Carbowax 20M Capillary Columns Research Articles

Development of techniques for capillary chromatography of terpene hydrocarbons and oxygenated components of essential oils

The analysis of existing techniques for chromatographic study of essential oils has shown that under the same chromatography conditions of terpenes and their oxygenated derivatives, poor separation of peaks in the chromatogram, their imposition or masking of one peaks by some other is observed.The paper presents the study of the conditions of the gas chromatographic analysis of essential oils on capillary columns with a maximum separation of terpene hydrocarbons and oxygenated components. When developing techniques, stationary phases were chosen, gas-carrier and its rate, heating temperatures of columns, detector, injector were selected. According to the results of experiments, Carbowax 20M capillary column with a polar stationary phase was used in the separation technique of oxygenated aromatic components of essential oils.For the separation of terpene hydrocarbons, a column with a nonpolar stationary phase - HP-5MS (crossliness 5 % PHME siloxane) FilmThickness: 0,25 mm, lenght 30 m, phaseratio 250, column ID 0,25 mm was used in the technique.Both techniques are characterized by high separation efficiency of the essential oil components and allow to determine their quantitative ratios with the total error į=15 %, with p=0,95.The developed techniques can be implemented on the flame ionization detector chromatograph, contain all the necessary data to study the composition of essential oils of both essential oil plants and aromatic plants of the new selection.

Fast analysis of important wine volatile compounds: Development and validation of a new method based on gas chromatographic–flame ionisation detection analysis of dichloromethane microextracts

A method for the simultaneous determination of major (10–200 mg/l) and minor (0.1–10 mg/l) volatile compounds from wine has been optimised and validated. A 3-ml volume of wine is diluted with water (7 ml), salted with 4.5 g of ammonium sulfate and extracted with 0.2 ml of dichloromethane. The extract is injected in the split mode in a GC system, separated on a Carbowax 20M capillary column and detected by flame ionisation detection. Volatiles from wine are divided into four groups according to their behaviour in the extraction, and a specific internal standard has been selected for each group. The method allows satisfactory determination of more than 30 volatile compounds of wine. Compounds analysed include acetaldehyde, diacetyl, acetoine (3-hydroxy butanone), fusel alcohols and their acetates, and fatty acids and their ethyl esters. The linear dynamic range of the method covers the normal range of occurrence of analytes in wine and extends from at least one magnitude order to more than two, with typical r 2 between 0.9938 and 0.9998. Reproducibility ranges from 3.1 to 10% (as RSD) with 5.5% as the average. The analysis of spiked samples has shown that matrix effects do not significantly affect method performance.

Influence of temperature and n-alkane pair on the methylene increments to the thermodynamic functions of solution on SE-30 and Carbowax-20M capillary columns

The contributions of the methylene group to the standard free energy, enthalpy and entropy of solution were measured on SE-30 and Carbowax-20M capillary columns. The slight decrease of the absolute value of the free energy increment with the carbon number of the homologues has been confirmed for different temperatures and columns. The absolute values of all increments decrease with temperature, and for Carbowax-20M depend on the film thickness. There is a linear enthalpy–entropy correlation in a series of data measured at different mean temperatures of the range. A short review is included.

The aroma of Grenache red wine: hierarchy and nature of its main odorants

A young Grenache red wine from 1995 harvest was continuously extracted with Freon-11 and the extract cleaned up with aqueous NaHCO3 in order to remove fatty acids. An Aroma Extract Dilution Analysis was carried out with that extract in a Carbowax 20M capillary column with simultaneous MS and olfactometric detections. The AEDA analysis showed that there are 43 flavour active regions in the chromatogram whose aromatic intensities ranged from less than 16 to more than 1000 arbitrary flavour dilution coefficients. To isolate the odorants, the extract was further washed with propylglycol, concentrated, and then fractionated by normal phase HPLC with UV detection at 220 nm in order to obtain 29 fractions. All the fractions were concentrated and analysed in the same HRGC-MS-olfactometric system in which the AEDA experiment was performed. The strategy allowed to isolate most of the odorants, and 30 of them, among which were the most important, could be clearly identified. Some others could not be identified but their mass spectra are given. Among the most important odorants there are some well known fermentation esters but, surprisingly, the role played by some minor esters, such as the ethyl esters of isobutyric, isovaleric and 2-methylbutyric acids, seems to be very important. Equally important could be the role played by some volatile phenols, terpenols, lactones and some nor-isoprenoids. © 1998 SCI.

Direct Measurement of Total trans- and cis-Octadecenoic Fatty Acids Based on a Gas--Liquid Chromatographic Class Separation of trans-18:1 and cis-18:1 Fatty Acid Methyl Esters

A gas-liquid chromatographic (GLC) class separation is described whereby the contents of total trans- and cis-octadecenoic fatty acids can be obtained for relatively simple samples such as margarines and for more complicated food mixtures and biological specimens. The method is an adjunct to the standard process commonly used for quantitating the general fatty acid profile of a sample (extraction of lipids, preparation of methyl ester derivatives of fatty acids, GLC separation on Carbowax-20M capillary columns). There is no incremental work beyond the addition of one chromatographic run on a cyanosilicone capillary column at 242°C that lasts only 20-25 min. The chromatograms provide a composite trans peak and a composite cis peak with sufficient resolution between them to provide direct estimation of total trans- and cis-octadecenoic fatty acids. A concurrent analysis for the general profile of fatty acids in an unknown (using Carbowax20M columns) is included with every analysis for trans content to check for internal consistency and for general quality control.

Production of Acetylacetoin by Bacterial Fermentation

Bacillus sp. YUF-4 did not produce acetylacetoin with general culture media, such as bouillon medium containing glucose or acetoin. When diacetyl was added to a medium cultured for 18–20 h in the presence of glucose or acetoin, AAC was produced as culture continued. AAC was assayed by GLC with a Carbowax 20M capillary column. The AAC produced was purified by several steps: the final HPLC using a Shodex E411 column was effective. The yield of AAC was 346 mg per liter of the medium (7.5% recovery) and the purity was 97%. AAC was identified by 1H-NMR and 13C-NMR.

A Rapid, Precise Determination of C1-C4 Normal Volatile Fatty Acids in Aqueous Solutions by Gas Chromatography

The objective of this work is to develop a rapid and precise method for determining free volatile fatty acids (VFAs) in cellulosic polymers. The VFAs are extracted with water and determined quantitatively by gas chromatography (GC). A thermal conductivity detector (TCD) is used to detect formic acid, and separation of the VFAs is achieved by using a wide-bore fused-silica Carbowax 20M capillary column. The method is rapid and precise, and a coefficient of variation of 3% for formic acid is determined.

Analytical reference materials. Part V. Development of a sediment reference material for chlorobenzenes and hexachlorobutadiene

The development of the first lake sediment reference material for the determination of chlorobenzenes and hexachlorobutadiene is described. Approximately 500 kg of lake sediment were collected, freeze-dried, crushed, sieved and blended before 5000 sub-samples were bottled and stored at 4 °C in the dark. Sub-samples were extracted using a Soxhlet apparatus, cleaned with Florisil and analysed by gas chromatography using both OV-1 and Carbowax 20M capillary columns interfaced to either an electron-capture or a mass-selective detector. Reference concentrations for six chlorobenzenes and hexachlorobutadiene were generated and no sign of loss or degradation for those components in the reference material was observed after 4 years of cold storage. This sample is suitable for long-term in-house or inter-laboratory quality assurance applications.

A quantitative determination by capillary gas-liquid chromatography of neutral and amino sugars (as O-methyloxime acetates), and a study on hydrolytic conditions for glycoproteins and polysaccharides in order to increase sugar recoveries

Complete gas-liquid chromatographic separation of O-methyloxime acetates ( syn and anti isomers) prepared from eight neutral sugars, three hexosamines, and muramic acid has been obtained, using a fused-silica Carbowax 20M capillary column. A single hydrolytic step for carbohydrate-containing biological material (≤2.5· 10 −3 m sugar solution in 4 n trifluoroacetic acid at 125°C for 1h) has been developed, and results have been compared with those obtained with standard hydrolytic conditions in order to ensure complete release of amino sugars from glycoproteins, together with minimum losses of neutral sugars. The combination of this acid hydrolysis with the above improved derivatization procedure for the gas-liquid chromatographic analysis has led to a simple, rapid, and sensitive analytical method, which has been successfully tested on three glycoproteins (fetuin, mucin, and peroxidase) and two plant cell-wall polysaccharide fractions (soluble fibers from carrots and soybeans).

Stimultaneous quantitative analysis using dual capillary columns of different polarities

AbstractComplex organic mixtures, such as coal liquefaction and oil shale products and by‐products, are comprised of hundreds or thousands of individual components. State‐of‐the‐art high resolution gas chromatography does not always provide sufficient resolution to allow accurate quantitation or identification of many compounds of interest. The concept of dual capillary column chromatography combines the different resolving characteristics of two capillary columns coated with different stationary phases into a single chromatographic run. In this approach, both columns are connected to the same injection port. Analysis of complex mixtures in this fashion can confirm the identification and quantitation of components on two columns of different polarity with little increased analysis time, can provide a means of obtaining quantitative data for individual components which are known to coelute on any one column, and can alert one to unknown coelution problems that would be undetected by gas chromatographic analysis on a single capillary column.Simultaneous dual column analysis was applied to three samples, the neutral polycyclic aromatic hydrocarbon (PAH) fraction of a Solvent Refined Coal‐II (SRC‐II) heavy distillate, the nitrogen‐containing polycyclic aromatic compound (N‐PAC) fraction of an SRC‐II heavy distillate, and the basic fraction from a shale oil process water. Fused silica capillary columns coated with SE‐54 and Durawax 3 were used for the analyses of the heavy distillate, while SE‐54 an Carbowax 20M capillary columns were used for the analysis of the process water.

Gas chromatographic study of acetyl derivates of chlorinated guaiacols

The gas chromatography of acetyl derivatives of guaiacol and all chlorinated guaiacols has been studied on SE-30, OV-351 and Carbowax 20M capillary columns. The retention order and relative retention times under isotermal and temperature-programmed conditions are discussed. Different retention times for all mono- and dichloro compounds have been observed on the SE-30 column. However, all trichloroguaiacol isomers were separated only on polar columns. The best overall temperature-programmed separations have been achieved on an SE-30 capillary column.