone, l-α-acetylmethadol and its metabolites.

Rapid Determination of Butylated Hydroxyanisole, tert-Butylhydroquinone, and Propyl Gallate in Edible Oils by Electron Capture Gas-Liquid Chromatography

A rapid method is described for the determination of 2- and 3-tert-butyl-4-hydroxyanisole (2- and 3-BHA), tert-butylhydroquinone (TBHQ), and propyl gallate (PG) as their heptafluorobutyrates in edible oils. A solution of the oil in ether-benzene is treated with heptafluorobutyric anhydride (HFBA) in the presence of trimethylamine as catalyst. Excess HFBA is destroyed and a suitably diluted aliquot is analyzed by electron capture gas-liquid chromatography. An internal standard is added before derivatization to aid quantitation and identification of the antioxidants. Average recoveries from an oil spiked at 1, 5, 5, and 5 ppm TBHQ, 2-BHA, 3-BHA, and PG were 110, 105, 106, and 102%, respectively. At these low levels, however, some late-eluting peaks interfered. Butylated hydroxytoluene is not determined by this method.

The effects of propranolol, practolol and metoprolol on exercise-induced tachycardia in relation to plasma levels in man.

1. The effects of single oral doses of propranolol, practolol and a new cardioselective beta-adrenoceptor blocking drug, metoprolol, on exercise-induced tachycardia in relation to plasma levels were studied in six normal volunteers. 2. Exercise undertaken on treadmill was submaximal which, under control conditions, increased the heart rate from 74-3 (s.e.m. = 6-8) to 153-8 (s.e.m. = 9.8) beats/min. 3. Plasma concentrations of propranolol and practolol were assayed fluorometrically and of metoprolol by electron-capture gas liquid chromatography, the details of which are described. 4. Between 1-5 and 2 h after drug ingestion 80 mg of propranolol associated with plasma level of 50-60 ng/ml (half-life 2-75 h), reduced the exercise-induced tachycardia by 27%, 250 mg of practolol with plasma levels of 1050-1100 ng/ml reduced it by 28% and 100 mg of metoprolol with plasma concentrations of 140-150 ng/ml (half-life 1-7 h), reduced it by 30%. 5. The resting heart rates were reduced significantly by propranolol and metoprolol but not by practolol. 6. Metoprolol is a potent short-acting beta-adrenoceptor antagonist; its advantages as a cardioselective agent over practolol in therapeutic use are discussed.