Effect of wire eccentricity on the performance of cylindrical proportional counters

A theoretical and experimental investigation of the influence of eccentricity of the multiplication wire on the performance of cylindrical proportional counters is presented. The electric field in the counter is calculated by the method of images, and the Townsend formalism is used to derive the gas gain. The experimental determination of detector performance is carried out with³⁷Ar. The dependence of the gas gain and of the counter resolution on eccentricity is discussed, and it is shown that eccentricities up to 0.2 are of no concern in microdosimetric measurements with cylindrical proportional counters.     

Determination of prostaglandins and thromboxane as their pentafluorobenzyl-trimethylsilyl derivatives by electron-capture gas chromatography

The optimization of the parameters affecting the chromatographic properties and separation of prostaglandin pentafluorobenzyl derivatives by gas chromatography using electron-capture detection is described. The effects of composition and flow-rate of carrier gas, temperatures of detector and column, and nature of stationary phases on the detector response to different pentafluoroebenzyl (both oxime and ester) trimethylsilyl ether derivatives of prostaglandins were systematically examined. The stability of some selected prostaglandin derivatives at ?20°C was also determined. After standardizing these parameters, prostaglandins and related compounds from biological samples, e.g. semen, rat aorta, dog serum and trout gill were successfully analyzed. Identification of prostaglandins was confirmed by gas chromatography—mass spectrometry.     

Nature and Amount of Auxin in Algae : IAA from Extracts of Caulerpa paspaloides (Siphonales)

Evidence for the occurrence of indole 3-acetic acid in Caulerpa paspaloides extracts was obtained by bioassay, by high-performance liquid chromatography with an electrochemical detector, and by capillary gas chromatography combined with mass spectrometry. The amount of indole 3-acetic acid present was estimated to be about 1 milligram per kilogram fresh weight, with an error limit of one order of magnitude. This is in the range reported from angiosperms.     

Gas chromatographic determination of bromo and fluoro derivatives of benzodiazepine in human body fluids

A rapid, sensitive and accurate method for the determination of bromazepam and flunitrazepam in plasma and urine using gas chromatography has been developed. Bromazepam was extracted with diethyl ether and flunitrazepam with hexane at pH 7. A nitrogen detector was used to determine bromazepam and an electron-capture detector was used for flunitrazepam.     

Gas chromatographic determination of eugenol in ethanol extract of cloves

An ethanolic extract of cloves was analyzed by gas chromatography directly to identify eugenol and other major phenolic compounds without previous separation of other components. Separation was performed on a fused-silica capillary column of 30 mx0.53 mm I.D., 0.53 μm film thickness. The detector was a flame ionization detector. Helium gas at a flow-rate of 3 ml/min was used as a carrier gas. The analysis were performed with linear temperature programming. Nine components were detected and special attention was given to the major phenolic compound, eugenol.     

A time-saving thin-layer chromatography plate-scraping system

A system for efficiently scraping thin-layer chromatography plates is described. A height-adjustable rack for holding the thin-layer chromatography plate is constructed of transparent acrylic plate. The base provides a surface on which to slide vial holders and also gives stability to the rack. The plate is scraped with a single-edge razor blade cut to an appropriate width and the scrapings fall into a polypropylene funnel which sits on a vial that is in either a test tube rack or a cassette from a scintillation counter. The plate-scraping system reduces scraping time by more than 60% and increases the accuracy of results.     

The measurement and mass spectral identification of indole-3-pyruvate from tomato shoots

Endogenous indole-3-pyruvate has been identified by full-scan combined gas chromatography-mass spectrometry and measured using gas chromatography with an electron capture detector. High specific-activity [5-3H]indole-3-pyruvate was synthesized from [5-3H]tryptophan and used as an internal standard. In order to allow purification of the labile indole-3-pyruvate it was stabilised by the formation in the crude extract of its pentafluorobenzyl oxime derivative. This derivative also allowed sensitive detection and measurement of indole-3-pyruvate in the picogram range using a gas chromatograph with an electron capture detector. Endogenous levels were found to be between 8-10 ng/g f.wt. of tomato shoots which is comparable to that of the indole-3-acetic acid pool size, 11 ng/g f.wt., in this tissue.     

A monoclonal antibody to (S)-abscisic acid: its characterisation and use in a radioimmunoassay for measuring abscisic acid in crude extracts of cereal and lupin leaves

A monoclonal antibody produced to abscisic acid (ABA) has been characterised and the development of a radioimmunoassay (RIA) for ABA using the antibody is described. The antibody had a high selectivity for the free acid of (S)-cis, trans-ABA. Using the antibody, ABA could be assayed reliably in the RIA over a range from 100 to 4000 pg (0.4 to 15 pmol) ABA per assay vial. As methanol and acetone affected ABA-antibody binding, water was used to extract ABA from leaves. Water was as effective as aqueous methanol and acetone in extracting the ABA present. Crude aqueous extracts of wheat, maize and lupin leaves could be analysed without serious interference from other immunoreactive material. This was shown by measuring the distribution of immunoreactivity in crude extracts separated by thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC), or by comparing the assay with physicochemical methods of analysis. Analysis of crude extracts by RIA and either, after TLC purification, by gas chromatography using an electron-capture detector or, after HPLC purification, by combined gas chromatography-mass spectrometry (GC-MS) gave very similar ABA concentrations in the initial leaf samples. However, RIA analysis of crude aqueous extracts of pea seeds resulted in considerable overestimation of the amount of ABA present. Determinations of ABA content by GC-MS and RIA were similar after pea seed extracts had been purified by HPLC. Although the RIA could not be used to analyse ABA in crude extracts of pea seeds, it is likely that crude extracts of leaves of several other species may be assayed successfully.Abbreviations ABA abscisic acid - DW dry weight - FW fresh weight - GC-ECD gas chromatography using an electron capture detector - GC-MS combined gas chromatographymass spectrometry - HPLC high-performance liquid chromatography - McAb monoclonal antibody - PVP soluble polyvinylpyrrolidone - RIA radioimmunoassay - TLC thin-layer chromatography     

Quantitative gas chromatographic determination of 3-methylhistidine in biological fluids

The gas chromatographic procedure is suggested to determine 3-methylhistidine in biological fluids. The amino acid fraction containing 3-methylhistidine is separated by ion-exchange chromatography. Amino acids are transformed into N-trifluoroacetyl-O-isobutyl esters which are analyzed by the gas chromatography instrument with micropacked columns and ionization-resonance detector. The limit of the quantitative determination of 3-methylhistidine is 50 ng per a probe.     

Rapid,sensitive and specific electron capture—gas chromatographic method for the quantitation of 6-chloro-2-(1-piperazinyl)pyrazine in biological fluids

A highly specific and sensitive gas chromatographic method for the determination of 6-chloro-2-(1-piperazinyl)pyrazine (MK-212), a central serotonin-like agent, in biological fluids is described. MK-212 and a related internal standard are extracted into benzene from an alkaline solution, back-extracted into acid and then re-extracted into benzene at an alkaline pH. The amines are converted to the trifluoroacetyl derivatives (characterized by gas—liquid chromatography—mass spectrometry), chromatographed and detected with a ⁶³Ni electron capture detector. The sensitivity of the method is such that 10 ng of drug can be measured per aliquot of biological fluid. The precision and accuracy of the method are well within acceptable limits. Specificity of analysis was established by gas—liquid chromatography—mass spectrometry techniques.     

The specific nature of plant cell wall polysaccharides

Polysaccharide compositions of cell walls were assessed by quantitative analyses of the component sugars. Cell walls were hydrolyzed in 2 n trifluoroacetic acid and the liberated sugars reduced to their respective alditols. The alditols were acetylated and the resulting alditol acetates separated by gas chromatography. Quantitative assay of the alditol acetates was accomplished by electronically integrating the detector output of the gas chromatograph. Myo-inositol, introduced into the sample prior to hydrolysis, served as an internal standard.     

Separation and determination of mass and radioactivity of fermentation gases.

A procedure is described for the separation of permanent gases on a gas chromatograph, the determination of each component by means of a thermal conductivity detector and the simultaneous measurement of radioactivity in each peak by means of a proportional counter.Procedures for calibration of the apparatus and for calculation of absolute radioactivities in samples are given.The capabilities of the apparatus are illustrated by some results of experiments with an artificial rumen using ¹⁴C- and ³H-labeled compounds.     

Dosimetry of low-energy neutrons using low-pressure proportional counters

Measurements in nearly monoenergetic beams of 144, 24.5, and 2 keV neutrons and of thermal neutrons have been performed with low-pressure proportional counters. The suitability of a tissue-equivalent proportional counter (TEPC) for dosimetry of low-energy neutrons has been investigated. In contrast to higher neutron energies, the modification of the primary radiation field by the detector wall and the contribution of secondaries produced in the gas are significant. These effects have been investigated by additional measurements with a carbon-walled proportional counter. The various physical processes of neutron interaction with wall and gas of the TEPC have been analyzed, and absorbed dose, kerma, and kerma contributions from the various processes are presented. In addition, dose contributions from contaminating neutrons and photons have been obtained for the calibration fields used. The results have been related to neutron fluence. The comparison with tabulated kerma factors shows excellent agreement, indicating the suitability of the TEPC method for dosimetry of low-energy neutrons.     

Gas chromatographic—mass spectrometric procedure for the quantitation of chlorpromazine in plasma and its comparison with a new high-performance liquid chromatographic assay with electrochemical detection

A gas chromatographic—mass spectrometric assay using selected ion monitoring is compared with a high-performance liquid chromatographic assay using an electrochemical detector for single-dose studies of the psychotherapeutic phenothiazine drug chlorpromazine. Measurements were made after extraction of chlorpromazine and the internal standard, prochlorperazine, from basified plasma with an isopropanol—pentane solvent mixture. Following evaporation of the organic solvents the residue was reconstituted in a small volume of methanol and subjected to gas chromatographic—mass spectrometric selected ion detection. The residual sample was then evaporated and made up in a larger volume of acetonitrile and analyzed by high-performance liquid chromatography using an electrochemical detector. These specific methods display excellent correlation for plasma concentration determinations in the range of 0.25–10 ng ml⁻¹ and will allow for the study of the pharmacokinetics of chlorpromazine following single low doses of the drug.     

SEARCH FOR MITOGENETIC RADIATION BY MEANS OF THE PHOTOELECTRIC METHOD

The intensity of mitogenetic radiation was estimated from data given by Gurwitsch. The sensitivity of the biological method and of the physical methods were compared. With onion-base pulp and onion roots as mitogenetic inductors, the photographic method gave no perceptible blackening for exposures up to 184 hours. A photoelectric counter tube was described with cadmium as photoelectric metal. Its sensitivity was such that a radiation intensity of 10 to 15 quanta per cm.² per second of the Hg line 2536 A was detectable. Spurious effects produced by the counter tube were described and means for their avoidance given. A number of different biological materials, all supposed to be excellent mitogenetic radiators, were investigated by means of the counter tube. No mitogenetic radiation could be detected.     

Decontamination ofFusarium mycotoxins,nivalenol, deoxynivalenol,and zearalenone,in barley by the polishing process

Korean dehusked and unhusked barley naturally contaminated withFusarium mycotoxins were polished using a Satake Grain Testing Mill. The pearled barley and bran fractions with different degrees of polishing were analyzed for nivalenol (NIV) and deoxynivalenol (DON) by gas chromatography with an electron capture detector, and for zearalenone (ZEN) by high-performance liquid chromatography with a fluorescence detector. NIV was detected in all the pearled barley fractions, but DON and ZEN were not detected in ≥27 % pearled barley fractions from dehusked barley and ≥36% pearled barley fractions from unhusked barley. However, for all degrees of polishing, NIV, DON, and ZEN were detected in bran fractions. The levels of NIV, DON, and ZEN in the bran fractions increased several fold over the original barley. Polishing was effective in removing DON and ZEN from the naturally contaminated barley, but not NIV.     

Simultaneous determination of isosorbide dinitrate and its mononitrate metabolites in human plasma by capillary gas chromatography with electron-capture detection

A method for the simultaneous determination of isosorbide dinitrate (ISDN) and its mononitrate metabolites (2- and 5-ISMN) in human plasma by capillary gas chromatography with electron-capture detection was developed. Two internal standards were used: isomannide dinitrate (IMDN) for the determination of ISDN and isomannide mononitrate (IMMN) for the determinations of 2- and 5-ISMN. After addition of the internal standards, the compounds were isolated from plasma by solid-liquid extraction. They were determined by gas chromatography using an electron-capture detector. The reproducibility and accuracy of the method were found suitable in the range of concentrations 2.5–83 ng/ml for ISDN, 2.6–208 ng/ml for 2-ISMN and 2.3–1010 ng/ml for 5-ISMN. The limit of quantitation (LOQ) was about 2.5 ng/ml for each compound. The method was applied to clinical samples.     

A Comparative Study on the Analysis of Herbicide “Bromacil” Using ECD-gas Chromatography and Mass Fragmentography

Analysis methods of a herbicide “bromacil” were studied comparatively in soil and mandarin orange fruit. Bromacil content in tissue of mouse was also measured. Measurement was performed by gas chromatography with electron capture detector (ECD). Mass fragmentography was also studied, which was found to be useful for the residue analysis of this herbicide.     

Determination of methenamine in biological samples by gas—liquid chromatography

Methenamine (hexamethylenetetramine), a urinary disinfectant, was determined in human plasma and urine by gas—liquid chromatography with a short (10 m) open-bone glass capillary column (split ratio 1:20) and nitrogen-selective detector. An almost quantitative recovery (92.1%) was achieved by simple dilution of water-containing samples (0.5 ml) with acetone (4.5 ml). After centrifugation and aliquot (2 μl) of the supernatant was injected into the gas chromatograph. Selectivity and sensitivity of the nitrogen detector allowed the quantitation of unchanged methenamine in plasma and urine up to 24 h after a single therapeutic dose of 1 g.Reproducibility of the method was 7.6 and 2.1% (C.V.) in serum and urine, respectively. The time required for the analysis of one sample was approx. 2 min. Due to the simple extraction and short analysis time it was possible to analyze the samples concurrently with sample taking. Absorption of standard tablets and an enterosoluble preparation of methenamine hippurate was compared.     

Possibilities and problems with identification and determination of "new" hypnotics

Authors discuss problems with identification and determination of flunitrazepam and zolpidem in biological material (BM). Over the recent years, these two structurally different substances have become the most frequently used as well as abused hypnotic drugs. This study presents applicability of immunochemical methods in the screening of flunitrazepam, one of the most commonly prescribed drugs among the benzodiazepines. Herein described techniques, a liquid-liquid (L-L) extraction, solid phase extraction (SPE) and the so-called "freeze out" method are used for isolation of the above mentioned compounds from BM. Besides the thin layer chromatography (TLC) and gas chromatography - mass spectrometry (GC-MS) applied in qualitative analysis, the study also describes a gas chromatography with electron capture detector (GC-ECD) and gas chromatography with nitrogen phosphorus detector (GC-NPD) optimized for the determination of flunitrazepam and zolpidem in blood (serum). Successful analyses of these two substances are of major importance, especially in interpreting the results of forensic toxicological examinations.