Data for the gas-liquid chromatographic analysis of essential oils. Determination of the composition of the essential oil of Marjoram

Summary By identification of the essential oil component ‘cis-sabinene hydrate acetate’ of marjoram we demonstrate that the mass spectrum—furnish to the chemical composition and molecular configuration of compounds—can lead to incorrect qualitative identification if retention data are not taken into consideration. We studied also the temperature-dependence of the retention data of different compounds, and our measurements showed that because of the different temperature-dependence, a change in the temperature of the analysis results in a change in order of elution. The use of this phenomenon, originating from the change of the retention data, both increases the safety of qualitative identification and aids determination of the optimum measurement conditions in both isothermal and temperature-programmed modes of operation. Presented at Balaton Symposium '01 on High-Performance Separation Methods, Siófok, Hungary, September 2–4, 2001     

Structure-retention correlations of hydrocarbons in GLC and GSC alkenylbenzenes

Summary For the study of relationships between retention behaviour and molecular structure in GLC and GSC the retention indices of alkenylbenzenes with 2–6 carbon atoms in a straight or branched side chain and of isotopological alkylbenzenes were determined on capillary columns coated with OV-1 and Ucon LB and on a micropacked column filled with graphitized thermal carbon black. From the values obtained index differences corresponding to the increments of the double bond in the side chain were derived. These differences depend significantly on the structure of the side chain and of the position of the double bond. In the case of 1-phenyl-1-alkenes the double bond close to the aromatic ring gives rise to an increase of retention values, especially for the trans-isomers, causing remarkable retention differences between the cis and transisomers. The alkenylbenzenes which exhibit a terminal double bond are less strongly retained than the isotopological alkylbenzenes. Partly presented on the 15th International Symposium on Chromatography 1984 in Nürnberg.     

Hydride generation atomic absorption spectrometry with different flow systems and in-atomizer trapping for determination of cadmium in water and urine-overview of existing data on cadmium vapour generation and evaluation of critical parameters

An overview of literature data on vapour generation techniques for cadmium and comparison with own experiments by means of several different types of hydride generation-electrothermal atomic absorption spectrometric systems (HG-ETAAS) (batch, semi-batch (SB), continuous-flow (CF) and flow-injection (FI) as well as different gas-liquid separators (GLS) exhibits apparent variations and inconsistency. However, if data for optimal chemical conditions are re-plotted in another coordinates: C_HCl (mol l⁻¹) vs. the ratio of reductant-to-acid molar input rates (i.e. millimoles per minute), [BH₄⁻]:[H⁺], much better consistency of data is revealed: more than half of data are clustered around 0.2-0.3 mol l⁻¹ HCl which appears an optimal acidity at moderate BH₄⁻ concentrations; the tetrahydroborate molar input rates should always be in excess versus the H⁺ molar input rates (1.1 to tenfold); relatively high flow rates of argon purge gas are required (≥120 ml min⁻¹); special attention to the blank control at ng l⁻¹ levels as well as to the construction of gas-liquid separator and vapour transfer lines should be paid. ‘Milder’ conditions for HG could be provided with some of the examined systems and GLSs, thus minimizing reagent consumption, blanks, vigorous reactions, foaming, aerosol production and drift in measurements: e.g. 0.4 mol l⁻¹ HCl—3% m/v NaBH₄ with the semi-batch system and 0.25 mol l⁻¹ HCl—2% m/v NaBH₄ in continuous flow mode. Experimental system is based on the Transversely Heated Graphite Atomizer coupled with flow injection system FIAS 400. Integrated platforms are treated for permanent modification with Zr (110 μg) or W (240 μg) and then with Ir (8 μg). Temperatures of trapping, pyrolysis and atomization are 350, 500 and 1300 °C, respectively. The best overall efficiency of HG, transportation and trapping is 41%. The characteristic mass for peak area measurements is m_o=2.8 pg and the limit of detection is 0.002 μg l⁻¹. The long-term stability of characteristic mass (within-day, 8 h) is m_o=2.8±0.1 pg (R.S.D. 4.0%, n=8), whereas the corresponding between-day figures (1 mo) are m_o=2.8±0.2 pg (R.S.D. 6.6%, n=6). The linear range is 0.002-0.12 μg l⁻¹ with a sample loop of 1.8 ml, being strongly impaired with smaller sample volumes in FI mode. The sample throughput rate is 10 h⁻¹ with the semi-batch system. Applications to real human and bovine urine samples and CRMs of sea water (CASS-3), river water (SLRS-1 and SLRS-3) and urine (SRM 2670) are presented.     

An investigation of the changes in column efficiency accompanying the oxidation of apolar gas chromatographic stationary phases

Summary The effect of on-column oxidation upon the efficiency of apolar gas chromatographic columns is investigated. With an unsaturated hydrocarbon liquid phase and air as carrier gas dramatic changes of column efficiency are observed. Evidence is presented that suggests that this catastrophic deterioration of column performance is due to the oxidative crosslinking of the liquid phase molecules.     

Mass and heat transfer effects in continuous production scale gas-liquid chromatographic equipment

Summary A study has been made of the temperature and related solute concentrations in a 12 column (7.6 cm OD×61 cm) sequential continuous chromatograph at feed rates of up to 1400 cm³hr^–1 of Arklone P-Genklene P. Moving the feed point from the middle of a column to the end cone was found to be particularly beneficial. Besides increasing throughput it enabled the system Arklone P and dichloromethane (separation factor 1.17) to be separated, not previously possible with a central feed point.     

Simultaneous GLC determination of fenitrothion,aminocarb and their corresponding hydrolysis products in water

Summary A method has been developed for the simultaneous determination of fenitrothion, aminocarb, and their respective hydrolysis products, in water. These hydrolysis products are phenols and they are first derivatized to the corresponding esters with acetic anhydride directly in water. Extraction with methylene chloride successfully recovers the four chemicals which are then analysed by gas liquid chromatography using a nitrogen-phosphorous selective detector.     

Recent advances in solvation models for stationary phase characterization and the prediction of retention in gas chromatography

Summary Rapid progress has been made in the last few years in the development of solvation models for gas chromatography. These models are based on the free energy of transfer of a solute from the gas phase to solution consisting of the additive processes of cavity formation and solute-solvent interactions expressed as dispersion, orientation, induction and hydrogen-bond formation. The adaptation of these models to characterize solvent selectivity for a wide range of common stationary phases and to the prediction of retention is critically discussed. The need to use high quality retention data in the further elaboration of solvation models is also demonstrated.Dedicated to Professor Leslie S. Ettre on the occasion of his 70th birthday.     

Chromatography of diols. Regularities in the retention of linear diprimary diols in gas-solid and gas-liquid chromatography

Summary Using various sorbents in gas-liquid chromatography and gas-solid chromatography, the dependence of the retention of diprimary linear diols of the HOCH₂(CH₂)_nCH₂–OH type (n=0–4) on different parameters characterizing the physicochemical properties of the diols was studied. As shown, the relationship between the logarithm of the retention volume, or the boiling point, molecular mass, number of CH₂-groups, density, refractive index, molecular refraction, and the logarithm of the retention volumes obtained on another stationary phase is either linear or nearly linear. The linear regression coefficients of the various relationships are given.A change in the free adsorption energy (F) of the diols on Polysorb, Tween and polyethylene glycol 2000 with respect to ethylene glycols was studied. It is shown that Polysorb appeared to be the most specific stationary phase.Nauchno-proizvodstvennoe ob'edunenie (Research-industrial Company), Olajne, USSR.     

Trace analysis of N-formylmorpholine in hydrocarbons and water by gas-liquid chromatography

Summary N-Formylmorpholine, which is a solvent used in the extraction of benzene, toluene and xylenes extraction from petroleum feedstocks, is determined in trace amounts in water and in aromatic hydrocarbons by gas-liquid chromatography using two stationary phases. Traces of N-formylmorpholine in hydrocarbons was determined on a column packed with 2.3% Bentone 34+4.6% DEGA on Chromosorb W AW treated with 1% KOH. Traces of N-formylmorpholine in water was determined on 20% SE-30 on Chromosorb W AW. The developed methods were examined and proved to give quantitative results.