Temperature-programmed Gas Chromatography Research Articles

Use of equivalent chain lengths for the characterization of fatty acid methyl esters separated by linear temperature-programmed gas chromatography

C 12C 26 fatty acid methyl esters (FAMEs) were separated by glass capillary gas chromatography on SP 2340 as stationary phase, both isothermally in the temperature range 150–220°C and using linear temperature-programmed capillary gas chromatography (LTPCGC) with gradients of 0.5–3.5°C/min. The dependences of the equivalent chain lengths on temperature are linear. An equation as well as a graphic procedure are derived for the prediction of the retention temperatures of FAMEs separated by LTPCGC on SP 2340. Good agreement between predicted and experimental retention temperatures was found.

Threshold temperatures for solute mobility. Their determination and effect on programmed temperature gas chromatographic separations

AbstractThe threshold temperature for solute mobility is defined as that temperature at which a solute band, which was initially cold trapped at the head of the column, begins moving through the column. It is shown that the separation of compounds by programmed temperature gas Chromatography (PTGC) occurs primarily at the head of the column as a result of differences in threshold temperatures. Additional column length beyoud that needed to trap the compounds improves resolution, primarily by delaying emergence (while maintaining the temperature and time spacing) thus allowing the column temperature to rise, the solute terminal velocities to increase, and narrower peak widths to be recorded. For maximum resolution in minimum analysis time, the initial temperature must be at or below the threshold temperature of the most volatile compound in the mixture to be separated.Three methods for determining threshold temperatures are presented.

Cuticular Lipids for Species Recognition of Mole Crickets (Orthoptera: Gryllotalpidae) I. Scapteriscus didactylus, Scapteriscus imitatus, and Scapteriscus vicinus

Whole-body cuticular extracts of Scapteriscus didactylus and Scapteriscus imitatus collected from Puerto Rico, and of Scapteriscus vicinus collected in Florida, were analyzed by isothermal and temperature programmed gas chromatography. Calculated Kovats Indices indicated an homologous series of straight-chain and branched-chain alkanes in the cuticular lipids of each mole cricket. No differences were found between the sexes of species, but small variations in qualitative and quantitative patterns were present among individuals. The profiles of GC peaks were easily distinguishable, providing data for species and region of origin recognition, and supporting morphological and acoustical evidence that the crickets represent 3 species.

Detection of Drugs in Saliva of Impaired Drivers

This study examined the feasibility of detecting drugs using saliva samples obtained from impaired drivers. Screening procedures on 1- to 2-mL samples were for cannabinoids, volatiles, benzodiazepines, and other acidic/neutral/basic drugs. Methodology consisted of enzyme multiple immunoassay technique (EMIT) and temperature programmed gas chromatography with confirmation by gas chromatography/mass spectrometry (GC/MS). Fifty-six samples were obtained from drivers arrested for suspicion of impaired driving. Other than alcohol, the major drugs detected were cannabinoids and diazepam. Cocaine was found in one case.

Emergence temperatures as physical constants for measuring analyte retention in programmed temperature gas chromatography

Emergence temperatures are physical constants useful for describing analyte retention when progrmmed temperature gas chromatographic operating parameters are properly standardized. A combination of all the column operating conditions is standardized by the proposed method, therefore a wide variety of conditions (column length, program-rate, flow-rate, amount of stationary phase, etc.) may be used. Reproducibility is unaffected by the size, shape, or polarity of the analytes. In addition, tables of emergence temperatures provide an excellent means of identification of unknowns because reference compounds can be selected that emerge close to the compounds to be identified.

Application of Tenax Trapping to Analysis of Gas Phase Organic Compounds in Ultra-Low Tar Cigarette Smoke

Abstract A method well suited to the analysis of gas phase organic compounds in ultra-low tar delivery cigarette smoke has been developed. The cigarette is smoked directly through a filter and a Tenax trap arranged in series. The components collected on Tenax are analyzed by thermal-desorption programmed-temperature gas chromatography. Components are then quantitated by the use of external standards. The smoke from high tar delivery cigarettes also can be analyzed by thermal desorption gas chromatography of portions of well mixed solid dilutions of the trapping Tenax. Deliveries of 34 gas phase components were determined for 4 ultra-low tar cigarettes having tar deliveries ranging from <0.01 to 3 mg tar/cigarette, and 24 components for 5 cigarettes delivering 7 to 45 mg tar/cigarette.

An application of trimethylsilyl derivatives with temperature programmed gas chromatography to the senior analytical laboratory

In this instrumental analysis program, the authors describe how they have devised an experimental procedure to teach students about TPGC and the importance of derivatizing many classes of substrate...

Compensation of baseline drift in temperature-programmed capillary gas chromatography with electron-capture detection

Compensation of baseline drift in temperature-programmed capillary gas chromatography with electron-capture detection

Stationary Spatial Temperature Gradient in Gas Chromatography

Abstract Imposing an increasing stationary temperature gradient along the length of a gas chromatographic column is proposed as a technique for improving separation. Side outlet ports with control valves would allow the process to have the same advantages of programmed temperature gas chromatography without the disadvantages of temperature transients. For a simple model of gas chromatography the analysis provides expressions for temporal moments at any point along the column as a function of the temperature gradient. Reduced retention times, sharpening of peaks, and higher symmetry are predicted due to increasing the temperature gradient. The relationship to chromathermography is discussed.

Triclocarban and Cloflucarban: I. Gas-Liquid Chromatography of Triclocarban, Cloflucarban and Related Anilines after Silylation

Abstract A method is presented for the simultaneous determination of Triclocarban (N-(4-chlorophenyl)-N'-(3,4-dichlorophenyl)urea, [101-20-2] Cloflucarban (N-(4-chlorophenyl)-N'-[4-chloro-3-(trifluoromethyl)phenyl]urea, [369-77-7]) and the related anilines, 4-chloroaniline, 3,4-dichloroaniline and 4-chloro-3-trifluoromethyl aniline.∗ Temperature programmed gas chromatography, after preparing trimethylsilyl derivatives is employed, using MSTFA (N-methyl-N-trimethyl-silyl trifluoroacetamide) as the derivatizing agent and a column with Dexsil 400 as the stationary phase. On a glass column quantitative results are obtained and linear calibration plots are obtained using phenanthrene as an internal standard, for 20-400 ng Triclocarban with a flame-ionization detector. Well-resolved gas chromatograms are obtained for the several compounds.

Characterization of commercial waxes by high-temperature gas chromatography

Sixteen different waxes (including two oils) were characterized by temperature-programmed gas chromatography up to 400°C, using flame ionization detection. Chromatographic patterns were obtained for the untreated samples and for samples treated with diazomethane and acetic anhydride. Included with the patterns are physical characteristics, origins of the waxes, and where available, references to gas—liquid chromatographic work done by others.

Programmed temperature gas chromatography using a constant-frequency electron capture detector

Programmed temperature gas chromatography using a constant-frequency electron capture detector

Linearized response of a constant-frequency electron capture detector and its application to programmed temperature gas chromatography

Linearized response of a constant-frequency electron capture detector and its application to programmed temperature gas chromatography

The Use of Retention Indices and Temperature-Programmed Gas Chromatography in Analytical Toxicology

Data for temperature-programmed gas chromatography, useful for toxicological screening procedures, are reported for 289 compounds for SE-30, OV-7, and OV-17 stationary phases. A review and discussion of important considerations affecting precision and reproducibillty are included.

A rapid gas chromatographic method for the determination of plasma polyamines and its application to the prediction of tumour response to chemotherapy

Isobutyloxycarbonyl derivatives of the polyamines, spermidine, spermine and putrescine in 1 ml plasma were analysed on a mixed phase, 1.5% SE-30, 0.15% FFAP, column by temperature-programmed gas chromatography using a nitrogen-sensitive glass bead detector. Levels in 60 normal subjects (mean ±2 S.D.) were 0.13 ± 0.08 μmol/l for spermidine, 0.02 ± 0.04 for spermine and ⩽ 0.18 for putrescine. Elevated spermidine levels were found pre-treatment in only 20% of patients with advanced metastatic cancer, reflecting the lack of sensitivity of polyamines as markers for malignant disease. However, serial studies in 26 patients undergoing remission induction chemotherapy showed that a significant rise in plasma spermidine within 48 h correlated with subsequent clinical response ( p < 0.001). Tumour response to chemotherapy can be predicted by the assay of plasma polyamines.

Soil Injection of Insecticides for Control of Citrus Blackfly in Dooryard Citrus

We studied the effects of 3 soil injected systemic insecticides for control of both high and low density Aleurocanthus woglumi Ashby infestations on citrus in an urban environment. Acephate injected at 3 rates provided acceptable levels of control while oxydemetonmethyl and dimethoate did not produce significant control. Presence of acephate and its metabolite methamidophos in citrus leaves was confirmed through the use of temperature programmed gas chromatography. Aggregated field mortality data suggested that the soil injection approach would be more consistent with developing management strategies rather than as a component of more absolute goals such as eradication. The lack of spray drift and the highly localized nature of application can make soil injection a potentially valuable insect management tool in highly urbanized environments.

Determination of adsorption enthalpies and entropies of inorganic halides by temperature-programmed gas chromatography

The possibilities of using temperature-programmed gas-solid chromatography for the determination of adsorption enthalpies and entropies of inorganic chlorides are investigated. This method is suitable, if data of limited accuracy are acceptable, whereas for more precise data isothermal gas chromatography is recommended. The advantage of temperature-programmed experiments is that simultaneous investigations can be made of compounds with very different volatilities. The results of these investigations support the picture of “surface complexes” between the adsorbed molecules (metal halides or oxyhalides, e.g.. ReCl 5, SnCl 4, PoCl 4, etc.) and the adsorbent (alkali metal halides, SiO 2).

Quick identification and analysis of plasticizers in PVC by programmed‐temperature gas chromatography using the best stationary phases

AbstractA quick and safe identification method is shown for plasticizers in PVC using programmed‐temperature gas chromatography. Plasticizers were identified by their retention index values measured by using normal paraffins. Several stationary phases with quite different polarity are proposed: with silicone polymers (SE 30, OV 17, and QF 1) and a porous polymer such as Tenax. Operational conditions were optimized. The initial column temperatures was chosen at a low value of 100°C with the first three phases and 180°C for the fourth. The best rate of temperature increase with time seemed to be 10°C/min. The calculation method for retention values (temperature, time, indices) was chosen just because it needed no approximation. Thermodynamic values for the solution of plasticizers were measured by using isothermal chromatography with all the stationary phases. Our method allows the analyst to operational conditions (solvent, percent, temperature) for chromatography, to solve his own problem by making use of a pocket computer. Quantitative analysis of plasticizers was obtained with good accuracy after a previous extraction and the addition of normal paraffin as internal standard.

Moment Theory of Band Spreading, Skew ness, and Resolution in Programmed Temperature Gas Chromatography

Abstract Expressions for first, second, and third moments are developed for a simple model of gas-liquid partition Chromatography with linear temperature programming. The results show how increased heating rate causes increased sharpening of output peaks, even though resolution is decreased. Second and third central moments are nearly inversely proportional to heating rate.

Differential programmed temperature gas chromatography

Differential programmed temperature gas chromatography