Post-Extraction Losses of Volatile Aromatic Hydrocarbons During Capillary Extraction–HRGC Analysis: A Quantitative Assessment

Benzene, toluene, ethylbenzene and o-, m-, and p-xylenes (BTEX), were extracted from aqueous samples by capillary extraction (CEx), a manual form of in-tube microextraction inherently compatible with capillary GC, and analyzed by HRGC analysis in order to quantify the post-extraction losses of these volatile organic compounds. Accuracy of the VOC determination by CEx–HRGC is dependent on these losses. The used active extraction devices were fused silica open-tubular capillaries of 0.25 mm i.d., with lengths in the range of 3–15 cm, coated with a 0.25 μm film of PTE-5 (5% phenyl methylpolysiloxane) stationary phase. The losses decreased remarkably when the extractor lengths were increased. In particular, the losses were modest or negligible for capillary extractors of usual length, though the losses increased with rising solute volatility and ‘lag time’ (the length of time required to connect in-line the laden capillary extractors with the HRGC column). BTEX losses between 2% (benzene) and 0.5% (o-xylene) resulted from CEx conducted under very usual conditions, independently from sample concentration. The short-term precision of the CE–HRGC experiments, expressed as relative standard deviation, was 0.8–4.9% (n = 5).     

Differentiation of strawberry varieties through purge-and-trap HRGC-MS,HRGC-FTIR and principal component analysis

The aroma composition of three different Fragaria anannassa cul-tivars Selva, Chandler, and Osso Grande) is studied by purge-and-trap HRGC and the components identified by MRGC-MS and HRGC-FTIR. The chromatographic aroma profiles from four different maturation stages in each variety are compared and the similarities accessed by principal component analysis (PCA). The contents in n-hexanal and hex-2(Z)-enal are characteristic features of the green stage in the three varieties where the content differences in methyl, ethyl, and butyl acetates act as typifying variables among varieties. Ethyl acetate acts as an important differentiation variable for the Selva variety. In the mature stage, the three cultivars may be distinguished from each other through their relative contents of methyl and ethyl 2-methylbutyrate (Selva), methyl 2-methyl-butyrate, methyl butyrate (Chandler), methyl and ethyl butyrates, and methyl caproate (Osso Grande).     

HRGC/FID and HRGC/MSD Analysis of the Secondary Metabolites Obtained by Different Extraction Methods from Lepechinia schiedeana,and in Vitro Evaluation of Its Antioxidant Activity

Steam distillation (SD), simultaneous distillation-solvent extraction (SDE), microwave-assisted solvent extraction (MWE), and supercritical (CO₂) extraction (SFE) were used to isolate secondary metabolites from Lepechinia schiedeana. The various extracts were analyzed by capillary gas-chromatography, on poly (dimethylsiloxane) (DB-1) and poly(ethyleneglycol) (INNOWAX), 60 m columns, using FID or MSD (EI, 70 eV). Kováts indexes, mass spectra, or standard compounds were employed for compound identification. 43, 61, 67, and 79 compounds at concentrations above 0.01% were detected in the SD, SDE, MWE, and SFE extracts, respectively. Ledol, C₁₅H₂₆O, was the major constituent (20.04–36.87%) in all extracts. Oxygenated sesquiterpenes (24.36–43.14%), C₁₀H₁₆, monoterpenes (27.70–39.87%), and C₁₅H₂₄, sesquiterpenes (10.04–22.22%) were the main groups of compounds present in SD, SDE, MWE, and SFE extracts. Heavy hydrocarbons (C_n > 15), diterpenoids, and phytosterols were found only in MWE and SFE extracts. The antioxidant activity of Lepechinia schiedeana was measured by the HRGC quantification of the volatile carbonyl compounds, final products of lipoxidation, released in a model lipid system (sunflower oil) by the effect of the Fenton reagent. The concentration of volatile carbonyl compounds decreased by 65% when lipid oxidation was induced in the presence of macerated Lepechinia plant. The protection of polyunsaturated acids in sunflower oil was also studied by measuring their concentrations after heating of the oil (180°C, 2 h) with and without macerated Lepechinia plant.     

Static and dynamic superheated water extraction of essential oil components from Thymus vulgaris L.

Superheated water extraction (SWE) performed in both static and dynamic condition (S‐SWE and D‐SWE, respectively) was applied for the extraction of essential oil from Thymus vulgaris L. The influence of extraction pressure, temperature, time, and flow rate on the total yield of essential oil and the influence of extraction temperature on the extraction of some chosen components are discussed in the paper. The SWE extracts are related to PLE extracts with n‐hexane and essential oil obtained by steam distillation. The superheated water extraction in dynamic condition seems to be a feasible option for the extraction of essential oil components from T. vulgaris L.     

HRGC and GC–MS analysis of essential oil from colombian ylang-ylang (Cananga odorata Hook fil. et Thomson,forma genuina)

Samples of essential oil from Colombian ylang-ylang trees were analyzed by means of HRGC, HRGC–MS, IR and ¹H- and ¹³C-NMR. 57 components were detected, 51 of which were positively identified. Camphene and anethol were identified in ylang-ylang essential oil for the first time. Among the composition-determining variables studied (extraction time, part of the flower, and flower freshness), the extraction time and the flower condition (fresh versus dry) were found to have the largest incidence in the quality of the essential oil.     

Comparative chemical analysis of commercial creosotes and solvent refined coal-II materials by high resolution gas chromatography

The chemical composition of a commercially available creosote was compared to a direct coal liquefaction product, i.e., solvent refined coal-II fuel oil blend (SRC-II FOB) using high resolution gas chromatography (HRGC). In addition, hydrogenated products of these materials were studied. Samples were fractionated by chemical class on neutral alumina. Those fractions previously shown to be the most mutagenic and tumorigenic in laboratory bioassays of coal-derived materials were analyzed and compared by HRGC and gas chromatography/mass spectrometry (GC/MS). Individual components were tentatively identified and quantitated. Although similar chemical components were present in the creosote and SRC-II FOB fractions studied, the creosotes had higher concentrations of heavy molecular weight materials and a lower ratio of alkylated to parent polycyclic aromatic compounds than the coal liquefaction products. The creosote samples also had a significantly higher concentration of components which eluted in the polycyclic aromatic hydrocarbon (PAH) chemical class fraction. Amino-substituted PAH were present in both nonhydrogenated coal liquid and creosote materials. The creosote and SRC-II FOB crudes and nitrogen-containing polycyclic aromatic compound (NPAC) chemical class fractions expressed similar microbial mutagenicity. Based on chemical analysis data, the predicted tumorigenic potency of the creosote in laboratory bioassay systems would be equivalent to or greater than the SRC-II FOB.     

C4-C14-alkyl nitrates as organic trace compounds in air

The long chain alkyl nitrates (C _n >5) form a complex spectrum of natural and anthropogenic organic trace compounds in air. HRGC/ECD and HRGC/MSD using 56 amu as the signal reveal a standard pattern of isomeric n-alkyl nitrates in semi-rural air. This is regulated by the input of the corresponding alkanes, their rate constants for the reaction with OH, the rate constant of the alkylperoxy radicals for the reaction to alkyl nitrates, the atmospheric concentrations of NO/NO₂ and by the rate constants of the alkyl nitrates for the reaction with OH radicals as the major removal reaction. The complex pattern of signals given by the ECD in the retention index range between 700 and 2000 has been observed before but this is the first time that it has been assigned to a defined group of chemical compounds.The environmental impact of the occurrence of the different groups of alkyl nitrates has yet to be evaluated. Their general property as organic stabilizers for NO/NO₂ and therefore as precursors of NO ₃ ^- ions in rain and their biological potentials are also known. The long chain alkyl nitrates act as lipophilic carriers for nitric acid.     

HRGC separation of hydroperoxides formed during the photosensitized oxidation of (R)—(+)-Limonene

(R)—(+)-Limonene was photooxidized in the presence of Rose Bengal as catalyst. After TLC isolation, the hydroperoxides formed were separated directly by HRGC and analyzed by MS (El; Cl). Each hydroperoxide isomer was then isolated by HPLC for structure determination which after reduction of the HOO group with sodium borohydride was performed by ¹H-NMR and ¹³C-NMR. Six hydroperoxide isomers formed by oxidation of the endocyclic double bond were identified. The compounds eluted from the HRGC column in the following order (proportions are given in brackets) I (40.1%) (1S, 4R)-p-mentha-2, 8-diene 1-hydroperoxide; II (5.8%) (1R, 4R)-p-mentha-2, 8-diene 1-hydroperoxide; III (20.6%) (2R, 4R)-p-mentha-[1(7), 8]-diene 2-hydroperoxide; IV (8.5%) (2R, 4R)-p-mentha-6, 8-diene 2-hydroperoxide; V (4%) (2S, 4R)-p-mentha-6, 8-diene 2-hydroperoxide; and VI (21.0%) (2S, 4R)-p-mentha-[1(7), 8]-diene 2-hydroperoxide. Direct HRGC separation of the limonene hydroperoxides offers, inter alia, the possibility of determining their flavor qualities by HRGC/effluent sniffing.     

Essential oil composition of Citrus medica L. Cv. Diamante (Diamante citron) determined after using different extraction methods

In this paper, we report the qualitative and quantitative composition of the volatile and the oxygenated heterocyclic fraction of citron (Citrus medica L. cv. Diamante (Diamante citron)). The fruits selected for the extraction were of three types: green citron of little size, green citron of big size, and yellow citron after 1 month from the harvest. The essential oils were extracted using three different methods. The nine samples of oil thus obtained were analyzed by high resolution GC (HRGC)‐flame ionization detection (FID), HRGC‐MS, and RP‐HPLC. They differ only in the quantitative composition, while the qualitative profile was the same. The volatile fraction of every sample of oil is characterized by a high content of limonene, γ‐terpinene, and monoterpene aldehydes and a lower content of α‐ and β‐pinene and myrcene, sesquiterpenes, and aliphatic aldehydes. Enantioselective (Es)‐GC analysis of the extracts allowed the determination of the enantiomeric distribution of five terpenoid compounds; a prevalence of four dextrorotatory isomers was observed. Oxypeucedanin was the main component of the oxygenated heterocyclic fraction in the extracts of green fruits, while citropten was the major oxygenated compound in the oil obtained from yellow citron.     

Determination of the Free Radical Scavenging Activity of Lycium Extracts

Lycium species growing in Turkey have not so far been studied sufficiently. For this reason, non-polar and polar extracts obtained from the fruits of Lycium barbarum L. and L. Ruthenicum Murray (Solanaceae) were assessed both in vitro for their potential as free radical scavenger crude extracts and their phenolic composition. Fruits of Lycium species were sequentially extracted with petroleum ether, ethyl acetate, methanol, n-butanol, and water in a Soxhlet extractor. All the extracts were assessed for the scavenging of the nitrogen-centered free radical 1,1-diphenyl-2-picrylhydrazyl (DPPH^.) by in vitro method. Furthermore, the composition of each extract was investigated both in terms of its Folin-Ciocalteau reactive components and its qualitative content. The phenolic compounds within the extracts were determined as benzoic acid and hydroxycinnamic acid derivatives, flavonoids, and anthocyanins according to their retention time and UV spectral data by HPLC-DAD system.     

Phytochemical analysis of non-polar solvent extracts of the Wisteria sinensis leaves

A comparative study on the phytochemical composition of the n-hexane and chloroform extracts from Wisteria sinensis leaves collected in June and October is described. Continuous extraction in Soxhlet apparatus, as well as ultrasound-assisted technique, was used for the preparation of the extracts. All the extracts were analysed by GC/MS method. As a result, α-tocopherol was identified as the main component (56%) of the extracts from October leaves, whereas, β-sitosterol was identified as the main compound (47%) in the extracts from the June leaves. Additionally, pure α-tocopherol was isolated from n-hexane extract of the October leaves using column chromatography. A total of 6.25 mg of α-tocopherol was isolated from 1 g of dried leaves. The presence of the vitamin E in extracts from W. sinensis leaves is described here for the first time.     

Development of new cleanup method of polychlorinated dibenzo-p-dioxins/dibenzofurans in fish by freezing-lipid filtration

Freezing-lipid filtration as a new method has been developed for the rapid determination of polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDDs/Fs) in biological samples. This method can effectively reduce the time of sample pretreatment, labor and amount of solvents compared with conventional methods. By freezing-lipid filtration procedure, about 90% of lipids in extract could be removed without any significant loss of PCDD/Fs. For further cleanup of extracts after freezing-lipid filtration, automatic parallel LC columns including silica gel, alumina and carbon columns were applied. During automatic parallel LC columns cleanup, most of co-extracted interferences such as residue lipids and fatty acids could be eliminated and dioxins could be separated from many other dioxin-like congeners such as polychlorinated biphenyls by this procedure. The extracts after cleanup were analyzed by high-resolution gas chromatography (HRGC)/high-resolution mass spectrometry (HRMS) using an isotope dilution method. The average recoveries and relative standard deviation (R.S.D.) of 17 native congeners in the spiked fish samples at 8-80 pg/g (n = 3) were ranged between 85.3 and 117.2% and 5.7-20.3%, respectively.     

Optimized cleanup method for the determination of short chain polychlorinated n-alkanes in sediments by high resolution gas chromatography/electron capture negative ion-low resolution mass spectrometry

The performances of three adsorbents, i.e. silica gel, neutral and basic alumina, in the separation of short chain polychlorinated n-alkanes (sPCAs) from potential interfering substances such as polychlorinated biphenyls (PCBs) and organochlorine pesticides were evaluated. To increase the cleanup efficiency, a two-step cleanup method using silica gel column and subsequent basic alumina column was developed. All the PCB and organochlorine pesticides could be removed by this cleanup method. The very satisfying cleanup efficiency of sPCAs has been achieved and the recovery in the cleanup method reached 92.7%. The method detection limit (MDL) for sPCAs in sediments was determined to be 14 ng g⁻¹. Relative standard deviation (R.S.D.) of 5.3% was obtained for the mass fraction of sPCAs by analyzing four replicates of a spiked sediment sample. High resolution gas chromatography/electron capture negative ion–low resolution mass spectrometry (HRGC/ECNI–LRMS) was used for sPCAs quantification by monitoring [M−HCl]⁻ ions. When applied to the sediment samples from the mouth of the Daliao River, the optimized cleanup method in conjunction with HRGC/ECNI–LRMS allowed for highly selective identifications for sPCAs. The sPCAs levels in sediment samples are reported to range from 53.6 ng g⁻¹ to 289.3 ng g⁻¹. C₁₀- and C₁₁-PCAs are the dominant residue in most of investigated sediment samples.     

Rapid structural determination of alkaloids in a crude extract of Stemona saxorum by high‐performance liquid chromatography/electrospray ionization coupled with tandem mass spectrometry

The electrospray ionization (ESI) mass spectrometric behavior of five Stemona alkaloids, stemokerrin, oxystemokerrin, oxystemokerrilactone, oxystemokerrin N‐oxide and stemokerrin N‐oxide, was studied using an ESI tandem mass technique (MSⁿ). These compounds, isolated from Stemona saxorum endemic in Vietnam, represent a class of alkaloids containing a pyrido[1,2‐a]azepine A,B‐ring core with a 1‐hydroxypropyl side chain attached to C‐4. Their fragmentation pathways were elucidated by ESI‐MSⁿ results and the elemental composition of the major product ions was confirmed by accurate mass measurement. In order to rationalize some fragmentation pathways, the relative Gibbs free energies of some product ions were estimated using the B3LYP/6‐31+G(d) method. Based on the ESI‐MSⁿ results of five reference compounds, a reversed‐phase high‐performance liquid chromatography with tandem mass spectrometry (RP‐HPLC/MSⁿ) method was developed for the characterization of Stemona alkaloids with a pyrido[1,2‐a]azepine A,B‐ring core from the extract of S. saxorum. A total of 41 components were rapidly identified or tentatively characterized, of which 12 compounds were identified as Stemona alkaloids with a pyrido[1,2‐a]azepine A,B‐ring core, including four new compounds. This method is convenient and sensitive, especially for minor components in complex natural product extracts. Copyright © 2009 John Wiley & Sons, Ltd.     

Analysis and Identification of the Chemical Constituents of Ding‐Zhi‐Xiao‐Wan Prescription by HPLC‐IT‐MSn and HPLC‐Q‐TOF‐MS

Ding‐Zhi‐Xiao‐Wan (DZXW) is a famous traditional Chinese medicine (TCM) formula, which is composed of four herbs, Ginseng Radix, Poria, Polygala Radix and Acori Tatarinowii Rhizoma. It has been popularly used for the treatment of emotional disease, like Alzheimer's disease, Parkinson's disease, depression, anxiety, forgetfulness and neurasthenia. In this research, a high‐performance liquid chromatography coupled with ion‐trap tandem mass spectrometry (HPLC‐IT‐MSⁿ) method along with a high‐performance liquid chromatography coupled with quadrupole time‐of‐flight mass spectrometry (HPLC‐Q‐TOF‐MS) method in negative ion mode was established to investigate the major constitutions in DZXW. The extracts were prepared by ultra‐sonication in ethyl acetate, n‐butanol, 95% ethanol and deionized water sequentially as well as in deionized water directly. A Kromasil C18 column was used to separate the extracts of DZXW. Acetonitrile and 0.1% aqueous formic acid (V/V) were used as the mobile phase. A total of 64 components were characterized, including 16 triterpenoids, 14 Polygala saponins, 10 oligosaccharide esters, 6 sucrose esters, 2 xanthone C‐glycosides and 16 ginsenosides.     

HRGC-MS and HPLC-MS identification of new ketosterols in an extract of wheat straw

An ethereal extract of wheat (Triticum aestivum) straw with a positive biological assay for allelopathic activity, has been analyzed by HRGC. By means of HRGC-MS the extract composition was assessed as a complex mixture of organic acids and sterolic compounds. The sterolic fraction was subsequently separated and further studied by HRGC-MS and HPLC-MS. Among the thirty seven components identified, some described for the first time in wheat straw, two new ketostero's were characterized by means of their MS spectra. The potential of the particle-beam (PB) interface in HPLC-MS studies of unknown mixtures is exemplified and compared with that of HRGC-MS.     

Chemical composition of Helietta parvifolia and its in vitro anticholinesterase activity

The chemical composition of the essential oil and the n-hexane (Hex), Ethyl Acetate (EtOAc) and butanol (BuOH) extracts from the leaves of Helietta parvifolia were determined by detailed GC-MS analysis, spectroscopic and spectrometric data. Eighty-four compounds were identified, revealing a furoquinoline alkaloid-rich composition. The phytochemical analysis of the extracts allowed the isolation of eigth furoquinoline alkaloids. Retention indices in GC-MS for six of this alkaloids are reported for the first time. Furoquinoline alkaloids are acethylcholinesterase inhibitors. Thus, the essential oil and extracts were submitted to this in vitro assay. The EtOAc and BuOH extracts showed potent activity, with IC₅₀ of 9.7 and 12.9 μg mL^?1, respectively. Additionaly, a correlation of their chemical constituents, established by principal component analysis (PCA) demostrated a similar profile and a high content of alkaloids. It is for these reasons that we can assume that the alkaloid content in these extracts could be responsible for their anticholinesterase activity.     

Flavor analysis by HRGC/FT-IR: Cherimoya (Annona cherimolia,mill.) fruit volatiles

The volatiles of fresh cherimoya (Annona cherimolia, Mill.) fruit pulp were separated by combined high-vacuum distillationliquid/liquid extraction (pentane/dichloromethane 2+1). After preseparation by liquid chromatography on silica gel three fractions (I-III) were obtained by eluting with pentane (I), pentane/diethyl ether (9+1) (II), and diethyl ether (III), and fractions II and III were subjected to HRGC/FT-IR analysis. 26 volatile compounds comprising nearly all the main components (range, 10–300 μg/kg fruit pulp) were identified by this technique for the first time in cherimoya fruit.     

A new indole alkaloid,antioxidant and antibacterial activities of crude extracts from Saccocalyx satureioides

Abstract

The new acylated indole alkaloid glucoside indole-3-carboxylic acid-(6'-O-caffeoyl)-β-D-glucoside 1 has been isolated from the ethyl acetate (EtOAC) extract of Saccocalyx satureioides Coss. & Dur. (Lamiaceae) together with eight known secondary metabolites 2-9. Two indoles 2 and 3, five methylated flavone aglycones 4-8 and one monoterpene glucoside 9 were reported for the first time in the genus Saccocalyx. The structural elucidation of these compounds was accomplished by spectroscopic methods including 1?D (¹H and ¹³C) and 2?D (COSY, HSQC and HMBC) NMR techniques, and mass spectrometry, and by comparison with literature data. Light petroleum, EtOAc, chloroform and n-butanol (n-BuOH) extracts of S. Satureioides were screened for their antioxidant activity using DPPH radical scavenging and β-carotene bleaching methods. The antibacterial activity of these extracts indicates that n-BuOH and EtOAc extracts possess the strongest activity.     

Chemical composition,antioxidant and antibacterial properties of Pteranthus dichotomus from Algerian Sahara

The phytochemical study of ethyl acetate and n-butanol extracts of Pteranthus dichotomus Forssk. led to the isolation and identification of 11 compounds, including three glycolipids 1–3, one lignan 4, three flavonoids 5–7 and four phytosterols 8–11. Structures of the isolated compounds have been elucidated by analysis of 1D and 2D NMR data, and mass spectrometry EI-MS and ESI-MS and by comparison with literature data. Furthermore, the ethyl acetate and n-butanol extracts were examined for their antioxidant and antibacterial activities. The results showed that both extracts (PDAC and PDBU) had a moderate antioxidant activity (IC50 = 375.514 μg/mL and 691.333 μg/mL) respectively.