Gas Chromatography With Flame Ionization Detection Research Articles

Lipid Profile Determination by Direct Infusion ESI-MS and Fatty Acid Composition by GC-FID in Human Milk Pools by Folch and Creamatocrit Methods

Human milk (HM) is extremely important to the baby, containing a varied and balanced range of nutrients fundamental to the ideal development of the newborn. Among these nutrients, HM lipids provide 40-60% of the energy. In HM banks, the creamatocrit method is employed as a quick and solvent-free tool, however, since Folch methodology is considered reference for lipid extraction, this study compared the fatty acid (FA) composition and the lipid profile by gas chromatography with flame ionization detector (GC-FID) and direct infusion by electrospray ionization mass spectrometry (DI-ESI-MS) in pools of different HM phases, obtained from Folch and creamatocrit methods, in order to elucidate which method provides better information about HM lipids. Lipid compositon results by Folch were superior to the results obtained by creamatocrit in HM pools investigated. It means, the lipid profiles of all HM pools were more intense, and the number of FA identified by Folch was also higher in comparison to the creamatocrit method (21 and 6 FAs, respectively). GC-FID analysis in combination with principal component analysis (PCA) divided the methods, confirming a greater contribution of the Folch method. Therefore, Folch methodology revealed an effective lipid extraction in comparison to creamatocrit method.

Effect of Benzene Exposure on the Urinary Biomarkers of Nucleic Acid Oxidation in Two Cohorts of Gasoline Pump Attendants.

(1) Background: The oxidized guanine derivatives excreted into urine, products of DNA and RNA oxidation and repair, are used as biomarkers of oxidative damage in humans. This study aims to evaluate oxidative damage in gasoline pump attendants occupationally exposed to benzene. Benzene is contained in the gasoline but it is also produced from traffic and from smoking. (2) Methods: Twenty-nine gasoline pump attendants from two major cities of Saudi Arabia and 102 from Italy were studied for urinary 8-oxo-7,8-dihydroguanine (8-oxoGua), 8-oxo-7,8-dihydro-2′-deoxyguanosine (8-oxodGuo), 8-oxo-7,8-dihydroguanosine (8-oxoGuo), and S-phenyl-mercapturic acid (SPMA) for benzene exposure and urinary cotinine for smoking status assessment by liquid chromatography-tandem mass spectrometry. Airborne benzene was also assessed in the Italian group by gas-chromatography with flame ionization detector (GC-FID). (3) Results: The results suggest that high levels of benzene exposure can cause an accumulation of SPMA and bring about the formation of the oxidation biomarkers studied to saturation. At low exposure levels, SPMA and oxidation biomarker levels were correlated among them and were associated with the smoking habit. (4) Conclusions: The study confirms the association between benzene exposure and the excretion of nucleic acid oxidation biomarkers and enhances the importance of measuring the smoking habit, as it can significantly influence oxidative damage, especially when the exposure levels are low.

Matrix Extension with Fitness for Purpose and Stability Assessment of DHA and Additional Fatty Acids in Individual Whole Chicken Eggs

The consumption of long chain polyunsaturated fatty acids (LC-PUFA) is associated with several human health benefits. Most notable of these LC-PUFA is docosahexaenoic acid (DHA C22:6) whose inclusion is considered essential for optimum human health. Biofortification of common foods such as eggs with DHA has emerged as a specific approach to increase the intake of DHA in human populations. This can be achieved by supplementing poultry rations with feeds like microalgae or fish oil that are rich in DHA, which results in an increased uptake in the egg. Gas chromatography with flame ionization detection (GC-FID) is the method of choice when analyzing food such as eggs for DHA and other fatty acids. For regulatory studies it is desirable to demonstrate that the method is specifically suitable for the analysis of DHA and fatty acids in eggs. The purpose of this paper is to further extend the scope of the AOAC 996.06 methodology examined in the paper by Dillon et al., and to demonstrate the fitness for purpose of the method by examining specific validation parameters. It is a further objective to investigate the stability of DHA and other fatty acids of short and long timepoints. A validation of the method for the determination of DHA and three other fatty acids in eggs is thus presented.

Validation and application of a chromatographic method for evaluation of commercial vegetable oils possibly adulterated

A method of separation, identification and quantification of fatty acid methyl esters (FAMEs) was developed by gas chromatography with flame ionization detector (GC-FID) using a basic transesterification. In this sense, there were analyzed FAMEs in commercial samples of vegetable oils from soybean and olive oil. The referred method was linear (r>0.99), accurate and precise for palmitic (C16:0), linoleic (C18:2), oleic (C18:2), linolenic (C18:3) and stearic (C18:0) acids. The limits of detection (LOD) and quantification (LOQ) were from 0.03 to 0.31 and 0.08 to 0.94 mg.mL-1 for the five fatty acids, respectively. The results demonstrated that the unsaturated fatty acids were the most abundant for the two samples, being the oleic acid (C18:1) the major in three brands of olive oil (D, E and F), and the linoleic acid (C18:2) the most abundant in soybean oil and the other brands of olive oil (G, H and I), suggesting a possible adulteration in these brands. The proposed method could be considered a tool for the investigation of adulteration in commercial vegetable oils for guaranteed reliability in the results to be comparable with correlated legislations.

Biodiesel synthesis from eucalyptus oil by utilizing waste egg shell derived calcium based metal oxide catalyst

Heterogeneous catalysts have emerged as potential alternatives to their homogenous counterparts, since they could successfully overcome the shortcomings encountered in homogenous catalytic trans-esterification of tri-acyl glycerides. In the present study, application of pure as well as doped CaO derived from waste chicken egg shells was studied for conversion of oil into biodiesel. Waste eggshells were calcined at 900 °C to get CaO which was then incorporated into transition metals by incipient wet impregnation method. The catalyst prepared has been characterized by Scanning electron microscope (SEM), Thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) techniques. The basicity and surface area of catalysts were ascertained in order to figure out the catalytic activity. The conversion of oil to Fatty acid methyl esters (FAME) has been confirmed by Thin-layer chromatography (TLC) and the percentage yield of eucalyptus biodiesel was verified by Gas chromatography with Flame ionization detector (GC-FID). The catalytic property of these mixed metal oxides has been studied in trans-esterification of Eucalyptus Oil. Zn-CaO (waste egg shell) was observed to be the most promising catalyst providing with appreciable yield of bio-diesel (FAME) among all the three catalysts. Transesterification was carried out at different process variables to optimize the best reaction conditions. Employing waste chicken egg shell derived CaO doped with transition metals (Zn, Cu) as catalyst puts forward the economic and efficient scheme for trans-esterification of Eucalyptus oil for biodiesel generation.

Separation of Volatile Metabolites from the Leaf-Derived Essential Oil of Piper mollicomum Kunth (Piperaceae) by High-Speed Countercurrent Chromatography.

The technique of high-speed countercurrent chromatography was applied to the isolation of compounds in essential oil derived from the leaves of Piper mollicomum species. Plant leaves (200.0 g) were submitted to hydrodistillation in a modified Clevenger apparatus. The resulting crude leaf essential oil was analyzed by gas chromatography with flame ionization detector (GC-FID) and gas chromatography-mass spectrometry (GC-MS) to determine the profile of the components. The purified fractions were composed of monoterpenes and sesquiterpenes such as camphor (85.0 mg at 98.5% purity), (E)-nerolidol (100.0 mg at 92.8% purity), and camphene (150.0 mg at 82.0% purity). A minor component of the essential oil, bornyl acetate (16.2 mg at 91.2% purity) was also isolated in the one-step separation protocol in 2 h. The countercurrent chromatography technique proved to be a fast and efficient method for the separation of volatile metabolites that conserved the solvent while delivering various fractions of high purity.

Chemical characterization of natural and anthropogenic-derived oil residues on Gulf of Mexico beaches

Oil residues originating from the Deepwater Horizon (DWH) incident persist on Gulf of Mexico beaches alongside oil from offshore industrial activity, natural seepage, and asphalt from parking lots and roads. To determine the primary differences in the chemical composition of these oil residues, a variety of samples were collected from beaches from Florida to Alabama over a two-year period from 2015 to 2017. Bulk chemical characteristics of the oil residues were examined via gas chromatography with flame ionization detection (GC-FID) and mass spectrometry (GC–MS), as well as thin layer chromatography with flame ionization detection (TLC-FID), and attenuated total reflectance Fourier transform infrared spectroscopy (ATR FT-IR). These bulk chemical analyses revealed features unique to the different sample types, expanding our understanding of the chemical composition and variability of persistent oil residues, and providing a means to detect and monitor their long-term fate in the coastal environment.

Photocatalytic oxidation of benzene by ZnO coated on glass plates under simulated sunlight

The photocatalytic oxidation of benzene by ZnO nanoparticles coated on glass plates was studied under simulated sunlight. ZnO nanoparticles were coated on three glass plates by heat attachment method. To evaluate the photocatalytic removal of benzene, coated plates were irradiated by metal halide lamp in a rectangular reactor in batch mode. The effect of initial pollutant concentration, temperature, relative humidity, irradiation time, concentration of zinc oxide suspension, were assessed. The surface morphology and structure of ZnO nanoparticles and ZnO coated on glass plates were characterized by scanning electron microscopy, X-ray diffraction and field emission scanning electron microscopy. Sampling and analysis of benzene were performed according to NIOSH method. To analyze the concentration of benzene, gas chromatography with flame ionization detector (GC-FID) was used. Results indicated that photocatalytic process by ZnO under irradiation of metal halide lamp could remove benzene at optimum experimental conditions. Coating of glass plates by ZnO suspension, resulted in 57% removal of benzene as concentration of 50 ppm at 45 °C, and relative humidity of 40% after 240 min irradiation of metal halide lamp. Results indicated that photocatalytic oxidation process by ZnO nanoparticles can be used as a proper and environmentally friendly method for removing low concentrations of benzene from polluted air under simulated sunlight.

Photo Oxidation Reaction Kinetics of Ethyl Propionate with Cl Atom and Formation of Propionic Acid

Temperature-dependent rate coefficients for the photo oxidation reaction of ethyl propionate with Cl atom were investigated experimentally using the relative rate technique. Gas chromatography with flame ionization detector (GC-FID), gas chromatography-mass spectrometry (GC-MS), and GC-infrared spectroscopy (GC-IR) were used to follow the concentrations and identification of reactants and products. The kinetics of ethyl propionate with Cl atoms was investigated over the temperature range of 263-363 K at atmospheric pressure, relative to C2H6 and C2H4. Theoretical calculations were also performed at CCSD(T)/6-311++G(d,p)//BHandHLYP/6-311G(d,p) level of theory, and the rate coefficients for H-abstraction reactions were calculated using canonical variational transition state theory (CVT) with interpolated single point energies (ISPE) method over the temperature range of 200-800 K. The temperature-dependent rate coefficients for the reaction of ethyl propionate with Cl atom were obtained both experimentally as well as theoretically and are kExpt( T) = [(6.88 ± 1.65) × 10-24] T4.5 exp[(1108 ± 87)/ T] cm3 molecule-1 s-1 and kTheory( T) = (6.73 × 10-19) T2.74 exp[(571)/ T] cm3 molecule-1 s-1, respectively. On the basis of product analysis on the title reaction and the computational studies, we have proposed the atmospheric degradation mechanism and various pathways for Cl atom-initiated photo oxidation of EP. Propionic acid is identified as the major product in the degradation of ethyl propionate on reaction with Cl atom. The thermochemistry, branching ratios, and cumulative lifetime of ethyl propionate are calculated and presented in this Article.

In Vitro Study of Multi-Therapeutic Properties of Thymus bovei Benth. Essential Oil and Its Main Component for Promoting Their Use in Clinical Practice

Thymus bovei Benth. (TB) is an important plant in the traditional medicine of the Mediterranean region. This study investigates the health-promoting properties of TB essential oil (TB-EO) for its possible use in clinical practice with regards to its cytotoxic, anti-herpes simplex virus type 2 (HSV-2), and antihypertensive (through inhibition of human angiotensin-converting enzyme; ACE) properties. The phytochemical profile of EO (99.9%) was analyzed by Gas Chromatography with Flame-Ionization Detection (GC-FID) and Gas Chromatography-Mass Spectrometry (GC-MS). In this study, all biological methods were performed at the level of in vitro studies. The results showed that TB-EO exerted remarked cytotoxic properties against human cervical carcinoma cells, colon cancer cells, and lung adenocarcinoma cells with the half-maximal inhibitory concentration (IC50) values of 7.22, 9.30, and 8.62 µg/mL, respectively, in comparison with that of standard anticancer drug cisplatin with IC50 values of 4.24, 5.21, and 5.43 µg/mL, respectively. Fascinatingly, TB-EO showed very weak cytotoxicity on the healthy human fetal lung fibroblast cells with an IC50 value of 118.34 µg/mL compared with that of cisplatin (IC50 = 10.08 µg/mL). TB-EO, its main component geraniol, TB-EO combined with acyclovir (ACV) along with standard ACV, have displayed pronounced inhibitory properties against the replication of HSV-2 with the half-maximal effective concentration (EC50) values of 2.13, 1.92, 0.81 and 1.94 µg/mL, respectively, with corresponding selectivity indices (SI) 98.59, 109.38, 259.26 and 108.25, respectively. TB-EO and geraniol at a concentration of 15 µg/mL showed prominent inhibitory activities against ACE with % of inhibition 95.4% and 92.2%, respectively, compared with that of standard inhibitor captopril (99.8%; 15 µg/mL). Molecular docking studies were performed to unveil the mechanism of action of geraniol as well as structural parameters necessary for anti-HSV-2 activity (through the inhibition of HSV-2 protease) and ACE inhibition. This is the first report on the chemical composition of Egyptian TB-EO along with the above-mentioned biological activities. Our results may be considered as novel findings in the course of a search for new and active anticancer, anti-HSV-2 and antihypertensive agents, and expand the medicinal value of this plant and its phytochemicals in clinical practice.

Intraspecific chemical variability of the essential oils of Moroccan endemic Origanum elongatum L. (Lamiaceae) from its whole natural habitats

In this study, the chemical variation of the essential oils of the endemic species Origanum elongatum has been studied in its biogeographical context. Essential oils of 168 individual plants collected from 30 populations growing wild in two Moroccan mountains: Rif and Middle Atlas, were analyzed by GC-FID (Gas Chromatography with Flame Ionization Detector), GC/MS (Gas Chromatography/Mass Spectrometry) and 13C NMR (Nuclear Magnetic Resonance). Origanum elongatum produces an EOs yielding after hydrodistillation from 0.81% to 3.12% based on the dry weight of the original biomass. 28 compounds were identified, with a majority of oxygenated monoterpenes among them carvacrol, thymol and p-cymene constitute the most represented compounds. Moreover, a great amount of α-terpinene, limonene, thymoquinone and thymohydroquinone were reported in some samples. Four chemical groups have been identified, namely; carvacrol, carvacrol/thymol, carvacrol/p-cymene and thymol. The geographic distributions of these chemotypes appear to vary since the carvacrol chemotype was the most distributed, while the thymol was found more abundantly in populations from Rif. However, the carvacrol/p-cymene chemotype was revealed only in Taza region. For the first time the whole chemical picture of the EOs of O. elongatum is presented in relation to their geographical distribution such knowledge is primordial in developing a breeding program in order to protect this species widely and intensively used for both medicinal and food uses but also supply the continuous market needs by producing high quality and stable raw material.

Oxidative stability of sunflower oil flavored by essential oil from Coriandrum sativum L. during accelerated storage

The aim of the work was to assess the oxidative stability of sunflower oil flavored by the essential oils extracted of Coriandrum sativum (coriander, CEO) during the accelerated storage of 24 days. In the study, CEO was extracted by Soxhlet apparatus, and its chemical composition was analyzed by gas chromatography with flame ionization detector (GC-FID) and gas chromatography and mass spectrometry (GC-MS), and then, the evaluation for antioxidant effect in vitro displayed that CEO possessed markedly antioxidant potential. Furthermore, after the addition of CEO, acid value (AV), peroxide value (PV), iodine value (IV), p-anisidine value (AnV), thiobarbituric acid reactive substances (TBARS), free fatty acid (FFA), total polar compounds (TPC), tocopherols (TOC) in sunflower oils during the accelerated storage were measured every 4 days, and the results herein exhibited the addition of CEO at 1200 ppm could not only increase the oxidative stability of the sunflower oils, but also exert synergistic effect with TBHQ. Meanwhile, the values of K232 and K268 and fatty acid composition were investigated. The sensory evaluation of the oil samples revealed that the addition of CEO at 1200 ppm could increase aroma flavor and consumers' acceptability, so that it could be developed as convenient condiment.

Magnetic frame work composite as an efficient sorbent for magnetic solid-phase extraction of plasticizer compounds

Two metal–organic frameworks (MOFs) TMU-23 and TMU-24, containing amide-functionalized pores, have been fabricated. Their applications were evaluated for the magnetic solid phase extraction of plasticizer compounds benzylbutylphthalate (BBP), di-2-(ethylhexyl) phthalate (DEHP) and di-n-butyl phthalate (DBP) prior to analysis by gas chromatography with flame ionization detector (GC-FID). Due to the large surface area and unique porous structure of the MOFs as well as hydrogen bonding formation, π-π and hydrophobic interactions between the analytes and the MOF ligands, the prepared sorbents showed a high affinity towards the target analytes. The studies reveal that TMU-24 has a better adsorption capability than TMU-23. A magnetic TMU-24 was then fabricated by in-situ synthesis of a magnetic core-shell nanocomposite. The material was chosen as an efficient sorbent for the extraction of the target analytes, followed by their determination by GC-FID. Under optimal conditions, preconcentration factors and relative recoveries of the studied compounds were obtained in the range of 189–278 and 92.0–102.0% respectively. The calibration curves were obtained in the range of 0.5–250 μg L−1 with reasonable linearity (R2 >0.99) and the limits of detection (LODs) ranged between 0.2 and 0.4 μg L−1 (based on S/N = 3). The precision of the method, expressed as relative standard deviation for extraction and determination of the 100 μg L−1 analytes in the samples solution was in the range of 3.9–5.9%.

Prediction of Relative Density, Distillation Temperatures, Flash Point, and Cetane Number of S500 Diesel Oil Using Multivariate Calibration of Gas Chromatographic Profiles

In the present study, hierarchical cluster analysis was used to select 150 S500 diesel fuel samples from an initial set of 1320 samples assayed through official standards according to ANP Brazilian Regulation No. 50/2013. Four physicochemical properties were analyzed, namely, relative density, distillation temperatures (T10%, T50%, and T85%), flash point, and cetane number. Selected samples were also analyzed by gas chromatography with flame ionization detection (GC-FID), a very common technique used for fuel quality control due to its convenience, accuracy, simplicity, and possible association of the chromatographic profiles with multivariate analyses. PLS regression models were obtained aiming at predicting the four physicochemical properties of the diesel fuel samples. From a maximum chromatographic analysis time of 108 min, regression models with unbiased predictions and good prediction capability for all properties were obtained, with average relative errors lower than 6%.

Malarial infection alters wax ester composition of preen oil in songbirds: Results of an experimental study

ABSTRACT Increased exposure to parasites and other pathogens is one of the principal costs of group living, and animals have evolved diverse behavioral adaptations to detect and avoid parasitized conspecifics. In mammals, it is well established that parasitic infection can affect host body odor and that individuals use this chemical information in mate choice and other social contexts. In birds, despite intense interest in condition-dependent sexually selected displays as indicators of health status, chemical signaling of infection status remains largely unexplored. However, compounds in feather preen oil are increasingly recognized as candidate substances that may mediate chemical signaling in birds. We inoculated Song Sparrows (Melospiza melodia) with hemosporidian parasites (Plasmodium sp.) to determine whether parasitic infection alters the chemical composition of preen oil. We used gas chromatography with flame ionization detection (GC-FID) to separate and quantify the wax esters in preen oil and com...

Gas‐phase rate coefficients for a series of alkyl cyclohexanes with OH radicals and Cl atoms

AbstractThe rate coefficients of the reactions of OH radicals and Cl atoms with three alkylcyclohexanes compounds, methylcyclohexane (MCH), trans‐1,4‐dimethylcyclohexane (DCH), and ethylcyclohexane (ECH) have been investigated at (293 ± 1) K and 1000 mbar of air using relative rate methods. A majority of the experiments were performed in the Highly Instrumented Reactor for Atmospheric Chemistry (HIRAC), a stainless steel chamber using in situ FTIR analysis and online gas chromatography with flame ionization detection (GC‐FID) detection to monitor the decay of the alkylcyclohexanes and the reference compounds. The studies were undertaken to provide kinetic data for calibrations of radical detection techniques in HIRAC. The following rate coefficients (in cm3 molecule−1 s−1) were obtained for Cl reactions: k(Cl+MCH) = (3.51 ± 0.37) × 10–10, k(Cl+DCH) = (3.63 ± 0.38) × 10−10, k(Cl+ECH) = (3.88 ± 0.41) × 10−10, and for the reactions with OH radicals: k(OH+MCH) = (9.5 ± 1.3) × 10–12, k(OH+DCH) = (12.1 ± 2.2) × 10−12, k(OH+ECH) = (11.8 ± 2.0) × 10−12. Errors are a combination of statistical errors in the relative rate ratio (2σ) and the error in the reference rate coefficient. Checks for possible systematic errors were made by the use of two reference compounds, two different measurement techniques, and also three different sources of OH were employed in this study: photolysis of CH3ONO with black lamps, photolysis of H2O2 at 254 nm, and nonphotolytic trans‐2‐butene ozonolysis. For DCH, some direct laser flash photolysis studies were also undertaken, producing results in good agreement with the relative rate measurements. Additionally, temperature‐dependent rate coefficient investigations were performed for the reaction of methylcyclohexane with the OH radical over the range 273‐343 K using the relative rate method; the resulting recommended Arrhenius expression is k(OH + MCH) = (1.85 ± 0.27) × 10–11 exp((–1.62 ± 0.16) kJ mol−1/RT) cm3 molecule−1 s−1. The kinetic data are discussed in terms of OH and Cl reactivity trends, and comparisons are made with the existing literature values and with rate coefficients from structure‐activity relationship methods. This is the first study on the rate coefficient determination of the reaction of ECH with OH radicals and chlorine atoms, respectively.

Aliphatic Hydrocarbon Fingerprints of Some Crude Oil Polluted Soils from Niger Delta, Nigeria

Crude oil-polluted soil samples were collected from five different oil polluted sites at Etche, Ahoada, Bodo, Ebocha and Bille in Niger Delta. The samples were analyzed using Gas chromatography with Flame ionization detector (GC-FID) for the Total Petroleum Hydrocarbon (TPH) to determine the different oil fractions and thus provide evidence of hydrocarbon contamination at the affected sites. The Pristane/Phytane ratios of the samples indicated that the released oil had both oxidizing and reducing source input. Similarly, the n-alkane distribution gave carbon preference index (CPI) values that pointed to both marine and terrestrial source input. The similarities in pattern from the star diagram also points to the marine and terrestrial source inputs to the oils. Depletions of nC21-nC23 hydrocarbon fractions and disappearance of nC8-nC21 fractions from gas chromatogram showed serious degradation on the sites.

Methane Synthesis from Automotive Paint Sludge via Microwave Assisted Pyrolysis

Methane gas, which has one atom of carbon and four atoms of hydrogen, is a valuable energy resource, which can be used in the energy sector. The purpose of this research work is to identify methane synthesis from Automotive Paint Sludge (APS) using microwave assisted pyrolysis. APS is known as a hazardous waste since it contains various chemicals that categorized as heavy metals and toxic substances. A modified conventional kitchen microwave was used to pyrolise the APS. The microwave was set with the power level of 600 W and 50 minutes radiation time. Through the experiment, pyrogas was collected into tedlar bag and was analysed using Gas Chromatography with Flame Ionization Detector (GC-FID). Results from the GC-FID were shown that the retention time of 3.3583, 3.2733, and 3.2267 min are proved to be methane gas. The results obtained are resembled with the results from the literature. This indicates methane gas was presented in the pyrogas of pyrolysis of APS and there is a possibility of producing methane gas. The research study suggests that it is possible to synthesize methane gas from the APS via microwave assisted pyrolysis, and in the meantime reduce the volume of APS in the landfill.

1,3-Butadiene. Determination in workplace air

1,3-Butadiene is a colorless gas with a mild, aromatic odor. It is produced worldwide on a large industrial scale. The aim of this study was to develop and validate a method for determining concentrations of 1,3-butadiene in workplace air. The determination method is based on the adsorption of 1,3-butadiene on activated charcoal (200/50 mg sections), desorption with carbon disulfide and the analysis of the resulting solution with gas chromatography with flame ionization detection (GC-FID). A capillary column Rtx-5ms (60 m × 0.32 mm, i.d. × 0.25 μm film thickness) was used. The method is linear within the working range from 0.98 µg/ml to 19.6 µg/ml, which is equivalent to air concentrations from 0.22 to 4.36 mg/m3 for a 4.5-L air sample. The analytical method described in this paper enables selective determination of analytes in workplace air in presence of coexisting substances. The method is precise, accurate and it meets the criteria for procedures for measuring chemical agents listed in Standard No. EN 482. The method can be used for assessing occupational exposure to 1,3-butadiene and associated risk to workers’ health. The developed method of determining 1,3-butadiene has been recorded as an analytical procedure (see appendix).

Hydrodechlorination of chlorophenols over Pd catalysts supported on zeolite Y, MCM-41 and graphene

Hydrodechlorination (HDC) reaction of chlorophenols was carried out using Pd catalysts supported over zeolite Y, MCM-41 or graphene. Pd-MCM-41 and Pd-Y zeolite were prepared by impregnation and ion-exchange method, respectively. Pd-graphene (Pd-G) was prepared by hydrazine hydrate reduction of palladium ion dispersed on graphene oxide. The catalysts were characterized by several analytical tools such as X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS). These catalysts were subjected to HDC reaction of chlorophenols, such as 4-chlorophenol (4-CP), 2,4-dichlorophenol (2,4-DCP), 2,6-dichlorophenol (2,6-DCP) and 3,4-dichlorophenol (3,4-DCP). The reaction rate of HDC of chlorophenols catalyzed by Pd catalysts with various solid bases, such as KF/Al2O3 (alumina), sodium acetate (NaOAc) and K2CO3 was compared. First, Pd-MCM-41 and Pd-Y catalysts were compared. 2,4- and 3,4-DCPs were completely decomposed within 6 h, in the case of Pd-MCM-41 with NaOAc. Using Pd-Y instead of Pd-MCM-41 with NaOAc, much faster decomposition was observed. Faster decomposition of 4-CP and DCPs was observed with NaOAc base than K2CO3 or KF/Al2O3 under the same condition. In the case of Pd-Y with KF/Al2O3, slower decomposition of 4-CP and DCPs was observed. These base effects were interpreted using the solubility of NaCl and KCl in alcohol and the basic sites of KF/Al2O3. Because the solubility of NaCl is known to be larger than KCl solubility in alcohol, byproduct NaCl could be easily dissolved and ionized in solvents. For Pd-Y with KF/Al2O3, the small pore size of Y zeolite can interfere with the diffusion of HCl to KF/Al2O3 basic site. Second, three catalysts, including Pd-graphene, were compared. 2,4-DCP was decomposed within 2 h using Pd-G with either K2CO3, NaOAc or KF/Al2O3. Pd-G catalyst showed the highest catalytic activity among Pd-G, Pd-MCM-41 and Pd-Y catalysts. The high activity and stability of the Pd-G could be attributed to the strong metal–support interaction with an electron-deficient site and a critical Pd particle size (ca. 3.5 nm) of Pd-G nanocatalyst with a stronger resistance to the deactivation and good affinity toward aromatic organic molecules, especially phenols. The progress of HDC reaction was monitored by gas chromatography with flame ionization detection (GC/FID), and a feasible degradation process could be explained by analyzing the degradation products such as phenol, cyclohexanone and cyclohexanol from resulting GC chromatograms. The effect of reaction temperature on HDC in Pd-G catalyst was also discussed. In conclusion, Pd-G is an efficient catalyst for decomposition of chlorophenols and can be applied to remediation of chlorophenol-contaminated water under mild conditions.