Steroid analysis by gas chromatography with SCOT and wide-bore WCOT columns

Glass capillary columns are ideal for analysis of urinary steroid profiles (i.e. the total steroid neutral fraction without prior separation into sub-groups). In this paper performance of both SCOT and wide-bore WCOT columns has been compared, resulting in no significant quantitative difference on urine extracts run as trimethylsilyl ether derivatives. However, because of increased efficiency the WB-WCOT column exhibited more sensitivity in measurement of small amounts of 11-ox-aetiocholanolone. Sensitivity of other steroids was greatly enhanced by use of either SCOT or WB-WCOT, leading to an almost tenfold increase over conventional packed columns (e.g. androsterone and aetiocholanolone < 40 μg per 24 h urine sample). A simple splitless injection system (based on a design of Dr. W. Greenaway, Oxford University) is presented. Experiments were also carried out using a SCOT column in conjunction with an FM-electron capture detector. Whilst efficiency was impaired due to the design of the detector, use of He (carrier) and N₂ (make up gas) showed that several steroid derivatives could be easily measured at well below the 10^?10 g level with much more rapid retention times than with a 1½m packed column. Highly successful separation of 19 amino acids (as fluoro-acyl derivatives) was achieved in 35 minutes using a SCOT (30 m) SP2100 column.     

High resolution gas chromatographic determination of permanent gases with a helium ionization detector

The capability of the helium ionization detector (HID) to operate in connection with capillary columns for trace gas analyses has been evaluated. Two different capillary columns were considered: a PLOT fused silica column with molecular sleve and a thick film WCOT glass column with PS-255. The determination of trace impurities in gases can be achieved with evident advantages over classical adsorption columns, even using a split injection system. Direct on-column injections also have been investigated with promising results.     

Stainless steel capillary columns for high temperature gas chromatography

A layer of elemental silicon has been deposited on the surface of stainless steel tubing by means of chemical vapor deposition (CVD). Two kinds of capillary column were prepared from the deactivated tubing: cross-linked, silanol-terminated polydime-thylsiloxane wall coated open tubular (WCOT) columns and molecular sieve 13X porous layer open tubular (PLOT) columns. Unlike fused silica capillary columns, stainless steel WCOT and PLOT columns can be operated at temperatures in excess of 400°C. High temperature simulated distillation has been performed successfully with a macro bore WCOT column and rapid PNA (paraffin, naphthene, and aromatic) analysis with a multidimensional gas solid chromatographic (GSC) system using PLOT columns.     

Development of a Dual Capillary Column GC Method for the Trace Determination of C2–C9 Hydrocarbons in Ambient Air

An analytical method based on a dual capillary gas chromatographic technique combining the advantages of GasPro PLOT and a non polar narrow bore WCOT column was developed for the analysis of air samples containing C2–C9 NMHCs. A refocusing step was not required due to the fast heating rate of the sample preconcentration trap and the resolving power of the PLOT column for C2 and C3 NMHCs. Water had to be removed from the air samples to avoid plugging of the columns if the initial GC oven temperature was below ambient temperature. To dry air samples, a scrubber and a cryogenic technique were employed. The interferences caused by carbon dioxide were reduced by purging the loaded sample preconcentration trap with helium. The dual column system was compared to a method employing a refocusing device and a single narrow bore WCOT column. Both systems provided a high degree of precision. However, the dual column approach was superior to the single column system due to better resolution of low molecular weight components.     

The efficiency of open tubular gas chromatographic columns

Summary A new parameter, the mean specific plate number, is proposed for assessing the efficiency of support coated open tubular (SCOT) and wall coated open tubular (WCOT) columns and for comparing the efficiency of different open tubular columns. It has the advantage over most previously used parameters in that it has only a small dependence on the partition ratio and it allows for the column diameter.A graphical presentation is given of the maximum theoretical mean specific plate number as a function of the partition ratio for SCOT columns having a range of relative porous layer thicknesses and for WCOT columns with a range of phase ratios.This presentation permits ready visual comparison of the potential efficiency of different columns and enables a simple evaluation of the percentage utilization of theoretical efficiency from experimentally determined values of the maximum mean specific plate number. For a given column the percentage utilization of theoretical efficiency at optimum average gas velocity and that at optimum practical gas velocity or at a higher average gas velocity are shown to be equal provided that corrections for column pressure drop are made.     

Drug matrix effect on the determination of residual solvents in bulk pharmaceuticals by wide-bore capillary gas chromatography.

A wide-bore capillary gas chromatographic method has been developed to study the drug matrix effect on the determination of residual solvents in bulk pharmaceuticals. A selective method is achieved on a Restek wide-bore (0.53-mm i.d. x 30 m) open-tubular fused-silica column coated with a 5-micron film of 95% dimethyl-5% diphenyl polysiloxane protected by a phenyl-methyl siloxane deactivated, uncoated fused-silica guard column. Utilizing this method, several common process solvents in weakly acidic, weakly basic, and neutral drug matrices are evaluated by recovery and linearity studies to show whether or not a drug matrix effect exists in their determination.     

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

A 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 (N_eff) per meter. Chromatograms showing practical application of the WCOT columns prepared using both methods is given.     

Gas chromatography for in situ analysis of a cometary nucleus III. Multi-capillary column system for the cometary sampling and composition experiment of the Rosetta lander probe

The cometary sampling and composition (COSAC) experiment is one of the principal experiments of the surface lander probe of the European Space Agency Rosetta mission to be launched in January 2003. The instrument is designed for the in situ chemical analysis of a cometary nucleus as the details of the nucleus composition are of primary importance for understanding both the formation of the solar system, and the origin of life on Earth. The COSAC experiment consists of an evaporation/pyrolysis device and two analytical systems: a multi-column gas chromatograph and a high-resolution time-of-flight mass spectrometer which may either be operated alone or in a coupled mode. The gas chromatograph includes five general purpose chromatographic columns and three chiral ones, all mounted in parallel. Taking into account the chemical species potentially present in the cometary nucleus as well as the space constraints, a set of five complementary columns was selected to perform the separation and identification of the compounds present in the cometary nucleus. This set of columns includes a carbon molecular sieve porous-layer open tubular (PLOT) column used for the separation of both the noble and other permanent gases, and the C1-C2 hydrocarbons. A second PLOT column uses a divinylbenzene-ethylene glycol-dimethylacrylate porous polymer as stationary phase for the analysis of a wide range of C1-C2 organic molecules, Two complementary wall-coated open tubular (WCOT) columns with polydimethylsiloxane (PDMS) liquid stationary phases, one containing cyanopropyl-phenylsiloxane and the other diphenylsiloxane groups, are designed to target the same range of organic compounds (C3-C7) which could be representative of the widest range of cometary compounds. A third WCOT column with an apolar stationary phase made of non-substituted PDMS is used for the separation and identification of higher-molecular-mass compounds (up to C10) and aromatic species (monoaromatic and polyaromatic). This paper describes these five general-purpose capillary PLOT and WCOT columns, selected to be used in the COSAC GC system. The analytical capabilities are examined with a special emphasis on the exobiological and planetological implications.     

Topical administration of ibuprofen in man. Simultaneous determination of the drug and its metabolites in urine by high resolution gas chromatography

A selective and sensitive high resolution gas chromatography assay for simultaneous determination of Ibuprofen and its major metabolites in urine is described. Biological samples were collected from healthy volunteers after a single topical administration of the drug in gel form. The chromatographic system, developed on a WCOT OV-1 glass capillary column, ensured a clear separation of Ibuprofen and its metabolites and their quantitative evaluation.     

Indirect fluorescence detection in capillary gas chromatography

Post-column addition of naphthalene vapour to the effluent from a wide-bore capillary gas chromatographic column, prior to gas-phase fluorescence detection, was used to detect fluorescent and non-fluorescent species as positive and negative peaks, respectively. Quenching constants were determined for nitrobenzene and cyclohexanone using indirect detection.     

Noncryogenic FSOT column separation of sulfur-containing gases

Fused 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.     

An optimized gas chromatographic determination of priority pollutant phenols

Priority pollutant phenols are determined by gas chromatography on an SE-30 WCOT column using hydrogen carrier and flame ionization detection with dual internal standards. Linear responses over ranges ca. 12–125 ng per component are achieved and detection limits at or below 1 ng are obtained. Carrier flow and temperature program are optimized to maintain baseline resolution while affording an analysis time of less than 15 minutes.     

Injection of large-volume samples into wide-bore capillary columns

Some parameters (injected sample volume and the completeness of sample transfer) in the injection of large-volume gas-vapor and liquid samples into a wide-bore capillary column with intermediate sorption preconcentration were examined. It was demonstrated that this sample injection technique can be used in analytical practice.     

Comparison of surface modification techniques used for the preparation of wall coated open tubular glass capillary columns

Summary Comparison of different techniques for modifying internal glass surfaces to accept a substrate loading on wall coated open tubular columns (WCOT) were examined. Inner surfaces pretreated with a non-extractable Carbowax 20M layer, barium carbonate and silica whiskers were prepared and coated with a Carbowax 20M liquid phase. The columns were evaluated for efficiency, acidic-basic and adsorption properties, thermal stability and coating efficiency. Column performances were also assessed for deactivated surfaces. Each column was applied to a standard mixture of Aroclor 1016.     

Gas chromatographic determination of chlorinated phenols in the form of various derivatives

Derivatization of chlorophenols prior to gas chromatographic analysis resulted in a significant improvement of their chromatographic behaviour. Chlorophenols in the form of anisoles, acetates, and pentafluorobenzyl ethers were separated either on a HP-1 wide-bore capillary column or on a capillary column coated with a film of SE-54. Due to an enhancement of the poor electron-capture detection response of mono- and dichlorophenols, pentafluorobenzylation made it possible to determine trace amounts in spiked water. Moreover, simultaneous analysis of phenoxyalkanoic acids was accomplished under the same conditions.     

Wide-bore capillary column for the direct analysis of ethanolamines and ethylene glycols

Summary The GC separation of a mixture of three ethanolamines and four ethylene glycols without any preliminary derivatization, on a wide-bore capillary column coated with Carbowax 20M is described. These high-boiling and polar compounds elute giving simmetrical peaks and show good resolution. The analysis is completed in less than 14 minutes.     

Characterization and determination of PCB isomers by high resolution gas chromatography and HRGC/mass spectrometry

An integrated analytical procedure for polychlorinated biphenyl (PCB) multiresidues in environmental samples has been developed and applied to well-characterized samples. PCB residues are characterized and quantified using wall coated open tubular column (WCOT) gas chromatography or HRGC/MS-selected ion monitoring. An automated data system based on a Spectra Physics SP-4200 computing integrator is used to select and quantitate peaks of individual congeners and homolog groups. This procedure consistently yields results with a reproducibility within 3 percent for HRGC-ECD and 3.7 percent for HRGC/MS-SIM technique respectively.     

裂解气相色谱－红外光谱联用分析聚合物结构（Ⅱ）

采用国产ＳＣ－７型色谱仪及ＪＰ－０１型居里点裂解器、Ｎｉｃｏｌｅｔ１７０ＳＸ红外光谱仪及接口组成的裂解气相色谱－傅里叶变换红外光谱（ＰＧＣ／ＦＴＩＲ）分析仪、ＨＰ－１７型大口径毛细管色谱柱，分析了两个复杂组成的聚合物样品。从主要裂解碎片峰的定性结果及形成机理出发，逐步推出了原样品的组成和结构。常规红外光谱分析方法被用来作为对比，但它获得的信息有限，无法得到能与ＰＷＢＣＧＣ／ＦＴＩＲ分析结果相媲美的结论，充分显示了ＰＷＢＣＧＣ／ＦＴＩＲ用于聚合物分析的优越性。     

Semipreparative-scale gas-chromatographic separation of filbertone enantiomers

The enantioselectivity of heptakis(2,3-di-O-acetyl-6-O-tert-butyldimethylsilyl-beta-CD) toward racemic filbertone (E-5-methyl-hep-2-en-4-one) was studied by performing the chiral separation on a capillary column, a thick-film wide-bore column and a semipreparative column. The semipreparative enantioseparation of filbertone was achieved at 80 degrees C by using a packed column providing (R)- and (S)-enantiomers of filbertone with ee 90 and 96%, respectively. The isolated enantiomers (approximately 250 microg each, ee = 90-96%) may be used for studies on the relationship of chirality and biological activity by olfactory screening and toxicological studies.     

Determination of clozapine in human serum by capillary gas chromatography

A gas chromatographic method using a fused-silica wide-bore capillary column and a nitrogen-specific detector for the determination of the antipsychotic agent clozapine in human serum is described. This method was found to be suitable for the determination of serum levels down to 1-2 ng/ml. The sensitivity, precision and accuracy of this method are adequate for studies on pharmacokinetics and bioavailability.