GC Retention Indices Research Articles

Identification of unknown compound extracted from the hair of exhumed human remains using mass spectrometric and gas chromatographic data

The real example of GC-MS identification of unknown constituent of human hair extract belonging to the exhumed remains is considered. The identification of this constituent (molecular weight 238 Da) was unsuccessful using both its standard mass spectrum (electron ionization) in combination with lib­ra­ry search, and its GC retention index value (~1540 on semi-standard non-polar polydimethyl siloxane stationary phases with 5% phenyl groups). However, its identification appea­red to be possible using the original algorithm of data processing. This approach implies revealing the structural analogues of unknown analytes, primarily their homologues which differ by molecular masses on ± 14 Da and by composition on CH2 homolo­go­us difference. This approach allowed revealing such analogues of unknown analyte as Flavesone (2,2,4,4-tetramethyl-2-isobutyrylcyclohexa-1,3,5-trione), Leptospermone (2,2,4,4-tetramethyl-2-isopentanoylcyclohexa-1,3,5-trione), and some others. All these compounds belong to a rather “exotic” class of natural compounds knows as cyclic b-triketones. Based on the obtained data, the possible structure of the constitu­ent under the consideration was proposed as 2,2,4,4-tetramethyl-2-propionylcyclohexa-1,3,5-trione. The principal fea­ture of cyclic b-triketones is their existence in a few tautomeric forms. Another tautomer of triketone under discussion is 5-hydroxy-2,2,6,6-tetramethyl-4-propionyl-4-en-1,3-dio­ne (CAS № 87552-01-0). This compound is found to be the constituent of Leptosper­mum scoparium essential oil and some other plants, and it belongs to the group of structural analogues of Flave­sone. The most known pharmaceutical application of essential oils containing these compounds are the components of conditioners for hair and skin. The results confirm this formerly un­known component does not belong to the group of toxic substances. This excludes the criminal origin of the remains.

Chemical Constituents Analysis of Ethyl Acetate Extract from MSR-1707 by GC-MS

Aims: To analyze the chemical constituents of ethyl acetate extract from MSR-1707 to promote the rational utilization of the mushroom resources.
 Methodology: MSR-1707 belongs to the genus Nigrospora sp. It was extracted by ethyl acetate, then the extract was analyzed by Gas Chromatography-Mass Spectrometer (GC-MS). Identification of compounds was achieved according to their GC retention indices (RI) and database search using the library of NIST05, as well as a comparison of the fragmentation pattern of the mass spectra with data published in the literature.
 Results: Seventy-three compounds were separated by gas chromatography. Based on the NIST05 spectral library and corresponding literature information, fifty-three compounds were identified. Their relative percentage of contents accounted for 95.62% of the outflow peak. Some of the identified peaks are 9-Octadecenoic acid, methyl ester(E)(18.50%),9-Tricosene(Z)(8.30%), 13-Docosenamide (E)(5.26%) and Myristic acid glycidyl ester (3.11%).
 Conclusion: This is the first report of chemical constituents of the ethyl acetate extract of Nigrospora sp. using GC-MS, which offer some theoretical basis for the further exploration and application of this mushroom.

Comparative gas chromatographic/mass spectrometric characterization of di- and trialkyl phosphites.

Homologous series of alkyl esters of phosphorus-containing acids, namely, dialkyl phosphonates (synonym: dialkyl phosphites) and trialkyl phosphites, were characterized by electron ionization (EI) mass spectra and gas chromatographic retention indices (GC RI) on semi-standard non-polar stationary phases. It is confirmed that GC/MS characterization of any sets of homologues should not be restricted to independent registration of these analytical parameters. Their joint processing in the form of so-called homologous increments of GC RIs means, firstly, a novel way of evaluating the chromatographic polarity of analytes and, secondly, a new algorithm for the prediction of their molecular weights if no peaks of molecular ions are registered in the mass spectra. A standard GC/MS technique, including determination of GC RIs on semi-standard nonpolar stationary phases in temperature-programmed regime and electron ionization (EI) mass spectra was used. A total of 31 dialkyl phosphonate homologues and 37 trialkyl phosphite homologues were characterized by EI mass spectra and GC RIs for the first time. Joint processing of these analytical parameters allows the calculation of so-called homologous increments of GC RIs, which are useful parameters for evaluating the chromatographic polarity of analytes and predicting their molecular weights. GC/MS characterization of any sets of homologues should not be restricted to independent registration of the mass spectra and chromatographic retention parameters. Their joint processing in the form of so-called homologous increments of GC retention indices means, firstly, a novel way of evaluating the chromatographic polarity of analytes and, secondly, a new algorithm for predicting their molecular weights.

Identification of terpenes and essential oils by means of static headspace gas chromatography-ion mobility spectrometry.

Static headspace gas chromatography-ion mobility spectrometry (SHS GC-IMS) is a relatively new analytical technique that has considerable potential for analysis of volatile organic compounds (VOCs). In this study, SHS GC-IMS was used for the identification of the major terpene components of various essential oils (EOs). Based on the data obtained from 25 terpene standards and 50 EOs, a database for fingerprint identification of characteristic terpenes and EOs was generated utilizing SHS GC-IMS for authenticity testing of fragrances in foods, cosmetics, and personal care products. This database contains specific normalized IMS drift times and GC retention indices for 50 terpene components of EOs. Initially, the SHS GC-IMS parameters, e.g., drift gas and carrier gas flow rates, drift tube, and column temperatures, were evaluated to determine suitable operating conditions for terpene separation and identification. Gas chromatography-mass spectrometry (GC-MS) was used as a reference method for the identification of terpenes in EOs. The fingerprint pattern based on the normalized IMS drift times and retention indices of 50 terpenes is presented for 50 EOs. The applicability of the method was proven on examples of ten commercially available food, cosmetic, and personal care product samples. The results confirm the suitability of SHS GC-IMS as a powerful analytical technique for direct identification of terpene components in solid and liquid samples without any pretreatment. Graphical abstract Fingerprint pattern identification of terpenes and essential oils using static headspace gas chromatography-ion mobility spectrometry.

Determination of volatile compounds by headspace-solid phase microextraction - gas chromatography / mass spectrometry: Quality evaluation of Fuji apple

The volatile components in 'Fuji' apple were effectively determined by a headspace solid-phase microextraction (HS-SPME) combined with gas chromatography-mass spectrometry (GC-MS). A total of 48 volatile components were identified and tentatively characterized based on National Institute of Standards and Technology (NIST) MS spectra library and the Kovats GC retention index I (RI). The harvested Fuji apples were divided into two groups: 1-methylcyclopropene (1-MCP) treated and non-treated (control) samples for finding important indicators between two groups. The major volatile components of both apples were 2-methylbutyl acetate, hexyl acetate, butyl 2-methylbutanoate, hexyl butanoate, hexyl 2-methylbutanoate, hexyl hexanoate and farnesene. No significant differences of these major compounds between 1-MCP treated and non-treated apples were observed during 1 month storage. Interestingly, the amount of off-flavors, including 1-butanol and butyl butanoate, in 1-MCP treated apples decreased over 5 months, and then increased after 7 months. However, non-treated apples did not show significant changes for off-flavors during 7 month storage (p<0.05). The non-treated apples also contained the higher levels of two off-flavors than 1-MCP treated apples. These two compounds, 1-butanol and butyl butanoate, can be used as quality indicators for the quality evaluation of Fuji apple.

Ambiguousness of GC-MS identification of spiro[2.4]hepta-4,6-diene in natural objects

The publications on the GC-MS identification of spiro[2.4]hepta-4,6-diene in various natural objects were critically considered. Significant similarity of the mass spectra and coincidence of the GC retention indices on standard nonpolar phases of spiro[2.4]hepta-4,6-diene (761±3) and its isomer (toluene, 760±8) do not allow one to assert that the spirocyclic hydrocarbon was found in all the cases. Additional analytical parameters should be applied to differentiate such isomers.

Revealing compounds unstable during gas chromatographic separation. Non-substituted hydrazones of carbonyl compounds

Evaluating the content of contemporary GC-MS databases (including the NIST database) allows revealing compounds not enough characterized both mass spectra, and GC retention indices ( RI ). Among relatively simple objects of this type there are the products of carbonyl compounds interaction with hydrazine – non-sub­sti­tu­ted hydrazones and azines. Revealing the reasons for the lack of reference information for these compo­unds indicates that non-substituted hydrazones are thermally unstable and converts into azines inside chromatographic column during separation. It is resulted in the appearance of specific profiles of chromatograms and leads to irreproducibility of relative peak areas of these compounds, strong variations of retention times and, hence, low reproducibi­lity of their retention indices. Nevertheless, more then do­zen of non-substituted hydrazones and the same number of corresponding azines were characterized first time by stan­dard EI mass spectra and RI values on stan­dard non-polar polydimethyl siloxane stationary phases. On the example of reaction mixtures of alkyl aryl ketones with hydrazine (un­der medium conversion of substrates into derivatives) the new effect in chroma­to­graphy is revealed. The chromatograms of these samples contain the diffused zo­nes of hydrazones with retention times less then retention times of such hydra­zones from reaction mixtures. The explanation of this anomaly is the for­ma­tion of volati­le hydrazine during hydrazone decomposition, followed by its secon­dary interac­tion with initial carbonyl compound taking place in another part of chromato­gra­phic column. Keywords: Gas chromatography, instability of analytes during separation, non-substituted hydrazones, thermal conversion into azines, mass spectra, retention indices, secondary reactions in gas chromatographic column DOI: http://dx.doi.org/10.15826/analitika.2017.21.2.002 Igor G. Zenkevich, Nikita E. Podol’skii St. Petersburg State University, Universitetskii prosp., 26, St. Petersburg, 198504, Russian Federation

Spectral and chromatographic characterisation of the onoceroid, ambrane: A potential novel biological marker

The gas chromatography–mass spectrometry (GC–MS) characteristics, including GC retention indices and mass spectra, of isomers of the tricyclic onoceroid C30 hydrocarbon, ambrane (1,1,4a,6-tetramethyl-5-{4-methyl-6-[2,2,6-trimethylcyclohexyl]hexyl}decahydronaphthalene) are reported. Ambrane is yet to be reported in sediments or petroleum: other biochemically-related onoceroids, such as onoceranes and serratanes, have been. Now that GC–MS data are available, a search for ambranes in geochemical samples may be both feasible and warranted.

Composition and Chemical Variability of the Cone Oil from Algerian Tetraclinis articulata

Very little is known about the yield and chemical composition of the essential oil isolated from cones of Tetraclinis articulata (Vahl) Masters (Cupressaceae). In continuation of our on-going work devoted to the valorisation of medicinal and aromatic plants from Tlemcen Province (North-Western Algeria), cones have. been harvested in eight locations (coastal township and highlands) and 40 oil samples have been isolated by hydrodistillation. Six oil samples were analyzed by a combination of chromatographic [GC(Retention indices)] and spectroscopic techniques (GC-MS, "C NMR). Then, the remaining 34 oil samples. were analyzed by [GC(RI)] and 13C NMR and the 40 compositions were submitted to statistical analysis. Essential oil yields varied substantially from sample to sample (0.17 to 1.13%, w/w). The cone oils consisted mainly of monoterpenes, with α-pinene (47.1-73.6%) and limonene (6.5-21.9%) being the main components. (E)--Caryophyllene and germacrene D were the major sesquiterpenes. Diterpenes, (Z) and (E)-biformene were identified for the first time-in T. articulata essential oil. PCA analysis of the data allowed the distinction of two groups, the second group being sub-divided into two sub-groups. Groups and sub-groups were differentiated with respect to their contents of a-pinene and limonene and, to a lesser extent, of sesquiterpenes.

Mass spectral studies on vinylic degradation products of sulfur mustards under gas chromatography/mass spectrometry conditions.

Sulfur mustards are a class of vesicant chemical warfare agents that rapidly degrade in environmental samples. The most feasible degradation products of sulfur mustards are chloroethyl vinylic compounds and divinylic compounds, which are formed by the elimination of one and two HCl molecules from sulfur mustards, respectively. The detection and characterization of these degradation products in environmental samples are an important proof for the verification of sulfur mustard usage. In this study, we synthesized a set of sulfur mustard degradation products, i.e., divinylic compounds (1-7) and chloroethyl vinylic compounds (8-14), and characterized using gas chromatography/mass spectrometry (GC/MS) under electron ionization (EI) and chemical ionization (CI) (methane) conditions. The EI mass spectra of the studied compounds mainly included the fragment ions that resulted from homolytic cleavages with or without hydrogen migrations. The divinylic compounds (1-7) showed [M-SH](+) ions, whereas the chloroethylvinyl compounds (8-14) showed [M-Cl](+) and [M-CH2CH2Cl](+) ions. Methane/CI mass spectra showed [M+H](+) ions and provided molecular weight information. The GC retention index (RI) values were also calculated for the studied compounds. The EI and CI mass spectral data together with RI values are extremely useful for off-site analysis for the verification of the chemical weapons convention and also to participate in official Organization for the Prohibition of Chemical Weapons proficiency tests.

Simple QSPR Modeling for Prediction of the GC Retention Indices of Essential Oil Compounds

A Quantitative structure-property relationship (QSPR) was developed to predict the retention index (RI) of 151 essential oil compounds. The predictive quality of the QSPR model was tested for an external set of 30 compounds, randomly chosen out of 151 compounds. A suitable set of molecular descriptors was calculated and the best-fitting descriptors were selected by using stepwise multiple linear regressions (SW-MLR). A simple SW-MLR model with three selected descriptors was obtained. The stability and the predictive performance of the proposed model was verified using both internal (cross-validation by leave one out, leave group out, bootstrap, Y-scrambling) and external validations. The model applicability domain (AD) was checked by the leverage approach to verify prediction reliability. This model, with high statistical significance (R2train = 0.933, R2test =0.945, R2adj =0.932, Q2LOO =0.928, Q2LGO =0.910, Q2Boost =0.928), could be used to predict the retention indices of the studied molecules.

Identification and quantification of six-ring C₂₆H₁₆ cata-condensed polycyclic aromatic hydrocarbons in a complex mixture of polycyclic aromatic hydrocarbons from coal tar.

We applied a combination of normal-phase liquid chromatography (NPLC) with ultraviolet-visible spectroscopy and gas chromatography with mass spectrometry (GC/MS) for the fractionation, identification, and quantification of six ring C26H16 cata-condensed polycyclic aromatic hydrocarbons, PAHs, in the Standard Reference Material 1597a, Complex Mixture of PAHs from Coal Tar. For the characterization analysis, we calculated the GC retention indices of 17 C26H16 PAH authentic reference standards using the Rxi-PAH and DB-5 GC columns. Then, we used NPLC with ultraviolet-visible spectroscopy to isolate the fractions containing the C26H16 PAHs, and subsequently, we used GC/MS to establish the identity and quantity of the C26H16 PAHs using authentic reference standards. Following this procedure, 12 C26H16 cata-condensed PAHs benzo[c]pentaphene, dibenzo[f,k]tetraphene, benzo[h]pentaphene, dibenzo[a,l]tetracene, dibenzo[c,k]tetraphene, naphtho[2,3-c]tetraphene, dibenzo[a,c]tetracene, benzo[b]picene, dibenzo[a,j]tetracene, naphtho[2,1-a]tetracene, dibenzo[c,p]chrysene, and dibenzo[a,f]tetraphene were identified and quantified for the first time, and benzo[c]picene was quantified for the first time in an environmental combustion sample.

Study on Quantitative Structure-Retention Relationships (QSRR) for Oxygen-Containing Organic Compounds Based on Gene Expression Programming (GEP)

Gene Expression Programming (GEP) is a novel genetic algorithm, a highly effective, stable random searching method. We take GEP to make models of Quantitative Structure-Retention Relationship (QSRR) for a series of oxygen-containing organic compounds of GC retention index, and compare the predictive results with Artificial Neural Network (ANN) and Multiple Linear Regression (MLR). The correlation coefficient on OV-1 column is 0.9919, 0.9891 and 0.9911 for GEP, ANN and MLR respectively, on SE-54 column is 0.9955, 0.9892, and 0.9917. It is shown that the predicted results by GEP are in good agreement with experimental ones, better than those of ANN and MLR.

Gas chromatographic retention index as a basis for predicting evaporation rates of complex mixtures

Models that predict the fate of petroleum fuels in the environment are often required for effective remediation of fuel-contaminated sites. In this research, an environmental fuel spill was simulated by means of a diesel/water microcosm, in which the temporal changes in composition were assessed during evaporation by gas chromatography–mass spectrometry (GC–MS). First-order kinetic rate constants were calculated for 51 selected compounds and utilized to develop predictive models for evaporation rate constants, using GC retention indices on a nonpolar stationary phase. Models were initially developed to predict rates of evaporation of compounds from individual classes (normal alkane, branched alkane, alkyl benzene, and polycyclic hydrocarbon) and then expanded to include all compounds (comprehensive model). Using the comprehensive model, the rate constants were predicted with a mean absolute percent error (MAPE) of 10%, whereas the class-specific models resulted in less error (4–8%). These models were employed to predict the fraction remaining of the total fuel (6% error) as well as the fraction remaining of individual compounds (13% MAPE). Accurate models such as these will facilitate remediation of environmental releases of petroleum products.

Composition and Chemical Variability of Eucalyptus bosistoana Essential Oil from Algerian Sahara

The composition of eight oil samples isolated from leaves of Eucalyptus bosistoana F. Muell., acclimatized in Tamanrasset (southern Algeria, Saharan climate), has been investigated by GC (retention indices), GC-MS and 13C NMR spectroscopy. T wo groups may be distinguished. The five samples of group I have their composition dominated by p-cymene (32.0-39.5%), cryptone (11.5-15.6%), 1,8-cineole (7.8-10.5%) and spathulenol (6.8-16.5%). The three oil samples of group II contained mainly 1,8-cineole (55.3-63.9%) and alpha-pinene (11.6-12.1%).

P-Tolyl isocyanate derivatization for analysis of CWC-related polar degradation products by mass spectrometry

Most of the precursors and/or degradation products related to the Chemical Weapons Convention (CWC) are polar. Identification of these molecules in environmental samples provides clues regarding the alleged usage and/or synthesis of the parent toxic chemicals. Such polar compounds need to be derivatized in order to analyze them by gas chromatography-mass spectrometry (GC-MS). In this study, we developed a new derivatizing reagent, para-tolyl isocyanate (PTI), for derivatization of polar CWC-related compounds. The PTI reagent selectively derivatizes the -OH and/or-SH functional groups with high efficiency, but does not react with carboxylic acid (-COOH) or phosphonic acid (-(O)P(OH)2) groups. The PTI derivatives of dialkyl aminoethanols, dialkyl aminoethanol-N-oxides, and 3-quinuclidinol were successfully eluted through GC, and their electron ionization (EI) mass spectra were distinct and provided the structure information by which the isomeric compounds can be easily distinguished. We also calculated the GC-retention index values that can be used for further confirmation of the target compounds. All the studied PTI derivatives can be analyzed by EI-MS with direct insertion probe and/or by direct electrospray ionization mass spectrometry (ESI-MS) together with the MS-MS data; both sets of data provide full structure information. The PTI reagent was found to be better in some respects than the conventional bistrimethylsilyl trifluoroacetamide (BSTFA), a trimethyl silylating reagent. The PTI reagent is commercially available, and the PTI derivatives are highly stable for months and are not sensitive to moisture. The applicability of the PTI derivatization for trace-level determination of the target CWC-related polar compounds in environmental matrices and in human plasma samples is also evaluated.

Chemical composition and antibacterial activity of Pinus halepensis Miller growing in West Northern of Algeria

ObjectiveTo find new bioactive natural products, the chemical composition and to sudy the antibacterial activity of essential oil components extracted from the aerial parts of the Algerian aromatic plant Pinus halepensis Miller (P. halepensis) (needles, twigs and buds). MethodsThe essential oil used in this study was isolated by hydrodistillation using a Clevenger-type apparatus according to the European Pharmacopoeia. The chemical composition was investigated using GC-retention indices (RI) and GC-MS. ResultsForty-nine compounds, representing 97.9% of the total collective oil, were identified. Essential oil was dominated by hydrocarbon compounds (80.6%) especially monoterpenes (65.5%). The major compounds from ten oils stations were: myrcene (15.2%–32.0%), α-pinene (12.2%–24.5%), E-β-caryophyllene (7.0%–17.1%), terpinolene (1.8%–13.3%), 2-phenyl ethyl isovalerate (4.8%–10.9%), terpinene-4-ol (1.0%–8.2 %) and sabinene (1.5%–6.3%). The intra-species variations of the chemical compositions of P. halepensis aerial parts essential oils from ten Algerian sample locations were investigated using statistical analysis. Essential oil samples were clustered in 2 groups by hierarchical cluster analysis, according to their chemical composition. The essential oil revealed an interesting antimicrobial effect against Lysteria monocytogenes, Enterococcus faecalis, Pseudomonas aeruginosa, Acinetobacter baumanii, Citrobacter freundii and Klebsiella pneumoniae. ConclusionsThese results suggest that the essential oil from P. halepensis may be a new potential source as natural antimicrobial applied in pharmaceutical and food industries.

Leaf Oil from Vepris Madagascarica (Rutaceae), Source of (E)-Anethole

The volatile components isolated from leaves of Vepris madagascarica (Baillon) H. Perier (Rutaceae), an endemic species of north-eastern, sub-humid forests of Madagascar, were investigated by GC (Retention Indices), GC-MS and 13C NMR spectroscopy. Oil samples obtained on laboratory and industrial scales exhibited similar composition, dominated by phenylpropanoids. (E)-anethole (78.2% and 78.6%) was the major component followed by estragole (15.6% and 15.4%). In addition, trunk bark oil also contained (E)-anethole as its major component (84.6%), as well as various sesquiterpenes in low contents.

Essential oil of Tanacetum dumosum as a new source of fragranol

Tanacetum (tansy) belongs to the tribe Anthemideae, which is one of the largest tribes of Asteraceae family, comprising about 111 genera and ca. 1800 species worldwide [1]. In the flora of Iran, this genus is represented by 31 annual and perennial species, of which 15 are endemic [2]. The essential oils of several Iranian tansies, including T. bachtiaricum Mozaff. [3], T. fruticulosum Ledeb. [4], T. canescens and T. turcomanicum [5], and T. polycephalum Schultz-Bip. [6], were analyzed by different authors and found to have monoterpenoids as major constituents. Among them, pinenes, 1,8-cineol, camphor, chrysanthenol derivatives, and thujones are detected more frequently. In addition to the above regular monoterpenoids, irregular monoterpenes such as artemisia ketone, santolina triene, and yomogi alcohol are found in some tansy species, including T. kotschyi [7] and T. santolinoides [8]. To the best of our knowledge, this is the first report on characterization of the chemical composition of the essential oil of T. dumosum. The aerial parts of Tanacetum dumosum Boiss. were collected from Dena mountain at an altitude of 3200 m in July 2011. The plant material was identified by one of us (MA), and a voucher specimen (No. PC-87-113) was deposited at the herbarium of our institute (MNCRS), Shiraz, Iran. The essential oil of the leaves and flowers of the plant (70 g) was extracted by hydrodistillation to yield 0.2 mL of pale-yellow oil, dried over anhydrous sodium sulfate, and analyzed by gas chromatography-mass spectrometry (GC-MS) and GC-flame ionization detector (GC-FID). Twenty seven monoand sesquiterpenoids were identified in the oil using GC retention indices (RRI) and mass spectral (MS) data, obtained from GC and GC-MS experiments, and comparison of these data to those reported for the standard volatiles in the literature [9, 10] (Table 1). Among them, the monoterpene hydrocarbons santolina triene (2.2%) and -pinene (2.2%) and the oxygenated monoterpenes fragranol (26.7%), 1,8-cineol (5.7%), fragranyl acetate (23.6%), and trans-carvyl acetate (10.1%) were detected as the major constituents. Helifolenol A, -sesquiphellandrene, caryophyllene oxide, and germacrene D are the major sesquiterpenes detected in this oil, but they are still in smaller quantities compared to the monoterpenoids fraction (Table 1). Fragranol, the E isomer of 2-isopropenyl-1-methylcyclobutane ethanol, was reported previously in the oils of Achillea santolina [9], A. nobilis [11], and A. falcata [12], but to the best of our knowledge for the first time in tansy species. Previously, fragranol was reported by one of us (ARJ) in the oil of Artemisia haussknechtii [13], a member of Anthemideae, which grows nearby T. dumosum. Grandisol, the Z-isomer of fragranol, is reported to be an aggregation and sex-attractant pheromone for several weevil insects [14, 15], and recently together with camphor and 1,8-cineol as the major constituent of an anti-insect essential oil of Artemisia vestita [16]. The antibacterial and insecticidal activity of the essential oils of the above plant species with similar chemical composition reported here for T. dumosum suggests that this plant is a potential medicinal plant to be explored in the future [9, 11, 12]. The good smell of the plant may be due to the presence of fragranol and its acetate ester and suggests that this plant can be used in the perfume industry. GC-MS and FID Analyses. GC-MS analysis was carried out on an Agilent 7890A GC coupled to an HP-6890 mass spectrometer operating in EI mode at 70 eV. The GC was equipped with a J&W DB-5 ms Scientific column (30 m 0.25 mm i.d., 0.25 m film thickness). The oven temperature was programmed from 60 C to 220 C at 5 C/min and kept for 10 min at 220 C. The carrier gas was helium (He) with a flow rate of 1 mL/min, and the injector temperature was set at 260 C in the split mode for the pure essential oil (1:100). The injection volume was 0.1 L. The GC-FID analysis was performed using the above instrument coupled to a FID with the same analytical conditions, but the column was replaced by a DB1 column with the same dimension as that used in GC-MS with the temperature of the FID set at 260 C.

Analysis of Cleistopholis patens Leaf and Trunk Bark Oils Using Combined GC‐ Flame Ionisation Detection, GC‐Retention Index, GC–MS and 13C‐NMR

Germacrenes A-C are secondary metabolites produced by various plants. They are sesquiterpene hydrocarbons bearing the (E,E)-1,5-cyclodecadiene structure known to undergo thermal rearrangement through a [3.3]-sigmatropic reaction. Such a rearrangement was evidenced by comparing the contents of a given germacrene and the corresponding elemene calculated by GC-flame ionisation detection (FID) with the relative intensities of the signals of both molecules in the (13) C-NMR spectrum of the mixture, recorded at room temperature. To develop a protocol to identify and quantify germacrenes A, B and C and in parallel the corresponding elemenes, using a combination of GC-FID and (13) C-NMR and then provide a correct analysis of Cleistopholis patens essential oils. The essential oil was submitted to GC-FID, GC-retention index, GC-MS and (13) C-NMR analyses. The relative percentages of every couple of germacrene and elemene measured by GC-FID were summed. Then, the relative ratio of the mean intensities of the signals of the protonated carbons of a given germacrene and the corresponding elemene was calculated. The contents of both compounds were obtained by combining GC-FID and (13) C-NMR data. The true content of germacrene A/β-elemene, germacrene B/γ-elemene and germacrene C/δ-elemene in leaf and root oils from C. patens was evaluated by combination of GC-FID and (13) C-NMR data. Correct analysis of the essential oils was provided. Combined analysis of essential oil including (13) C-NMR without isolation of the components, appeared really efficient to identify and quantify germacrene isomers and in parallel elemene isomers in essential oils.