A new, generally applicable procedure for the preparation of glass capillary columns

Capillary Gas Chromatographic Separation Performances of a Tetraphenyl Porphyrin Stationary Phase

Tetraphenyl porphyrin (TPP) has enormous potential for use as gas chromatography stationary phases because it has a distinctive extended π–π conjugated coplanar structure and a range of interesting properties such as a good solubility in dichloromethane, high melting point, and good thermal stability. In this work, a TPP column was successfully prepared using a static method. The column was nonpolar and had a high efficiency. The chromatographic selectivity of the TPP column was assessed. The TPP column showed superiority retention and higher resolution for alicyclic, aromatic molecules through ring matching and π-π stacking interaction comparable to HP-5MS column. The unique mechanisms through which the TPP column retained polychlorinated biphenyls allowed the peak pair of 2,2ʹ,5-trichlorobiphenyl and 4,4ʹ-dichlorobiphenyl to be resolved better on the TPP column than the HP-5MS column. The TPP column was thermally stable even at 260°C for 2 h and gave results of a high degree of precision (run-to-run and column-to-column) with relative standard deviations <0.05% and <4.96%, respectively. The results indicated that porphyrin derivatives will be useful gas chromatography stationary phases.

Polymer-Coated Fibrous Stationary Phases in Packed-Capillary Gas Chromatography

Fibrous synthetic polymers have been introduced as the support material for packed capillaries in gas chromatography. The filaments of the polymers were packed longitudinally into a fused-silica capillary, followed by the conventional coating process for open-tubular capillaries. With various polysiloxane-based polymeric materials coated onto these filaments, it was demonstrated that the retentivity was significantly improved over conventional wall-coated capillaries of the same length and that the selectivity can be tuned by selecting different coating materials chosen for the various purposes. The results clearly showed the contribution of the fibrous support and the polymer-coating to the retention of analytes. They also showed the bright possibility for a novel usage of fine fibrous polymers as the support material, which can be combined with a newly-synthesized coating materials designed for particular separations.

Determination of the total and partial cohesion parameters of lipophilic liquids by gas-liquid chromatography and from molecular properties

The total and partial cohesion parameters of seven lipophilic liquids (one alkane, two alcohols, one acid, and three esters) have been determined. The proposed procedure involves knowledge of the structure, and determination of dipole moment, refractive index, and dielectric constant of the substances. The total cohesion parameters are experimentally determined for four liquids by gas-liquid chromatography, and also calculated for these and three additional liquids according to Fedors by summation of group increments. The dispersion cohesion parameter is calculated from the refractive index, and the polar cohesion parameter by Taft's polarity function, and Carr's relationship. The hydrogen bonding cohesion parameter is then obtained by difference. The results are self-consistent and coherent. In particular, it may be seen that the difference between the various lipophilic liquids, from the point of view of intermolecular interactions, is essentially due to the variation in strength of hydrogen bonds and dipole-dipole interactions, whereas the interactions stemming from the dispersion forces are similar.

Chiral-phase capillary gas chromatography and mosquito repellent activity of some oxazolidine derivatives of (+)- and (-)-citronellol

Fourteen stereoisomeric mixtures of six oxazolidine heterocycles and one amino alcohol were obtained from commercial samples of (+)-, (-), or (+/-)-citronellol and evaluated in a cloth test system as mosquito repellents. A technical sample of 3-acetyl-2-(2',6'-dimethyl-5'-heptenyl)oxazolidine, evaluated initially as a mixture of two pairs of enantiomers, was an effective repellent against two of the three species of mosquitoes. To study repellency-stereochemistry relationships, 1 was isolated as fractions G-1, G-2, I-1, and I-2, corresponding to representative samples of the four possible stereoisomers. The enantiomeric composition of 1, but not of the other derivatives, could be determined by chiral-phase capillary gas chromatography with Chirasil-Val. Two chiral phases showed that experimental samples of 1, and hence the commercial samples of 2, were composed of not more than 90% of one enantiomer. Differences in repellency of isomerically enriched samples were generally small. Fraction G, a mixture of diastereoisomers readily prepared from (+)-2, was considerably more effective than standard insect repellents in bioassays with three mosquito species.

Assay of lipids in dog myocardium using capillary gas chromatography and derivatization with boron trifluoride and methanol

The fatty acids of three lipid classes (free fatty acids, triglycerides, and cholesteryl esters) from dog heart were analysed by gas chromatography. Samples of the left ventricle were homogenized and total lipids were extracted. After separation by thin-layer chromatography, the bands of the lipid classes studied were scraped off, transmethylated according to the boron trifluoride-methanol procedure, and the fatty acid methyl esters were extracted and analysed. The problems related to the quantitation of fatty acids were investigated, namely transmethylation procedure, thin-layer chromatography, and gas chromatographic conditions. Fatty acid methyl esters were separated on capillary columns coated in the laboratory with SP 2340 stationary phase. The high performance of the separation ensured the reliability and the precision of the analysis.

Analysis of anabolic steroids in body fluids by capillary gas chromatography with a two-channel detection system and a computer

A method is described for analysis of multi-component mixtures of steroid metabolites in biological fluids by means of capillary gas chromatography with glass and fused-silica columns and simultaneous detection of methoxylamine-trimethylsilyl derivatives with universal flame-ionization and selective nitrogen alkali flameionization detectors. A data system was applied to the on-line treatment of the results. Computer programs were designed for precise calculation of Kováts retention indices from the known values for selected natural urinary steroids. The programs allow the selection of nitrogen-containing components, normalized chromatogram plotting for both detection channels and qualitative and quantitative analysis. Results are presented on the detection of metabolites of methandrostenolone, 17 alpha-methyltestosterone, 19-nortestosterone and fluoxymesterone.

Capillary gas chromatographic analysis of human skin surface lipids after microsampling on ground-glass platelets

Small amounts of human skin surface lipids, in the 1-20 micrograms range, sampled on ground-glass platelets are investigated using capillary gas chromatography. A first system allows the separation of the neutral lipids, up to the triglyceride fraction. A second system reveals the distribution of the free fatty acids or of the free + glyceride fatty acids, after a methylation or transesterification step. Examination of samples from nine subjects shows that the unsaturation of the free fatty acids increases during a four-day period of accumulation. Comparison of the free fatty acid fraction and the free + glyceride fatty acid fraction shows that the fraction is more saturated than the latter. It is concluded that the bacterial lipases which cleave the fatty acids from the ester bond favor the liberation of straight-chain saturated fatty acids from sebum triglycerides. This result is confirmed by comparison of the free fatty acid fraction with the glyceride fatty acid fraction separated from bulk samples of skin surface lipids from hair and scalp.