Gas Chromatographic Properties Research Articles

Gas chromatographic, sensory profile and biological properties evaluation of Egyptian Jasminum grandiflorum essential oil produced industrially by steam distillation

ABSTRACT The present study aimed to investigate the chemical composition and antimicrobial activity of Jasminum grandiflorum L. essential oil produced for the first time at industrial level by steam distillation. Volatile and chiral compositions were analyzed by GC-MS and GC-FID. In total 130 volatile compounds were identified, which constituted more than 98% of the oils. The results revealed significant differences in terms of volatile compounds between jasmine essential oil and the absolute. Sensorial evaluation revealed the essential oil had a youthful and dynamic character with a bright, floral scent, while the absolute had a more mature and sensual scent that was richer. Antimicrobial activity of both products against eighteen human pathogens and cosmetic contaminants was evaluated. The results showed that essential oil exhibited greater antimicrobial activity, inhibiting 8 out of 17 microbial strains within the MIC range ≤800 µg/mL, compared to 2 out of 17 in the case of the absolute.

Gas chromatography properties and mass spectrometry fragmentation of anabolic androgenic steroids in doping control.

Aim: This study aimed to investigate the gas chromatographic properties and mass spectrometric fragmentations of anabolic androgenic steroids (AASs) after trimethylsilylated derivatization. Materials & methods: A total of 113 AASs were analyzed through gas chromatography-mass spectrometry in the full-scan mode. Results: New fragmentation pathways yielding m/z 129, 143and 169 ions were analyzed. Based on the characteristics of the A-ring, seven classes of drugs were identified and analyzed. Conclusion: The fragmentation pathway of a new classification of 4-en-3-hydroxyl was reported for the first time. The relationship between the chemical structures of AASs and their retention time, along with their molecular ion peak abundance, was also reported herein for the first time.

Determination of mononitrophenols in water by gas-chromatography

Nitrophenols are highly toxic hydrophilic organic compounds. Nitrophenols prevalence in the biosphere is associated with both human industrial activity and with natural processes in the atmosphere and hydrosphere. Nitrophenols determination using gas chromatography requires chemical modification in order to reduce the hydrophilicity and polarity of the analytes. The derivatization must be carried out before the extraction concentration stage, but in most methods of the nitrophenols determination in water this approach is not implemented. The method of determination of mononitrophenols (2-, 3-, and 4-nitrophenols) in water was developed. It involved the nitrophenols bromination directly in the water, bromoderivatives liquid extraction with toluene, silylation by N-tert-Butyldimethylsilyl-N-methyltrifluoroacetamide (MTBSTFA) extract and gas chromatographic determination with the electron-capture detector ( GC-ECD ). The nitrophenols bromination conditions in aqueous solutions were optimized (pH value, bromination duration, bromide-ions concentration). In order to reduce the oxidizing activity of bromine, the nitrophenols bromination was recommended in the presence of bromide anions. The extraction (degree of extraction) and gas chromatographic (retention indices, ECD relative molar responses) properties and nitrophenols bromoderivatives properties were studied. It was shown that the degree of extraction of brominated nitrophenols in the toluene/water system exceeded 80% and the subsequent silylation of the bromoderivatives significantly improved their chromatographic properties. The analytical range of nitrophenols in water was 0.02-10 µg/dm 3 with an error of 10-35%, the detection limits were 0.05-0.07 μg/dm 3 , the sample volume for analysis was 50 cm 3 , the analysis duration was 90 min. Key words : mononitrophenols, chemical modification, gas-chromatography, electron-capture detector DOI: http://dx.doi.org/10.15826/analitika.2020.24.2.006 I.V. Gruzdev, B.M. Kondratenok, E.I. Lyu-Lyan-Min Institute of Biology of Komi Scientific Centre of the Ural Branch of the Russian Academy of Sciences (IB FRC Komi SC UB RAS), Kommunisticheskaya st., 28, Syktyvkar, 167982, Russian Federation

Gas chromatographic properties of methacrylate polymers modified by silver nanoparticles

The gas chromatographic properties of the porous methacrylate polymers, copolymers of 2,3-epoxypropyl methacrylate (2,3-EPMA) and ethylenedimethacrylate (EDMA), modified by silver nanoparticles were studied. The modification of the initial methacrylate copolymer by silver nanoparticles almost does not change the ability of the copolymer to dispersion interaction but results in an increase in polarity and enhances the possibility of specific interactions to occur. The aminated copolymer (copolymer of 2,3-EPMA and EDMA modified by diethylenetriamine using the reaction at the epoxy group) modified by silver nanoparticles demonstrates a higher ability to dispersion interactions and a lower polarity. Possibly, the sorption of silver particles on amino groups of the polymer is a reason for decreasing polarity of the polymer.

Characterization of Bromethalin and its Degradation Products in Veterinary Toxicology Samples by GC-MS-MS.

Bromethalin is a neurotoxicant with unusual instability and chromatographic behavior that make it difficult to analyze by gas chromatography (GC) in forensic examination of non-target animal deaths. Physicochemical breakdown of bromethalin produced multiple unique products with discernible mass spectra. This paper describes an investigation of the GC electron impact-mass spectrometric properties of bromethalin and its capacity to generate up to twenty heat- or light-induced breakdown products. Two principal breakdown products are isomeric with one another and involve release of both fluorine and methyl groups to develop dehydrofluorodesmethylbromethalin products. These compounds have proven to be excellent surrogate markers in screening forensic samples for bromethalin exposure, particularly in veterinary samples in which the active metabolite desmethylbromethalin has not yet accumulated to any appreciable extent, such as baits and animal stomach contents. The compounds as well as their parent bromethalin were easily monitored by GC interfaced with a tandem-quadrupole mass spectrometer using multiple-reaction monitoring (MRM) modes. Unusual gas chromatographic properties of bromethalin included: (i) specific requirements for a maximum oven temperature; (ii) non-linear increases in detector response on increased injection volumes, hypothesized to result from variable diffusion coefficients. We report here the development of GC strategies that facilitate detection of bromethalin and its breakdown products, as well as their MRM analysis by tandem-quadrupole mass spectrometry. The developed approaches are applicable to feed, baits and stomach contents as well as extracted tissue samples such as liver and kidney.

Alkyl-Dimethylpyrazines in Mandibular Gland Secretions of Four Odontomachus Ant Species (Formicidae: Ponerinae).

Ponerine ants are known to contain mixtures of pyrazines in their mandibular glands. We analyzed the mandibular gland contents of four ponerine species (Odontomachus chelifer, O. erythrocephalus, O. ruginodis, and O. bauri) by gas chromatography coupled with mass spectrometry, and found that each species contains specific mixtures of trisubstituted alkylpyrazines among other volatiles. Attempts to identify alkylpyrazines solely by mass spectral interpretation is unrealistic because spectra of positional isomers are indistinguishable. To avoid misidentifications, we synthesized a large number of reference compounds and compared their mass spectral and gas chromatographic properties with those present in the Odontomachus species under investigation. Most of the compounds identified were 2-alkyl-3,5-dimethylpyrazines. Interestingly, when the third substituent was an isopentyl group, the two methyl groups were found to be located at the 2 and 5 ring positions. Using our data, we recognized several misidentifications in previous publications.

QSRR prediction of gas chromatography retention indices of essential oil components

A comprehensive and largest (to the best of our knowledge) database of 791 essential oil components (EOCs) with corresponding gas chromatographic retention properties has been built. With this data set, Quantitative structure–retention relationship (QSRR) models for the prediction of the Kovats retention indices (RIs) on the non-polar DB-5 stationary phase have been built using the DRAGON molecular descriptors and the regression methods: multiple linear regression (MLR) and artificial neural networks (ANN). The obtained models demonstrate good performance, evidenced by the satisfactory statistical parameters for the best MLR (R 2 = 96.75% and $$Q_{\text{ext}}^{2}$$ = 98.0%) and ANN (R 2 = 97.18% and $$Q_{\text{ext}}^{2}$$ = 98.4%) models, respectively. In addition, the built models provide information on the factors that influence the retention of EOCs over the DB-5 stationary phase. Comparisons of the statistical parameters for the QSRR models in the present study with those reported in the literature demonstrate comparable to superior performance for the former. The obtained models constitute valuable tools for the prediction of RIs for new EOCs whose experimental data are undetermined.

Methyl 3-(5-(prop-1-yn-1-yl)thiophen-2-yl)propanoate: A Rare Acetylene Derivative from Artemisia absinthium Root Essential Oil

Methyl 3-(5-(prop-l-yn-l-yl)thiophen-2-yl)propanoate (1), biosynthetically and structurally related to dehydromatricaria ester, was isolated from the root essential oil of Artemisia absinthium L. (0.7% of the total oil). This is the second record of this compound and the very first one regarding it as an essential-oil constituent. In this paper, we give details regarding its isolation, structural elucidation and gas chromatographic properties (RI on DB-5 MS column: 1694). The NMR-based identification of the compound was corroborated by simulation of its 'H- and "C-NMR spectra using a GIAO method (DFT level of theory). A tentative biosynthetic pathway, possibly leading to this compound, is also proposed.

End Group Effect on the Thermal and Gas Chromatographic Properties of Some para-Substituted Non-Symmetrical Nematogens

Non-symmetrically substituted nematic liquid crystals with different moieties as terminal substituents at one end and n-heptyloxy group at the other end were synthesized and characterized. The common structural features of the compounds are that they consist of the same terminal substituent at one end. The five present nematogens structurally related nematogens are compared to evaluate the effect of the type of end group on the thermal and analytical properties. The compounds were characterized by elemental analysis, FTIR, 1H-NMR spectroscopy and chemical ionization mass spectrometry. The materials’ thermal behavior and phase characterization were investigated by differential scanning calorimetry and polarizing optical microscopy. All the compounds are mesomorphic in nature, showing the nematic phase over a wide temperature range. Differential scanning calorimetry showed that the transition temperatures as well as the nematic range are strongly influenced by the type of end group attached at only one end of the nematic core molecule. Gas chromatographic properties of the compounds were determined and shown to have excellent separation capabilities of various classes of compounds, including polycyclic aromatic hydrocarbons (PAH), substituted benzenes and volatile organic compounds present in the essential oil. The separation mechanism of only some isomers was discussed in detail and, however, a relative basis for given isomers, taking into account the type of chemical bonding, molecular shape and size, the intermolecular forces (IMFs) and other factors has been proposed.

Identification and characterisation of a novel mono-unsaturated highly branched isoprenoid (HBI) alkene in ancient Arctic sediments

The occurrence of a novel C25 highly branched isoprenoid (HBI) mono-unsaturated hydrocarbon in Arctic marine sediments from the Fram Strait is described. The structure was determined following synthesis from a closely related diene and NMR spectroscopic analysis. The position of the double bond was confirmed by oxidation (RuO4) and comparison of the mass spectrum of the resulting C19 ketone with that of an authentic sample synthesised previously. The same C19 ketone was also present following oxidation of the Fram Strait sediment extracts. The source of the novel HBI monoene biomarker is not known, but is believed to be certain marine diatoms on the basis of structural similarities with other HBIs from such sources. It does not, however, appear to be biosynthesised by Arctic sea ice diatoms, unlike its regio isomer, IP25, an established proxy for Arctic sea ice. Alternatively, it may represent a diagenetic product of the sea ice diatom biomarker IP25; this seems unlikely, however, on the basis of their respective structures. Since the new HBI monoene and IP25 possess similar gas chromatographic and mass spectral properties, but probably have contrasting sources, we suggest that future paleo sea ice reconstruction studies based on the occurrence of IP25 should pay further attention to the rigorous assignment of this biomarker in marine sediment extracts. Some suggestions for achieving this, based on analytical purification and mass spectrometric measurements, are provided.

Silica and alumina based functional materials: Substructures, adsorption and gas chromatographic properties

Modification of nano- and adsorption textures of alumina and silica as well as study of their chemical surface properties have been made. The use of specific templates as structure directing agents allowed varying their textural characteristics and obtaining macroporous and mesoporous functional materials with preferred influence of the substructures on the chromatographic properties of the materials. As packings of chromatographic columns structured materials gave an opportunity to carry out gas chromatographic analysis of mixtures faster than their unstructured analogs. In some cases, the efficiency of columns packed by such materials was just over than those packed by nontemplated counterparts. Modification of silica and alumina by carbonization allowed varying the chemical nature of initial surface and expanding the number of functional materials based on them. It was shown that adsorption potential of dispersion (non-specific) interaction of n-paraffins with carbonized silica and alumina was much higher compared to that of the noncarbonized materials. Some examples of successful application of the studied materials in practical gas chromatography are presented.

Adsorption and gas-chromatographic properties of silver-modified silicas

Ag0 and Ag(I) nanoparticles are immobilized on the surface of a macroporous silica and amino silica. The adsorption kinetics of a basic dye, methylene blue (MB), from aqueous solutions and the adsorption isotherms of alkyne phenylacetylene from an octane solution are measured. The dependence of the rate constants of MB adsorption on the conditions of immobilization and silver reduction is considered. Silica containing immobilized Ag(I) is shown to have a high adsorption activity with respect to phenyl acetylene. By gas chromatography, it is shown that silver-modified silica has a higher selectivity with respect to alkenes. The reduction of silver on the silica surface and the complexation of silver ions with aminopropyl groups of amino silica lead to a significant decrease in the selectivity of composites.

An LC and GC Study of a New Phenyldiazene Liquid Crystal

A new phenyldiazene liquid crystal α with a methylene group in the ortho position to the diazo linkage was cyclized by heating. Differential scanning calorimetry was used to precisely identify the nature of the liquid crystal in its initial and final states, and the exothermic enthalpy of the cyclization. The complete kinetics of cyclization (kinetic order, reaction constants and activation energy) was determined by LC. Gas chromatographic properties of the final compound (β) were determined and showed to have excellent separation capabilities for phenols and polyaromatic compounds.

Non-target screening analysis of river water as compound-related base for monitoring measures

Building up a comprehensive accurate monitoring program requires the knowledge on the contamination in principal, complemented by detailed information on individual contaminants. The selection of pollutants to be considered in monitoring actions is based dominantly on the information available about their environmental relevance (e.g., persistence, bioaccumulation potential, toxicological and ecotoxicological properties) and their occurrence within the affected environmental system. Therefore, this study focused on the identification of organic contaminants in selected German and European rivers to demonstrate the usefulness of a screening approach as complementary base for the compound selection process within monitoring activities. Gas chromatography-mass spectrometry-based screening analyses were performed on five and six samples from German and European rivers, respectively. Identification of individual contaminants was based on the investigation of mass spectral and gas chromatographic properties compared with databases and reference materials. This study summarized the results of non-target screening analyses applied to river water samples and focused dominantly on, so far, unnoticed organic contaminants. Numerous compounds have been identified belonging to the groups of pharmaceuticals, technical additives, pesticides, personal care products, and oxygen-, nitrogen-, and sulfur-containing compounds of obviously anthropogenic origin. They are discussed in terms of their structural properties, their possible application or usage, and the environmental information available so far. Generally, two different groups of compounds have been differentiated that might contribute to potential monitoring programs. Firstly, more specific contaminants characterizing the individual riverine systems have been depicted (e.g., 4-chloro-2-(trifluoromethyl)aniline, di-iso-propylurea). The consideration of these substances in monitoring analyses to be applied to the corresponding catchment areas is recommended in order to monitor the real state of pollution. Secondly, contaminants have been introduced that appeared with higher multiplicity throughout the different river systems (e.g., TMDD, TXIB). Since these compounds tend to obviously have an elevated environmental stability accompanied by a widespread distribution, it is recommended to consider them in international high-scale monitoring programs. For monitoring purposes, a fundamental knowledge on the diversity of pollutants is an important precondition, which can be supported by screening analyses. Obviously, numerous organic contaminants have been neglected so far in environmental studies on river water, comprising also investigation on potential harmful effects and, therefore, their implementation in monitoring activities has been hindered. Therefore, based on the results of this study, screening analyses should be established as principle tools to improve and complement the substance spectra for monitoring purposes. Secondly, scientific efforts should be strengthened to expand our knowledge on actually appearing organic contaminants in riverine systems.

Gas chromatographic behavior of fatty acid derivatives for mass spectrometry on low‐polarity capillary columns

AbstractThe gas chromatographic properties of four derivatives of fatty acids (FA), namely fatty acid methyl esters, picolinyl esters, N‐acyl pyrrolidides and 4,4‐dimethyloxazoline derivatives, which contain various structural features (double bonds, branching, hydroxyl group) in their acyl chains have been compared on a low‐polarity capillary column with a mass spectrometer as detector. Temperature programming rates yielding the highest resolution were optimized for each derivative by means of computer‐assisted column temperature optimization software. Indeed, the Drylab software represents a valuable assistance for estimating the optimum analysis conditions. Time and efforts required for such method development can greatly be reduced. Different parameters (derivatization procedure, total run time, resolution and response factor) are discussed. N‐Acyl pyrrolidides and picolinyl esters appear quite powerful for structure elucidation of polyunsaturated FA by GC‐MS, and both these types of FA derivatives can be very well separated on a low‐polarity phase.

Gas Chromatography on Zeolite-Based Adsorbents

The adsorption and gas chromatographic properties of zeolites, both modified with carbon and supported as a surface-porous layer, have been studied. Carbonization of zeolites changes the chemical nature of their surface and their molecular sieve properties. In comparison with other adsorbents (carbons, polymers, etc.), modified and supported zeolites are characterized by better selectivity for separation of light-boiling compounds formed in many catalytic reactions. Zeolite-based adsorbents have been used for gas chromatographic analysis of mixtures the analysis of which was a problem or was impossible with traditional chromatographic columns.

The effect of chemical modification on the chromatographic properties of polymeric adsorbents polysorb-1 and hisep Q and the diatomite carrier chromosorb P NAW

Polytrimethylsilylpropyne with the decomposition temperature 205°C was synthesized and characterized. The effect of chemical modification by polytrimethylsilylpropyne on the gas chromatographic properties of polymeric adsorbents and the diatomite carrier for the selective separation of C1–C10 hydrocarbons, alcohols and aromatic and sulfur-containing compounds was studied.

Trigonal Tricationic Ionic Liquids: A Generation of Gas Chromatographic Stationary Phases

Trigonal tricationic ionic liquids (ILs) are a new class of ILs that appear to be unique when used as gas chromatographic stationary phases. They consist of four core structures; (1) A = mesitylene core, (2) B = benzene core, (3) C = triethylamine core, and (4) D = tri(2-hexanamido)ethylamine core; to which three identical imidazolium or phosphonium cationic moieties were attached. These were coated on fused silica capillaries, and their gas chromatographic properties were evaluated. They were characterized using a linear solvation parameter model and a number of test mixtures. On the basis of the literature, it is known that both monocationic and dicationic ILs possess almost identical polarities, solvation characteristics, and chromatographic selectivities. However, some of the trigonal tricationic ILs were quite different. The different solvation parameters and higher apparent polarities appear to generate from the more rigid trigonal geometry of these ILs, as well as their ability to retain the positive charges in relatively close proximity to one another in some cases. Their unique selectivities, retention behaviors, and separation efficiencies were demonstrated using the Grob mixture, a flavor and fragrance test mixture, alcohols/alkanes test, and FAME isomer separations. Two ILs C1 (methylimidazolium substitution) and C4 (2-hydroxyethylimidazolium substitution) had higher apparent polarities than any know IL (mono, di, and tricationic ILs) or commercial stationary phases. The tri(2-hexanamido)ethylamine core IL series proved to be very interesting in that it not only showed the highest separation efficiency for all test mixtures, but it also is the first IL stationary phase (containing NTf(2)(-) anions) that eliminates peak tailing for alcohols and other H-bonding analytes. The thermal stabilities were investigated using three methods: thermogravimetric analysis (TGA) method, temperature programmed gas chromatographic method (TPGC), and isothermal gas chromatographic method. The D core series had a high working temperature range, exceptional selectivities, and higher separation efficiencies than comparable polarity commercial columns. It appears that this specific type of multifunctional ILs may have the most promising future as a new generation of gas chromatographic stationary phases.

Doping control analysis of trenbolone and related compounds using liquid chromatography–tandem mass spectrometry

Trenbolone (17β-hydroxy-estra-4,9,11-trien-3-one) and its derivatives such as 17α-methyltrenbolone represent a class of highly potent anabolic–androgenic steroids, which are prohibited in sports according to the regulation of the World Anti-Doping Agency (WADA). Due to marginal gas chromatographic properties of these compounds but excellent proton affinities resulting from a large and conjugated π-electron system, liquid chromatography–tandem mass spectrometry (LC–MS/MS) has been the method of choice for the detection of these analytes in sports drug testing. Recent findings of trenbolone and methyltrenbolone in doping control urine samples of elite athletes demonstrated the importance of a sensitive and robust analytical method, which was based on an enzymatic hydrolysis of target compounds, liquid–liquid extraction and subsequent LC–MS/MS measurement. Diagnostic product ions obtained after collision-induced dissociation of protonated molecules were found at m/ z 227, 211, 199 and 198, which enabled targeted screening using multiple reaction monitoring. Using 7 model compounds (trenbolone, epitrenbolone, methyltrenbolone, ethyltrenbolone, propyltrenbolone, 17-ketotrenbolone and altrenogest), the established method was validated for specificity, lower limits of detection (0.3–3 ng/mL), recovery (72–105%), intraday and interday precision (≤20%).

Development of a database of gas chromatographic retention properties of organic compounds

A comprehensive database of gas chromatographic retention properties of chemical compounds has been developed using multiple literature sources. The National Institute of Standards and Technology (NIST) database of retention data for non-polar and polar stationary phases currently contains 292,924 data records for 42,888 compounds. The database includes data for Kováts indices, linear indices, Lee indices, retention times and retention volumes. The first release of this database for non-polar stationary phases is available with NIST/US Environmental Protection Agency (EPA)/National Institutes of Health (NIH) Mass Spectral Database (June 2005) and through the internet (NIST Chemistry WebBook). The paper describes the database and the process by which it has been compiled. The format of data presentation and the quality control procedures are described. Data sources of gas chromatographic retention data are also discussed.