Types Of Capillary Columns Research Articles

In-Tube Solid-Phase Microextraction Directly Coupled to Mass Spectrometric Systems: A Review

Since it was introduced in 1997, in-tube solid-phase microextraction (in-tube SPME), which uses a capillary column as extraction device, has been continuously developed as online microextraction coupled to LC systems (in-tube SPME-LC). In the last decade, new couplings have been evaluated on the basis of state-of-the-art LC instruments, including direct coupling of in-tube SPME to MS/MS systems, without chromatographic separation, for high-throughput analysis. In-tube SPME coupling to MS/MS has been possible thanks to the selectivity of capillary column coatings and MS/MS systems (SRM mode). Different types of capillary columns (wall-coated open-tubular, porous-layer open-tubular, sorbent-packed, porous monolithic rods, or fiber-packed) with selective stationary phases have been developed to increase the sorption capacity and selectivity of in-tube SPME. This review focuses on the in-tube SPME principle, extraction configurations, current advances in direct coupling to MS/MS systems, experimental parameters, coatings, and applications in different areas (food, biological, clinical, and environmental areas) over the last years.

Identification of the Female-Produced Sex Pheromone of an Invasive Greenhouse Pest, the European Pepper Moth (Duponchelia fovealis).

The European pepper moth (Duponchelia fovealis, Lepidoptera, Crambidae, Spilomelinae) is an invasive pest of greenhouses in many countries, causing serious damages to horticultural plants. Coupled gas chromatographic-electroantennographic detection analysis of the female gland extract revealed two antennally active peaks. Using coupled gas chromatography-mass spectrometry (GC-MS), one was identified as (Z)-11-hexadecenal (Z11-16:Ald); however, further analysis on different types of capillary columns indicated that the second active compound has two different isomers, (E)-13-octadecenal (E13-18:Ald) and (Z)-13-octadecenal (Z13-18:Ald). The approximate ratio of E13-18:Ald, Z13-18:Ald and Z11-16:Ald in the crude pheromone gland extract was 10:1:0.1, respectively. Single sensillum recordings showed that there was one sensory neuron that responded with a high amplitude spike to both E13-18:Ald and Z13-18:Ald, while another neuron housed in the same sensillum responded to Z11-16:Ald. Field evaluation of the identified compounds indicated that the E13-18:Ald was necessary to evoke the attraction of males; although the presence of Z13-18:Ald and Z11-16:Ald increased the catches in traps. The highest number of caught males was achieved when E13-18:Ald, Z13-18:Ald and Z11-16:Ald were present in baits in the same ratio as in the female gland extract. This pheromone can be used in a monitoring strategy and could potentially lead to the development of mating disruption.

Improving the method of determining wax-like substances in vegetable oils using high-temperature gas-liquid chromatography

The article defines the scientific approaches regarding the improvement of the standardized method of determining wax-like substances using high temperature gas-liquid chromatography. Experimental studies matched the type of capillary column, type of stationary phase, the composition eluent and the feed rate, temperature parameters of the chromatographic separation. The results of the monitoring of sunflower oil with different content of wax-like substances have confirmed the ability of the method. The possibility of qualitative identification of waxes by using chromatographic profiles is shown. Process conditions of the chromatographic analysis were established. There are gradient programming thermostat and temperature, the optimal injector temperature, composition and feed rate eluent (1 drop/s); selected internal standard – hexatriene (paraffin C36). The result of the monitoring of sunflower oil with different content of the waxes is shown that the improved method of determining wax-like substances is reliable and can be recommended for technical control of raw materials and finished products in the production of refined oils. It is experimentally confirmed that in the presence of external standard (sunflower wax) wax-like substances in vegetable oils is possible qualitative identify by comparison of the chromatographic profiles of the standard and sample.

Recent advances on capillary columns, detectors, and two-dimensional separations in capillary electrochromatography.

As a typical miniaturized analytical technique, CEC has attracted much attention because of its low sample and solvent consumption, high efficiency, high selectivity, high resolution, and fast speed. In this review, we mainly cover the development of capillary columns and detection techniques in the CEC since 2009. Herein, three types of capillary columns, namely, open-tubular capillary columns, monolithic columns and packed columns, and several types of detectors are reviewed in detail. Moreover, a 2D separation system based on CEC is also reported.

Fingerprint Development for Ginkgo biloba Extracts by Pressurized Capillary Electrochromatography: Comparison of Column Types

A pressurized capillary electrochromatographic (pCEC) fingerprint of Ginkgo biloba leaf extract was developed on three different types of capillary columns. A commercial column packed with 3-microm particles and an in-house column packed with 5-microm particles were investigated for their performance. Additionally, a monolithic column was included in the fingerprint study as a potential alternative to the conventional packed columns. The effects of experimental parameters, such as the composition of the mobile phase, the concentration and pH of the buffer, and the applied voltage, were studied. Binary mobile phases consisting of acetonitrile and a 5 mM sodium dihydrogen phosphate electrolyte at pH 2.8 were used in gradient elution mode with an applied voltage of 5 kV. Under optimal gradient conditions, at least 45 peaks were observed within 60 min on the commercial packed column, whereas only about 20 peaks were separated on the methacrylate-based monolithic and the in-house packed columns. The commercial column thus clearly outperforms the two other. However, the properties of the monolithic stationary phase still might be adapted (i.e., by changing the polymerization-mixture composition, the porosity, and thus the selectivity of the phase might be changed), which could lead to an improved efficiency.

Determination of potent odorants in apple by headspace gas dilution analysis

Gas chromatography–olfactometry with headspace gas dilution analysis was used to evaluate the odor potencies of volatile compounds in Fuji apple. To improve the resolution of volatile compounds, the dilution analysis was conducted on two types of capillary columns with different polarities. Thirty three and 20 compounds were identified on DB-WAX and DB-5 columns, respectively. Methyl 2-methylbutanoate, isobutyl acetate, ethyl butanoate, ethyl 2-methylbutanoate, isopentyl formate, butyl acetate and hexyl acetate as well as hexanal were important odor contributors in the headspace gas of apple on the basis of high Flavor Dilution (FD) factors. Threshold values-in-air of these compounds were also estimated from the relationships between their FD factors and concentrations. Methyl 2-methylbutanoate and ethyl 2-methylbutanote were considered as the most potent odorants because of their lowest threshold values. In addition, the threshold values-in-air of isopentyl formate, isopentyl acetate and butyl isobutanoate, which have never been reported, were estimated at 0.149, 1.95 and 0.00607 μl/l, respectively.

Analysis and characterization of aroma‐active compounds of Schizandra chinensis (omija) leaves

AbstractVolatile components from leaves of Schizandra chinensis (omija), a native plant of Korea, were extracted by simultaneous distillation–extraction (SDE) and analyzed by gas chromatography–mass spectrometry (GC‐MS) using two types of capillary column with different polarities (DB‐5MS and DB‐Wax). The GC‐MS analysis of volatile compounds obtained by SDE revealed that germacrene D is the most abundant compound (22.6%) in omija leaves, followed by β‐elemene (17.4%), (E)‐2‐hexenal (8.7%), and (E)‐β‐ocimene (7.2%). Aroma‐active compounds were determined by gas chromatography–olfactometry (GC‐O) using the aroma‐extract‐dilution analysis method. (E,Z)‐2,6‐Nonadienal (cucumber) was the most intense aroma‐active compound due to its higher flavor‐dilution factor (243–729) than any other compound. (Z)‐3‐Hexenal (green/apple), (E)‐2‐hexenal (green/fruity), and (E)‐β‐ocimene (wither green/grass) were also identified as important aroma‐active compounds by GC‐O. In addition, the volatile compounds were extracted by solid‐phase microextraction (SPME), and the quantitative analysis of the SPME samples gave slightly different results, depending on the type of SPME fiber, compared with those from SDE, However, the aroma‐active compounds identified in SPME were similar to those in SDE. Copyright © 2004 Society of Chemical Industry

Characterization of aroma‐active compounds of Abies nephrolepis (Khingan fir) needles using aroma extract dilution analysis

AbstractVolatile components in the needles of Abies nephrolepis (Khingan fir), a conifer native to Korea, were extracted by simultaneous distillation–extraction. Gas chromatography–mass spectrometry using two types of capillary column with different polarities (DB‐5MS and DB‐WAX) revealed that α‐pinene (23.2%) is the most abundant compound, followed by limonene (12.7%), bornyl acetate (9.9%) and β‐caryophyllene (10.8%). Aroma‐active compounds of A. nephrolepis were determined using gas chromatography–olfactometry by aroma extract dilution analysis. a‐Pinene showed the highest flavour dilution factors, ranging from 38 to 39 with characteristic pine aroma. (Z)‐3‐Hexenal and γ‐terpinene were also identified as important aroma‐active compounds. Copyright © 2004 John Wiley & Sons, Ltd.

Capillary GLC: a robust method to characterise the triglyceride profile of cocoa butter — results of an intercomparison study

AbstractThe results of a method intercomparison study, in which 13 laboratories applied high‐temperature capillary GLC on fused‐silica columns coated with medium‐polarity stationary phases to determine the triglyceride profile of cocoa butter, are reported. The participants did not apply a uniform GLC procedure based on a standard method, but were requested to use their own methodology. However, certain requirements relating to the separation efficiency and the accuracy, had to be fulfilled. The relative standard deviation of the reproducibility was less than 5% for the major triglyceride components of cocoa butter. The results of the present study indicate that neither the type of capillary column employed nor sample injection techniques or other chromatographic conditions influenced to a measurable degree the agreement of results between the participating laboratories. Therefore, we conclude that high‐temperature capillary GLC is a robust and reliable technique for the characterisation of cocoa butter by determining its triglyceride pattern.

A new type of capillary column for gas chromatography

A new type of capillary column for gas chromatography was proposed. A sorbent layer (for example, stationary liquid phase) is supported on the internal capillary surface, and the internal (interstitial) volume is packed with nonporous large particles of a sorbent (particle diameter is 0.1—0.6 of the capillary internal diameter). The external surface of the particles can also be coated with the sorbent layer (for example, stationary liquid phase). The specific separation efficiency (number of separation) on the new type column is by 1.6—2.3 times higher than that of the initial classical capillary column.

Pressure-assisted and pressure-programmed capillary electrophoresis/electrospray ionization time of flight-mass spectrometry for the analysis of peptide mixtures.

Pressure assisting and pressure programming the inlet of the capillary electrophoresis instrument were used for the analysis of peptide mixtures and protein digests using capillary electrophoresis/electrospray ionization-mass spectrometry (CE/ESI-MS). CE/ESI-MS of peptide mixtures and tryptic digests of proteins was studied using three different types of capillary columns: (i) a freshly aminopropylsilane (APS)-treated column, (ii) an untreated column, and (iii) a degraded APS-treated column. To maintain a constant and adequate buffer flow toward the CE capillary outlet for stable CE and ESI operation, low pressure was applied to the inlet of the CE when an untreated or degraded APS capillary was used. By programming the inlet pressure, CE/ESI-MS analysis time was reduced to 1/3 of its original time. The utility of this technique is demonstrated by CE/ESI-MS analysis of a hemoglobin variant (hemoglobin-S) and its tryptic digests. Identification of the mutant peptide in the tryptic digest of hemoglobin-S was achieved by collision-induced dissociation (CID) of the protein digests using CE/ESI time of flight-mass spectrometry (TOF-MS).

Retention time repeatability as a function of the injection automatism in the analysis of trace organochlorinated compounds with high-resolution gas chromatography

Short-term precision in retention time determination of different injection systems (three manual and three autosamplers) is assessed in the present study. This evaluation has been performed on eight different instrumental set-ups equipped with the same type of capillary column (30 m, 5% phenyl-95% methyl) which have been used for the analysis of standard mixtures of α,, γ-, and δ-hexachlorocyclohexanes. The results show that, as expected, retention time repeatability increases with the degree of automatization of the injection system. They also show that only the autosamplers and the manual injector provided with the syringe-operated start device are suitable for analysis of compounds with retention time differences in the order of 0.1 min. Conversely, none of the systems included in the study, not even the autosamplers, is adequate for the analysis of analytes having retention time differences of about 0.01 min.

CAPILLARY GAS CHROMATOGRAPHY USING CARBON DIOXIDE AS THE CARRIER GAS

Capillary Gas Chromatography(GC) system using carbon dioxide as the carrier gas was evaluated. The outdoor measurement is often required in environmental analysis using portable GC. But portability and operation time is limited by the carrier gas cylinder volume. We tried to solve this problem by using liquefied gas, such as CO 2 , instead of he as the carrier gas. We compared the differences between CO 2 and he and analyzed environmental air samples using different types of capillary columns. Similar resolution was obtained at flow rate around 1 ml/min in both cases

Trace analysis of halogenated hydrocarbons in gaseous samples by capillary gas chromatography. Part II: Quantitative aspects and ECD calibration

In part I of this work an analytical procedure was presented for the capillary gas chromatographic determination of volatile hydrocarbons in gases. Here, various quantitative aspects of GC analysis and Electron Capture Detection are emphasized. The performance of several types of capillary columns is studied and a compromise is suggested between column inner diameter, film thickness, stationary phase and oven temperature. The influence of several experimental parameters like pulse voltage, standing current and the detector temperature on the quantitative results of EC detection are discussed. ECD calibration by coulometric detection in the Constant Frequency mode is compared to Constant Current EC detection using gas standards. The gas standards were prepared either by static or dynamic dilution procedures. Accurate and highly reproducible concentrations between ppm's and ppb's were obtained by a newly designed permeation gas system, of which a detailed description is given. The applicability of the total procedure is demonstrated by the quantitative analysis of a series of stratospheric air samples collected at altitudes between 10 and 30 km.

PoraPLOT Q: A porous layer open tubular column coated with styrene‐divinylbenzene copolymer

AbstractA porous polymer is deposited on the inner wall of fused silica capillary columns. The retention characteristics of this porous polymer were evaluated and found to be comparable with Porapak Q. The porous polymer has a high retention volume which enables the separation of permanent gases at ambient temperatures or higher. The hydrophobic character of the porous polymer allows the injection of water containing samples without changing retention due to adsorption of water. The inertness of the porous polymer allows the elution of a range of apolar and polar compounds. The maximum temperature of the porous polymer was estimated to be 250°C. With this new type of capillary column, high resolution separations are obtained in combination with short analysis times.

High temperature gas chromatography: The development of new aluminum clad flexible fused silica glass capillary columns coated with thermostable nonpolar phases: Part 1

AbstractWith the simultaneous development of blank aluminum clad flexible fused silica glass capillary tubing capable of withstanding temperatures up to 500°C, coincident with a series of special high temperature methyl polysiloxane polymers, it was possible to produce for the first time, long lived fused silica capillary columns containing thin films of thermostable stationary phases which could be maintained isothermally at 400425°C and temperature programmed to 425–440°C. The “bleed rate” here for a well conditioned column was 5 picoamperes or less. Under these circumstances, alkanes with carbon numbers in the C‐90 to C‐100 area were rapidly and efficiently eluted from these columns. By extrapolation here, one can easily detect certain compounds with boiling points in the 750°C range. Since this type of capillary column was found to possess certain favorable properties, it was thought that it will soon replace the packed column and will probably be more popular than the borosilicate capillary column for many high temperature applications. Moreover, evidence has now accumulated which leads us to further believe that the majority of analyses of “high molecular weight” compounds performed by Supercritical Fluid Chromatography (SFC), utilizing very narrow bore fused silica capillary columns at several hundred atmospheres, can be much more simply, much more rapidly, much more economically, and much more efficiently accomplished by gas chromatography utilizing this new generation of high temperature capillary columns.

Determination of surface hydroxyl concentration on glass and fused silica capillary columns

The concentration of surface hydroxyl groups on three types of capillary columns was determined by exchanging the hydroxyl protons with tritium. The tritium was quantified by combustion to tritiated water followed by scintillation counting. The number of hydroxyl groups on a leached and presumably hydroxylated Pyrex glass capillary column was found to be about 2.8 groups per square nanometer. This value was slightly less than the 4.6 groups per square nanometer that is generally accepted for a fully hydroxylated porous silica. Dehydroxylation of the same glass by heating at 600°C left only 0.4 groups per square nanometer while an untreated fused silica had only 0.2 groups per square nanometer.

High-resolution gas chromatographic analysis of phenolic acids and alcohols using capillary columns

The application of the two types of capillary column, wall-coated open tubular and support-coated open tubular to the analysis of volatile derivatives of phenolic acids and alcohols is critically assessed. The latter columns were more versatile and suitable for urinary analysis. Because capillary columns possess high resolving ability, it has been possible to separate such geometrical isomers as 4-hydroxy-3-methoxyphenylacetic acid and 3-hydroxy-4-methoxyphenylacetic acid from biological samples. The most satisfactory results were obtained using a serial connection of a 50 ft OV-I7 and a 50-ft SE-30 column.