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The mechanism of reaction in isobutane/2-butene alkylation systems is extremely complicated, accompanied by numerous side reactions. Therefore, a comprehensive understanding of the reaction pathways in this system is essential for an in-depth discussion of the reaction mechanism and for improving the selectivity of the major products (clean fuel blend components). The alkylation of isobutane/2-butene was studied using a self-made intermittent reaction device with a metering, cooling, reaction, vacuum and analysis system. The alkylates were qualitatively and quantitatively analyzed using a capillary gas chromatography-mass spectrometry-data system (CGC-MS-DS) and capillary gas chromatography with flame ionization detection (CCGC-FID), respectively, and the precision and recovery of the quantitative analytical methods were verified. The results showed that the relative standard deviation (RSD) of the standard sample was below 0.78%, and the recoveries were from 98.53% to 102.85%. Under the specified reaction conditions, 79 volatile substances were identified from the alkylates, and the selectivity of C8 and trimethylpentanes (TMPs) reached 63.63% and 53.81%, respectively. The changes of the main chemical components in the alkylation reaction with time were tracked and analyzed, based on which reaction pathways were determined, and a complex reaction network containing the main products’ and the by-products’ generation pathway was constructed.

Analysis was done of the statistical results obtained by following recommended AOCS Collaborative Study Procedure M-86 to evaluate the performance of Official Method AOCS Ce 1i-07, which provides a gas-liquid chromatography (GLC) procedure for the determination of the fatty acid composition of oils containing long chain polyunsaturated fatty acids (PUFAs). The method obtains relative between-lab reproducibility (%RSDR) values on the order of 5% or less for most fatty acids that are present above ~0.5% w/w; however, the reproducibility worsens dramatically for analytes below this threshold. Apparently, several participating labs had problems identifying small peaks in the sample chromatograms. They also had problems correctly identifying certain larger peaks that occurred in a congested area of the sample chromatograms, including the 9c-16:1, 9c-11c-22:1, and 6c,9c,12c,15c-16:4 fatty acids. Finally, several analytes with chain lengths between 16 and 18 and between 21 and 22 carbons that were present at moderate concentrations had worse than expected reproducibilities due to severe overlap of these analytes' peaks. A detailed inspection of the contributed data shows that the relatively poor between-lab reproducibility for analytes in this region is due to differences in the labs' chromatographic efficiencies and perhaps in their methods of quantifying highly overlapped peaks.

Background and Aims In the global distribution of persistent organic pollutants (POPs) forests play a key role due to the forest canopy effect. In this study, mountain beech forests were selected to identify the level and distribution of selected POPs. Methods Organochlorine pesticides (OCPs) and polybrominated diphenyl ethers (PBDEs) were analyzed by capillary gas chromatography with an electron capture detector (GC–ECD). Analysis of polychlorinated biphenyls (PCBs) was performed by gas chromatography with a mass spectrometry detector (GC–MS). The polycyclic aromatic hydrocarbons (PAHs) were analyzed by liquid chromatography with a diode array detector (HPLC–DAD). Results The total ∑ 20 OCP concentrations in the soil from mountain beech forests at a depth of 0 – 40 cm ranged from 24.46 µg kg −1 to 331.11 µg kg −1 , and at a depth of 40 – 80 cm from 15.80 µg kg −1 to 247.12 µg kg −1 . The mass concentration for ∑ 6 PCB ranges from 9.21 to 95.28 µg kg −1 in the surface soil layer and from 8.07 to 66.56 µg kg −1 in the soil sublayer. The total concentration of ∑ 7 PBDE congeners measured in soil samples from mountain beech forests across Europe was from 1.38 to 29.68 µg kg −1 in the surface soil layer and from 1.01 to 53.31 µg kg −1 in the soil sublayer. The total concentration of ∑ 16 PAH varied from 271.52 to 1154.52 µg kg −1 in the surface soil layer and from 318.95 to 1052.54 µg kg −1 in the soil sublayer. Conclusion The results of this study can serve as an important basis for international, national, and regional measures of environmental protection of beech forests from POPs pollution.

An approach using pyrolysis with comprehensive two-dimensional gas chromatography with flame ionization detection is introduced for identifying common isolated plastic polymers. A quadrupole mass spectrometer is employed as a parallel detector to aid method development and improve polymer identification in complex matrices. Common plastic polymers including polyethylene , polypropylene , polystyrene , polyvinyl chloride , polyamide , poly(methyl methacrylate) , styrene-butadiene rubber , and polyethylene terephthalate are accurately identified within a total analysis time of 45 min. A strategy to enhance compatibility of high-resolution capillary gas chromatography using a 150-µm internal diameter column technology and a larger internal volume microfurnace–based pyrolyzer is discussed. This strategy resulted in minimizing the band broadening effect caused by the pyrolyzer’s internal volume and overcoming the slow pressure buildup when the sample is inserted into the furnace. Prolonged pressure buildup to reach a final pressure setting can cause a safety shutdown to the pneumatic control system. The developed approach is complementary to spectroscopic techniques by offering mass based, chemical composition analysis of plastics.

The level of D-arabinitol (DA) and the ratio of D-/L-arabinitol (DA/LA) in the urine of children with autism were investigated. The changes in DA/LA after probiotic treatment in urine samples of children with autism were studied. DA and LA and the DA/LA ratio were identified by capillary gas chromatography/mass spectrometry in urine before and after the probiotic therapy. The level of DA is significantly higher (P < 0.05) in the urine of autistic children before (A) and after probiotic supplementation (A1) (160.04 ± 22.88 μmol/mmol creatinine and 89.53 ± 37.41 μmol/mmol creatinine, respectively). Nonetheless, the probiotic supplementation let to a significant decrease in DA and DA/LA and to a significant improvement in ability of concentration and carrying out orders. The use of probiotics seems to be helpful in reducing the level of DA and the ratio of DA/LA in the urine of children with autism.

Processing of fish in aquaculture generates considerable amounts of by-products that remain underused and/or unexploited. We evaluated the nutritive content of fish by-products (head, gills, intestines, trimmings, bones, and skin) from meagre and gilthead sea bream fish species reared in Greece in order to estimate their nutritional value for future development of high added-value products. The proximate composition of the fish samples (total protein, total lipid, ash, moisture, and macro-element content) was determined using the Association of Official Analytical Chemists (AOAC) and International Organization for Standardization (ISO) official methods. The content of fatty acids was determined using capillary gas chromatography, and the protein profile was estimated employing scientific orbitrap mass spectrophotometer methodology. The nutrient composition of fish by-products presented fluctuations among the different by-products. Skin was the most significant protein source, trimmings and bones were high in calcium, and the head, intestines, and bones were a good source of lipids. The most abundant lipid acids found in by-products were oleic, palmitic, linoleic, and eicosenoic acids, whereas the most abundant proteins were adenosine triphosphate (ATP) synthase subunit epsilon, mitochondrial nicotinamide adenine dinucleotide (NADH) dehydrogenase, and mitochondrial cytochrome b-c1 complex subunit 8. These data suggest that by-products constitute valuable sources of nutrients and could therefore be exploited in accordance with the principles of a circular economy.

Objective In this study, we aimed to develop a headspace capillary gas chromatography method to quantify residual methanol, acetone, methylene chloride, diisopropyl ether, ethyl acetate, and n,n-dimethylformamide (DMF), in raw clobetasol propionate. Methods The headspace gas chromatography method employs a chromatographic column packed with 6% cyanopropylphenyl-94% dimethylpolysiloxane as the stationary phase. The column temperature program initiated at 40 °C, was held for 10 min, then ramped up at 10 °C per minute to 220 °C, and maintained for 1 min. Nitrogen served as the carrier gas at a flow rate of 4.84 ml/min. The injection port temperature was set at 140 °C; the flame ionization detector (FID) operated at 250 °C, and the headspace equilibrium temperature was maintained at 105 °C with a 30 min equilibration time. Results All six residual solvents exhibited complete separation, displaying strong linearity and achieving high recovery rates. Furthermore, the residual solvent levels in the six samples tested remained comfortably below the permissible limit. Conclusion Our method is accurate, reliable, rapid, and sensitive, making it well-suited for the detection of organic residual solvents in raw clobetasol propionate. Graphical Abstract

This work presents the first example of utilization of amphiphilic block copolymer PCL-PEG-PCL as a stationary phase for capillary gas chromatographic (GC) separations. The PCL-PEG-PCL capillary column fabricated by static coating provides a high column efficiency of 3951 plates/m for n-dodecane at 120 °C. McReynolds constants and Abraham system constants were also determined in order to evaluate the polarity and possible molecular interactions of the PCL-PEG-PCL stationary phase. Its selectivity and resolving capability were investigated by using a complex mixture covering analytes of diverse types and positional, structural, and cis-/trans-isomers. Impressively, it exhibits high resolution performance for aliphatic and aromatic isomers with diverse polarity, including those critical isomers such as butanol, dichlorobenzene, dimethylnaphthalene, xylenol, dichlorobenzaldehyde, and toluidine. Moreover, it was applied for the determination of isomer impurities in real samples, suggesting its potential for practical use. The superior separation performance demonstrates the potential of PCL-PEG-PCL and related block copolymers as stationary phases in GC and other separation technologies.

•Maternal dietary patterns could be classified by using a principal component analysis.•Energy, carbohydrate, and protein intake exhibited differences among dietary patterns.•The proportions of saturated, polyunsaturated, and n-6 polyunsaturated fatty acids in breast milk varied among the patterns. [Display omitted] Fatty acids (FA) in human milk play an important role in meeting the nutritional demands and promoting the growth and development of breastfeeding infants. Breast milk FA is sensitive to maternal dietary habits, and dietary patterns are better used to explain the effect of diet on FA. Few studies have examined the association between maternal dietary patterns and the FA components of breast milk in developing countries. In this study, we aimed to determine whether dietary patterns affect the FA profile of breast milk in lactating Chinese mothers with the overall goal to optimize the management of infant feeding. A total of 274 lactating women ranging from 22 d to 6 mo postpartum were included, and samples of their breast milk were collected together with completed questionnaires. Using a principal component analysis, four dietary patterns were identified in a rotated component matrix. FA profiles were detected using capillary gas chromatography and presented as the percentage by weight of total FA. Maternal intake of energy, carbohydrates, and proteins showed differences between the different dietary patterns. In addition, there were significant differences in the total proportions of saturated, polyunsaturated, and ω-6 polyunsaturated fatty acids in breast milk among the four patterns (P < 0.001; P = 0.025; P = 0.038, respectively). The results demonstrate that maternal dietary patterns can affect macronutrient intake levels and milk FA profiles in lactating Chinese women. These results are of great significance in understanding how a maternal diet can both improve maternal macronutrient intake and the FA nutritional status of breast milk.

The occurrence of pollutants in environment displays its maximum impact on human health and on the global “quality” of life in the places where humans spend most of their time, i.e., indoors. A field study was undertaken in the region of Touggourt, Algeria. The goal was that of obtaining information on the main sources of indoor pollutant emissions (n-alkanes and polycyclic aromatic compounds) associated with deposition dusts (DDs) and suspended particulates (PM10). A multi-service clinic, two schools, a coffee bar, three houses, and an asphalt distribution center were investigated. Forty-five samples in total were collected, including 31 deposition dusts and 14 airborne particulates. That would improve the current understanding of pollution features in central Algeria reached through previous investigations in the Touggourt region. Capillary gas chromatography coupled with mass spectrometric detection was adopted to determine the concentrations of n-alkanes and PAHs. In deposition dust, total n-alkanes (TNAs) ranged between 37 and 794 ng/(m2 day) in the summer and 33–1,724 ng/(m2 day) in the fall. Meanwhile, TNAs loads in the PM10 samples ranged between 778 and 2,024 ng/m3. According to Carbon Preference Index (CPI), Cmax, and wax n-alkanes (WaxCn) approaches, both DD and PM10 were released overall by anthropogenic sources, though the contribution of natural emissions could not be neglected. Total polycyclic aromatic hydrocarbons (TPAHs) associated with DD ranged from 4.4 ng/(m2 day) to 127 ng/(m2 day) during the summer period, and 2.0–224 ng/(m2 day) in the fall; TPAHs’ concentrations in PM10 ranged between 40 ng/m3 and 984 ng/m3. Preliminary information about the sources of PAHs was drawn by calculating the concentration ratios between diagnostic pairs (DRs) of PAHs. According to PAH DR values, the pollution sources influenced at distinct extents all of the sites and locations investigated. Anyway, the PAH occurrence was associated with petrogenic sources, with the prevalence of gasoline fuel cars, at most sites. A wide variability was also observed by comparing the concentrations of pollutants observed in the summer and in the fall. This was in agreement with the results of n-alkanes emissions.