High-speed Gas Chromatography Research Articles

Peer Reviewed: High-speed gas chromatography

Emerging technologies have made high-speed GC practical and useful for an increasing range of applications.

The fate of char-nitrogen in low-temperature oxidation

Nitrogen release during the oxidation of coal char has been studied in a thermogravimetric analyzer (TGA) at 873 K with 2% O2 in He. Species profiles are determined using Fourier transform infrared (FTIR) spectroscopy (NO, NO2, CO, CO2, N2O, and HCN) and high-speed gas chromatography (N2), which allows all of the char-N to be accounted for in the gas phase. Char-N is released predominantly as N2 with smaller amounts of NO and HCN also present. The proportion of char-N released to the gas phase as N2, NO, and HCN is relatively constant throughout burnout. At the low-temperature conditions of this study, N2O is not produced and the results suggest that HCN is a primary product formed via heterogeneous oxidation and not by slow or secondary devolatilization. The gaseous product species profiles suggest that nitrogen is preferentially retained in the char as the carbon is oxidized and this is confirmed directly by X-ray photoelectron spectroscopy (XPS) and elemental analysis of partially oxidized char samples. Analysis of the XPS results also shows that enrichment of the char in nitrogen is a surface effect that occurs with an increase in the pyridinic N content of the char relative to pyrrolic N. At low temperatures, the enrichment of the char in nitrogen as burnout proceeds is the major contributing factor to the increase in the [NO]/([CO2]+[CO]) ratio.

Novel preconcentration technique for on-line coupling to high-speed narrow-bore capillary gas chromatography: sample enrichment by equilibrium (ab)sorption: I. Principles and theoretical aspects

In recent years, there has been substantial progress in the field of high-speed narrow-bore capillary gas chromatography (GC) in general, and in the development of (trans)portable gas chromatographs for fast and accurate analysis in field applications in particular. Due to the limited (concentration) sensitivity of instrumentation for high-speed (portable) GC, environmental applications of this technique frequently require a preconcentration step. The equilibrium (ab)sorption technique described in this article was found to be very promising for on-line coupling to high-speed narrow-bore capillary GC and field portable GC instruments. Enrichment factors up to at least 100 can be obtained rapidly without the use of complicated instrumentation. The new preconcentration technique is shown to have clear advantages over enrichment based on conventional adsorption, i.e. thermal desorption techniques. It can be carried out at ambient trapping temperatures, gives uniform desorption profiles, reduces water effects, uses inert adsorption materials and does not require a (cryogenic) refocusing step. Moreover, the new preconcentration method allows the enrichment factors to be predicted from tabulated chromatographic data, thereby facilitating calibration.

Novel preconcentration technique for on-line coupling to high-speed narrow-bore capillary gas chromatography: sample enrichment by equilibrium (ab)sorption: II. Coupling to a portable micro gas chromatograph

The technique of equilibrium (ab)sorption has been proven to be a powerful method for preconcentration of gaseous samples for high-speed narrow-bore capillary gas chromatography (GC) in general and field-portable GC instruments, often referred as micro GCs, in particular. Using a simple experimental set-up equipped with the open-tubular enrichment column it is possible to produce a homogeneously enriched sample plug, allowing reproducible injections of an enriched sample into the micro GC. Using a non-polar trapping column enrichment factors found for n-alkanes in the range of C 7 to C 10 ranged from 15 to 150 and agree well with calculated values. Using a highly retentive Thermocap column, the enrichment factor observed for heptane was above 500. As the use of this new preconcentration method requires only minimum modification of the micro GC, the chromatographic performance of the instrument was not compromised by direct coupling to the preconcentration device. Examples of on-line enrichment with portable micro GC analysis of VOCs from air are shown. These examples clearly demonstrate the potentials of the new method in field analysis.

High speed gas chromatography—how fast is fast enough?

Journal of High Resolution ChromatographyVolume 20, Issue 10 p. 521-521 Editorial High speed gas chromatography—how fast is fast enough? Wolfgang Bertsch, Wolfgang BertschSearch for more papers by this author Wolfgang Bertsch, Wolfgang BertschSearch for more papers by this author First published: 11 April 2005 https://doi.org/10.1002/jhrc.1240201002Citations: 3AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article.Citing Literature Volume20, Issue10October 1997Pages 521-521 RelatedInformation

High speed solvating gas chromatography using packed capillaries containing sub-5 μm particles

In this study, fused-silica capillaries of 250 μm I.D. were packed with spherical porous and nonporous octadecyl bonded silica particles having diameters of 1.5 and 3 μm. These capillaries were used with CO 2 as mobile phase at elevated temperatures. At the column inlet, the mobile phase was a supercritical fluid, while at the column outlet, it was a gas. The mobile phase gradually changed from a supercritical fluid to a gas within the column. Because the mobile phase exhibited solvating ability for the analytes being separated, in contrast to conventional gas chromatography (GC) in which the mobile phase is only a carrier, this variation has been named “solvating gas chromatography” (SGC). Using this technique, capillaries packed with small particles produced column efficiencies as high as 1200 plates s −1 for retained solutes. Therefore, packed capillary SGC is the method of choice to carry out high speed GC separations. The effects of column inlet pressure, column length and particle characteristics on mobile phase linear velocity, retention factor, column efficiency, speed of analysis and resolution were investigated.

Use of region II of the a/q stability diagram for fast scanning of a linear quadrupole mass spectrometer

For evaluation as a detector for high-speed gas chromatography, a linear quadrupole mass spectrometer was operated in rf only mode by using Region II (a = 0; 7.514 < q < 7.580) of the Mathieu a/q stability diagram. The available power supply and the diameter of the quadrupole rods of the mass spectrometer placed an upper mass limit of ∼ m/z 93. Scan rates of 1000 scans/s were obtained with mass spectral peaks resolved over an 80-u range The m/z 91 and 92 ions produced from the electron ionization of toluene are resolved with an R1/2 of 135. A potential difference between the source and the quadruple mass filter of up to 1000 V was used to accelerate ions into the quadrupole. Broadening of mass-to-charge ratio peaks results from the time constant of the signal amplification rather than the small number of rf cycles the ions experience. The expected loss of sensitivity relative to Region I is observed, and the problem of mass aliasing is discussed.

High-speed gas chromatography using packed capillary columns

High-speed gas chromatography using packed capillary columns

High-speed gas chromatography using packed capillary columns

High-speed gas chromatography using packed capillary columns

A modified inlet system for high speed gas chromatography using inert metal tubing with a carbon dioxide cooled cryotrap

AbstractTen different metal tubings were investigated for thermal decomposition of analytes when used as the trap tube in a cryotrap/thermodesorption inlet system. No noticeable sample decomposition of hydrocarbons, chlorinated hydrocarbons and a brominated hydrocarbon was observed for six of the tubings with hydrogen as the carrier gas. This observation may be partly attributed to the developed deactivation techniques that produce inert metal tubings that are being widely adopted by many column manufacturers, the different trap materials used in comparison to previous studies and the decreased sample residence time in the hot trap tube. A cryotrap using carbon dioxide was constructed and tested as a alternative to the previously used liquid nitrogen based systems. This cryotrap was able to trap compounds with a boiling point of 80°C.

An improved method for rapid analysis of the fatty acids of glycerolipids

An improved rapid procedure to determine the fatty acid composition of glycerolipids is described. The procedure includes KOH-catalyzed transesterification and high-speed gas chromatography. Glycerolipids (20-40 mg) were mixed with 2 mL of hexane and 0.2 mL of 2 M methanolic KOH at room temperature for 1-2 min. The fatty acid methyl esters in the hexane layer were analyzed by gas chromatography on 10% SP-2340 at 240 degrees C. Methyl linolenate and docosahexaenoate eluted within 2 and 5 min, respectively. Analysis was thus completed within 5 min for common vegetable oils and 8 min for fish oils.

High-speed capillary column GC for rapid screening of gasoline to diesel range organic compounds

A high-speed gas chromatography (GC) instrument has been developed for near real-time screening of soil gas samples continuously generated from a cone penetrometer (CPT) equipped with a heated probe tip. The GC instrument uses a cryofocusing inlet system which can preconcentrate gasoline and diesel vapor and introduce a very narrow vapor plug into the capillary separation column. The GC instrument can be operated either in a high-speed screening mode or in a higher resolution advanced field analysis mode. In the high speed mode, a short capillary separation column is used with a photolonization detector to selectively detect aromatic (BTEX) compounds in petroleum fuel spills in a time frame of 10–20 s and with detection limits in the ppb range. In the advanced field mode, a longer column and flame ionization detector are used to obtain a finger-print chromatogram which is useful in determination of fuel type. In this mode, analysis times are typically about 200 s. The high-speed GC instrument is designed to be located in the CPT truck and connected directly to a heated gas transport line. In the high-speed screening mode, continuous sampling and near real-time analysis provide very high spatial resolution as well as high speed for site characterization. © 1996 John Wiley & Sons, Inc. Field Analyt Chem Technol 1: 97–102, 1996.

Valve injection for gas chromatographic analysis on small-bore open tubular columns

An injection valve with a small internal loop actuated by pneumatic switching was used for high-speed gas chromatography (GC). Small internal diameter (50 and 100 μm i.d.) open tubular columns were used for investigations of the injector performance. Several valve injection systems have been tested. The influence of the sample solvents, the injection temperature, the connection methods, and the time-split technique under GC conditions have been investigated. High resolution, fast separation speed, and reproducible GC analyses have been achieved. This study indicates that valve injection onto small internal diameter open tubular columns is a promising technique for high-speed and high-resolution GC analysis. © 1996 John Wiley & Sons, Inc.

High‐speed capillary column GC for rapid screening of gasoline to diesel range organic compounds

A high-speed gas chromatography (GC) instrument has been developed for near real-time screening of soil gas samples continuously generated from a cone penetrometer (CPT) equipped with a heated probe tip. The GC instrument uses a cryofocusing inlet system which can preconcentrate gasoline and diesel vapor and introduce a very narrow vapor plug into the capillary separation column. The GC instrument can be operated either in a high-speed screening mode or in a higher resolution advanced field analysis mode. In the high speed mode, a short capillary separation column is used with a photolonization detector to selectively detect aromatic (BTEX) compounds in petroleum fuel spills in a time frame of 10–20 s and with detection limits in the ppb range. In the advanced field mode, a longer column and flame ionization detector are used to obtain a finger-print chromatogram which is useful in determination of fuel type. In this mode, analysis times are typically about 200 s. The high-speed GC instrument is designed to be located in the CPT truck and connected directly to a heated gas transport line. In the high-speed screening mode, continuous sampling and near real-time analysis provide very high spatial resolution as well as high speed for site characterization. © 1996 John Wiley & Sons, Inc. Field Analyt Chem Technol 1: 97–102, 1996.

High-Speed Gas Chromatography Using Simultaneous Temperature Gradients in Both Time and Distance along Narrow-Bore Capillary Columns

A novel technique for high-speed gas chromatography that uses simultaneous temperature gradients in both time and distance along a narrow-bore capillary column is described. An electrical resistance gradient along the column provides a temperature gradient such that the head of the column is always at a higher temperature than the end of the column. The gradient along the column continuously refocuses eluting bands, counteracting part of the chromatographic band spreading. With a properly defined temperature gradient surface, each substance reaches a focus capacity factor that is determined by the ratio of gradients in time and distance and by carrier gas velocity. The numerical value of this focus capacity factor is independent of the substance involved, but its trajectory in time and distance along the column depends on the thermodynamics of an individual substance's interaction with the stationary phase. A high-speed gas chromatogram showing baseline separation of 13 components within 3.5 s is shown to demonstrate the potential of this technique for very fast and efficient separations.

On-Column Temperature Programming in Gas Chromatography Using Temperature Gradients along the Capillary Column

A unique technique for high-speed gas chromatography using on-column temperature programming is described. Simultaneous temperature gradients in time and distance can be applied to a fused-silica capillary column by direct resistive heating of the column through a thin electrical conductive film applied to the outside of the column. A controlled current ramp provides a thermal gradient in time analogous to conventional temperature programming. An electrical resistance gradient provides a temperature gradient along the column, and the head of the column is always at a higher temperature than the end of the column. The gradient along the column continuously refocuses eluting bands, counteracting part of the chromatographic band spreading. The rear of the band is at a higher temperature than the front and, thus, moves at a slightly higher velocity. With a properly defined temperature gradient surface, each substance reaches a focus capacity factor that is determined by the ratio of gradients in time and distance and by carrier gas velocity. The numerical value of this focus capacity factor is independent of the substance involved, but its trajectory in time and distance along the column depends on the thermodynamics of an individual substance's interaction with the stationary phase. The theory of simultaneous temperature gradients in time and distance along the column is also described, and the mathematical expressions for focus capacity factor and resolution are included. Several examples, including chromatograms as often as one every 2 s, are shown to support and complement the theory.

Pressure-Tunable Selectivity for High-Speed Gas Chromatography

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPressure-Tunable Selectivity for High-Speed Gas ChromatographyMichael. Akard and Richard. SacksCite this: Anal. Chem. 1994, 66, 19, 3036–3041Publication Date (Print):October 1, 1994Publication History Published online1 May 2002Published inissue 1 October 1994https://doi.org/10.1021/ac00091a008RIGHTS & PERMISSIONSArticle Views104Altmetric-Citations39LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (613 KB) Get e-Alerts Get e-Alerts

Comprehensive supercritical fluid extraction/gas chromatographic analysis for organic compounds in soil matrices with an element-selective radiofrequency plasma detector

A coupled supercritical fluid extraction (SFE), high-speed gas chromatography (GC), and element-selective radiofrequency plasma detection (RPD) system was evaluated for the analysis of volatile organic compounds in soil matrices. The effect of GC carrier gas (carbon dioxide) and plasma reagent gas (oxygen) on the selectivity and sensitivity of the RPD was studied to establish the optimal operational conditions. The selectivities obtained were 3500 (Cl/C) for chlorine and 2600 (S/C) for sulfur. The detection limits were 24.8 and 9.2 pg s -1 for chlorine and sulfur, respectively. Complete quantitative analysis could be easily accomplished within 10 min

Column Bifurcation with Tunable Selectivity for High-Speed Gas Chromatography

Column Bifurcation with Tunable Selectivity for High-Speed Gas Chromatography

High-speed, thermally modulated SFE/GC for the analysis of volatile organic compounds in solid matrices

A coupled supercritical fluid extraction (SFE) and high-speed gas chromatography (GC) system was developed which permits simultaneous sample extraction and analysis. A thermal desorption modulator at the head of a 50-μm i.d. capillary column was used as an interface between the SFE and GC. The extraction fluid was first split between the modulator and a waste collection vessel. The substances introduced into the modulator were concentrated in the stationary phase and then released as a sharp injection pulse to the analytical column by electrical resistance heated thermal desorption. The modulator was operated at 10-s time intervals, which generated consecutive concentration pulses to the column. These concentration pulses were separated into individual chromatograms by high-speed GC. A set of chromatograms could be generated while the extraction proceeded. With this system, the extractant was sampled continuously so that the SFE process could be monitored in real time for selected components. Quantitative results could be extrapolated before extraction was complete from curves obtained by signal averaging of segmented chromatograms from the set.