Open Tubular Capillary Column Research Articles

Noncryogenic FSOT column separation of sulfur‐containing gases

AbstractFused silica open tubular (FSOT) capillary column GC separations of low molecular weight, reactive sulfur‐containing gases (S‐gases) are significant improvements over packed column separations in terms of resolution, detection limits, and conditioning effects. Nevertheless, some of the problems with current FSOT capillary systems include matrix Injection incompatibilities; detector dead volumes; the necessity for cryogenic initial oven temperatures to separate CO2, H2S, COS, and SO2; and relatively long analysis times to separate later, closely eluting compounds. A noncryogenic FSOT GC‐FPD system that either reduces or eliminates these problems is reported. Baseline separation of seven common S‐gases (H2S‐DMDS) is achieved in less than 5 min with ambient initial oven temperatures via this system, which is a combination of (1) a cryogenic sample concentration/injection design that is flow compatible with a wide‐bore FSOT column; (2) a combined DB‐1/DB‐WAX thick phase, wide‐bore FSOT column for greater capacity, retention, and tuned selectivity; and (3) a reduced dead volume FPD to minimize peak width and tailing.

Determination of Purgeable Halocarbons and Aromatics by Photoionization and Hall Electrolytic Conductivity Detectors Connected in Series

The applicability of the purge-and-trap technique, combined with a photo ionization detector (PID) and a Hall electrolytic conductivity detector (EICD) connected in series to the determination of 46 volatile organic compounds, is investigated. Both packed and open tubular capillary columns are evaluated. Twenty compounds arranged in nine groups coelute on the 1% SP-1000 on Carbopack B column, and 15 compounds arranged in five groups coelute on the n-octane/Porosil column. Preliminary experiments with wide-bore capillary columns indicate that either the VOCOL or the DB-624 open tubular capillary column can be used for the primary analysis of Methods 8010 and 8020 compounds. However, neither column is able to completely resolve all compounds. Twenty compounds arranged in eight groups coelute on the VOCOL (diphenyl dimethyl polysiloxane with crosslinking moieties, Supelco, Inc.) open tubular capillary column and 11 compounds arranged in five groups coelute on the DB-624 (cyanopropyl phenyl dimethyl polysiloxane, J&W Scientific) open tubular capillary column. Method precision of the purge-and-trap technique with a PID and a Hall EICD connected in series, as assessed from the instrument response at a known concentration per compound, is better than ± 30% (except for dichloromethane) and has a mean value of ± 12%. Method accuracy ranges from 82 to 104% for groundwater samples. Method detection limits vary with each compound and range from 0.1 to 0.9 ppb for water samples and 1 to 5 ppm for soil samples.

Supercritical fluid chromatographic separation of low- to medium-polarity compounds that are difficult to elute from packed columns

Abstract Supercritical fluid chromatography with flame ionization detection of unsubstituted and substituted heavy carboxylic acids (C18–C30) and of various polymer additives (PAs) is demonstrated. All compounds were easily eluted with carbon dioxide or nitrous oxide from open-tubular capillary columns with non-polar methylsilicone (DB-1) or phenylmethylpolysiloxane (SE-54) stationary phases in less than 20 min. Comparison of the two mobile phases showed taht nitrous oxide was not suitable for pressure programming and flame ionization detection due to a severe baseline drift caused by the high background level. On packed C18 or cyano bonded phase columns, aliphatic amine (Armostat 400) or amide (Oleamide, Erucamide) PAs as well as carboxylic acids were strongly adsorbed, whereas an alphatic disulphide (Hostanox SE-10) was eluted witht eh same mobile phases. The peak symmetry was measured and was found to decrease drastically with increasing loads of compounds with polar substituents, compared to a non-polar aliphatic hydrocarbon.

Quality criteria for chromatographic analytical systems of polyunsaturated fatty acids metabolites

The most powerful technique for eicosanoids identification is gas chromatography prior to mass spectrometry. Results are highly dependent upon the choice of appropriate gas chromatographic systems ; the critical point of the system being the quality of the column. Our work is intended to provide a general overview of open tubular capillary columns which can be used for separation, identification and quantification of eicosanoids.

Dynamically modified capillary columns for liquid chromatographic separations of biological compounds.

Dynamically modified open tubular capillary columns were evaluated for separations of biological and clinical interest. Small diameter, dynamically modified columns were readily prepared by simple addition of cetyltrimethylammonium salts to the mobile phase. Separations similar to those obtained on conventional reversed-phase columns were observed for neutral solutes, and ion-pair reversed-phase separations were observed for charged solutes. Borosilicate and standard flint glasses were evaluated with respect to common etching procedures. A potential clinical application is presented in the separation of antitumor drugs.

Bonded Fused Silica Capillary Column GLC Determination of BHA and BHT in Chewing Gums

ABSTRACTA gas chromatographic method was developed for the quantitation of BHA and BHT in toluene plus 2‐propanol extracts of chewing gum samples. The method uses a thick film (1.0 micron) bonded fused silica open tubular capillary column which resolves antioxidants from flavor oil volatiles and gum base components as confirmed by mass spectral analysis. The chromatographic method is reproducible at 4.0 ppm and detects as little as 2.0 ppm. Regression analysis of antioxidant‐biphenyl internal standard peak area ratios to antioxidant concentrations resulted in a highly linear equation with a correlation coefficient (R) of 0.99 for the 10 ‐ 150 ppm range.

New Methods for Characterization of Supercritical Fluid Solutions

AbstractThe dependence of the solvating power of a supercritical fluid on pressure allows this property to be continuously changed from that of a gas to approaching that of a liquid. This ability has led to the development of new analytical, separation, and extraction methods. These methods include open tubular capillary column supercritical fluid chromatography, direct fluid injection‐mass spectrometry, and the direct combination of these techniques. The direct fluid injection process enables the transfer of nonvolatile or thermally labile compounds to the gas phase allowing the use of mass spectrometry and other analytical techniques. In addition, the rapid development of capillary column supercritical fluid chromatography now allows the high resolution separation of complex mixtures. Several examples are given to demonstrate the application of these methods for the characterization of complex supercritical fluid solutions and extracted mixtures.

Etude d'une surface de phase stationnaire deposee sur du verre sous ultrasons

Resume The inner glass surface which is obtained in open tubular capillary column preparation by ultrasonics is studied by scanning electron microscopy and X-Ray dispersion.

Gas chromatography — Mass-spectronometry of volatiles released from plastics used as building materials

The possibility of employing a number of adsorbents (polyphenylquinoxaline, Tenax GC, Carbopak C, graphitized thermal carbon black, silica gels modified with pyrocarbon or hexamethyldisilazane) for the trapping of organic traces from air has been investigated. Adsorption capacities of these adsorbents with respect to a number of volatiles released from certain plastics used as building material (polyvinylchloride, Relin, Acronal, etc.) have been measured. A number of the volatiles were identified by gas chromatography — mass-spectrometry after trapping on the adsorbents investigated. Chromatographic separation after trapping on the adsorbents was carried out on wall-coated open-tubular capillary columns as well as in capillary columns packed with graphitized thermal carbon black.

Polyamide-Coated Open- Tubular Micro-Capillary Column for Liquid Chromatography

Abstract An open-tubular micro capillary column was prepared by coating the inner wall of a pyrex tube (50 μm i.d.) with polyamide. Chromatographic behaviors of trace amounts of various phenolic compounds, benzoic acid derivatives and aromatic amino and nitro compounds, were examined on this column.

Capillary GC and GC-MS of porphyrins and metalloporphyrins

Despite their inherent low volatility, a wide range of alkyl porphyrins and their various metallo-derivatives have been successfully analysed by gas chromatography on wall coated open tubular (WCOT) capillary columns. As a result of their superior peak shape (comparable ton-alkanes of similar retention times) and relatively low Kovat's retention indices (3300–3900), the bis(trialkylsiloxy)Si(IV) derivatives offer the greatest potential for the GC analysis of geological mixtures of alkyl porphyrins. Similar derivatives of porphyrins of biomedical importance, possessing polar side chains, are also amenable to GC and GC-MS analysis.

Capillary columns-from London to London in 25 years

The paper presents an overview of the evolution of open tubular (capillary) columns introduced 25 years ago by M.J.E. Golay. This evolution is divided into five stages: the formulation of the theory and the basic work laying down the foundations for future work; learning the influence of the variables on column performance; development of columns with increased surface area; development of glass and fused-silica columns; and, finally, the introduction of open tubular columns in liquid chromatography. In each stage, the pioneering activities are summarized and the most important references given.

Glass capillary gas chromatography of C1−C4 mononitroalkanes. Pre-calculation of the relative retention

The separation of C1−C4 mononitroalkanes on four wall-coated glass open tubular (capillary) columns (liquid phases: OV-101, Ucon-LB-550X, NPGS and Carbowax 20M) was investigated. Retention indices were determined and the influence of the different factors (analysis temperature, method of determining the gas holdup time and the nature of the stationary phases) on their reproducibility were studied. Linear regression equations permit the pre-calculation of the retention indices of C1−C4 mononitroalkanes from their properties on all liquid phases studied.

Analysis of steroids in urine for differentiation of pseudohypoaldosteronism and aldosterone biosynthetic defect.

The salt-losing syndromes in the neonatal period and early infancy due to adrenal disease can be differentiated by the pattern of excretion of steroids in urine. The presence or absence of metabolites of cortisol, aldosterone, and corticosterone as well as certain precursors can be established in a single analysis of steroids in urine by using gas chromatography with open tubular capillary columns. The profiles of steroid excretion in the urine of 8 infants with renal tubular insensitivity to aldosterone were compared with those in 5 infants with isolated aldosterone biosynthetic defects. The excretion in urine of 18 hydroxytetrahydro-compound A was elevated in all 13 children, but relative to the excretion of tetrahydroaldosterone, a high ratio was found for the biosynthetic defect and clearly distinguished the 2 conditions. Age-related changes in steroid metabolism are described. The diagnosis in each case was supported by clinical investigation together with determinations of PRA and aldosterone concentrations.

The trace sterols of the red alga Laurencia papillosa investigated by open tubular capillary column gas chromatography-mass spectrometry

1. 1. An extract of the red alga Laurencia papillosa was examined for the presence of sterols by computerized gas chromatography-mass spectrometry with two different open-tubular capillary columns. 2. 2. Cholesterol was found to be the major component (about 97%) in agreement with findings in other red algae. 3. 3. The minor and trace sterols identified are 22-dehydrocholesterol, brassicasterol, 24-methylene-cholesterol, campesterol, sitosterol (or poriferasterol) and fucosterol. 4. 4. Several other C 27-, C 28- and C 29-sterols were detected including two 24-ethyl sterols for which the C 24 configuration could not be assigned. 5. 5. A trace of 28-isofucosterol was also indicated. 6. 6. The particular mass spectral properties of sterol t-butyl dimethylsilyl ethers allowed the rapid and simultaneous detection of the trace sterols by mass chromatography even in the presence of a huge excess of cholesterol without prior fractionation and concentration. 7. 7. The combined technique offers great potential for the ready detection of new trace sterols and possibly active sterol metabolites in variety of extracts.

Capillary gas-liquid chromatography of faecal free and esterified neutral sterols

A method is described for the analysis of faecal free and esterified neutral sterols by high-resolution capillary gas-liquid chromatography (GC). After homogenization and filtration of the sample, free and esterified sterols are separated by reversed-phase Lipidex-5000 chromatography. The esterified sterols are saponified and analysed by GC. The free sterols are further fractionated on a Lipidex-5000 straight-phase column into oxo- and hydroxysterols, respectively. The GC separation of the compounds is achieved with an SE-30 open-tubular silica capillary column. The mean recoveries of the authentic sterols are 90.0% +/- 5.8% (SD) and the mean within-assay coefficients of variations are 3.7% +/- 2.9% (SD). The method permits determination of (A) the main animal sterols (cholesterol, coprostanol, epicoprostanol, cholestanol, coprostanone and cholestanone), (B) the amount of total plant sterols (beta-sitosterol, campesterol, stigmasterol and their metabolic conversion products) and (C) the degree of esterification of neutral sterols. In addition results obtained in faecal samples from eight healthy young men eating normal Finnish food are presented.

Dimethylisopropylsilyl ether derivatives in gas chromatography mass spectrometry of prostaglandins and thromboxane B2

The dimethylisopropylsilyl ether derivatives of PGF1α and PGF2αmethyl esters and PGD2, PGE1, PGE2, 6-Keto PGF1α and thromboxane B2 methoxime-methyl esters were separated completely within 15 min by gas chromatography using open tubular glass capillary column coated with SE-30. The methylene unit values of these derivatives were slightly greater than those of the corresponding dimethyl-n-propylsilyl ether derivatives. The use of the dimethylisopropylsilyl ether derivatives made it possible to perform the baseline separation of PGs and thromboxane B2 which were not separated by the trimethylsilyl ether derivatives. The mass spectral fragmentation of these dimethylisopropylsilyl ether derivatives was similar to those of the corresponding trimethysilyl ether derivatives, reported in a previous paper. Their mass spectra were characterized by the molecular ion, [M]+., and the ions [M—15]+ and [M—43]+ like those in the hydroxysteroid dimethylisopropylsilyl ether derivatives reported previously. The ion [M—34]+, which is produced by the elimination of isopropyl group from [M]+., was observed as an intense peak. The appearance of this ion in the high mass region was very useful for quantitation of trace amounts of PGs and thromboxane B2 in biological fluids without disturbance of endogenous substances by selected ion monitoring. The detection limit of the dimethylisopropylsilyl ether derivative of PGF2α methyl ester was found to be 5 pg with a signal-to-noise ratio of 10:1 when monitoring the ion [M—43]+ (m/z 625).

Wall-coated open-tubular capillary column system for gas chromatographic analysis of neutral and acidic fermentation end-products

The separation of 18 neutral and 17 acidic fermentation end-products by capillary column gas chromatography is described. A wall-coated open-tubular column, 30 m × 0.25 mm I.D., with SP 1000 as stationary phase, was found to combine high efficiency with rapidity of analysis. Non-volatile acids and formic acid were analysed (after methylation) either isothermally at 130°C, 160°C, 170°C and 180/dgc or with a temperature programme from 90°C to 160°C. Volatile acids were chromatographed isothermally at 130°C, 160°C, 170°C or 180°C; while alcohols, aldehydes, ketones, diketones, diethyl ether and acetoin could be resolved on the same column isothermally at temperatures ranging from 90°C to 170°C. Volatile neutral compounds and acids (C 4) and higher were resolved when the column was programmed from 110°C to 170°C. The column proved satisfactory for the analysis of fermentation products of a wide range of bacteria.

A chemically bonded glass-whisker column for gas chromatography

Silica whiskers were grown on the inside of an open-tubular glass capillary column according to a modified version of Schieke's method. The surface of the silica whiskers was modified by reaction with a flowing solution of octadecylsilyl trichloride and hexamethyl-disilazane, then with a mixture of trimethylchlorosilane and hexa-methyldisilazane. The whiskers grown and the surface modifications were examined with a scanning electron microscope and an electron microprobe X-ray analyser. Finally, the chemically bonded glasswhisker columns thus prepared were evaluated with mixtures of hydrocarbons, fatty acid methyl esters andn-alcohols under isothermal or programmed-temperature conditions.

The excretion of urinary steroids by the owl monkey (Aotus trivirgatus) studied using open tubular capillary column gas chromatography and mass spectrometry.

Abstract A qualitative analysis of steroids excreted in urine by the owl monkey (Aotus trivirgatus) is presented. The study was carried out using the high resolving power of wall coated open-tubular glass capillary column gas chromatography and mass spectrometry. Oestrone was the major oestrogen excreted by the female animal and was also present in greater amounts than testosterone in the male monkey. The principal progesterone metabolites were identified to be 6β-hydroxypregnanolone and 16-hydroxypregnanolone isomers. Corticosteroid metabolism was also characterized by the presence of 16-hydroxylated in addition to C-20 reduced metabolites.