Gas Chromatographic Retention Data Research Articles

Simulation of the weathering of gasolines using gas chromatographic retention data

A method of calculation based on a simple equation derived from batch distillation theory is evaluated. This accounts for the evaporation loss of volatile components during the weathering of inflammable liquids. The relative volatility data required for the calculation are obtained from the capacity factors of the components in the gas chromatographic analysis. Starting from the gas chromatogram of a weathered sample of a gasoline, the chromatogram of the purported source sample is simulated. Generally, concentration patterns of residue samples can be correlated with those of reference samples, providing the evaporation loss has not exceeded 30%. This procedure could allow the tracing back of liquid samples from an arson scene to samples found in the possession of a suspect.

Simulation of concentration changes in complex volatile mixtures during evaporation by using gas chromatography

A method is proposed for the simulation of weathering and aging of mixtures of organic components of similar polarity, e.g. gasolines. Semi-empirical equations are derived and tested which correlate the composition of samples after evaporation with the composition of the original material. In this way, changes in composition during partial evaporation of the liquid mixture can be predicted. In the context of forensic investigations this procedure can be helpful for tracing back the composition of the liquid remaining to that of the original unweathered liquid. To perform this simulation, the relative volatilities of the individual components in the mixture have to be known. These are determined by gas chromatographic retention data simultaneously with the concentrations of the volatile components. The paper evaluates the semi-empirical equations employed and discusses the influence of the simplifying assumptions introduced on the accuracy of the simulation.

Derivatization and gas chromatographic—mass spectrometric detection of anabolic steroid residues isolated from edible muscle tissues

A method was developed for the detection of anabolic steroid residues in edible muscle tissues. After enzymic digestion of the tissue and purification on disposable C 18 solid-phase extraction columns, the extract was injected onto a C 18 reversed-phase high-performance liquid chromatographic column. Three fractions or windows were collected, each containing specific analytes. After evaporation to dryness, the residues were subjected to a derivatization procedure which yielded suitable derivatives. After gas chromatographic—mass spectrometric analysis, both gas chromatographic retention data and mass spectral data were used for the detection and identification of nortestosterone, testosterone, estradiol, ethinylestradiol, trenbolone, methyltestosterone, chlormadinone acetate, medroxyprogesterone acetate and megestrol acetate.

Gas chromatographic‐mass spectrometric confirmation of 19‐nortestosterone in the urine of untreated boars — effect of the administration of Laurabolin®

The presence of 17 beta-19-nortestosterone (nandrolone, NT, 17 beta-19-NT) and its epimer 17 alpha-19-nortestosterone (epiNT, 17 alpha-19-NT) was investigated in the urine of six untreated boars, obtained from experimental farms. The presence of 17 beta-19-nortestosterone was screened by RIA and HPTLC and confirmed by GC-MS analysis. Additionally, the two epimers (NT and epiNT) were investigated in the urine of a boar (two-year-old miniature male pig weighing 50 kg) before and after injection of 100 mg Laurabolin (nortestosterone laurate, Intervet N.V., Belgium). The isolation of the steroids was based on sample clean-up with solid phase extraction and subsequent high-performance liquid chromatography. Both gas chromatographic retention data and mass spectrometric data (selected ion monitoring and full spectrum) were used for detection and identification. The presence of 17 beta-19-nortestosterone in the urine of the boars that were not injected proves the endogenous production of the steroid. The absence of the 17 alpha-epimer in the urine of the injected boar suggests that 17 alpha-19-nortestosterone is not a major metabolite of 17 beta-19-nortestosterone.

Regression against temperature of gas chromatographic retention data

Specific retention volumes were measured in the range 25–75°C for benzene + squalane, benzene + triethylene glycol and n-hexane + squalane and in the range 15–55°C for benzene + tetraethylene glycol dimethyl ether, each in steps of 5°C. Values for the solution thermodynamic properties and their errors were obtained by fitting the experimental data to equations with two or more constant by using the method of Clarke and Glew. The best thermodynamic results were obtained by means of the three-constant equation; adding a fourth constant did not improve the adjustment. However, when the objective is interpolation, the results obtained with the classical, two-constant equation, are of adequate accuracy.

Application of gas chromatographic techniques for characterizing vapor sorption on soils: A review

Renewed interest in vapor phase transport of volatile organic compounds (VOCs) through soils and other geologic materials has emphasized the need to better characterize the adsorption of VOCs on a variety of adsorbents and over a wide range of water contents. Although a number of conventional batch equilibrium techniques are available, adapting gas-chromatography (GC) methods for measuring VOC sorption offers a number of advantages, including speed and the ability to make an unlimited number of measurements on the same sorbent. In addition, mixtures of VOCs can easily be accommodated with GC methods for the study of competitive sorption effects. In this paper, we review the current status of physicochemical measurements by GC, the use of soil and other natural materials for GC columns, and the use of water as a liquid phase in GC. Although a number of authors have used GC retention data to derive adsorption isotherms for VOCs, questions remain concerning the reproducibility of the isotherms on different columns and what factors affect isotherms derived from soil columns. Studies of VOC sorption on water films using GC appear to have been restricted to relatively high water contents and to dilute VOC concentrations (i.e., Henry's region).

Empirical correlations between gas-chromatographic retention data and physical or topological properties of solute molecules

Kováts retention indices (I) and relative retention times (τ) using Silicone oil 550 or Bentone 34 as the stationary phase were measured for 20 hydrocarbons (mainly alkylbenzenes). Statistical analysis of repeated determinations indicated that the empirical distribution function of retention indices is not normal; the relative standard deviations decrease with increasing retention index. Several models were examined to describe the retention data as a function of boiling point ( T B) and molar refraction, molar volume, connectivity indices, etc. A universal fitting equation y i = A exp ( BT Bi ) + Cx 2 i + D (where y i =I or τ, and x 2 i is one of the properties mentioned) proved to be best on the basis of statistical characteristics (examination of residuals, multiple correlation coefficient, residual mean square, variance ratio tests) which were also evaluated. The results were compared to equations recommended in the literature.

Preparation, stability and quantitative analysis by gas chromatography and gas chromatography—electron impact mass spectrometry of tert.-butyldimethylsilyl derivatives of some alkylphosphonic and alkyl methylphoshonic acids

Studies of tert.-butyldimethylsilylation of several alkyl methylphosphonic, alkylphosphonic and chlorine-substituted alkylphosphonic acids by several derivatizing reagents under differing reaction conditions are reported and a simple procedure for formation of these derivatives is identified. Determination of the stabilities of representative derivatives are reported and capillary column gas chromatographic (GC) retention data for all the derivatives studied are tabulated. General sensitivities for detection and quantitation of these compounds by GC—flame photometric detection and GC—electron impact mass spectrometry in both full-scan and multiple-ion detection modes are presented.

Factor analysis of the solute-stationary phase interactions in gas-liquid chromatography using the oblique procrastes transformation.

Factor analyses have been carried out for the gas-chromatographic retention data on 21 stationary phases and 190 solutes using the techniques of the principal factor analysis and the oblique procrastes transformations. The eigenvalues showed the necessity of three factors to explain fully the variations of the retention volumes. Further analyses by using the factor scores after the oblique procrastes transformations have disclosed the meanings of the three factors. Namely, the first factor reflects the dispersion interactions and the formation of cavities in the stationary phase, the second one reflects the polar interactions, and the third one reflects the hydrogen-bonding interactions.

Use of retention temperatures for the identification of phenols separated on OV-1701 capillary columns using linear temperature-programmed gas chromatography

A procedure is described by means of which linear temperature-programmed gas chromatographic (LTPGC) retention data can be predicted from isothermal Kováts retention indices of substituted phenols separated on capillary columns coated with OV-1701 under LTPGC conditions. The identification algorithm included the comparison of retention temperatures predicted from isothermal data ( T R, P) in retention temperatures obtained experimentally under LTPGC conditions ( T R, E) in a window which was within 1.5°C. The identification of phenol sample constituents based on the comparison of retention data was checked using spectra obtained by gas chromatography-mass spectrometry because in the identification window several sample constituents overlapped.

Correlation between molar refraction and gas chromatographic retention data

A study was made of the correlation between the measured molar refractions of 22 heterocyclic nitrogen-containing compounds with related structures, the molar refractions calculated from the bond refractions and the molar refractions predicted from gas chromatographic data. It was found that the time- and material-consuming experimental measurement of the molar refractions can be adequately substituted by calculation of the data, but in certain cases it is preferable to supplement the calculation with molar refraction values predicted via other experimentally obtained parameters such as I apol and I pol.

Correlation of structure with retention index for chlorinated dibenzo- p-dioxins

The method presented here allows calculation of the retention indices for the chlorinated dibenzo- p-dioxins under a specific set of experimental conditions, using a limited data set. This technique provides a simple say to obtain retention index data for those isomer standards not readily available. Thus, the technique can aid in structure assignment of specific congeners whether obtained from synthesis or found in environmental monitoring efforts. These calculations have proved highly successful in checking gas chromatographic retention data for internal consistency.

Characterization of the polycyclic aromatic hydrocarbons from two standard reference material air particulate samples

Polycyclic aromatic hydrocarbon (PAH) mixtures were isolated from two air particulate materials, which are available from the National Bureau of Standards as Standard Reference Materials. High-resolution liquid chromatography (LC), gas chromatography (GC), and gas chromatography-mass spectrometry were used to provide a detailed characterization of these two samples. Thirteen PAH were quantified in each of the two samples by using LC with spectrofluorometric detection and capillary GC with flame ionization detection. The PAH mixtures were separated into 10 subfractions using normal-phase LC on an aminosilane column. By use of this multidimensional chromatographic approach, quantitative information on over 180 PAH was obtained for these two samples including positive identification of approximately 55 compounds based on mass spectral data, fluorescence excitation and emission spectra, and comparison of LC and GC retention data for authentic reference compounds. The extensive qualitative and quantitative information obtained for these two materials is extremely useful because these samples are available to other laboratories for use in the comparison of analytical methods and results.

Microanalytical methods in the structure elucidation of sex-specific components in the large pine weevil, hylobius abietis l. ( coleoptera, curculionidae)

The sex-specific components isolated from ovaries of the large pine weevil, Hylobius abietis L., were studied by microchemical methods in combination with gas chromatography and mass spectrometry. A boric acid reaction loop prepared in a glass capillary was used for detection of alcohols in the hydrolysate of the sex-specific components. Gas chromatographic retention data and electron impact and chemical ionization mass spectra were used in the identification of the sex-specific components and their hydrolysis products. Double bond positions were determined and the absence of chain branching verified by recording the electron impact mass spectra of nicotinic acid esters of the hydrolysed sex-specific components. With this method, the double bond positions and chain branching could be determined from a sample of a few tens of nanograms. The female-specific components identified were hexadecyl acetate, octadecyl acetate, Z-9-octadecenyl acetate and eicosyl acetate.

Occurrence of 2,6,10-trimethyl-7-(3-methylbutyl)-dodecane and related hydrocarbons in the green alga Enteromorpha prolifera and sediments

The isoprenoid alkane 2,6,10-trimethyl-7(3-methylbutyl)-dodecane, a related monoene and a pseudohomologous C 25 diene have been identified in field specimens of the green alga Enteromorpha prolifera. The identifications were based on gas chromatographic retention data, microscale hydrogeneration, mass spectral evidence and, for the C 20 alkane, comparison with the synthesised hydrocarbon. The same compounds, and related hydrocarbons with the same two carbon skeletons, appear to occur widely in freshwater and marine sediments and sedimenting particles from different parts of the globe. Some of these highly branched sedimentary compounds may be algal in origin.

Vapor pressure estimates of individual polychlorinated biphenyls and commercial fluids using gas chromatographic retention data

The liquid phase vapor pressures at 25°C of 27 polychlorinated biphenyls were plotted versus published retention indices on two gas chromatographic stationary phases. Good fits were obtained ( r 2  0.996-0.999) for data on an intermediate polarity (Dexsil-410) capillary and a non-polar (OV-101) packed column. Estimates of vapor pressures for 134 polychlorinated biphenyls found in five commercial Aroclor fluids were made using these two plots and published retention indices. Vapor pressure estimates of the five fluids were calculated using individual polychlorinated biphenyl vapor pressures and Aroclor compositional information, assuming Raoult's law. The resulting vapor pressures at 25°C for Aroclors 1248, 1254 and 1260 were ca. 2.3-3.3 times lower than values previously reported, whereas the vapor pressure of Aroclor 1242 was 1.4 times higher.

Quantification of polycyclic aromatic hydrocarbons and nitro-substituted polycyclic aromatic hydrocarbons and mutagenicity testing for the characterization of ambient air particulate matter

As part of a study to identify mutagenic and potentially carcinogenic compounds in urban air particulate extracts, the polycyclic aromatic hydrocarbon (PAH) mixture isolated from a large sample collected in Philadelphia, PA, was characterized by liquid chromatography (LC), gas chromatography (GC), and gas chromatography-mass spectrometry (GC-MS). After isolation of the aromatic fraction from the extract using classical liquid-liquid partitioning and silica gel column chromatography, the PAH fraction was isolated by normal-phase LC. A number of the major PAH constituents were quantified by GC and LC. Quantification of the minor constituents was accomplished by further subfractionation of the PAH mixture into eight fractions based on the number of aromatic carbons in the PAH. These fractions were then characterized by GC and GC-MS. More than 100 PAH components were quantified in this sample. Approximately 40 unsubstituted PAH and 10 methyl-substituted PAH were identified based on GC retention, LC retention, fluorescence, and/or mass spectral data. Several nitro-substituted PAH were also found in the PAH fraction and the more polar fractions isolated from the original aromatic fraction.

1-Octen-3-ol. A potent olfactory stimulant and attractant for tsetse isolated from cattle odours

Recording of electroantennographic (EAG) responses from tsetse, Glossina pallidipes and G. morsitans morsitans (Diptera: Glossinidae) has been used to detect olfactory stimulants in volatiles from cattle. The most potent stimulant in cattle odours collected on Porapak resin has been identifiedas 1-octen-3-ol by gas chromatographic retention data and mass spectrometry. The rate of production of 1-octen-3-ol by a normal ox was estimated to be 0.043 mghr−1, and the natural material was shown to be predominantly the (R)-(−)enantiomer. No 1-octen-3-ol was collected under the conditions used in the absence of an ox. EAG dose-response curves to 1-octen-3-ol showed it to be about 106 times more potent than acetone, a known attractant for tsetse, with the maximum response of about 1 mV occurring to approx. 1 ng at source. 1-octen-3-ol caused increased upwind flight by tsetse in a wind tunnel bioassay, and in the field it was attractive to tsetse by itself and also increased the attractiveness of both ox odour and of mixtures ofcarbon dioxide and acetone.

Capillary column gas chromatographic determination of nitro polycyclic aromatic compounds in particulate extracts

A method for the determination of nitro polycyclic aromatic compounds in particulate extracts was developed and applied to the analysis of a diesel exhaust extract. Silicic acid column chromatography combined with reduction of the nitro compounds with KBH/sub 4/ catalyzed with copper(II) chloride and derivatization with pentafluoropropionic anhydride yielded an enriched nitro fraction. Nitro polycyclic aromatic compounds present in this fraction as pentafluoropropyl amides were subsequently analyzed by capillary gas chromatography with electron capture, nitrogen-selective thermionic, and flame ionization detection and by gas chromatography/mass spectrometry. Ten nitro polycyclic aromatic compound isomers were positively identified based on comparisons of gas chromatographic retention data of standard compounds, gas chromatography/mass spectrometry, and low-resolution mass spectral data. Over 120 nitro polycyclic aromatic compounds were tentatively identified. 16 references, 4 figures, 2 tables.

Evaluation of a gas chromatographic method calculating vapor pressures with organophosphorus pesticides

The vapor pressures of 20 organophosphorus pesticides varying widely instructure, polarity and volatility were calculated using a method based upon gas chromatographic (GC) retention data. For seven of the pesticides, vapor pressures were determined experimentally by a standard gas saturation method for comparison with the GC-calculated values. Several experimental variables, including the number of GC temperatures and spread between them, nature of the liquid phase in either packed or capillary columns, and nature of the reference compound, were studied for their influence on the GC method's error. The GC calculation, using a short SE-30 capillary column, single reference compound (methyl parathion), and melting point correction for those test compounds which are solids at room temperature, provided vapor pressures agreeing with an average factor of approximately 4 with experimental vapor pressures. The agreement improved when the comparison was with test compounds which are liquids at room temperature and when the polarity of the GC reference compound approximated that of the test compounds.