Fused-silica Column Research Articles

Determination of triazolam in serum by deactivated metal capillary gas chromatography with electron-capture detection

A method for the determination of trace amounts of triazolam in serum by deactivated metal capillary gas chromatography with electron-capture detection was established. The column used exhibits excellent thermostability in high-temperature analysis and easy handling and a long lifetime of the column and well shaped peaks on the chromatograms are obtained. With the metal capillary column, it was found to be easier to maintain suitable analytical conditions for the routine assay of triazolam than with a fused-silica column. With this method, 0.5 ng/ml of triazolam in serum can be determined. The method is useful for pharmacokinetic and therapeutic purposes.

Calculation of elemental ratios by on-column radiofrequency plasma atomic emission detection coupled with capillary gas chromatography

Atomic emission from a 350-kHz helium plasma was evaluated for the calculation of C/Cl and C/Br ratios in compounds separated by capillary gas chromatography. When the plasma was sustained inside the end of a 0.32 mm I.D. fused-silica GC column in 2 ml/min of GC carrier gas + 18 ml/min of make-up gas (helium), 94% of the elemental ratios obtained deviated by less than 20% from the theoretical values. These results with the on-column r.f. discharge were comparable to data obtained with a commercial GC-atomic emission detection system based on a microwave-induced plasma.

Analysis of modified oligonucleotides by capillary electrophoresis in a polyvinylpyrrolidone matrix coupled with electrospray mass spectrometry

This paper describes the coupling of capillary electrophoresis (CE) with a olyvinylpyrrolidone (PVP) matrix and electrospray mass spectrometry for the analysis of a series of short modified oligonucleotides. The separation of modified oligonucleotides, four, five and six bases in length, was accomplished by CE in a coated fused-silica column filled with an aqueous solution of PVP. The resolved components were then identified by electrospray mass spectrometry with negative-ion detection. Importantly, oligonucleotides with the same length and sequence but differing only by the presence or absence of a small modification (such as a methyl group) on a single base were easily resolved by CE. This observation suggests that the matrix, PVP, is behaving as a pseudo-phase in which oligomers with hydrophobic modifications are retained longer than their normal unmodified analogs.

Implicit characteristic parameter of a programmed temperature retention index database

In a programmed temperature retention index (PTRI) database, there exists a characteristic parameter rt0/β that can be calculated if the experimental parameters are clearly given. This characteristic parameter can be used to flexibly reproduce the original PTRI data under chromatographic conditions different from those originally given. As this characteristic parameter is not explicitly given, it is suggested to name this parameter as the implicit characteristic parameter (TCP) of a PTRI database. The ICP in White's PTRI database was easily found and used satisfactorily to reproduce PTRI of some test compounds using either a Hewlett-Packard ultra-performance OV-1 column or a self-coated OV-1 column. The reproduction of PTRI could not be realized on columns of different materials. The fact that several PTRI databases measured on glass capillary columns could not satisfactorily be reproduced on fused silica column is explained.

Simultaneous determination of zolpidem and zopiclone in human plasma by gas chromatography-nitrogen-phosphorus detection

A simple, specific and selective method for the simultaneous determination of zolpidem and zopiclone in human plasma is described. After a liquid-liquid extraction, the extract is injected into a capillary gas chromatograph with an OV-1 fused-silica column coupled to a nitrogen-phosphorus detector. The detection limits are 1 and 2 ng/ml for zolpidem and zopiclone, respectivelly. The methood described is reproducible and linear over a range of concentrations, rendering it suitable for use for pharmacokinetic studies or toxicological evaluations. Absolute identification of the chromatographed compounds is accomplished by gas chromatography-mass spectrometry in both electron-impact and positive-ion chemical ionisation modes.

Sampling and analysis of 1,3-butadiene in air by gas chromatography on a porous-layer open-tubular fused-silica column

The preparation of standards for 1,3-butadiene analysis is complicated, because butadiene is a gas at room temperature. The method to prepare stock solutions developed in this study is reliably, as confirmed by a standard plot from these independent stock solutions. The qualitative and quantitative analysis was carried out using high-resolution gas chromatography with flame ionization detection (FID) and a fused-silica porous-layer open-tubular (PLOT) column. The use of acetonitrile as a desorption solvent gave a good recovery from charcoal and no interfering impurities were present. Active and passive sampling were tested in the laboratory and in petrochemical plants. These two methods had a very good correlation when tested in the field.

The analysis of C4–C11 hydrocarbons in naphtha and reformate with a new apolar fused silica column

AbstractThis paper deals with the separation of alkanes, naphthenes, and aromatic compounds in naphtha and reformate, on a newly developed apolar high resolution GC column. The selectivity of this apolar phase has been compared with those of squalane, DB‐1, and SE‐30. A total of 95 hydrocarbons were reliably identified, mostly by GC‐MS. Repeated measurements of Kováts retention indices are presented as evidence for the reproducible manufacture of fused silica columns coated with this phase.

Enhanced selectivity in the analysis of chlorobiphenyls on a carborane phenylmethylsiloxane copolymer gas chromatography phase (HT-8)

The congener specific analysis of polychlorinated biphenyls (PCBs) on a new chemically bonded stationary GC phase, HT-8 (1,7-dicarba-closo-dodecarborane phenylmethyl siloxane) is investigated. The incorporation of carborane in the polysiloxane backbone enhances selectivity and temperature stability of the phase. On a 60 m × 0.25 mm I.D. fused-silica column coated with 0.25 μm HT-8, a total of 106 congeners in Aroclor mixtures elute as separated peaks. By the use of mass spectrometric detection 138 congeners can be analysed without interference from coeluting PCBs. In literature, no other GC phase has been reported with such a high PCB selectivity. An interesting feature of HT-8 is its near-baseline separation of the critical pair CB138/CB163. Separations for these congeners on other GC phases are reviewed. The performance of a thin film (0.15 μm) version of the HT-8 column with fast temperature programming is tested. It is concluded that congener-specific, rapid screening of seven indicator PCBs (CB28, CB52, CB101, CB118, CB138, CB153 and CB180) with a total GC run-time of 13 min is feasible with an accuracy sufficient for most purposes.

Detection of sugar addition to citrus juices by capillary GC

AbstractA method is described for the detection of citrus juices adulterated by addition of industrial sugar products. The oligosaccharides maltotriose (DP3) and maltotetraose (DP4), both of which are absent from the natural sugar profile of citrus fruits, serve as markers. The sample preparation method includes clean‐up on a solid phase ODS cartridge, fractionation of DP3 and DP4 carbohydrates by LC on aminopropyl silica gel, and derivatization of the collected sugars to form the oxime‐trimethylsilyl derivatives. Capillary GC analysis is performed on a 30 m × 0.32 mm i.d. polydimethylsiloxane fused silica column applying cool on‐column injection and FID detection. The detection limit for maltotriose and maltotetraose is about 1 mg l−1. Several orange and grapefruit juices were evaluated on their authenticity. Adulteration with crystalline sugar products cannot be detected with the described procedure.

Comparison of spherically and irregularly shaped stationary phase packings in microcolumn liquid chromatography

AbstractSpherically and irregularly shaped reversed phase packings were used to slurry pack capillary fused silica columns. The selection of the packing solvents was based on the colloidal properties of the stationary phase particles and investigated by sedimentation experiments. The chromatographic performance of the microcolumns was measured with conventional parameters from plate and rate theories, and the column resistance parameter and separation impedance. Also studied was the time of analysis. The performance of spherical and irregular packings was comparable with a light preference for spherically shaped materials when time of analysis is concerned. © 1995 John Wiley & Sons, Inc.

Capillary GC on 50 micrometer I.D. Columns coated with thick films. Theory and selected practical results

AbstractThe chromatographic performance of 50 μm internal diameter (i.d.) fused silica columns coated with up to 2 μm films of immobilized SE‐54 (methyl phenyl (5%) silicone) is evaluated under gas chromatographic conditions. The influence of pressure drop on the plate height is discussed. In comparison to thick film 250–530 μm i.d. columns, much higher efficiencies and faster analyses are obtained. Practical examples, performed on a standard GC instrument, illustrate the features of thick film 50 μm i.d. columns.

Fast Temperature Programming on Fused-Silica Open-Tubular Capillary Columns by Direct Resistive Heating

A method for extremely fast temperature-programmed gas chromatography is described. The column is heated by passing an electric current through a thin conductive film applied to the outer surface of a fused-silica open-tubular column. The low thermal mass of the column allows rapid heating and cooling. A computer generated voltage ramp may be empirically adjusted to produce a linear separation of the members of a homologous series. Sample introduction is by on-column thermal modulation. High-speed detection is by a micro thermal conductivity detector. Repetitive chromatograms can be generated as often as 1/s with peaks as sharp as 40 ms at the baseline

Determination of Triazolam and Its Metabolites in Human Urine by EMIT, Gas Chromatography-Mass Spectrometry and Thermospray Liquid Chromatography-Mass Spectrometry.

EMIT, gas chromatography-mass spectrometric (GC-MS) and thermospray high performance liquid chromatography-mass spectrometric (LC-MS) methods for the determination of triazolam (TRZ) and its metabolites (1-hydroxymethyltriazolam (α-HT) and 4-hydroxytriazolam (4-HT)) in the human urine were investigated. TRZ was analyzed by EMIT st Urine Benzodiazepine Assay. EMIT cutoff was 50 ng/ml of TRZ. TRZ and its metabolites were extracted from the human urine using Sep-Pak C18 cartridge with dichloromethane-methanol (90 : 10 v/v) as the eluent. The eluate was evaporated to dryness under stream of N2. The residue was dissolved in 1 ml of methanol, 50 μl was injected into the LC-MS. LC analyses were performed on a TSKgel Octyl-80Ts in the solvent system of 100 mM ammonium acetate-methanol (50 : 50 v/v) at a flow rate of 1.0 ml/min. For GC-MS, the extract was derivatized at 90°C for 30 min with 50 μl BTZ. GC analyses were performed on a fused silica column DB-1. The column temperature was 290°C. The detection limits of these compounds by scan mode were 800 ng/ml for α-HT and 4-HT with GC-MS, 50 ng/ml for TRZ and α-HT, 100 ng/ml for 4-HT with LC-MS and those by selected ion monitoring mode were 50 ng/ml for α-HT, 100 ng/ml for 4-HT with GC-MS, 5 ng/ml for TRZ and α-HT, 10 ng/ml for 4-HT with LC-MS.

Separation of phenoxy acid herbicides and their enantiomers by high-performance capillary electrophoresis

Capillary electrophoresis conditions in the free solution mode (capillary zone electrophoresis) were established for the separation and detection of 2,4-dichlorophenoxyacetic acid and three optically active phenoxy acid herbicides (dichlorprop, mecoprop and fenoprop). A 50 m M acetate buffer at pH 4.5 gave the best separation, using a 50 cm (to detector) × 75 μm I.D. fused-silica column; the column temperature was 30°C. separation voltage 20 kV and optimum detector wavelength 230 nm. Separation of the four herbicides required less than 15 min under these conditions. Baseline separation of the two enantiomers of each of the three optically active herbicides, separately and in mixtures of the three, was accomplished by the addition of 25 m M tri-O-methyl-β-cyclodextrin to the acetate separation buffer. Di-O-methyl- β-cyclodextrin or α-cyclodextrin (CD) separated enantiomers of dichlorprop and mecoprop, but not those of fenoprop; β-CD provided very little separation and γ-CD gave no separation. Addition of methanol to the separation buffer increased separation, but doubled migration times. Over a variety of sample concentrations and injection times, reproducibilities of migration times of racemates and enantìomers ranged from 1.3 to 4.6% R.S.D.; peak area and peak height reproducibilities ranged from 1.6 to 17.9% R.S.D.

Characterization of food proteins by capillary electrophoresis

A simple analytical method for characterization of food proteins by capillary electrophoresis (CE) has been developed. Major proteins in chicken eggs and cow's milk are characterized and can be quantitated by the CE technique. Egg white proteins are well resolved while the yolk shows a substantially more complex protein separation pattern than that in the egg white. Caseins and whey proteins in fresh milk were resolved by CE in a similar buffer system. Separation of both milk and egg proteins was performed reliably and reproducibly in an untreated fused-silica column, 25 cm × 20 μm I.D. Diluted egg or milk samples can be directly loaded on an automated instrument with on-line injection, detection and real-time data analysis in less than 10 min.

Capillary Electrophoresis of Nucleotides on Ucon-Coated Fused Silica Columns

Ucon-coated columns have been used to isolate nucleotides, such as ribonucleotides, deoxyribonucleotides, and pyridine nucleotides, by capillary zone electrophoresis. This neutral, hydrophilic column coating (Ucon) significantly reduced macromolecule adsorption and electroosmotic flow, which provides the maximum resolution of the nucleotides separated under moderate buffer conditions (pH about 5-6), The relative standard deviations of the nucleotides were less than 1%. Low minimum detectable concentrations (about 2-8 μM) and quantities (about 70-360 fmol) of the ribonucleotides were obtained. A qualitative and quantitative analysis of the ribonucleotides in hybridoma cell extracts shows the applicability of the developed methodology for the determination of intracellular nucleotide pools under the desirable buffer conditions.

Pheromone chirality of african palm weevil,Rhynchophorus phoenicis (F.) and palmetto weevil,Rhynchophorus cruentatus (F.) (Coleoptera: Curculionidae)

There are four stereoisomers of both 3-methyl-octan-4-ol, the aggregation pheromone of the African palm weevil,Rhynchophorus phoenicis (F.) and 5-methyl-octan-4-ol, the aggregation pheromone of the palmetto weevil,Rhynchophorus cruentatus (F.). Synthetic stereoisomers of 3-methyl-octan-4-ol and 5-methyl-octan-4-ol were baseline-separated on a Cyclodex-B fused silica column. Use of this column in gas chromatographic-electroantennographic detection (GC-EAD) and GC-mass spectrometric (GC-MS) analyses revealed that only one stereoisomer, (3S,4S)-3-methyl-octan-4-ol and (4S,5S)-5-methyl-octan-4-ol, is produced by maleR. phoenicis and maleR. cruentatus, respectively, and elicits good antennal responses by conspecific male and female weevils. In field trapping experiments, withR. phoenicis in Côte d'Ivoire andR. cruentatus in Florida, (3S,4S)-3-methyl-octan-4-ol and (4S,5S)-5-methyl-octan-4-ol strongly enhanced attraction of fresh palm tissue, whereas other stereoisomers were behaviorally benign. Stereoisomeric 3-methyl-octan-4-ol and 5-methyl-octan-4-ol may be utilized to monitor and/or manage populations of these two palm weevils.

Capillary HPLC: A Method for Protein Isolation and Peptide Mapping

Capillary or microcolumn (<0.5-mm internal diameter) HPLC is an extremely powerful microseparation technique for proteins and peptides. It has distinct advantages over wider-bore column HPLC, such as increased mass sensitivity and lower flow rates, which make it particularly attractive for coupling to hyphenated detection techniques such as mass spectrometry. We describe a procedure for enhancing conventional HPLC systems to provide the accurate low flow rates (0.4-4 μl/min) and gradients necessary to operate slurry-packed capillary columns. A key component of this system is a commercial axial-beam longitudinal flow cell that can be fitted to a number of commercial UV detectors. Detailed procedures are given for the fabrication of ≤0.32-mm-internal-diameter polyimide-coated fused-silica columns, slurry-packed with reversed-phase chromatographic supports. The chromatographic performance of these columns is illustrated using a series of standard proteins and a mixture of peptides derived from a Staphylococcus aureus V8 protease digest of recombinant murine interleukin-6. We demonstrate that capillary HPLC is an effective method for separating and collecting peptides from one- and two-dimensional polyacrylamide gels, in quantities sufficient for obtaining amino acid sequence data using either Edman methods or mass spectrometry.

Capillary gas chromatography method for the analysis of the trans isomers of ceralure, a medfly attractant

A capillary GC method has been developed to analyze laboratory or commercial samples of the medfly attractant ceralure [ethyl 4- (and 5-)iodo- trans-2-methylcyclohexane-1-carboxylate]. The method utilizes a specially prepared fused-silica column with a bonded phenyl-methyl polysiloxane liquid phase. Baseline separation was achieved for three of the four trans-ceralure isomers. Difficulties encountered with other columns investigated are also discussed.

Factors affecting the capillary electrophoresis of ricin, a toxic glycoprotein

Conditions for the analysis of ricin with capillary electrophoresis were investigated. Uncoated and coated columns were tested with a variety of different buffer combinations which included different principal components, pH, ionic strength, and additives. Of the combinations tested, uncoated columns used with either zwitterionic salts or putrescine gave the best results. Multiple peaks were resolved with these conditions. Coated columns generally yielded between 1000 and 5000 plates with several buffer combinations. Ricin may be analyzed faster and with greater resolution with capillary electrophoresis employing untreated fused-silica columns than by using other chromatographic techniques.