Capillary Column Gas Research Articles

Quantitative structure–property relationship analysis for the retention index of fragrance-like compounds on a polar stationary phase

A quantitative structure–property relationship (QSPR) was developed for modeling the retention index of 1184 flavor and fragrance compounds measured using a Carbowax 20M glass capillary gas chromatography column. The 4885 molecular descriptors were calculated using Dragon software, and then were simultaneously analyzed through multivariable linear regression analysis using the replacement method (RM) variable subset selection technique. We proceeded in three steps, the first one by considering all descriptor blocks, the second one by excluding conformational descriptor blocks, and the last one by analyzing only 3D-descriptor families. The models were validated through an external test set of compounds. Cross-validation methods such as leave-one-out and leave-many-out were applied, together with Y-randomization and applicability domain analysis. The developed model was used to estimate the I of a set of 22 molecules. The results clearly suggest that 3D-descriptors do not offer relevant information for modeling the retention index, while a topological index such as the Randić-like index from reciprocal squared distance matrix has a high relevance for this purpose.

Separation performance of polydopamine-based cucurbit[7]uril stationary phase for capillary gas chromatography

Abstract Polydopamine (PDA) coating, a nature-inspired polymer, has attracted great attention in many areas due to its high adhesion strength and stability on almost all types of substrate surfaces. This work presents the first example of using PDA coating as a column pretreatment method in capillary gas chromatography (GC) and its employment in the column fabrication of cucurbit[7]uril (CB7) stationary phase. The fabricated PDA-CB7 column exhibited weakly polar nature and had advantages over CB7 column without PDA for the separations of some critical analytes in GC. This work demonstrates the advantage and potential of using PDA as a facile column pretreatment method in capillary GC column fabrication.

Preparation and characterization – including in situ Small Angle X-Ray Scattering – of gas chromatographic capillary columns with mesoporous silica thin films as stationary phases

In this study the preparation of various mesoporous silica thin films as new stationary phases for gas chromatography (GC) columns is presented. The synthesis was performed inside capillaries via a sol–gel process using a templating route. The as-obtained columns were found to be highly efficient for the fast separation of light n-alkanes (C1–C5) mixture; these columns exhibiting a normalized retention 30 times higher than that of a commercially available silica column used as standard. A particular effort was directed towards the characterization of the stationary phase physical features: thin film inspection by Scanning Electron Microscopy and, for the first time to our knowledge, in situ SAXS characterization using synchrotron radiation were used to study the impact of the pore-network structuration on the GC properties. Worm-like, cubic and hexagonal phases were observed for specific preparation conditions. Unexpectedly, the normalized retention relative to film thickness appeared higher with disordering of the pores network.

Identification of chemical warfare agents from vapor samples using a field-portable capillary gas chromatography/membrane-interfaced electron ionization quadrupole mass spectrometry instrument with Tri-Bed concentrator

A field-portable gas chromatograph–mass spectrometer (Hapsite ER system) was evaluated for the detection of chemical warfare agents (CWAs) in the vapor phase. The system consisted of Tri-Bed concentrator gas sampler (trapping time: 3s−1min), a nonpolar low thermal-mass capillary gas chromatography column capable of raising temperatures up to 200°C, a hydrophobic membrane-interfaced electron ionization quadrupole mass spectrometer evacuated by a non-evaporative getter pump for data acquisition, and a personal computer for data analysis. Sample vapors containing as little as 22μg sarin (GB), 100μg soman (GD), 210μg tabun (GA), 55μg cyclohexylsarin (GF), 4.8μg sulfur mustard, 390μg nitrogen mustard 1, 140μg of nitrogen mustard 2, 130μg nitrogen mustard 3, 120μg of 2-chloroacetophenone and 990μg of chloropicrin per cubic meter could be confirmed after Tri-Bed micro-concentration (for 1min) and automated AMDIS search within 12min. Using manual deconvolution by background subtraction of neighboring regions on the extracted ion chromatograms, the above-mentioned CWAs could be confirmed at lower concentration levels. The memory effects were also examined and we found that blister agents showed significantly more carry-over than nerve agents. Gasoline vapor was found to interfere with the detection of GB and GD, raising the concentration limits for confirmation in the presence of gasoline by both AMDIS search and manual deconvolution; however, GA and GF were not subject to interference by gasoline. Lewisite 1, and o-chlorobenzylidene malononitrile could also be confirmed by gas chromatography, but it was hard to quantify them. Vapors of phosgene, chlorine, and cyanogen chloride could be confirmed by direct mass spectrometric detection at concentration levels higher than 2, 140, and 10mg/m3 respectively, by bypassing the micro-concentration trap and gas chromatographic separation.

A highly sensitive and fast responsive semiconductor metal oxide detector based on In2O3 nanoparticle film for portable gas chromatograph

A highly sensitive and fast responsive semiconductor metal oxide detector based on In2O3 nanoparticle film was developed and evaluated. The mechanical structure of the detector was properly designed to obtain a small chamber volume in order to well fit to a commercial gas chromatographic capillary column. The detector was constructed by coating In2O3 nanoparticle film onto a small ceramic plate. Results indicate that the proposed semiconductor metal oxide detector in this study shows a fast response (several seconds) and a high sensitivity. Moreover, the detector can be operated at ambient condition, which largely simplifies the design of portable gas chromatograph. The fabricated detector was also used to detect gas mixtures with a detection limit down to several ppb. It is concluded that the semiconductor metal oxide detector based on nanostructured materials possesses great potential for constructing portable gas chromatograph.

Accumulation of organochlorines in the European clam (Ruditapes decussatus) and sediment of the Oualidia lagoon (Morocco).

This study focused on the analysis of organochlorine pesticides and PCBs in tissue samples of the clam, Ruditapes decussatus, in the Oualidia lagoon. Tissue assays were conducted during February to December 2005 and sediment (October 2005) was also tested. 13 organochlorine compounds and eight PCBs congeners were investigated, is HCB, γ-HCH, chlordane, cis-chlordane and trans-nonachlor, DDT and its metabolites DDD, DDE, heptachlor, its epoxide, mirex and PCBs (PCB28 + 50, PCB52, PCB101, PCB 118, PCB138, PCB153, PCB180). Analysis of these compounds was performed using a gas chromatography capillary column and an electron capture detector. Organochlorine contamination of clams and sediments in the lagoon did not exceed tolerable thresholds according to European standards. The levels of tPCB, tDDT and tOCP in clams are high at 49.4, 22.2, and 7.1 ng g(-1) dw respectively. Concentrations of trans nonachlor and mirex are low compared to other chlorinated pesticides. PCB28 + 50, PCB52 and PCB101 show typical values in sediment, at 18.5, 10.8 and 17.8 ng g(-1) dw respectively.

Development and validation of a GC–FID method for quantitative analysis of oleic acid and related fatty acids

Oleic acid is a common pharmaceutical excipient that has been widely used in various dosage forms. Gas chromatography (GC) has often been used as the quantitation method for fatty acids normally requiring a derivatization step. The aim of this study was to develop a simple, robust, and derivatization-free GC method that is suitable for routine analysis of all the major components in oleic acid USP-NF (United States Pharmacopeia-National Formulary) material. A gas chromatography–flame ionization detection (GC–FID) method was developed for direct quantitative analysis of oleic acid and related fatty acids in oleic acid USP-NF material. Fifteen fatty acids were separated using a DB-FFAP (nitroterephthalic acid modified polyethylene glycol) capillary GC column (30m×0.32mm i.d.) with a total run time of 20min. The method was validated in terms of specificity, linearity, precision, accuracy, sensitivity, and robustness. The method can be routinely used for the purpose of oleic acid USP-NF material analysis.

Gas chromatography for determination of N-butylbenzene in workplace atmosphere

To establish a method for the determination of N-butylbenzene in the workplace atmosphere by gas chromatography. N-butylbenzene in the workplace atmosphere was collected by activated charcoal tube, desorbed using carbon disulfide, and determined by capillary column gas chromatography. The method showed a linear relationship within the range of 0∼100 µg/ml. The regression equation was y = 0.870x-0.014, with the correlation coefficient r being 0.999 9. The limit of detection was 0.32 µg/ml. The minimum detectable concentration was 0.21 mg/m³ (with sampled air volume of 1.5 L). The average spike recovery rate was 97.8%∼102.6%. The within-run precision was 3.06% and the between-run precision was 3.64%. The rate of average desorption was 99.6%. The breakthrough volume was 6.34 mg. The sampling efficiency was 100%. The samples could be stored for at least 7 days at room temperature. All parameters of the method meet the requirements of GBZ/T 210.4-2008 "Guide for establishing occupational health standards-Part 4 Determination methods of air chemicals in workplace" and can be applied for the determination of N-butylbenzene in workplace atmosphere.

Rapid method for determination of selected organophosphorus pesticides in post Mortem Tissues by GC-NPD

A method for determination of selected organophosphorus pesticides (OPs) along with their degradation products in post mortem tissues is reported in the paper. Malathion, Dimethoate and Phorate are frequently found organophosphates in homicidal or suicidal poisoning cases. The separation of these pesticides along-with their oxon degradation products Malaoxon, Omethoate and Phorate-sulfone respectively is achieved by a programmed temperature capillary column gas chromatography coupled with a nitrogenphosphorus detector (NPD). Prior to analysis, pesticide residues were extracted by QuEChERS extraction method. Matrix matched calibration curves were linear with coefficients of correlation better than 0.995 for concentration range from 0.5 to 20 μg/gm while the limits of detection ranged from 0.05 to 0.85 μg/gm for all compounds. The method is simple, rapid and was used to detect the oxon degradation products of the original OP which otherwise were not detectable by other conventional methods used for routine analysis of post-mortem tissues in poisoning cases.

Analysis of Dioxins Concentration in Domestic Waste and Burnt Tyre Residue at Gosa Dumpsite in Abuja, Nigeria

This study examined the presence of dioxins – a persistent organic pollutant in domestic and burnt tyre waste residues and it’s comparison with German safety limits at the Gosa dumpsite in Abuja, Nigeria. The period of sampling and analysis was between January and March, 2011. Burnt tyre ashes and burnt solid waste residues from the dump sites were chemically analyzed to determine the concentration of the seventeen 2,3,7,8-substituted dioxins and furan congeners in absolute quantities using high resolution capillary column gas chromatography and low resolution mass spectrometry. The result of the analysis performed using the International Toxic Equivalent Factor (NATO/CCMS) for the calculation of the individual Toxic Equivalent Quotients (TEQs) of the seventeen 2,3,7,8- substituted dioxins and furan congers and a summation of the individual I-TEQs per sample shows that there is significant quantity of about 44 ng/kg TM of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), a contaminant in Agent Orange, in one out of the five (1/5) analyzed samples. The maximum Total Polychlorinated dibenzo-p-dioxins/furans (PCCD/F) concentration recorded in this study was 1,350 ng/kg TM from sample Point 3. This was greater than the German Federal Soil Protection and Contamination Sites Ordinance (GFSPCSO) for Total PCDD/F equivalents for target concentration, agricultural, playground and residential landuse (which dominate the area under study) but less than its industrial landuse equivalent. There was also the presence of dioxins in the burnt domestic waste analysed with the Total PCDD/F (TEQ) of 6.6 ng/kg TM. The land usage of the area under investigation is closely interwoven across the land mass. Therefore, the results indicate that the population and activities within the area of study are under threat of health hazards that may arise from the high concentration of dioxins recorded by this study.

Chemical compositions of the volatile extracts from seeds of Dendranthema nankingense and Borago officinalis

Volatile extracts from the seeds of Dendranthema nankingense Hand.-Mazz. and Borago officinalis L. were prepared using simultaneous distillation and extraction, and analyzed with gas chromatography–mass spectrometry on two capillary gas chromatography columns of different polarity. Ninety-five volatile compounds were identified in D. nankingense seeds, with hexanal, benzeneacetaldehyde, borneol, (−)-camphor, and 3-methyl-1-butanol being the predominant species. Sixty-five volatile compounds were identified in B. officinalis seeds, with 2-pentanone, 2,3-dihydro-benzofuran, 3-methyl butanal, and hexanal being the most abundant species. Thirty-three compounds, including short-chain aliphatic aldehydes, alcohols, and ketones, were common to both seeds. The volatile composition of both seeds varied significantly depending on their respective origins. The volatile terpenoids borneol and (−)-camphor could be key bioactive contributors to the characteristic flavor and cooling effects of D. nankingense. For the first time, coumaran was identified as an abundant species in plant seeds.

QSPR analysis for the retention index of flavors and fragrances on a OV-101 column

A predictive quantitative structure–property relationships (QSPR) is developed for modeling the retention index measured on the OV-101 glass capillary gas chromatography column, in a set of 1208 flavor and fragrance compounds. The 4885 molecular descriptors are calculated using the Dragon software and then are simultaneously analyzed through multivariable linear regression analysis using the replacement method (RM) variable subset selection technique. We proceed in three steps, the first one by considering all descriptor blocks, the second one by excluding conformational descriptors blocks, and the last one by analyzing only 3D-descriptors families. The models are properly validated through an external test set of compounds. Cross-validation methods such as leave-one-out and leave-more-out are applied, together with Y-randomization and applicability domain analysis. The results clearly suggest that 3D-descriptors do not offer relevant information for modeling the retention index, while a topological index such as the solvation connectivity index of first order has a high relevance for this purpose.

Extraction and determination of 4-methylthio-3-butenyl isothiocyanate in Chinese radish (Raphanus sativus L.) roots

4-methylthio-3-butenyl isothiocyanate (4-MTBI) is released from 4-methylthio-3-butenyl glucosinolate (4-MTBG) in radish roots by endogenous myrosinase hydrolysis. In this research, factors influencing the extraction of 4-MTBI from radish roots by an endogenous myrosinase method, such as the time for endogenous myrosinase hydrolysis under 37 °C, the storage time after hydrolysis, were optimized. A new GC method was developed to determine 4-MTBI in radish roots, which was identified by GC-MS and compared with the authentic 4-MTBI. Through optimization of the starting point and increasement of column temperature, both the internal standard allyl isothiocyanate (AITC) and 4-MTBI were clearly separated with a capillary gas chromatography column HP-5. Coefficient of variation (CV) of GC analysis was 3.883%. Recovery percentage of AITC remained 90.3–105.4%. CV of determination and recovery percentage of sinigrin were 5.35% and 91.3–101.9%, respectively.

Hapalindoles from the cyanobacterium fischerella: potential sodium channel modulators.

Hapalindoles make up a large group of bioactive metabolites of the cyanobacterial order Stigonematales. 12-epi-Hapalindole E isonitrile, 12-epi-hapalindole C isonitrile, 12-epi-hapalindole J isonitrile, and hapalindole L from Fischerella are acutely toxic for insect larvae; however, the biochemical targets responsible for the biological activities of hapalindoles are not understood. We describe here the electron impact mass spectra of these four hapalindole congeners; their structures were confirmed by nuclear magnetic resonance spectroscopy. In combination with the presented mass spectra of (15)N-labeled species and their retention times on a gas chromatography capillary column, a rapid and reliable determination should be possible in future research. The bioactivity of these hapalindoles was tested on mammalian cells focusing on their effects in the BE(2)-M17 excitable human neuroblastoma cell line. The fluorescent dye Alamar Blue was applied to monitor cytotoxicity, fura-2 to evaluate changes in the cytosolic calcium concentrations, and bis-oxonol to detect effects on membrane potential. Data showed that the hapalindoles did not affect cell viability of the neuroblastoma cells, even when they were incubated for 72 h. Neither depolarization nor initiation of calcium influx was observed in the cells upon hapalindole treatment. However, the data provide evidence that hapalindoles are sodium channel-modulating neurotoxins. They inhibited veratridine-induced depolarization in a manner similar to that of neosaxitoxin. Our data suggest hapalindoles should be added to the growing number of neurotoxic secondary metabolites, such as saxitoxins and anatoxins, already known in freshwater cyanobacteria. As stable congeners, hapalindoles may be a risk in freshwater ecosystems or agricultural water usage and should therefore be considered in water quality assessment.

Study on the Determination of Cypermethrin Residues in Vegetable

The paper establish an analysis method for determination Cypermethrin pesticide residue in vegetable. Using acetonitrile to extract cypermethrin in vegetable, and purified by Agilent Florisil column, NH2 column and C18 column solid phase extraction column for the samples, using capillary column gas chromatography as a detection method, GC-ECD to qualitative analyze. The recovery rate of Cypermethrin is 91.2% ∼ 98% after Cleanert Florisil, the coefficient of variation is 0.53% ~ 3.67%, the detection limit is 0.0015 mg • kg -1. The first day, spraying the fenvalerate, dimethoate, chlorothalonil pesticides residues in lettuce was higher than the greenhouse tomato; pesticides (dimethoate, chlorothalonil, fenvalerate) residues in vegetables were higher than those in the open field, pesticide degradation speed is obviously higher than in greenhouse. Subsidence of pesticide is an important factor affecting greenhouse pesticide residues.

A capillary gas chromatographic analysis of the characteristics of ionic liquid films

Ionic liquid films are a promising material for the preparation of capillary columns in gas chromatography because they provide new opportunities for chromatographic analysis. In this work the properties of ionic liquid films are studied by capillary gas chromatography. Ionic liquids based on 4-methylpyridinium cation and also 1,2-dimethylimidazolium cations are analyzed. For comparison the Carbowax 20M polyethylene glycol film is used. Diffusion properties are studied by determining the dependence of the height equivalent to a theoretical plate on the carrier gas rate. It turns out that the films based on ionic liquids are characterized by shorter diffusion times in comparison with polyethylene glycol. The loading capacity of the films for which ionic liquids proved to be comparable with polyethylene glycol is also determined in the work.

Analysis of phytosterols and phytostanols in enriched dairy products by Fast gas chromatography with mass spectrometry.

A Fast gas chromatography and mass spectrometry method for plant sterols/stanols analysis was developed, using a short capillary gas chromatography column (10 m × 0.1 mm internal diameter × 0.1 μm film thickness) coated with 5% diphenyl-polysiloxane. A silylated mixture of the main plant sterols/stanols standards (β-sitosterol, campesterol, stigmasterol, campestanol, sitostanol) was well separated in 1.5 min, with a good peak resolution (>1.4, determined on a critical chromatographic peak pair (β-sitosterol and sitostanol)), repeatability (<13%), and sensitivity (<0.017 ng/mL). The suitability of this Fast chromatography method was tested on plant sterols/stanols-enriched dairy products (yogurt and milk), which were subjected to lipid extraction, cold saponification, and silylation prior to injection. The analytical performance (sensitivity < 0.256 ng/mL and repeatability < 10.36%) and significant reduction of the analysis time and consumables demonstrate that Fast gas chromatography-mass spectrometry method could be also employed for the plant sterols/stanols analysis in functional dairy products.

Forensic application of Carburane – a quality control software for the characterisation and differentiation of gasoline petroleum fractions used as fire accelerants. An intelligence approach

Commercial software Carburane, developed at the IFP Energies Nouvelles, was originally designed to accurately evaluate petroleum fraction quality. It can also be applied to forensic problems, and in particular to arson investigation. During a 15-month period, about 350 premium gasoline samples, representative of the three types available on the French territory (SP95, SP95-E10, SP98), were obtained from different oil companies and their associated distribution networks. Samples were collected in gas stations, placed in sealed containers, securely packaged, and were next analysed in the IRCGN laboratory by high resolution capillary column GC (gas chromatography) with flame ionisation detection for the separation and characterisation of different hydrocarbon families. Data processing using Carburane software provided accurate characterisation and comparison of premium gasoline samples that could have been used as fire accelerants. It could assess the closeness of unburned premium gasoline samples found at a crime scene, with similar samples from gas stations or from searched suspect premises. Application to the real case study of a burned residential house provided useful information to the investigators.

Liquid human milk fortifier significantly improves docosahexaenoic and arachidonic acid status in preterm infants

We report the fatty acid composition of mother׳s own human milk from one of the largest US cohorts of lactating mothers of preterm infants. Milk fatty acid data were used as a proxy for intake at enrollment in infants (n=150) who received human milk with a powder human milk fortifier (HMF; Control) or liquid HMF [LHMF; provided additional 12mg docosahexaenoic acid (DHA), 20mg arachidonic acid (ARA)/100mL human milk]. Mothers provided milk samples (n=129) and reported maternal DHA consumption (n=128). Infant blood samples were drawn at study completion (Study Day 28). Human milk and infant PPL fatty acids were analyzed using capillary column gas chromatography.DHA and ARA were within ranges previously published for US term and preterm human milk. Compared to Control HMF (providing no DHA or ARA), human milk fortified with LHMF significantly increased infant PPL DHA and ARA and improved preterm infant DHA and ARA status.

Effect of roasting on the volatile constituents of Trichosanthes kirilowii seeds

Roasted Trichosanthes kirilowii seeds have much more intense flavor than the raw seeds, and are commonly used as food and in the preparations of many medicinal formulations. Volatile constituents in the raw and roasted T. kirilowii seeds were separated by simultaneous distillation and extraction, and analyzed by gas chromatography–mass spectrometry on two capillary gas chromatography columns of different polarities (DB-WAX and HP-1). A total of 40 volatile compounds were identified in the raw seeds, with pentanal, 2-pentanol, styrene, (Z)-2-heptenal, (+)-calarene, and α-muurolene being the predominant compounds; 40 volatile compounds were also identified in the roasted seeds, with 3-methylbutanal, ethanol, 2-butanol, 2,3-butanediol, (E,E)-2,4-nonadienal, and 2-isopropyl-5-methyl-9-methylene-bicyclo[4.4.0]dec-1-ene being the most abundant compounds. A total of 15 compounds, mostly aldehydes, were common in both seeds. Roasting of T. kirilowii seeds resulted in a significant decrease in the levels of sesquiterpenes and short-chain aliphatic aldehydes. By contrast, high concentrations of 3-methylbutanal, ethanol, 2-butanol, and alkyl pyrazines were generated, which was responsible for the unique flavor of the roasted seeds. The study results may be useful for optimizing the roasting process and oil processing of T. kirilowii seeds.