Open Tubular Glass Capillary Columns Research Articles

Gas chromatographic resolution on polar open-tubular columns of saturated and unsaturated wax ester isomers differing in combinations of acyl and alcoholic groups

The gas chromatographic resolution of saturated and unsaturated wax ester isomers having the same carbon number and the same degree of unsaturation, prepared from various fatty acids and fatty alcohols, was carried out on open-tubular glass capillary columns coated with a cyanosiloxane, SP-2340. Satisfactory resolution was achieved at lower column temperatures (up to 240°C) by introducing very small amounts of samples (several nanograms per component) into a short column (15 m), with hydrogen as the carrier gas. Equivalent chain lengths (ECLs) of wax ester isomers with 32-42 carbon atoms and with 1-6 double bonds are presented. The ECLs of polyunsaturated wax esters were significantly dependent on column temperature. The influence of column temperature on resolution is discussed.

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).

Derivatization of estrogen conjugates for analysis by capillary gas chromatography.

By using 20 meter wall-coated open tubular glass capillary columns of high stability, analysis of methyl ester, methyloxime trimethylsilyl ether derivatives of estrogen glucuronides had been achieved. Relative retention times of five glucuronide conjugates on OV-1 stationary phase are reported. Estrogen sulfates conjugated at the 3-position were shown to be quantitatively hydrolyzed and derivatized in a single trimethylsilylation step, and this method of direct derivatization was compared to two solvolysis methods. These analytical methods could be further developed to allow rapid and quantitative analysis of estrogens in biological fluids, and may prove particularly useful for analysis of labile compounds.

Separation of complex long chain fatty acid mixtures by high-performance glass capillary gas chromatography

Detailed descriptions are given for the preparation of high resolution open tubular glass capillary columns using SP-1000, Silar-5 CP and Silar-10 C as stationary phases. A comparison has been made between HCl etched soda lime glass capillaries and HCl leached soda lime or borosilicate glass capillaries with BaCO 3 deposition. The best results were obtained with Silar-5 CP coated on HCl leached borosilicate capillaries with BaCO 3 deposition. These types of columns have been used for the separation of complex long chain fatty acid mixtures including positional and geometrical isomers. The technique recommended has been used for 3 years and can easily be reproduced. A modification of the all-glass solvent-less injection system is also described. The qualitative and quantitative features of the glass capillary gas chromatography system are discussed.

Preparation of wall-coated open tubular glass (pyrex) capillary columns with polar stationary phases, using superox™-4 as a surface pretreating and deactivating agent

Wall-coated open tubular (WCOT) glass (Pyrex) capillary columns were prepared with three different polar stationary phases (Carbowax 20M, Superox™-4, and SP-1000) using Superox-4 as a surface pretreating and deactivating agent. Methods for the laboratory preparation and practical application of these columns are given. Columns prepared by this technique were efficient, thermally stable, and low in surface activity. The Superox-4 pretreatment and deactivation technique produced high quality polar WCOT columns, and no surface roughening procedure was required. The technique offered a substantial decrease in column preparation time. In addition, columns prepared by this technique were comparable to those from commercial suppliers or those produced by conventional preparation techniques.

Separation of mono- and di-saccharide derivatives by high-resolution gas chromatography

The gas chromatographic analysis of NaBH4-reduced monosaccharide mixtures (either trimethylsilylated or acetylated) and NaBH4-reduced trimethylsilylated disaccharide mixtures in open tubular glass capillary columns is described. Complete separations of the investigated monosaccharides can be achieved if the same separation column and the appropriate method of derivatization are used. Kovats' retention indices of the derivatives are determined and their experimental repeatability is discussed.

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.

Determination of tranylcypromine in human plasma and urine using high-resolution gas--liquid chromatography with nitrogen-sensitive detection.

A precise and sensitive method is described for the determination of the antidepressant drug tranylcypromine in human plasma and urine using high-resolution gas chromatography. The drug, together with an added internal standard, is extracted from the plasma or urine sample, derivatized with heptafluorobutyric anhydride and analysed on an OV-225 support-coated open-tubular glass capillary column with nitrogen-sensitive detection. The method has been applied to the measurement of tranylcypromine levels in plasma and urine from both healthy volunteers and from psychiatric patients receiving a therapeutic dosage of the drug.

Gas chromatography of dimethylalkylsilyl ether derivatives of bile acid methyl esters

The gas chromatographic separation of the DMAS ether derivatives of ten bile acid methyl esters, namely DMES, DMnPS and DMiPS ethers, have been studied by use of an open tubular glass capillary column, coated with SE-30. The DMAS ether derivatives were eluted in sequence according to the number of hydroxyl groups except for 12-KCDCA, and separated. This contrasts with the poorly resolved gas chromatographic peaks produced by the TMS ether derivatives. The DMES ether derivatives were resolved with baseline separation in 30 min, but those of HCA and 12-KCDCA had similar methylene unit values.

Comparison of dynamically coated SE‐54, SP‐2250 and carbowax 20M wall‐coated open tubular (WCOT) glass capillary columns, prepared after surface pretreatment with Superox™‐4 or with BaCO3

AbstractA new surface pretreatment for the preparation of wall‐coated open tubular (WCOT) glass capillary columns has been evaluated. This technique involves the application of a non‐extractable layer of Superox™‐4, a 4,000,000 MW polyethylene glycol, to the glass surface as a pretreatment and deactivation agent. Unlike other polyethylene glycols, Superox‐4 is stable at high temperatures (> 300°C) in the absence of oxygen, coats smoothly onto a bare glass surface and resists droplet formation. WCOT columns (SE‐54, Carbowax 20M, and SP‐2250) prepared using this technique are compared to columns prepared using a modified Grob [2,3] BaCO3 procedure. The Superox‐4 pretreated columns were equal or superior in quality to the BaCO3 pretreated columns, based on the appearance of an activity standard and the effective theoretical plates (Neff) per meter. Chromatograms showing practical application of the WCOT columns prepared using both methods is given.

Gas chromatographic separation of some optical isomers on optically active copper complexes

Some enantiomers of hydroxyl acid esters, amino acid esters, and amino alcohols have been resolved by gas chromatography on optically active copper complexes of Schiff's bases with good separation factors. For example, DL-lactic acid isopropyl ester was resolved (α=1.16) on a 40m×0. 25mm i. d. open tubular glass capillary column coated with the binuclear copper complex of N-salicyliden-(R)-2-amino-1, 1-bis-(5-tert-butyl-2-octyloxyphenyl)-1-propanol (50 w/w% insilicone OV-101) within 10min at 70°C. The Disomer eluted prior to the L-isomer. These copper complexes which are a valuable catalyzer for the asymmetric synthesis have enabled the direct resolution of lactic acid enantiomers in their ester forms.

Determination of dinitrotoluene isomers in sea water and industrial effluent by high-resolution electron-capture gas chromatography with a glass capillary column

A method for the rapid determination, with base-line separation, of dinitrotoluene isomers in sea water and industrial effluent using gas chromatography with glass capillary columns and electron-capture detection is described. The samples were extracted with benzene and the extract was injected into the gas chromatography using a support-coated open-tubular (SCOT) glass capillary column coated with Apiezon L grease. The chromatogram was completed in 8 min. Sea water control samples were spiked at the levels of 0.8 and 8 µg l–1 of 2,6-, 2,3- and 2,5-dinitrotoluene, at 3.2 and 32 µg l–1 of 2,4- and 3,5-dinitrotoluene and at 1.6 and 16 µg l–1 of 3,4-dinitrotoluene. Recoveries of 91–102%(n= 5) were obtained for each isomer.The limits of detection were 0.059, 0.045, 0.031, 0.13, 0.12 and 0.17 µg l–1 for 2,6-, 2,3-, 2,5-, 2,4-, 3,4- and 3,5-dinitrotoluene, respectively.The method described in this work was applied successfully to the determination of dinitrotoluenes in sea water and industrial effluent without requiring further clean-up procedures.A Silar 10C column also gave base-line separation of the dinitrotoluenes.

Steroid excretion during the reproductive cycle and in pregnancy of the vervet monkey ( Cercopithecus aethiopus pygerythrus)

The qualitative analysis of the major steroids excreted in the urine of the vervet monkey ( Cercopithtcua aethiopus pygerythrus) is described using gas chromatography with wall coated open-tubular glass capillary columns and mass spectrometry. The excretion of the principal metabolites of progesterone and oestrogens were quantified by GC and radioimmunoassay over 40 consecutive days. The reproductive cycle of the vervet monkey, which was found to be 30 days, exhibited a close similarity to the human with respect to progesterone and oestrogen metabolism and excretion. Oestrone-3-glucuronide was the major oestrogen excreted and pregnanediol pregnenediol and 16-hydroxypregnanolone were the principal metabolites of progesterone. 6α-Hydroxylated corticosteroid metabolites were identified in significant amounts. Two interesting phenolic compounds, designated as Compound 180 410 and Compound 180 442 have been shown to exhibit significant quantitative changes during the menstrual cycle. The Chromatographie behaviour of these compounds resemble oestrogen steroids but preliminary studies suggest their structures may be non-steroidal. Maximum excretion occurs one day prior to the maximum excretion of pregnanediol in the luteal phase. In early pregnancy the quantitative excretion is high but as pregnancy proceeds their excretion decreases markedly. Both compounds have been detected in human urine and therefore work is ongoing to elucidate the structure and determine their physiological role.

Volatile composition of certain Amazonian fruits

The volatile constituents of several Amazonian fruits—bacuri, cupuacu, maruci and taperebá—were isolated by steam distillation-extraction of pulp or juice from the canned fruits. Essences were subjected to gas chromatographic analysis in high resolution wall-coated open tubular glass capillary columns; identification of the volatile constituents was based on mass spectral analysis, supported by gas chromatographic retentions under linearly temperature-programmed conditions. Considered individually, none of the compounds identified duplicates the aroma of any of these fruits. Many of them do, however, contribute fruity notes. This indicates that the typical aroma for each individual fruit is due not to one compound, but is probably the result of an integrated response to the contribution of a wide spectrum of compounds.

Gas chromatographic determination of optical isomers of 2-(4-chlorophenyl)isovaleric acid.

Gas chromatographic methods were developed for the determination of optical isomers of 2-(4-chlorophenyl)isovaleric acid (CPIA) which constituted the acid moiety of the insecticide Fenvalerate molecule. The enantiomers of CPIA were derivatized into diastereoisomeric l-menthyl esters quantitatively via their acid chlorides and separated from each other on a column of 10% silicone DC QF-1 (3 mm i.d. × 2.25m). They were also derivatized into isopropylamides in the presence of N,N′-dicyclohexylcarbodiimide and were resolved on an open tubular glass capillary column (0.25 mm i.d. × 40 m) coated with optically active N,N′-[2,4-(6-ethoxy-1,3,5-triazine)diyl] bis(l-valyl-l-valyl-l-valine isopropyl ester) (OA-300). The ratios of optical isomers were determined from their separated peak areas and analytical values obtained by two methods were in good agreement with each other.The chemical purity of CPIA was also determined by gas chromatography after derivatization to its methyl ester on a column of 2% DEGS (3 mm i...

Marine Sterols : IX. Evaluation of A C 87 hydrocarbon stationary phase for the analysis of marine sterols in glass open-tubular capillary columns

The recently introduced C 87-hydrocarbon thermostable stationary phase has been evaluated for its potential in separating the complex mistures of sterols which are commonly found in the marine environment. In glass open-tubular capillary columns it has proved to be a very useful phase with excellent separating efficiency, particularly for the difficult 5α-stanol-Δ5-sterol trimethylsilyl ether pairs which have been a common feature of some of the mixtures.

Glass open-tubular capillary columns with chemically bonded methyl-phenyl siloxane stationary phases of tailor made polarity

The previously described method yielding apolar, chemically bonded methyl polysiloxane glass capillary columns was extended to the production of capillary systems of controlled polarity. The approach involved prior synthesis of a reactive methyl-phenyl polysiloxane polymer by copolymerisation of a mixture of dimethyl and diphenyl chlorosilanes. The polymer was then chemically bonded to the capillary glass surface to yield remarkably stable, high resolution analytical systems which were shown to be particularly well suited to the separation of biochemical mixtures at the subnanogram level. The principle of copolymerisation of differently substituted silanes confers to the method a considerable flexibility which could be used to devise polar capillary systems tailor made for a given analytical problem.

High-resolution biomedical gas chromatography: Study of urinary steroid metabolite ratios of women with breast lesions using open-tubular glass capillary columns

High-resolution urinary steroid matabolic profiles have been utilized in a study of these groups of women with breast pathologies, a pre-menopausal group with benign fibrocystic lesions and two post-menopausal groups, one with benign lesions and one with malignant lesions. Sixty-meter borosilicate-glass open-tubular capillary columns coated with SE-30 containing dispersed particles of Silanox 101 were employed, with temperature programming from 200° at 1°/min. The theoretical plate efficiencies of the columns ranged from 125,000 to 150,000. Four products of liver enzymic reduction of the 3-oxo-4-ene moiety of the steroidal A/B ring system were quantified. Teh ratio of ethiocholanolone to androsterone (Et/An0 was taken as a reflection of the relative activities of 5β-H and 5α-H oxidoreductases acting on testosterone. The ratio of tetrahydrocortisol to allo-tetrahydrocortisol (THF/ a-THF) was taken as a reflection of the relative activities of 5β-H and 5α-H oxidoreductases acting on cortisol. Each individual was thus characterized by two sets of data detemined from two separate ratios of metabolites, one from testosterone and one from cortisol. Three out of four pre-menopausal females with benign breast lesions had both Et/An and THF/ a-THF ratios (“pattern B”) similar to those commonly associated with males. Moreover, a significant number of females in both post-menopausal lesion groups had metabolite ratios (“pattern C”) that have never been observed for healthy control subjects or for the pre-menopausal pathological group. Two questions are posed: (1) are low ratios of both Et/An and THF/ a-THF, viz., pattern B, in some way associated with the development of benign fibrocystic breast lesions by pre-menopausal women/; and (2) are unusually high metabolite ratis, viz., pattern C, associated with the development of breast lesions by women who have passed the menopause?

Detection, Identification, and Quantitation of Organic Compounds with Bioanalytical Systems Based on Mass Spectrometry

Abstract Bioanalytical systems which include a gas chromatograph, a mass spectrometer, and a computer provide the most effective analytical methods for organic compounds other than macromolecules. The use of computer and microprocessor/computer instrumental combinations is increasing. Electron impact mass spectrometry is used for identification purposes; chemical ionization is best for quantitative work. Current studies indicate that negative ion mass spectrometry with non-filament sources will be useful in analyses for toxic agents (pesticides, fungicides, herbicides). Future analytical systems will have both positive and negative ion mass analyzer capabilities. Sample preparation methods depend on the type of analysis. Liquid chromatography is useful when the concentration is low. Open tubular glass capillary columns are coming into wider use, both in gas chromatography alone and in combined systems. The limits of detection are now in the subpicogram range, but the determining factor is usually the nature of the compounds under analysis and the extent of adsorption.