Gas Chromatography Research Articles

Chiral porous organic cage used as stationary phase for gas chromatographic separation of chiral and achiral compounds

Porous organic cages (POCs) are a new type of molecular material. The well-defined cavities, abundant host-guest recognition ability, and good solubility of POCs render them attractive for use in various fields such as molecular recognition, gas adsorption, molecular containers, sensing, catalysis, chromatographic separation. In this study, a chiral POC (CPOC) was synthesized via the Schiff base condensation of 4,4',4″,4″'-(ethene-1,1,2,2-tetrayl)tetrabenzaldehyde with (R,R)-1,2-cyclohexanediamine. CPOC was characterized using nuclear magnetic resonance (NMR) spectroscopy, Fourier transform-infrared (FT-IR) spectroscopy, mass spectroscopy (MS), and thermogravimetric analysis (TGA). The FT-IR spectrum of CPOC showed a strong peak at 1638 cm-1, which was attributed to imine (-C=N-) absorption, as well as absorption peaks at 2928 and 2856 cm-1, which were attributed to the stretching vibrations of -CH2- and -CH-, respectively. MS analysis of CPOC revealed peaks at m/z=1801.9797, m/z=901.9914, and m/z=601.6631, corresponding to [M+H]+, [M+2H]2+, and [M+3H]3+, respectively, and indicating a molecular formula of CPOC (C126H120N12). The TGA curve of CPOC indicated high thermal stability up to 360 ℃; thus, the material is suitable for use as a stationary phase for gas chromatography (GC). CPOC was coated on the inner wall of a capillary column using the static coating method to prepare a GC column. Scanning electron microscopy (SEM) was used to characterize the coating condition of the fabricated column. The SEM images showed that the column had a uniform coating with a thickness of approximately 200 nm. Column efficiency was determined to be 3500 plates/m using n-dodecane as a target at 120 ℃. The polarity of the CPOC stationary phase was evaluated using McReynolds constants, which were measured using benzene, 1-nitropropane, 2-pentanone, pyridine, and 1-butanol as probe molecules at 120 ℃. The average McReynolds constant was 152, indicating that CPOC is a moderately polar stationary phase. The ability of the column to separate organic mixtures, isomers, and chiral compounds was subsequently investigated. All components of the four organic mixtures (n-alkanes, aromatics, n-alcohols, and Grob mixtures) tested achieved baseline separation on the column. In addition, nine positional isomers of disubstituted benzenes were well separated, and seven (o,m,p-nitrotoluene, o,m,p-nitrochlorobenzene, o,m,p-nitrobromobenzene, o,m,p-bromotoluene, o,m,p-dichlorobenzene, o,m,p-chloroaniline, and o,m,p-bromoaniline) achieved baseline separation. Some polar and apolar structural isomers, such as pentanol, dimethylphenol, dimethylaniline, butanol, and C9 aromatic hydrocarbon isomers, were also well separated on the column. Five cis/trans-isomers (nerol/geraniol, cis/trans-1,3-dichloropropene, cis/trans-1,2,3-trichloropropene, cis/trans-citral, and cis/trans-decahydronaphthalene) were baseline-separated on the column. More importantly, the column successfully separated 12 chiral compounds, indicating good chiral separation ability. Among these chiral compounds, five (ethyl 3-hydroxybutyrate, a valine derivative, a glutamic acid derivative, 1,2-butanediol diacetate, and 1,2-epoxybutane) achieved baseline separation. Six of these chiral compounds (ethyl 3-hydroxybutyrate, the valine derivative, the glutamic acid derivative, 1,2-epoxybutane, epichlorohydrin, and epibromohydrin) could not be separated on a β-DEX 120 column but were well separated on the developed column. Moreover, the separation efficiency of 1,2-butanediol diacetate and the isoleucine derivative on this column was better than that on the β-DEX 120 column. Separation of the glutamic acid derivative and o,m,p-nitrotoluene was performed before and after the column was used for repeated injections to explore its repeatability. The retention times and selectivity observed after 80, 160, and 500 injections were nearly unchanged compared with those obtained following the first use of the column, indicating that the column has good repeatability. The column was conditioned at 280 ℃ for a certain period to examine its thermal stability. Separation of 3-hydroxybutyrate and o,m,p-nitrochlorobenzene after the column was conditioned at 280 ℃ for 2, 4, or 8 h revealed no obvious changes compared with the first use of the column, indicating that the column had good thermal stability. Thus, CPOC is a stationary phase with good application potential for GC.

Comparative Nutritional Analysis of Zest and Pulp in Red and Yellow Grapefruit Varieties

The global cultivation and considerable demand for citrus fruits has given them a prominent place among fruit crops. With them being known for their virtues, health benefits, and characteristic aroma and taste, grapefruits have been accepted as an important food in our diets. Indeed, they play a key role in providing the nutrients to support good health. In this context, we sought to identify the nutritional characteristics of two varieties of grapefruit (citrus paradisi), namely yellow and red. We therefore investigated the water, protein, fiber, total sugar, and fat contents in the zest and pulp of these two species based on international food standards. We also quantified the various saturated and unsaturated fatty acids through gas chromatography. Our results revealed an interesting richness in these grapefruit varieties in terms of factors like total sugar, proteins, and fat, particularly in the peel, as well as a high-water content and energy value. Several fatty acids were also identified, mainly palmitic, oleic, and linoleic acids, which are highly sought after for their therapeutic benefits. This nutrient density highlights the value of these fruits and demonstrates that promoting its consumption can help improve human health and quality of life. This assortment of nutrients found in our samples, as well as the abundance of phenolic compounds already noted in other research studies, highlight this fruit and show the importance of its various parts - peel and pulp - in improving quality of life and human mental and physical health.

Two different rims functionalized pillar[5]arene stationary phase for capillary gas chromatography

Herein, we synthesized and used a novel pillar[5]arene with two functionalizable rims (AP5A-C10-OAc) as stationary phase in gas chromatography (GC). The AP5A-C10-OAc column (0.25 mm, i.d.) showed a high column efficiency of 4107 plates/m and medium polarity. The AP5A-C10-OAc stationary phase possesses unique amphiphilic structure, including a π-electron rich cavity and two functionalized arms composed of five nonpolar alkyl chains and five polar ester chains, and showed good separation performance for diverse types of analytes and isomers (apolar/polar, aliphatic/aromatic). Particularly, the AP5A-C10-OAc phase showed high selectivity for the challenging isomers of chloronitrobenzenes, bromonitrobenzenes, benzenediols, and iodoanilines with distinct advantages if compared with the commercial polysiloxane column.

From detection methods to risk prevention: Control of N-nitrosamines in foods and the role of natural bioactive compounds.

Food processing unavoidably introduces various risky ingredients that threaten food safety. N-Nitrosamines (NAs) constitute a class of food contaminants, which are considered carcinogenic to humans. According to the compiled information, pretreatment methods based on solid-phase extraction (SPE) were widely used before the determination of volatile NAs in foods. The innovation of adsorbents and hybridization of other methods have been confirmed as the future trends of SPE-based pretreatment methods. Moreover, technologies based on liquid chromatography and gas chromatography were popularly applied for the detection of NAs. Recently, sensor-based methods have garnered increasing attention due to their efficiency and flexibility. More portable sensor-based technologies are recommended for on-site monitoring of NAs in the future. The application of artificial intelligence can facilitate data processing during high-throughput detection of NAs. Natural bioactive compounds have been confirmed to be effective in mitigating NAs in foods through antioxidation, scavenging precursors, and regulating microbial activities. Meanwhile, they exhibit strong protective activities against hepatic damage, pancreatic cancer, and other NA injuries. Further supplementation of data on the bioavailability of bioactives can be achieved through encapsulation and clinical trials. The utilization of bioinformatics tools rooted in various omics technologies is suggested for investigating novel mechanisms and finally broadening their applications in targeted therapies.

Neopetasan, the main component of the essential oil from Cyperus sesquiflorus (Cyperaceae)

ABSTRACT Cyperus sesquiflorus is commonly called fragrant kyllinga, fragrant spikesedge, or fragrant flatsedge. It is a cespitose perennial herb with a Pantropical distribution. In Brazil, it is a native species, being commonly named fragrant grass due to its aromatic content. In this study, the essential oil (EO) of C. sesquiflorus was extracted by hydrodistillation with a Clevenger apparatus. Yields of the samples ranged between 0.12% and 0.27% (v/w) oils from fresh and dehydrated whole flowering plants (with roots) and the oil was analyzed by Gas Chromatography/-Mass spectrometry/flame ionization detection (GC-MS/FID) and Gas chromatography/Mass spectroscopy (GC/MS). The main constituent of the oil, neopetasan (3S,4aR,5S)-4a,5-dimethyl-3-(prop-1-en-2-yl)-4,4a,5,6,7,8 hexahydronaphthalen-2(3 H)-one, was isolated by preparative thin layer chromatography (PTLC) and its structure was elucidated by extensive one- and two-dimensional nuclear magnetic resonance (1D/2D-NMR) (COSY, HSQC, HMBC, and NOESY) and Fourier transform infrared (FTIR) spectroscopy in combination with MS and comparison with literature data.

A headspace injection double-column dual-detector gas chromatography system for the analysis of 12 volatile compounds such as ethanol in human blood

Based on the technical methods of GB/T 42430-2023 and GA/T 204-2019, this study established an analytical method for headspace injection double-column dual-detector (hydrogen flame ion detector) gas chromatography for the simultaneous analysis of at least 12 volatile compounds, including ethanol, in human blood using two different equipment platforms and chromatographic columns. A 100 μL blood or urine sample and a 0.04 g/L tert-butanol working solution prepared as an internal standard are introduced into the headspace sample bottle and then sealed, mixed, and placed on the headspace sampler rack. Using different equipment platforms and columns, methodological parameters such as the limit of detection (LOD), limit of quantification (LOQ), precision, and accuracy of the method were systematically evaluated. The chromatographic separation of acetone, alcohols and benzenes using the established method was satisfactory. The linear ranges, linear correlation coefficients (r), and LODs of acetone and six alcohols, including ethanol, were 0.10-3.00 g/L, >0.997, and 0.05 g/L, respectively. The LOQs were 0.10 g/L for all other compounds, excluding n-propanol (0.005 g/L). Additionally, the linear ranges, r values, LODs, and LOQs of benzene and four benzene derivatives were 0.05-50 mg/L, >0.995, 0.02 mg/L, and 0.05 mg/L, respectively (Column J&W DB-BAC1 UI and Column Rtx-BAC-PLUS 2). The average recoveries of compounds on J&W DB-BAC1 UI and Rtx-BAC-PLUS 2 columns ranged from 92.2% to 111.6%, and the relative standard deviations (RSDs, n=6) ranged from 0.4% to 7.4%. The LOD, LOQ, precision, accuracy, and linearity of the established method met the requirements of relevant standards, and no significant differences arose between the methodological parameters of the two platforms. CNAS-GL006 (2019) and JJF 1059.1-2012 were used as guides to evaluate the uncertainty of ethanol on two different sets of equipment platforms and chromatographic columns. The ethanol uncertainty was mainly derived from the calibration curve; however, the confidence probability was 95% (k=2). According to the analysis of the verification samples and real samples, the established method is suitable for the high-precision quantitative analysis of acetone and six alcohols and five benzene derivatives in human blood and other body fluids. It can be used in practical scenarios such as judicial identification and the detection of poisons.

Pesticides and winemaking: A comprehensive review of conventional and emerging approaches.

The use of pesticides in viticulture may play a crucial role in ensuring the health and quality of grapes. This review analyzes the most common pesticides used, illustrating their classification and toxicity, and their variations throughout the winemaking process. Fungicides are generally harmless or mildly toxic, whereas insecticides are classified as either highly or moderately hazardous. Potential alternatives to synthetic pesticides in wine production are also reviewed, thereby including biopesticides and biological agents. Analytical methods for detecting and quantifying pesticide residues in wine are then described, including liquid chromatography and gas chromatography coupled with mass spectrometry. This review also discusses the impact of the winemaking process on pesticide content. Pesticides with strong hydrophobicity were more likely to accumulate in solid byproducts, whereas hydrophilic pesticides were distributed more in the liquid phase. Grape's skin contains lipids, so hydrophobic pesticides adsorb strongly on grape surfaces and the clarification has been shown to be effective in the reduction of hydrophobic compounds. Therefore, the final wine could have more quantities of hydrophilic pesticides. Alcoholic fermentation has been shown to be crucial in pesticide dissipation. However, pesticide residues in wine have been shown an antagonistic effect on yeasts, affecting the safety and quality of wine products. Therefore, proteomic and genomic analyses of yeast growth are reviewed to understand the effects of pesticides on yeast during fermentation. The last section describes new effective methods used in removing pesticides from grapes and wine, thereby improving product quality and reducing harmful effects.

Study on the changes and transformation characteristics of intermediate liquid products in hydrogen sulfide production from lignite degraded by sulfate-reducing bacteria.

The changes and transformation laws of intermediate liquid-phase products during the anaerobic degradation of lignite by sulfate-reducing bacteria in the formation of hydrogen sulfide play an important role in supplementing and improving the existing theories on the genesis of hydrogen sulfide gas in coal mines. In this paper, H2S gas and key intermediate liquid-phase products produced during the anaerobic degradation of lignite by sulfate-reducing bacteria were detected and analyzed by gas chromatography and gas chromatography-mass spectrometry. The results showed that the process of hydrogen sulfide production from lignite degradation by sulfate-reducing bacteria can be roughly divided into four stages: slow production phase, rapid growth phase, steady production phase, and slight decline phase. In this reaction system, the SO42- concentration showed a decreasing trend, the pH value showed an increasing trend, and the ORP value decreased and then slightly increased with time. Ten volatile component types were detected during the experiment: straight-chain alkanes, branched-chain alkanes, alcohols, aldehydes, ketones, olefins, amines, lipids, acids and phenols. The key components in the intermediate liquid phase products were straight chain alkanes, straight chain alkanes, acids, alcohols, phenols and amines. PAHs, alkanes, and phenols are closely related to H2S production, while amides stimulate nitrogen production. The process is divided into three stages: hydrolysis stage, H2S gas production stage, and decay stage. Liquid-phase intermediates play an important role in the formation process of coal mine BSR hydrogen sulfide and the mechanism of coal mine H2S genesis.

Postmortem Fatty Acid Abnormalities in the Cerebellum of Patients with Essential Tremor.

Fatty acids play many critical roles in brain function but have not been investigated in essential tremor (ET), a frequent movement disorder suspected to involve cerebellar dysfunction. Here, we report a postmortem comparative analysis of fatty acid profiles by gas chromatography in the cerebellar cortex from ET patients (n = 15), Parkinson's disease (PD) patients (n = 15) and Controls (n = 17). Phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidylinositol (PI)/ phosphatidylserine (PS) were separated by thin-layer chromatography and analyzed separately. First, the total amounts of fatty acids retrieved from the cerebellar cortex were lower in ET patients compared with PD patients, including monounsaturated (MUFA) and polyunsaturated fatty acids (PUFA). The diagnosis of ET was associated with lower cerebellar levels of saturated fatty acids (SFA) and PUFA (DHA and ARA) in the PE fraction specifically, but with a higher relative content of dihomo-γ-linolenic acid (DGLA; 20:3 ω-6) in the PC fraction. In contrast, a diagnosis of PD was associated with higher absolute concentrations of SFA, MUFA and ω-6 PUFA in the PI + PS fractions. However, relative PI + PS contents of ω-6 PUFA were lower in both PD and ET patients. Finally, linear regression analyses showed that the ω-3:ω-6 PUFA ratio was positively associated with age of death, but inversely associated with insoluble α-synuclein. Although it remains unclear how these FA changes in the cerebellum are implicated in ET or PD pathophysiology, they may be related to an ongoing neurodegenerative process or to dietary intake differences. The present findings provide a window of opportunity for lipid-based therapeutic nutritional intervention.

Life Cycle Assessment of Natural Gas Production in Java Sea-East Java Province, Indonesia

Energy products including natural gas play a very important role in the context of global economic, industrial, and infrastructure development. However, it is undeniable that the production process from raw material extraction to ready-to-use products has an impact on the environment. This study was conducted to evaluate the environmental impact of natural gas production in the Kepodang field, East Java Province, Indonesia. The next objective is to analyze the magnitude and significance of the impact or hotspot analysis. The characterization results for 4 main categories show: Global Warming Potential 70.02 kg CO₂ eq, Ozone Layer Depletion 1.11E-06 kg CFC-11 eq, Acidification Potential 0.65 mol H+ eq, Marine Eutrophication 0.30 kg N eq, and Freshwater Eutrophication 2.17E-03kg P eq. The results also show that throughout the life cycle of this product, the largest contributor to environmental impacts is in the downstream phase, especially the user gas metering unit process. This is due to the 200 km of pipelines for product transportation from the Central Processing Platform (CPP) to the user gate. Pipeline parameters (Ecoinvent database) refer to long-distance pipelines with high capacity. In addition, hotspots were also identified in the core phase: gas measurement and chromatography, gas turbine generators, and flare gas.

Metabolite profiling highlights the effect of microbial intervention in the soaking step of tempe

SummarySoaking of soybeans is an essential step in tempe fermentation. Owing to the uncontrolled microflora, spontaneous soaking during tempe production leads to inconsistencies in tempe quality. Common methods to control it include the addition of acids or microbial starters. Despite knowing the benefits, their impact on tempe's composition was less understood. In this study, prior to tempe fungal fermentation, soybeans were soaked with Lactiplantibacillus plantarum NBRC 101978 and Pichia burtonii NBRC 0844. Tempe samples were subjected to comprehensive analysis using a widely targeted gas chromatography–mass spectrometry (GC–MS) metabolomics approach and evaluation of physical characteristics. A total of 100 metabolites of sugars, amino acids, fatty acids, and organic acids were annotated in all samples. Principal component analysis (PCA) explaining 47.6% of the variance showed that microbial interventions led to alterations in the metabolome of all samples, including the accumulation of amino acids in lactic acid bacteria (LAB)‐soaked soybean tempe and tyramine in yeast‐soaked soybean tempe. Unlike chemically added soaked soybean tempe, microbial intervention significantly reduced the relative intensity levels of several sugars by more than twofold. Furthermore, microbial interventions in the tempe‐soaking step significantly elevated the levels of bioactive metabolites more than twofold. The introduction of microbial interventions in the tempe‐soaking step also influences the physical characteristics of the end product. These findings merit further consideration for tempe development and the food industry.

Rice sheath blight disease control by native endophytic Bacillus subtilis from Kuttanad, a Globally Important Agricultural Heritage System

ABSTRACT Kuttanad in India is known as ‘the rice bowl of Kerala’ and renowned for its unique rice cultivation system that is below sea level. However, rice production in this wetland ecosystem is seriously threatened by sheath blight disease caused by the fungus Rhizoctonia solani, which has resulted in a significant decline in grain quality and a 50% loss in yield. In the present study, we isolated two endophytic Bacillus subtilis strains, NIIST B616 and NIIST B627, from the roots of rice plants growing in the Kuttanad region and tested their efficacy in controlling sheath blight disease. We found that rice plants inoculated with a combination of both Bacillus strains and R. solani had a 64.71% lower disease incidence and a 31.02% higher harvest index than plants treated with R. solani alone. An analysis of defence-related enzymes and chemicals revealed that treatment with both isolates together greatly enhanced levels of l-phenylalanine ammonia-lyase (PAL; 2.8 fold), peroxidase (POX; 7.4 fold), polyphenol oxidase (PPO; 4.5 fold), and total phenol (8.5 fold) compared with plants treated solely with R. solani, indicating that these isolates significantly increased plant defence responses through induced systemic resistance (ISR), and this finding was validated through a split-root experiment. More detailed analysis using gas chromatography–tandem mass spectrometry (GC-MS/MS) and liquid chromatography–tandem mass spectrometry (LC-MS/MS) techniques revealed that cyclo-(Pro-Leu) and cyclo-(Pro-Phe) were the major components responsible for the antifungal properties of the two isolates and their capacity to trigger ISR in plants. Thus, the Bacillus strains and their metabolites may be deemed viable alternatives for controlling the prevalence of sheath blight disease in rice plants and augmenting rice production at unique locations such as Kuttanad.

Association between brominated flame retardants (BFRs) and periodontitis: Results from a large population-based study.

Brominated flame retardants (BFRs) are widely utilized to mitigate the flammability of various materials. Previous studies have revealed the impact of BFRs exposure on hormonal disruption and bone metabolism which are closely related to periodontitis. However, it remains unknown the potential relationship between BFRs and periodontitis. This study aimed to explore the association between BFRs exposure and periodontitis in US adults. The data analyzed in this study were obtained from the National Health and Nutrition Examination Survey (NHANES) 2009-2014. Twelve serum BFRs were quantified using isotope dilution gas chromatography high-resolution mass spectrometry. Univariable and multivariable logistic regression was employed to evaluate the association between serum BFRs and periodontitis. Bayesian kernel machine regression (BKMR) analyses were utilized to assess the association between mixtures of BFRs and periodontitis. A total of 3311 eligible participants were included. Serum BFRs (PBDE-47, PBDE-99, and PBDE-154) were significantly associated with periodontitis, and the odds ratios (ORs) and corresponding 95% confidence intervals(CIs) were 1.15(1.01,1.29), 1.10(1.01,1.20), and 1.12(1.01,1.25), respectively. Notably, these three BFRs were also significantly associated with the severity of periodontitis. Additionally, the BKMR model revealed a significant association between the mixture of all twelve BFRs and periodontitis. This preliminary study suggests a significant association between specific serum BFRs (PBDE-47, PBDE-99, and PBDE-154) and periodontitis and its severity. Further prospective and experimental studies are warranted to validate our findings.

A Comprehensive Assessment of Sample Preparation Methods for the Determination of UV Filters in Water by Gas Chromatography–Mass Spectrometry: Greenness, Blueness, and Whiteness Quantification Using the AGREEprep, BAGI, and RGB 12 Tools

A Comprehensive Assessment of Sample Preparation Methods for the Determination of UV Filters in Water by Gas Chromatography–Mass Spectrometry: Greenness, Blueness, and Whiteness Quantification Using the AGREEprep, BAGI, and RGB 12 Tools

Characterization of the Conversion System of Natural Rubber to Poly(3-Hydroxyalkanoate) in Piscinibacter gummiphilus Strain NS21T.

Poly(3-hydroxyalkanoate) (PHA), a bacteria-synthesized biodegradable polyester, is a useful alternative to fossil resources, and current systems for its production rely predominantly on edible resources, raising concerns about microbial competition for nutrients. Therefore, we investigated mechanisms underlying PHA production from non-edible resources by Piscinibacter gummiphilus strain NS21T. Strain NS21T can utilize natural rubber as a carbon source on solid media and potentially produces PHA. Gas chromatography and nuclear magnetic resonance analyses of NS21T cell extracts revealed the production of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and poly(3-hydroxybutyrate) from natural rubber and glucose, respectively. Transcriptional analysis suggested that phaC is involved in PHA production. An increased PHBV accumulation rate under nitrogen-limiting conditions indicates the potential of this strain to be used as a PHBV production enhancement strategy. Furthermore, the disruption of PHA depolymerase genes resulted in enhanced PHA production, indicating the involvement of these genes in PHA degradation. These findings highlight the potential of NS21T for PHBV production from natural rubber, a non-edible resource.

Gas Chromatography–Mass Spectrometry Analysis of Volatile Organic Compounds from Three Endemic Iris Taxa: Headspace Solid-Phase Microextraction vs. Hydrodistillation

Gas Chromatography–Mass Spectrometry Analysis of Volatile Organic Compounds from Three Endemic Iris Taxa: Headspace Solid-Phase Microextraction vs. Hydrodistillation

Development and Integration of an Ultraminiaturized Gas Chromatograph Prototype Based on Lab-on-a-Chip Microelectromechanical Systems for Space Exploration Missions

Development and Integration of an Ultraminiaturized Gas Chromatograph Prototype Based on Lab-on-a-Chip Microelectromechanical Systems for Space Exploration Missions

Organochlorine pesticides and their markers of exposure in serum and urine of children from a nodding syndrome hotspot in Northern Uganda, East Africa

Nodding syndrome (NS) is a neurologic disorder of unknown etiology characterized by vertical head nodding that has affected children aged 5-18 years in East Africa. Previous studies have examined relationships with biological agents (e.g., nematodes, measles, and fungi), but there is limited data on the possible contributions of neurotoxic environmental chemicals frequently used as pesticides/insecticides to the development and progression of this disorder. We examined the levels of persistent organochlorine pesticides (OCPs) in children (5-18 years old) from Kitgum District, Northern Uganda. These children previously lived in internally displaced people's (IDP) camps, where they were exposed to various health risks, including contaminated food and water. Exposure to OCPs through contaminated food and water is postulated here as a potential contributor to NS etiology. We analyzed serum (n = 75) and urine (n = 150) samples from children diagnosed with NS, and from seizure-free household controls (HC), and community controls (CC). Samples were extracted using solid-phase extraction (SPE) and extracts were analyzed for OCPs using gas chromatography with a triple quadrupole mass spectrometry (GC-MS/MS). Mean levels of total (∑) ∑OCPs in serum samples from NS, HC and CC subjects were 23.3 ± 2.82, 21.1 ± 3.40 and 20.9 ± 4.24 ng/mL, respectively, while in urine samples were 1.86 ± 1.03, 2.83 ± 1.42, and 2.14 ± 0.94 ng/mL, respectively. Correlation and linear regression analysis indicated that potential markers for ∑hexachlorocyclohexanes (HCHs), ∑chlordane compounds (CHLs), ∑endosulfan and ∑dichlorodiphenyltrichloroethanes (DDTs) were γ-HCH, heptachlor-exo-epoxide, endosulfan-α and p,p'-DDD in NS cases while in controls were α -HCH, heptachlor, endosulfan-α and p,p'-DDE, respectively. Since, in some instances, higher OCP levels were found in controls vs. NS cases, we conclude that exposure to organochlorine pesticides is unlikely to be associated with the etiology of NS.

Characterization of volatile aroma compounds in pak choi

Aroma is a key sensory factor in the flavor evaluation of pak choi (Brassica rapa L. ssp. chinensis var. Makino). The pak choi varieties Xiangqingcai (XQC) and Xiuhuajin (XHJ) have unique aroma characteristics, but the chemical profiles of these aromas are unknown. Here, the aroma profiles of three varieties of pak choi including XQC, XHJ, and Suzhouqing (CK, non-aromatic) were determined using gas chromatography–mass spectrometry (GC–MS) and relative odor activity values (rOAV). A total of 15 categories of 716 volatile metabolites were detected in the three pak choi varieties, with terpenoid metabolites identified as the major components, although in each sample the identity of the major terpenoid metabolite varied. There were 53 aroma components in XQC and 54 aroma components in XHJ with rOAV >1, which contribute to rice aroma and fishy odor of these varieties, respectively.

Convolutional neural networks enhance pyrolysis gas chromatography mass spectrometry identification of coated papers

Convolutional neural networks enhance pyrolysis gas chromatography mass spectrometry identification of coated papers