High Temperature High Resolution Gas Chromatography Research Articles

Hidrólise do óleo de Azadirachta indica em água subcrítica e determinação da composição dos triacilglicerídeos e ácidos graxos por cromatografia gasosa de alta resolução a alta temperatura e cromatografia gasosa de alta resolução acoplada à espectrometria de massas

The development of modern analytical tools plays an important role in quality control. The main purpose of this study was to explore the use of subcritical water as a versatile analytical tool, employed simultaneously as a reagent and solvent, as well as the application of high temperature-high resolution gas chromatography (HT-HRGC) to develop a procedure for the analysis of triacylglycerides and fatty acids in Azadirachta indica A. Juss. (Neem) oil without the need for solvents, chemical reagents, or catalytic agents. The developed method presented satisfactory results and is in agreement with the concepts of Green Analytical Chemistry (GAC).

Chemical compositions and antimicrobial activities of four different Anatolian propolis samples

Propolis means a gum that is gathered by bees from various plants. It is known for its biological properties, having antibacterial, antifungal and healing properties. The aims of this study were to evaluate the antimicrobial activity of four different Anatolian propolis samples on different groups of microorganisms including some oral pathogens and comparison between their chemical compositions. Ethanol extracts of propolis (EEP) were prepared from four different Anatolian propolis samples and examined whether EEP inhibit the growth of the test microorganisms or not. For the antimicrobial activity assays, minimum inhibitory concentrations (MIC) were determined by using macrodilution method. The MIC values of the most effective propolis (TB) were 2 μg/ml for Streptococcus sobrinus and Enterococcus faecalis, 4 μg/ml for Micrococcus luteus, Candida albicans and C. krusei, 8 μg/ml for Streptococcus mutans, Staphylococcus aureus, Staphylococcus epidermidis and Enterobacter aerogenes, 16 μg/ml for Escherichia coli and C. tropicalis and 32 μg/ml for Salmonella typhimurium and Pseudomonas aeruginosa. The chemical compositions of EEP's were determined by high-temperature high-resolution gas chromatography coupled to mass spectrometry. The main compounds of four Anatolian propolis samples were flavonoids such as pinocembrin, pinostropin, isalpinin, pinobanksin, quercetin, naringenin, galangine and chrysin. Although propolis samples were collected from different regions of Anatolia all showed significant antimicrobial activity against the Gram positive bacteria and yeasts. Propolis can prevent dental caries since it demonstrated significant antimicrobial activity against the microorganisms such as Streptococcus mutans, Streptococcus sobrinus and C. albicans, which involves in oral diseases.

Two decades of high temperature gas chromatography (1983–2003): what's next?

The evolution of the concept of High Temperature High Resolution Gas Chromatography (HT-HRGC) is presented together with examples highlighting its potentialities. The range of molecular weight and number of functional groups present in the molecules eluting at higher temperature, far exceeds (Kovats Indices of 120) the usual HRGC range for analytes (Kovats Indices of 40–45). With usual column lengths and film thickness, this will already extend the range of analytes by 400 Da. Short, thin film columns would acme another 500 Da to the molecular weight window traditionally dealt with by HRGC. This range (∼700–1500 Da) can be surpassed by molecules presenting peculiar structures, the ceiling being ∼5000 Da. It is currently tackled only for peptides, oligosaccharides and a few polymers, by conventional analytical techniques. However, higher molecular weight analogues of all other organic species and yet unknown carbon skeletons have been neglected because this range was only poorly accessible to usual analytical techniques dealing with complex mistures.

High-temperature gas chromatography–mass spectrometry with glass capillary columns for the screening of natural products

High-temperature high resolution gas chromatography (HT-HRGC) and HT-HRGC coupled to mass spectrometry (HT-HRGC–MS) are powerful but relatively unexplored tools for the analysis of crude extracts and fractions of natural products. To illustrate the scope of the technique the direct characterization of several compounds, present in crude extracts of leaves and stems of Croton hemiargyreus Muell. Arg. var. hemiargyreus was undertaken, without derivatization or clean-up procedures. Both practical aspects and limitations of HT-HRGC and HT-HRGC–MS were evaluated resulting in a simple, straightforward and extremely powerful technique for the analysis of complex mixtures.

Further lipophilic flavonols in Vellozia graminifolia (Velloziaceae) by high temperature gas chromatography: quick detection of new compounds.

Further lipophilic flavonols present in Vellozia graminifolia have been determined by high temperature high resolution gas chromatography (HTHRGC) and by HTHRGC coupled to mass spectrometry (MS). These methods resulted in the detection, isolation and characterisation of a monoisoprenylated flavonol 3,5,4'-trimethoxy-3'-hydroxy-6,7-(2"-isopropenyldihydrofurano)flavone from the ethyl acetate extract of the whole plant. The structural elucidation was accomplished using spectral data, including two-dimensional NMR, and on chemical transformations. Both HTHRGC and HTHRGC-MS were shown to be alternative and extremely valuable methods for the quick screening of flavonoid aglycones and other chemical metabolites of the Velloziaceae.

Estado da arte da cromatografia gasosa de alta resolução e alta temperatura

The developments in stationary phase synthesis and capillary column technology, have opened new perspectives in analysis of high molecular mass compounds (³600 daltons) and thermolabile organic compounds by High Temperature High Resolution Gas Chromatography (HT-HRGC). HT-HRGC is a new analytical borderline and its application to the analysis of high molecular mass compounds is still in its infancy. The apolar and medium polar gum phases can now be operated at temperatures up to 400-480oC, being used for the analysis of n-alcanes up to C-100, lipids, oligosaccharides, industrial resins, polyglycerols, cyclodextrins, porphyrins, etc. This technique should play a leading role as a powerful tool, for many different analysis types, in multidisciplinary fields of Science.

Rapid screening of natural products by high-resolution high-temperature gas chromatography.

The crude ethanol extracts from the leaves of three Croton hemiargyrus hemiargyreus plants are fractionated by thin-layer chromatography, yielding five fractions. The fractions and the crude extract are analyzed by high-temperature high-resolution gas chromatography coupled with mass spectrometry (HT-HRGC-MS). Several natural products, including thermolabile components, can be characterized directly in the samples, such as alkaloids, terpenes, flavonoids, acids, alcohols, etc. The cold on-column technique proves to be appropriate for the injection of these thermolabile compounds. HT-HRGC-MS is shown to be a valuable tool and an alternative technique to classical phytochemical procedures for the simple and fast routine analysis of natural products in crude extracts.

Analysis and quantitation of rotenoids and flavonoids in Derris (Lonchocarpus urucu) by high-temperature high-resolution gas chromatography.

A glass capillary column coated with PS-086 (15% phenyl-80% methylpolysiloxane, 15 m x 0.30-mm i.d., 0.1-microm film thickness) is used to analyze extracts from Lonchocarpus urucu (Derris urucu). Several secondary metabolites (8 flavonoids, 10 rotenoids) are characterized without derivatization, and the rotenoids are quantitated by high-temperature high-resolution gas chromatography (HTHRGC) and HTHRGC coupled with mass spectrometry (HTHRGC-MS). The limit of detection in flame ionization detection of rotenone is approximately 0.5 microg/mL, and the limit of quantitation was 2 microg/mL. Derris urucu bark is an excellent source of rotenone isomers (80 mg/g), deguelin (30 mg/g), and rotenolone (26 mg/g). Single solvent extractions (hexane, methylene dichloride, acetone, or methanol) are not able to fully extract the flavonoids and rotenoids. Complete extraction is achieved using a mixture of methanol-methylene dichloride (1:1), indicating a complex association of these compounds with the plant tissue. HTHRGC and HTHRGC-MS are shown to be quick and informative tools for the rapid analysis of crude extracts without the need for prior derivatization and fractionation.

Systematic study of high molecular weight compounds in Amazonian plants by high temperature gas chromatography-mass spectrometry.

The fractions of hexane and dichloromethane extraction from marupá (Simaruba amara) and (Bertholletia excelsa) leaves were analyzed by HT-HRGC (high temperature high resolution gas chromatography) and HT-HRGC coupled to mass spectrometry (HT-HRGC-MS). Several compounds can be characterized including unusual high molecular weight compounds.

Pentacyclic Triterpenoid Alkanoates in Propolis

A series of high molecular mass pentacyclic terpenoid wax esters (TTFAE) were characterized for the first time in hexane extracts of Brazilian propolis (Carangola, Minas Gerais State). Identification was by HT-HRGC (High Temperature High Resolution Gas Chromatography) and HT-HRGC coupled to mass spectrometry (HT-HRGC-MS).

Detection of High Molecular Weight Organic Tracers in Vegetation Smoke Samples by High-Temperature Gas Chromatography−Mass Spectrometry

High-temperature high-resolution gas chromatography (HTGC) is an established technique for the separation of complex mixtures of high molecular weight (HMW) compounds which do not elute when analyzed on conventional GC columns. The combination of this technique with mass spectrometry (i.e., HTGC−MS) is not so common and application to aerosols is novel. The HTGC and HTGC−MS analyses of smoke samples taken by particle filtration from combustion of different species of plants provided the characterization of various classes of HMW compounds reported to occur for the first time in emissions from biomass burning. Among these components are a series of wax esters (long chain alcohols esterified with long chain fatty acids) with up to 58 carbon numbers, aliphatic hydrocarbons (C15−C40; Cmax = C31; odd predominance), triglycerides, long chain methyl ketones (up to 37 carbons; Cmax = C33; odd predominance), alkanols (up to 40 carbons; Cmax = C32; even predominance), and a series of triterpenyl fatty acid esters (e.g., α- and β-amyryl stearate) which have been characterized as novel natural products. Long chain fatty acids with more than 32 carbon numbers are not present in the smoke samples analyzed. The HMW compounds in smoke samples from the burning of plants from Amazonia indicate the input of directly volatilized natural products in the original plants during their combustion. However, the major organic compounds extracted from smoke consist of a series of lower molecular weight polar components, which are not natural products but the result of the thermal breakdown of cellulose and lignin. In contrast, the HMW natural products may be suitable tracers for specific sources of vegetation combustion because they are emitted as particles without thermal alteration in the smoke and can thus be related directly to the original plant material.

High-temperature high-resolution gas chromatography: breaching the barrier to the analysis of polar and high molecular weight compounds

Developments in stationary phase synthesis and capillary column technology have opened new perspectives in the analysis of high molecular weight compounds (≥600 Da) and thermolabile organic compounds by high-temperature high-resolution gas chromatography (HT-HRGC). Apolar and medium polarity gum phases can now be operated at temperatures up to 400–480°C, and are being used for the analysis of compounds including n-alkanes up to C 100, lipids, oligosaccharides, industrial resins, polyglycerols, cyclodextrins, and porphyrins.

Application of High Temperature High Resolution Gas Chromatography to Crude Extracts of Propolis

The underivatized acetone and hexane fractions from propolis samples (predominant flora Citrus spp. and Vernonia polyanthes) were analyzed by HT-HRGC (high temperature high resolution gas chromatography) and HT-HRGC coupled to mass spectrometry (HT-HRGC-MS). Several compounds, including flavonoid aglycones, phenolic acids, and high molecular weight compounds were characterized in crude extracts by HT-HRGC-MS. HT-HRGC and HT-HRGC-MS were shown to be quick and informative tools for rapid analysis of crude extracts without need for prior derivatization and purification.

Application of High Temperature High Resolution Gas Chromatography to Crude Extracts of Propolis

The underivatized acetone and hexane fractions from propolis samples (predominant flora Citrus spp. and Vernonia polyanthes) were analyzed by HT-HRGC (high temperature high resolution gas chromatography) and HT-HRGC coupled to mass spectrometry (HT-HRGC-MS). Several compounds, including flavonoid aglycones, phenolic acids, and high molecular weight compounds were characterized in crude extracts by HT-HRGC-MS. HT-HRGC and HT-HRGC-MS were shown to be quick and informative tools for rapid analysis of crude extracts without need for prior derivatization and purification.

Application of High-Temperature High-Resolution Gas Chromatography to the Analysis of -Cyclodextrin Derivatives

Short (3 m) columns are used with high-temperature stationary phases in analyses of reaction mixtures and isolated single species of β-cyclodextrin derivatives. The stationary phases are 5% phenyl-95% methylpolysiloxane and 30% diphenylpolysiloxane-40% sildiphenylene-ether-30% dimethyl polysiloxane; the latter phase is the best phase for the resolution of mixtures of positional isomers of β-cyclodextrin derivatives.