GC-flame Ionization Detection Research Articles

Chemical composition of hydrosol volatiles of flowers from ten Paeonia × suffruticosa Andr. cultivars from Luoyang, China

Hydrosol volatiles from flowers of ten Paeonia × suffruticosa Andr. cultivars were analysed by gas chromatography–mass spectrometry (GC-MS) and GC–flame ionisation detector (GC-FID) for the first time. Fifty components were identified representing 97.6–99.8% of total composition, in which oxygenated compounds (87.4–99.8%) predominated. Hydrosol volatiles of five and two cultivars presented chemotypes of 2-phenylethanol (48.0–79.5%) and 1,3,5-trimethoxybenzene (72.8%, 50.2%), respectively. Hydrosol volatiles of ‘XYTH’ rich in β-citronellol (57.2%) probably represented a newly defined chemotype with β-citronellol percentage over 50%. ‘GFCC’ hydrosol volatiles presented a balanced profile with 1,3,5-trimethoxybenzene (31.9%), β-citronellol (31.5%) and 2-phenylethanol (23.0%). ‘LHZL’ hydrosol volatiles were distinct from others due to occurrence of 6,9-heptadecadiene (2.0%), 2-heptanol (1.8%), pentadecane (1.5%), (Z)-3-nonen-1-ol (1.1%) and geraniol (15.7%). Chemotype characterisation of P. × suffruticosa Andr. hydrosols was of significance considering numerous cultivars of the species and potential applications of the hydrosols.

Comparison of Yield Chemical Composition and Biological Activities of Essential Oils Obtained from Thymus pallidus and Thymus satureioides Coss. Grown in Wild and Cultivated Conditions in Morocco

Thymus pallidus and Thymus satureioides are two endemic Moroccan species of thyme that belong to the Lamiaceae family. They are exploited intensively from the wild for their essential oils (EOs) which are characterized by numerous therapeutic properties. In order to ensure the conservation and sustainable use of these species, the effect of cultivation on yield, chemical composition, antioxidant and antimicrobial activities of EOs were investigated over the course of three years. A slight decrease of EOs yield was obtained by steam distillation from cultivated thymes. As well as the yield, the scanning electron microscopy analysis of the leaves has also showed a decrease in the gland density. The gas chromatography/mass spectrometry (GC/MS) and GC/Flame Ionization Detector (GC/FID) analyses of EOs led to the identification of 32 compounds representing more than 98.4 % of the total oils. The major compounds of wild T. pallidus EOs were γ-terpinene (20.23-21.49 %), borneol (12.33-12.39 %) and α-phellandrene (11.63-12.58 %). Whereas EOs obtained from cultivated plants were dominated by γ-terpinene (17.27-17.32 %), borneol (12.39-8.3 %), camphene (10.67-10.97 %) and α-phellandrene (10.57-10.71 %). Carvacrol (26.07-26.18 %) and borneol (17.25-20.67 %) were the main chemical constituents in both wild and cultivated T. satureioides EOs. Regarding the antioxidant activity, the EOs of cultivated thymes were not highly affected by cultivation. Despite some chemical variability, our results show that cultivation also did not affect the antimicrobial activity of the essential oils of both species. These results imply that the cultivation process could be a promising alternative to ensure the sustainable use of the two endemic thyme species in threat.

Effects of Soil and Vineyard Characteristics on Volatile, Phenolic Composition and Sensory Profile of Cabernet Sauvignon Wines of Campanha Gaúcha

The influence of vineyard on wines was evaluated for the first time using a broader analytical approach: sensory analyses and several analytical techniques (gas chromatography-mass spectrometry (GC-MS), GC flame ionization detection (FID), GC-olfactometry-Osme technique (GC-O-Osme), GC × GC-MS), taking into account odoriferous compounds of Cabernet Sauvignon wines. Sensory attributes were correlated to the concentration of volatiles and also to favorable climate/solar exposition, less clayey/lower organic matter soil, and lower vegetative growth of one out of five vineyards, C1. Among 30 coelutions in GC-MS, 12 involved some of the odoriferous volatiles and GC × GC-MS was required to elucidate their identities. Higher concentrations of ethyl propanoate and diacetyl (related with red fruits/aromatic intensity) and of acetoin (aroma of dry fruits, but coeluted with octanal in first dimension (1D), which presents green odor) were found in C1 wine. It was also correlated with positive appearance attributes, gustatory persistence, body, smell and taste harmony, as well as with higher concentrations of phenolic acids, anthocyanins, flavonols, stilbenes, and flavanols.

Chemical diversity in leaf and stem essential oils of Origanum vulgare L. and their effects on microbicidal activities

Essential oils (EOs) from the stems and leaves of Origanum vulgare L. grown in Saudi Arabia and Jordan were analyzed by gas chromatography–mass spectrometry (GC–MS) and GC–flame ionization detector (FID) techniques on two different columns (polar and nonpolar). A detailed phytochemical analysis led to the identification of 153 constituents of these essential oils. Both Saudi and Jordanian plants are classified by chemotypes rich in cymyl-compounds. However, the Saudi Origanum contains carvacrol as the major component and is, thus, characterized as a carvacrol chemotype, while the Jordanian Origanum contains thymol as the major component, and, thus, it is classified as a thymol chemotype. In addition, the antimicrobial activities of the studied EOs and their major components, including carvacrol and thymol, were evaluated against various Gram-positive and Gram-negative microorganisms. All the tested compounds exhibited significant antimicrobial activity against all the tested bacteria. Among them, thymol demonstrated superior activity against all the tested organisms, followed by carvacrol. Moreover, results on oil composition and oil yield of O. vulgare L. from different parts of the world is compared in detail with the present outcomes.

Grouping of complex substances using analytical chemistry data: A framework for quantitative evaluation and visualization.

A detailed characterization of the chemical composition of complex substances, such as products of petroleum refining and environmental mixtures, is greatly needed in exposure assessment and manufacturing. The inherent complexity and variability in the composition of complex substances obfuscate the choices for their detailed analytical characterization. Yet, in lieu of exact chemical composition of complex substances, evaluation of the degree of similarity is a sensible path toward decision-making in environmental health regulations. Grouping of similar complex substances is a challenge that can be addressed via advanced analytical methods and streamlined data analysis and visualization techniques. Here, we propose a framework with unsupervised and supervised analyses to optimally group complex substances based on their analytical features. We test two data sets of complex oil-derived substances. The first data set is from gas chromatography-mass spectrometry (GC-MS) analysis of 20 Standard Reference Materials representing crude oils and oil refining products. The second data set consists of 15 samples of various gas oils analyzed using three analytical techniques: GC-MS, GC×GC-flame ionization detection (FID), and ion mobility spectrometry-mass spectrometry (IM-MS). We use hierarchical clustering using Pearson correlation as a similarity metric for the unsupervised analysis and build classification models using the Random Forest algorithm for the supervised analysis. We present a quantitative comparative assessment of clustering results via Fowlkes–Mallows index, and classification results via model accuracies in predicting the group of an unknown complex substance. We demonstrate the effect of (i) different grouping methodologies, (ii) data set size, and (iii) dimensionality reduction on the grouping quality, and (iv) different analytical techniques on the characterization of the complex substances. While the complexity and variability in chemical composition are an inherent feature of complex substances, we demonstrate how the choices of the data analysis and visualization methods can impact the communication of their characteristics to delineate sufficient similarity.

Electrochemically synthesised barium coordination polymer fibre: a new solid-phase microextraction hybrid coating for analysis of phthalate esters

ABSTRACT A new hybrid solid-phase microextraction coating, [Ba(5,5ʹ-dcbipy)(µ-H2O)2 (H2O)2]n and polypyrrole, has been prepared using an electrochemical method. The fibre was well characterised and showed superior properties. The fibre showed excellent thermal stability, adherently and chemical stability which were suitable for extracting analytes from harsh media and desorbing them in a high thermal inlet of a GC. Four phthalate esters were extracted with this fibre and then analysed via GC-flame ionisation detector. Salt concentration, temperature and time of extraction were optimised. The detection limits and linear ranges were 0.077–0.25 μg L−1 and 0.125–500 to 0.25–125 μg L−1, respectively. The intra-day and inter-day relative standard deviations were found to be 6.9–9.4 and 2.9–23.4%, respectively. The results then were compared with other works. Phthalates in two different aqueous samples of food products were successfully analysed with the proposed method.

Characterizing lignin: Combining lignin phenol, methoxy quantification, and dual stable carbon and hydrogen isotopic techniques

Lignin is a major structural plant biochemical and biogeochemical compound present in peat and lignite. Its monomeric (phenolic) and polymeric structures include varying amounts of ether-bonded methyl groups (i.e., methoxy or OCH3). These methoxy groups are generally underused targets for both structural characterization and isotopic analyses. We analyzed the quantity and C and H isotopic composition of methoxy groups within a range of substrates including lignin phenols, lignin, wood, peat, lignite, and sub-bituminous and bituminous coal. We used the Zeisel method to cleave the ether bonds with hydroiodic acid to yield iodomethane which can be analyzed by gas chromatography (GC). Finding inconsistent transfer and isotope effects associated with room temperature headspace injections, we instead used isooctane as a solvent for the iodomethane analyte (the liquid method). Using the liquid method, we obtained a linear response by GC-flame ionization detection (GC-FID) for iodomethane and a linear calibration and 85 ± 6% recovery of methyl from methoxy groups from solid standards of phenolic compounds of known stoichiometry. We introduced quantification via lignin phenolic compounds to calibrate both analytical and experimental yield. Methyl yields provided structural information and confirmed that lignin oxidation products (LOPs) from copper oxide oxidation underestimate the number of methoxy-bearing phenols (yield < 0.3 of expected based on stoichiometry); in combination the two approaches provide structural information and quantification. We found that concentrations of methyl from methoxy groups in geologic sediments (lignite, sub-bituminous and bituminous coal) initially increase with diagenesis as lignin to cellulose ratio increases, and then decline to low concentrations during coalification, offering new possibilities for characterizing the transformation of peat and lignite. We assessed an array of plant biochemicals and established that natural and synthetic methoxy groups span a broad range of dual stable carbon and hydrogen isotopic compositions indicating scope for biogeochemical and forensic applications.

Lipoprotein(a) concentration is associated with plasma arachidonic acid in subjects with familial hypercholesterolaemia.

Elevated lipoprotein(a) (Lp(a)) is associated with CVD and is mainly genetically determined. Studies suggest a role of dietary fatty acids (FA) in the regulation of Lp(a); however, no studies have investigated the association between plasma Lp(a) concentration and n-6 FA. We aimed to investigate whether plasma Lp(a) concentration was associated with dietary n-6 FA intake and plasma levels of arachidonic acid (AA) in subjects with familial hypercholesterolaemia (FH). We included FH subjects with (n 68) and without (n 77) elevated Lp(a) defined as ≥75 nmol/l and healthy subjects (n 14). Total FA profile was analysed by GC-flame ionisation detector analysis, and the daily intake of macronutrients (including the sum of n-6 FA: 18 : 2n-6, 20 : 2n-6, 20 : 3n-6 and 20 : 4n-6) were computed from completed FFQ. FH subjects with elevated Lp(a) had higher plasma levels of AA compared with FH subjects without elevated Lp(a) (P = 0·03). Furthermore, both FH subjects with and without elevated Lp(a) had higher plasma levels of AA compared with controls (P < 0·001). The multivariable analyses showed associations between dietary n-6 FA intake and plasma levels of AA (P = 0·02) and between plasma levels of Lp(a) and AA (P = 0·006). Our data suggest a novel link between plasma Lp(a) concentration, dietary n-6 FA and plasma AA concentration, which may explain the small diet-induced increase in Lp(a) levels associated with lifestyle changes. Although the increase may not be clinically relevant, this association may be mechanistically interesting in understanding more of the role and regulation of Lp(a).

Seasonal Variation of Essential Oil in Rosmarinus officinalis Leaves in Sardinia

Rosmarinus officinalis L. is an aromatic plant belonging to the Lamiaceae family widely distributed in the Mediterranean area. The interest on this species is related to the multiple uses of the plant as a food ingredient, in the pharmaceutical and cosmetic industries. The chemical composition of essential oil (EO) from 5 accessions of R. officinalis L., collected monthly through a full year in Sardinia, has been studied by gas chromatography (GC) and GC-mass spectrometry technique. The EO ranged from 0.29% to 0.89%. The qualitative determinations revealed the presence of 27 compounds belonging to 6 chemical groups (hydrocarbon monoterpene, alcohols, aldehydes, ketones, esters, hydrocarbon sesquiterpene). Overall the GC-flame ionization detector analysis showed the presence of 7 major compounds: α-pinene (26%-28%), camphene (5%-8%), 1,8-cineole (15%-25%), borneol (5%-11%), camphor (3%-12%), verbenone (6%-15%), and bornyl acetate (4%-7%). Chromatographic data were also subjected to a chemometric approach that evidenced discrimination of the samples according to the site of collection.

Oxylipin concentration, but not fatty acid composition, is altered in human donor milk pasteurised using both thermal and non-thermal techniques.

Human donor milk (DM) is Holder pasteurised (62·5°C, 30 min) to ensure its microbiological safety for infant consumption. In low-resource settings, flash heating is used to pasteurise milk. Although there is considerable interest in non-thermal alternatives (high hydrostatic pressure processing (HHP) and UVC irradiation) for pasteurisation, their effect on the fatty acid composition is not well understood. Of particular interest is the effect of pasteurisation on the generation of oxylipins. DM from eight mothers containing bacteria >5 × 107 colony-forming units/l was used. In a paired design, each pool of milk underwent four pasteurisation techniques: Holder; flash heating; UVC (250 nm, 25 min) and HHP (500 MPa, 8 min). Fatty acids were quantified by GC-flame ionisation detection and oxylipins derived from arachidonic acid; 18-carbon PUFA (α-linolenic acid, linoleic acid and γ-linolenic acid) and EPA/DHA were measured by liquid chromatography-tandem MS in aliquots of raw and processed milk. There were no significant changes to the composition of fatty acids following all pasteurisation techniques compared with raw milk. The n-6:n-3 ratio remained constant ranging from 6·4 to 6·6. Several arachidonic acid-derived oxylipins were highest post-UVC and elevated post-HHP compared with raw milk. Several oxylipins derived from 18-carbon PUFA (linoleic and α-linolenic acids) were elevated in UVC-treated milk. EPA/DHA-derived oxylipins were on average, unaffected by pasteurisation. Although some PUFA-derived oxylipins were increased following UVC and HHP, no method affected the fatty acid composition of human DM. Further research is needed to determine if varying levels of oxylipins in human DM as a result of processing can potentially mediate cellular signalling; proliferation and apoptosis, especially important for preterm infant development.

Methods for one– and two–dimensional gas chromatography with flame ionization detection for identification of Mycobacterium tuberculosis in sputum

Two simplified methods based on manual thermally–assisted hydrolysis and methylation (THM) GC and GC × GC with flame ionization detection (FID) were developed for the detection of mycobacteria and Mycobacterium tuberculosis (MTB) in sputum. A central composite design was employed to optimize the THM derivatization conditions. For the detection of MTB the known mycobacterial markers tuberculostearic acid (TBSA) and hexacosanoic acid (C26), as well as three MTB specific markers, the mycocerosates, were evaluated. We found that the optimum conditions for THM release of TBSA and C26 differ from those for maximum release of the mycocerosates. Higher reagent volumes, higher temperatures and longer incubation increase the mycocerosates yield. Application of these conditions unfortunately resulted in unacceptable safety hazards. A GC × GC–FID method was developed that allowed accurate detection of mycocerosates even at poor conversion yields of the derivatization reaction. Using spiked sputum samples from non–TB patients, the detection limit of the method based on TBSA and C26 was found to be comparable to that of microscopy, i.e. 104–105 bacteria/mL sputum. To validate the new test, we compared the results we found for fifteen sputum samples from patients from South Africa suspected of having tuberculosis with those of culture, the gold standard method. Based on the presence of TBSA and C26, all eight microscopy and culture positive samples, and even two microscopy negative but culture positive samples were positive by THM–GC–FID. All five microscopy and culture negative sputum samples were also negative for THM–GC–FID, giving a specificity of 100%. Using GC × GC–FID we could detect mycocerosates, the specific markers for MTB in seven out of ten MTB culture positive sputum samples. The five culture negative cases were also negative for mycocerosates in manual THM–GC × GC–FID giving again 100% specificity. The results obtained indicate that the new methods hold great potential for the early diagnosis of TB in developing countries.

Comparisons of analysis of fatty acid methyl ester (FAME) of microalgae by chromatographic techniques

In this study, we compared the performances of three gas chromatography (GC) based microalgal fatty acid methyl esters (FAMEs) analysis methods that are regularly applied to biofuel research using microalgae, specifically the GC-flame ionization detector (GC-FID) with packed and capillary column and a GC-mass spectrometry (GC–MS) with capillary column. Three strains of Chlorophyta from distinct genera were assayed, namely Scenedesmus obliquus, Coelastrella sp., and Chlorella vulgaris grown in both synthetic growth medium and municipal wastewater. One-way ANOVA indicates statistically significant (p < 0.05) discrepancies in total FAMEs quantification by GC, particularly in the case of the capillary GC-FID, which estimated lower values than the other two. FAMEs profiles were comparable between methods, while some minor differences were apparent; GC–MS showed the biggest divergence.

Headspace–solid-phase microextraction gas chromatography method to quantify Thymus vulgaris essential oil in polymeric nanoparticles

Background: Thymus vulgaris essential oil (Tv-EO) is known to have antibacterial, antifungal, and antioxidant activities. Encapsulation of Tv-EO in polymeric nanoparticles (NPs) can prevent volatilization of its components and can provide protection against external agents. Under these circumstances, it is crucial to assure the presence and quantity of the Tv-EO components (γ-terpinene, thymol, and carvacrol) in the NPs. Objective: To determine the chemical composition and physicochemical characterization of Tv-EO as well as develop and validate a HSPM-gas chromatography (GC) method for the analysis of Tv-EO components encapsulated in NPs. Materials and Methods: Tv-EO was characterized by physicochemical analysis for relative density, refractive index, and optical rotation and analyzed by GC flame ionization detector and GC-mass spectrometry. The headspace–solid-phase microextraction-gas chromatography (HS-SPME-CG) validation was assessed, Tv-EO-NPs were prepared by nanoprecipitation, and its properties were determined by photon correlation spectroscopy. Results: Tv-EO was characterized by physicochemical analysis for relative density (0.934 g/cm3), refraction index (1.559), and optical rotation (−0.084°). Seventeen components were identified in Tv-EO; among these, the sesquiterpenes, thymol (34.28%), o-cymene (31.78%) and γ-terpinene (13.22%). The method was validated for linearity (R2 ≥ 0.99), precision (intraday 7.02, 10.33, and 8.60 and inter-day 10.60, 10.60, and 10.99), accuracy (99.35, 109.4, and 98.84%) and robustness for γ-terpinene, thymol and carvacrol, respectively. The limit of detection and limit of quantification were calculated as 0.69, 0.40, and 0.39 μg/mL and 2.11, 1.22, and 1.20 μg/mL for γ-terpinene, thymol, and carvacrol, respectively. An encapsulation percentage of 47.51% of total essential oil was obtained. Conclusion: The experimental data show that HS-SPME reduces interference of the NP-matrix and concentrates the Tv-EO components. HS-SPME-CG can be considered as a good alternative to the already existing methods for analysis of essential oil encapsulated in NPs.

Traumatic Resin Duct Development, Terpenoid Formation, and Related Synthase Gene Expression in Pinus massoniana Under Feeding Pressure of Monochamus alternatus

Conifer-produced oleoresin is mainly composed of monoterpenoids, sesquiterpenoids, and diterpenoids that can protect conifers against herbivores and pathogens. Pinus massoniana Lamb. is an important economic species in southern China. However, the traumatic resin duct (TD) formation and terpenoid accumulation induced by adult Monochamus alternatus (Coleoptera: Cerambycidae) of P. massoniana have not been clearly reported. Here, we infested P. massoniana with M. alternatus and characterized the induced terpene defenses by microscopy, gas chromatography-mass spectrometry (GC-MS) and GCflame ionization detector (GC-FID), and quantitative reverse transcriptase PCR (qRT-PCR). The induced responses involve TD formation, tissue-specific terpenoid accumulation differentiation, and temporal related gene changes. Formation of TDs was observed in secondary xylem 7 days after feeding. GC-MS and GC-FID results showed terpenoid composition varied in bark and xylem tissue in response to infestation. Following feeding damage, most of the terpenoid synthase genes were up-regulated, which is consistent with the changes in terpenoid constitution. The genes were activated before terpenoid changes were detected indicating that this complex physiological and biochemical process requires time. This study provides evidence of the temporal sequence of changes in terpenoid defenses against herbivory in P. massoniana.

Bio-gasoline production of used cooking palm oil catalyzed by metal supported catalyst Ni/Natural Zeolite (Ni/NZ)

This work aims to synthesized Ni/Natural zeolite (Ni/NZ) catalyst and produces bio-gasoline (main product) and gas (byproduct) from used cooking palm oil by catalytic cracking reaction. Ni/NZ catalyst was prepared by impregnating Ni with various concentrations (0.05; 0.1; and 0.2 M) onto natural zeolite. Ni/NZ catalyst was the characterized by XRD, XRF, and Gas Sorption Analyzer (GSA) to know the specific surface area, pore distribution, and total pore volume. Characterization of product and byproduct conducted by Gas Chromatography (GC), GC-Thermal Conductivity Detector (GC-TCD), and GC-Flame Ionization Detector (GC-FID). From analysis XRD and XRF, showed successfully impregnated Ni onto natural zeolite. The best catalyst was Ni-0.1M/NZ with specific surface area, pore distribution, and total pore volume was 200.327 m2/g, 2.1884 x 10-1 Å, and 2.192 × 10-1 cm3/g, respectively. The product (bio-gasoline) resulted from catalytic cracking reaction was comparable to standard gasoline which had the same retention time of chromatogram at 3.06 min with 95.14 % area. Byproduct of this reaction were 31.94% hydrogen, 13.31% oxygen, 53.94 % nitrogen, 0.18 % CO gas, 0.24 % methane, and 0.39% CO2 gas.

Integrated Analytical Methods to Characterize Lipids from Prosopis spp. and Ceratonia siliqua Seed Germ Flour

Flour from seed germ of European carob (Ceratonia siliqua) and South American algarrobo (Prosopis spp.) is a potential ingredient for health-promoting baked products. Herein, lipids from germ of three Argentinean Prosopis (P. alba, P. nigra, and P. ruscifolia) and one European carob species were characterized in detail, exploiting an array of up-to-date analytical techniques. Total lipids ranged from 7.1 to 8.1% (w/w). Linoleic acid (C18:2, ω-6) predominated the GC flame ionization detector profiles of fatty acid in all samples (43.3–50.6%). Prosopis spp. contained 6–7% of C20–C24 fatty acids and, consistently, C56–C60 triacylglycerols, as detected by MALDI-TOF mass spectrometry (MS), which were practically missing in C. siliqua germ. Phospholipids were isolated by hydroxyapatite chromatography, characterized by MALDI-TOF MS and grossly quantified by attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy. Because of a relatively high content (9.5–11.8%, v/v), phospholipids might increase the antioxidant potential and improve the baking performances of flour fortified with carob and algarrobo seed germ.

Oxygenated Volatile Organic Compounds (Anti-freezing Agents) in Decorative Water-based Paints Marketed in Nigeria.

Background.Consumer products such as paints are a potentially significant source of volatile organic compounds (VOCs) and oxygenated VOCs. Paints for construction and household use have been rapidly changing from oil-based to water-based paints and are one of the commonly identified sources of oxygenated VOCs in indoor environments.Objectives.Four different anti-freezing agents were identified and analyzed in 174 waterbased paint samples, purchased from popular paint markets in two metropolitan cities in Nigeria, Lagos and Ibadan.Methods.Paint samples were solvent extracted using acetonitrile and milli-Q water. Antifreezing agents in the extracts were identified and quantified using gas chromatography (GC)-mass spectrometry and a GC-flame ionization detector, respectively.Discussion.Four different anti-freezing agents were identified in the samples, ethylene glycol, diethylene glycol, triethylene glycol and propylene glycol. Their levels ranged from 1,000-1,980 ppm, diethylene glycol; 1,000–3,900 ppm, triethylene glycol; 1,090–2,510 ppm, propylene glycol and 1,350–2,710 ppm, ethylene glycol. Levels of anti-freezing agents in all of the paint samples were above the permissible limits of the European Union for VOCs in paints of 500 ppm. Results of multivariate statistical analyses clearly showed that triethylene glycol was the most commonly used anti-freezing agent in paints despite its numerous harmful health effects.Conclusions.We concluded that water-based paints marketed in Nigeria contain high concentrations of anti-freezing agents, which have harmful environmental and human health effects, especially to sensitive individuals such as children.Competing Interests.The authors declare no competing financial interests.

Crystallization of microporous TiO2 through photochemical deposition of Pt for photocatalytic degradation of volatile organic compounds.

The photocatalytic mineralization efficiency of volatile organic compounds (VOCs) is determined by adsorption of reactants, separation of charge carriers, and reaction activity of catalyst surface. Herein, we provide a strategy to synthesize a novel catalyst, namely, PhPt-Micro, which is characterized by high adsorption ability, charge separation efficiency, and surface reaction activity. Toluene was chosen as the model VOC. The effects of photochemical deposition of Pt on the physical properties of microporous amorphous TiO2 (Micro) and toluene mineralization were studied using N2 adsorption/desorption, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, GC-flame ionization detection, and surface photovoltage spectroscopy (SPS) analyses. After photochemical treatment, the structure of Micro was optimized, and Pt nanoparticles were successfully deposited at the outlet of electrons on the catalyst surface. SPS result proved that the optimized structure enhanced the separation efficiency of charge carriers and the migration of photo-generated electrons to the PhPt-Micro surface. The quasi-equilibrium adsorption amount of toluene over PhPt-Micro was two times higher than that with commercial nano TiO2 (P25). The micropores concentrated toluene on the catalyst surface and hindered intermediate desorption. The mineralization efficiency of toluene over PhPt-Micro was 2.4 and 5.9 times higher than those over Micro and P25, respectively.

Use of light hydrocarbons for the oil-oil correlation in Pearl River Mouth Basin, South China Sea

The composition of 28 oil samples from Wenchang and Enping formations of Pearl River Mouth Basin (PRMB) was characterized and emphasis was placed on compositional variations in the gasoline range (i-C5H12-n-C8H18). The light hydrocarbons (LHs) were sensitively determined by gas purge microsyringe extraction (GP-MSE) coupled with gas chromatography-mass spectrometry (GC–MS) and GC-flame ionization detector (FID), respectively. According to the relative concentration of LHs, the Mango’s K1 parameter was calculated and a cross plot was obtained. Invariance in the K1 ratio was observed with a correlation coefficient approximately equal to 1 for all the studied crude oils, however, the absolute K1 values were different for each oil family, which indicates the distinct genetic features. Furthermore, several LH indicators were screened and a model was developed for correlating oils using LHs combined with multivariate statistical method. To validate the model, the correlation results based on routine biomarkers and LHs were compared by using normal oil samples, and consistent conclusions were achieved. As alternative to routine biomarkers, LHs show good potential in geochemical correlation of crude oils, especially when routine biomarkers are absent or at very low concentration in high maturated oil samples.

Evaluation of a portable gas chromatograph with photoionization detector under variations of VOC concentration, temperature, and relative humidity

ABSTRACTThe objective of this present study was to evaluate the performance of a portable gas chromatograph-photoionization detector (GC-PID), under various test conditions to determine if it could be used in occupational settings. A mixture of 7 volatile organic compounds (VOCs)—acetone, ethylbenzene, methyl isobutyl ketone, toluene, m-xylene, p-xylene, and o-xylene—was selected because its components are commonly present in paint manufacturing industries. A full-factorial combination of 4 concentration levels (exposure scenarios) of VOC mixtures, 3 different temperatures (25°C, 30°C, and 35°C), and 3 relative humidities (RHs; 25%, 50%, and 75%) was conducted in a full-size controlled environmental chamber. Three repetitions were conducted for each test condition allowing for estimation of accuracy. Time-weighted average exposure data were collected using solid sorbent tubes (Anasorb 747, SKC Inc.) as the reference sampling medium. Calibration curves of Frog-4000 using the dry gases showed R2 > 0.99 for all analytes except for toluene (R2 = 0.97). Frog-4000 estimates within a test condition showed good consistency for the performance of repeated measurement. However, there was ∼41–64% reduction in the analysis of polar acetone with 75% RH relative to collection at 25% RH. Although Frog-4000 results correlated well with solid sorbent tubes (r = 0.808–0.993, except for toluene) most of the combinations regardless of analyte did not meet the <25% accuracy criterion recommended by NIOSH. The effect of chromatographic co-elution can be seen with m, p-xylene when the results are compared to the sorbent tube sampling technique with GC-flame ionization detector. The results indicated an effect of humidity on the quantification of the polar compounds that might be attributed to the pre-concentrator placed in the selected GC-PID. Further investigation may resolve the humidity effect on sorbent trap with micro GC pre-concentrator when water vapor is present. Although this instrument does not fulfill the accuracy criterion specified in the NIOSH technical report No. 2012–162, it can be used as a screening tool for range finding monitoring with dry gases calibration in the occupational setting rather than compliance monitoring.