Gas Chromatograms Research Articles

Effectiveness of Essential Oils from Leaves of Two Plant Species in the Control of Anopheles gambiae

Background: The current method of controlling malaria vectors using synthetic chemicals has caused serious problems for human health and the environment. Hence, a need for alternative, cheap, readily available, and acceptable mosquito control methods. Objective: To evaluate the bioinsecticidal efficacy of Ocimum gratissimum and Mesosphaerum suaveolens against Anopheles gambiae using the bioassay method. Methods: Oil extracts in 5 ml, 25 ml, and 75 ml serially diluted twice in 100 ml of olive oil formed 0.05%, 0.25%, and 0.75%, while 1 m in 100 ml formed 1%. Olive oil only served as a control. Twenty-five female Anopheles mosquitoes, aged 2-4 days, were blown into tubes containing filter paper-coated essential oils of various concentrations in quadruplicates. Results: Over 50% mortality was recorded in mosquitoes exposed to 0.75% and 1% O. gratissimum compared to others (p <0.05). Knockdown time (KDT) was higher in mosquitoes exposed to 1% O. gratissimum compared to others (p <0.05). Generalized linear regressions showed that the essential oils of O. gratissimum and M. suaveolens contributed 4% (f2 = 0.042) and 14% (f2 = 0.167) to the variability of mortality with time. KDT50 (9.34 - 131.5 minutes) and KDT95 (77.6 - 275 minutes) of O. gratissimum as well as KDT50 (162.8 - 233.6 minutes) and KDT95 (302.8 - 415 minutes) of M. suaveolens were recorded. Stigmastane; 4,22-Stigmastadiene-3-one (Area: 45.88%) in O. gratissimum and gamma-Sitosterol (16.02%) in M. suaveolens were identified by Gas Chromatogram as the highest dose of chemical compounds. Conclusion: The low bioinsecticidal activities of these plant extracts could be attributed to the low occurrence of terpenoids and alkaloids.

Elevated blood-ethanol concentration promotes reduction of aliphatic ketones (acetone and ethyl methyl ketone) to secondary alcohols along with slower oxidation to aliphatic diols.

Many people convicted for drunken driving suffer from an alcohol use disorder and some traffic offenders consume denatured alcohol for intoxication purposes. Venous blood samples from people arrested for driving under the influence of alcohol were analyzed in triplicate by headspace gas chromatography (HS-GC) using three different stationary phases. The gas chromatograms from this analysis sometimes showed peaks with retention times corresponding to acetone, ethyl methylketone (2-butanone), 2-propanol, and 2-butanol in addition to ethanol and the internal standard (1-propanol). Further investigations showed that these drink-driving suspects had consumed an industrial alcohol (T-Red) for intoxication purposes, which contained > 90% w/v ethanol, acetone (~ 2% w/v), 2-butanone (~ 5% w/v) as well as Bitrex to impart a bitter taste. In n = 75 blood samples from drinkers of T-Red, median concentrations of ethanol, acetone, 2-butanone, 2-propanol and 2-butanol were 2050mg/L (2.05g/L), 97mg/L, 48mg/L, 26mg/L and 20mg/L, respectively. In a separate GC analysis, 2,3-butanediol (median concentration 87mg/L) was identified in blood samples containing 2-butanone. When the redox state of the liver is shifted to a more reduced potential (excess NADH), which occurs during metabolism of ethanol, this favors the reduction of low molecular ketones into secondary alcohols via the alcohol dehydrogenase (ADH) pathway. Routine toxicological analysis of blood samples from apprehended drivers gave the opportunity to study metabolism of acetone and 2-butanone without having to administer these substances to human volunteers.

Petroleum system analysis of the komombo basin, southern Egypt: Insights from basin modeling and hydrocarbon geochemistry

Komombo Basin is the only hydrocarbon-producing basin in southern Egypt. However, its petroleum system is still poorly understood, leaving numerous geological questions unanswered. This study integrates seismic, borehole, and geochemical data, coupled with 1D and 2D basin models, to evaluate the hydrocarbon potential and analyze the petroleum system within the Komombo Basin. Geochemical data reveal four main source rocks: the B member of Six Hills, upper Maghrabi, Quseir, and Dakhla. The B member is interpreted as a very good source rock, characterized by Kerogen type II to II/III. The upper Maghrabi and Quseir are considered good to very good source rocks with organic matter type III and II/III, respectively. Conversely, the Dakhla Formation is recognized as a source rock of good to excellent quality with a mixed kerogen type of II/III. Temperature models highlight two heat anomalies during the Early and Late Cretaceous, aligning with the identified rift phases in the basin. The present-day thermal maturity model indicates that the B member is the only mature source rock that has entered the main oil window. However, in the deepest part of the basin, it reaches the gas window. Although the hydrocarbon generation from the B member began in the Early Turonian, most of the kerogen transformed into hydrocarbons during the middle Santonian-early Maastrichtian. Three migration scenarios were tested, however, the first scenario with the invasion percolation migration method aligns more with known hydrocarbon accumulations in the basin. The predicted accumulation zones are found within several sand units, including the A member, C member, sandy intervals within D-G members of Six Hills, and Sabaya-Maghrabi reservoirs. These zones are predominantly situated within structural traps. Comparative analysis using gas chromatograms between recovered oils from the reservoirs and an extracted bitumen sample from the B member source rock reveals a strong correlation among them.

A compact breath breathalyzer for identifying the non-alcoholic fatty liver disease biomarker

Non-alcoholic fatty liver disease (NAFLD) is a prevalent chronic liver disease worldwide. Currently, its diagnosis relies primarily on imaging and histological examinations, which are invasive and prone to misdiagnosis in the early stage. To address these limitations, detection and analysis of volatile organic compounds (VOCs) in human breath can be a rapid and non-invasive screening method for NAFLD. In this study, a compact breath breathalyzer was developed, utilizing a miniaturized gas chromatography chip with the STM32 microcontroller as the main control chip to manage airflow, temperature, and receive terminal signals from the photoionization detector. In the experiment, a gas mixture comprising five VOCs (pentane, acetone, toluene, octane, and decane) was selected as the simulated typical disease biomarkers in human breath to investigate the breathalyzer's performance and optimize testing conditions for multi-polar and wide-boiling-range breath samples. Results show that the breathalyzer can detect low-boiling components (< 100°C) such as the isoprene and acetone, with a detection limit less than 50 ppb which are two commonly biomarkers of NAFLD. Furthermore, breath samples were collected from 35 non-diseased individuals, and NAFLD early-stage patient samples were simulated by increasing the isoprene concentration by 10 ppb. Convolutional neural network (CNN) were used to identify the VOC signatures in gas chromatograms with predictive accuracy of 85% for the classification model. Therefore, the compact breath breathalyzer has potential application in the rapid and early screening of NAFLD.

Optimization, Production, and characterization of cottonseed methyl ester based on Box-Behnken in response surface design and gas Chromatography-Mass spectrum analysis

Renewable energy sources have a significant approach to eco-friendly systems with economically cost-effective and efficient use of biodiesel. The creation of innovative catalysts is attracting the attention and concern of the chemical and manufacturing sectors to be used in the production of biodiesel. The main objective of this work is to produce the optimum biodiesel yield using BBD design and the base-catalyzed method. The production of biodiesel was achieved through experimental investigation (alkali-catalyzed transesterification) and optimized using the BBD design method.The most important parameters such as methanol to oil ratios, KOH as catalysts, and reaction times were provided with variable conditions. The variation of methanol to oil ratios has significant relationships and is highly correlated in findings. The physicochemical properties of cottonseed biodiesel were carried out according to ASTM and EN standards. The maximum yield was achieved at 96.708 at a molar ratio of 6:1, reaction time of 60 min, and catalyst concentration of 1 wt%. The strong correlation between actual and predicted values of COSME was analyzed using ANOVA variances. The F-value and P-value validated the outcomes of produced biodiesel having a model value of 43.68 and 0.00, respectively. The coefficient of determinations and adjusted R2 of CSOME were achieved at 98.7% and 98.6%, respectively. The gas chromatogram mass spectrum analysis was also obtained to identify the acid profile present in COSME. The major percentage of ester available in COSME has been determined using GC–MS analysis and presented by its weight percentages. The main esters have been including myristic acid methyl ester (1.7%), palmitic acid methyl ester (26.65%), methyl 9-cis,11-trans-octadecadienoate(44.05%), ethyl 9. Cis.11.trans octadecadienoate(9.67%), methyl 20-methyl-heneicosanoate(6.83%), 9,12-Octadecadienoic acid (Z,Z)-, 2-hydroxy-1-(hydroxymethyl)ethyl ester(1.93%), and Pentacosanoic acid, methyl ester(7.14%).

Analysis of GC × GC fingerprints from medicinal materials using a novel contour detection algorithm: A case of Curcuma wenyujin

This study introduces an innovative contour detection algorithm, PeakCET, designed for rapid and efficient analysis of natural product image fingerprints using comprehensive two-dimensional gas chromatogram (GC × GC). This method innovatively combines contour edge tracking with affinity propagation (AP) clustering for peak detection in GC × GC fingerprints, the first in this field. Contour edge tracking significantly reduces false positives caused by “burr” signals, while AP clustering enhances detection accuracy in the face of false negatives. The efficacy of this approach is demonstrated using three medicinal products derived from Curcuma wenyujin. PeakCET not only performs contour detection but also employs inter-group peak matching and peak-volume percentage calculations to assess the compositional similarities and differences among various samples. Furthermore, this algorithm compares the GC × GC fingerprints of Radix/Rhizoma Curcumae Wenyujin with those of products from different botanical origins. The findings reveal that genetic and geographical factors influence the accumulation of secondary metabolites in various plant tissues. Each sample exhibits unique characteristic components alongside common ones, and variations in content may influence their therapeutic effectiveness. This research establishes a foundational data-set for the quality assessment of Curcuma products and paves the way for the application of computer vision techniques in two-dimensional (2D) fingerprint analysis of GC × GC data.

Optimization of green microwave-assisted extraction of essential oil from lemon (Citrus limon) leaves: Bioactive, antioxidant and antimicrobial potential

This research delves into the analysis of essential oil derived from Citrus limon leaves cultivated in the northern region of Bangladesh, focusing on their potential attributes. The essential oil was extracted employing a microwave-assisted gravity station without using solvent. Optimization was carried out in terms of time, temperature and power as a function of oil yield. The study revealed the highest oil yield of 2.5 % after 50 min at 110 °C, maintaining a microwave power of 300 watt. Twenty-four (24) phyto-components were identified by Gas Chromatogram- Mass Spectrometer (GC-MS) where d-Limonene (34.10660 %) was dominant compound. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay was used to assess the antioxidant activity of essential oil. Notably, essential oil displayed superior DPPH radical scavenging activity (IC50 8.57 ppm) compared to butylated hydroxytoluene (BHT) (IC50 10.63 ppm), a common antioxidant standard. Furthermore, a variety of harmful microorganisms were used to evaluate the antimicrobial efficacy. The extracted essential oil exhibited the strongest antimicrobial effectiveness against bacteria Staphylococcus aureus (ZOI-27.50 mm, MIC-7.8 μL/mL) and the fungi Candida albicans (ZOI-32.83 mm, MIC-1.95 μL/mL). These findings demonstrate the Citrus limon leaves essential oil contains bioactive components with strong antioxidant and antimicrobial properties. The extracted essential oil holds significant potential for applications in the foods, pharmaceuticals and cosmetic industries.

Organic Geochemical Evaluation of the Black Shale interbeds Within the Lithological Succession of the Al Aziziyah Formation, NW Libya

The samples under investigation represent the black shale in interbeds within the Al Aziziyah Formation, located in the NW part of Libya and were analysed using geochemical techniques method and a variety of organic geochemical parameters. The aim of this study is to assess the type of organic matter, thermal maturity, and environment of deposition, based on biomarker distributions and Rock-Eval pyrolysis. The Gas chromatograms of the saturated hydrocarbon fractions of the study samples display a smooth high-end member distribution of the n- n-alkanes extending beyond nC34. The sample displayed evidence of biodegradation as suggested by the presence of the loss of some of the lower molecular weight n-alkanes. The predominance of high molecular weight n-alkane in the study sample suggests a significant input of higher land plant organic matter into these sediments. Geochemical (Rock-Eval, Tmax. values ranging from 416-4390C typical of immature range). Another related feature of these rocks extracted is the presence of a high relative abundance of gammacerane, indicating an anoxic marine hypersaline source depositional environment. The relatively high abundance of common land-plant-derived biomarkers, such as oleananes, is a clear indication of major terrigenous input to the source of these extractable organic matters. The high abundance of C24 tetracyclic terpanes could be associated with higher land-plant, algae, or microbial sources, thereby suggesting a mixed source input. TOC valued &lt; 0.5 wt.%, in the analyzed samples can be considered as a poor source rock generative potential. Based on this study, it can be said that the interbedded shales of the Al Aziziyah Formation seem to have received substantial amounts of land-derived organic matter that has been transported into an open marine subtidal depositional setting had prevailed and was deposited in a photosynthetic-organisms dominated environment (thereby suggesting a mixed source input).

Development of a safety analysis method for volatile organic compounds using 2-phenoxyethanol as solvent

Indoor volatile organic compounds (VOCs) are usually sampled using active carbon samplers and subsequently analyzed using gas chromatography-mass spectrometry (GC-MS) to assess the exposure risk to workers. Therefore, selection of a suitable solvent for VOC extraction is crucial. However, reports on the use of 2-phenoxyethanol—known for its low vapor pressure and low toxicity—as a solvent for extracting VOCs from activated carbon are lacking. Here, we show that 2-phenoxyethanol is a suitable alternative solvent with low toxicity and can extract a wide variety of VOCs without overlapping with target VOCs on the gas chromatogram. The recoveries of 2-phenoxyethanol were 57% (styrene) to 83% (methyl n-butyl ketone), which were higher than those of CS2, acetone, and n-hexane at room temperature. The recoveries improved to 67% (styrene) to 102% (isopentyl acetate) under 50 °C. Optimization of the GC conditions showed that a viscosity delay time of 3 s was required to avoid producing bubbles in the injection syringes. We selected DB-HeavyWAX as a column because it could be heated above the boiling point of 2-phenoxyethanol (247 °C), allowing the removal of 2-phenoxyethanol from the column. This study contributes to the development of analysis methods for VOCs under safe operating conditions.

Predicting Bordeaux red wine origins and vintages from raw gas chromatograms

Connecting chemical properties to various wine characteristics is of great interest to the science of olfaction as well as the wine industry. We explored whether Bordeaux wine chemical identities and vintages (harvest year) can be inferred from a common and affordable chemical analysis, namely, a combination of gas chromatography (GC) and electron ionization mass spectrometry. Using 12 vintages (within the 1990–2007 range) from 7 estates of the Bordeaux region, we report that, remarkably, nonlinear dimensionality reduction techniques applied to raw gas chromatograms recover the geography of the Bordeaux region. Using machine learning, we found that we can not only recover the estate perfectly from gas chromatograms, but also the vintage with up to 50% accuracy. Interestingly, we observed that the entire chromatogram is informative with respect to geographic location and age, thus suggesting that the chemical identity of a wine is not defined by just a few molecules but is distributed over a large chemical spectrum. This study demonstrates the remarkable potential of GC analysis to explore fundamental questions about the origin and age of wine.

Determination of 4-methyl-2-pentanol in workplace air by solvent desorption-gas chromatography

Objective: To establish a method for the determination of 4-methyl-2-pentanol in the air of workplace by gas chromatography. Methods: In January 2022, 4-methyl-2-pentanol in the air of workplace was collected by activated carbontube, eluted with dichloromethane-methanol (95∶5, V/V), separated by capillary column and determined by gas chromatogram. Results: The limit of detection for 4-methyl-2-pentanol was 0.04 μg/ml. The linear range of 4-methyl-2-pentanol was 0.16-1616.60 μg/ml, with the regression equation of y=1.94x-5.48, and the coefficient correlation was 0.99958, and the minimum detection concentration was 0.03 mg/m(3) (collected sample volume was 1.50 L). The within-run precisions were 1.08%-1.75% and the between-run precisions were 1.41%-2.52%. The desorption rates were 95.15%-99.91%. The samples could be stored at least 3 days at room temperature and 7 days at 4 ℃ without significant loss. Conclusion: The method has the advantages of good precision, high sensitivity and simple operation. It is suitable for the determination of 4-methyl-2-pentanol in the air of workplace.

Fluid property identification of the Lower Cretaceous reservoirs with complex oil-water contacts in Deseo Basin, Chad

Recently, exploration breakthroughs have been made in the Lower Cretaceous sandstone reservoirs in the Doseo Basin, but the identification of reservoir fluid property is difficult due to variable reservoir lithology, complex oil-water contact within and faint responses of the oil zone, which causes the lower accuracy of reservoir fluid property identification with conventional mudlogging and wirelogging techniques. Applying the geochemical logging, fluorescent logging, mud logging and cutting logging technology, in combination with formation test data, this paper distinguishes the crude oil types, analyzes the logging response characteristics of oil zone after water washing, and establishes the interpretation charts and parameter standards for reservoir fluid properties. The crude oil can be divided into two types, namely viscous-heavy and thin-light, based on total hydrocarbon content and component concentration tested by mud logging, features of pyrolysis gas chromatogram and fluorescence spectroscopy. The general characteristics of oil layers experienced water washing include the decrease of total hydrocarbon content and component concentration from mud logging, the decrease of S1 and PS values from geochemical logging, the decrease of hydrocarbon abundance and absence of some light components in pyrolysis gas chromatogram, and the decrease of fluorescence area and intensity from fluorescence logging. According to crude oil types, the cross plots of S1 versus peak-baseline ratio, and the cross plots of rock wettability versus fluorescence area ratio are drawn and used to interpret reservoir fluid property. Meanwhile, the standards of reservoir fluid parameter are established combining with the parameters of PS and the parameters in above charts, and comprehensive multiparameter correlation in both vertical and horizontal ways is also performed to interpret reservoir fluid property. The application in the Doseo Basin achieved great success, improving interpretation ability of fluid property in the reservoir with complex oil-water contact, and also provided technical reference for the efficient exploration and development of similar reservoirs.

The synergetic effect from the combination of different adsorption resins in batch and semi-continuous cultivations of S. Cerevisiae cell factories to produce acetylated Taxanes precursors of the anticancer drug Taxol.

In situ product recovery is an efficient way to intensify bioprocesses as it can perform adsorption of the desired natural products in the cultivation. However, it is common to use only one adsorbent (liquid or solid) to perform the product recovery. For this study, the use of an in situ product recovery method with three combined commercial resins (HP-20, XAD7HP, and HP-2MG) with different chemical properties was performed. A new yeast strain of Saccharomyces cerevisiae was engineered using CRISPR Cas9 (strain EJ2) to deliver heterologous expression of oxygenated acetylated taxanes that are precursors of the anticancer drug Taxol ® (paclitaxel). Microscale cultivations using a definitive screening design (DSD) were set to get the best resin combinations and concentrations to retrieve high taxane titers. Once the best resin treatment was selected by the DSD, semi-continuous cultivation in high throughput microscale was performed to increase the total taxanes yield up to 783 ± 33 mg/L. The best T5α-yl Acetate yield obtained was up to 95 ± 4 mg/L, the highest titer of this compound ever reported by a heterologous expression. It was also observed that by using a combination of the resins in the cultivation, 8 additional uncharacterized taxanes were found in the gas chromatograms compared to the dodecane overlay method. Lastly, the cell-waste reactive oxygen species concentrations from the yeast were 1.5-fold lower in the resin's treatment compared to the control with no adsorbent aid. The possible future implications of this method could be critical for bioprocess intensification, allowing the transition to a semi-continuous flow bioprocess. Further, this new methodology broadens the use of different organisms for natural product synthesis/discovery benefiting from clear bioprocess intensification advantages.

Application of Prussian Blue Analogue‐Derived Mn−Co Catalysts in the Hydrogenation of CO to Higher Alcohols

AbstractMnxCo3‐x[Co(CN)6]2 Prussian blue analogues were synthesized with Mn : Co ratios in the range from 7 : 10 to 1 : 11 and pyrolyzed at 600 °C to obtain a highly nitrogen‐ and oxygen‐functionalized carbon matrix with embedded reduced Mn and Co species. These catalyst precursors were applied in the CO hydrogenation to higher alcohols at 260 °C and a pressure of 60 bar using a H2/CO ratio of 1. Metallic Co0 formed during pyrolysis was partially transformed into Co2C under reaction conditions. With increasing Co content CO conversion increased up to 10.6 % reaching a total alcohol selectivity of 19 %. Gas chromatograms revealed the expected formation of primary short‐chain alcohols, but also of secondary alcohols, acetic acid and propionaldehyde indicating olefin hydration, carbonylation and hydroformylation as reaction pathways, respectively. The obtained hydrocarbon fractions had a very high olefinicity, which is beneficial for both olefin hydration to secondary alcohols catalyzed by adsorbed carboxylic acids and for hydroformylation. Whereas the carbide‐based reaction pathway and the reductive hydroformylation are assumed to occur at the Co2C/Co0 interface, carbonylation is presumably catalyzed by an additional Co‐based active site. Thus, a unique class of multifunctional catalysts was obtained with highly promising properties bridging the gap between heterogeneous and homogeneous catalysis.

Retention Time Trajectory Matching for Peak Identification in Chromatographic Analysis.

Retention time drift caused by fluctuations in physical factors such as temperature ramping rate and carrier gas flow rate is ubiquitous in chromatographic measurements. Proper peak matching and identification across different chromatograms is critical prior to any subsequent analysis but is challenging without using mass spectrometry. The purpose of this work was to describe and validate a peak matching and identification method called retention time trajectory (RTT) matching that can be used in targeted analyses free of mass spectrometry. This method uses chromatographic retention times as the only input and identifies peaks associated with any subset of a predefined set of target compounds. An RTT is a two-dimensional (2D) curve formed uniquely by the retention times of the chromatographic peaks. The RTTs obtained from the chromatogram of a sample under test and those pre-installed in a library are matched and statistically compared. The best matched pair implies identification. Unlike most existing peak-alignment methods, no mathematical warping or transformation is involved. Based on the experimentally characterized RTT, an RTT hybridization method was also developed to rapidly generate more RTTs and expand the library without performing actual time-consuming chromatographic measurements, which enables successful peak matching even for chromatograms with severe retention time drifts. Additionally, 3.15 × 105 tests using experimentally obtained gas chromatograms and 2 × 1012 tests using two publicly available fruit metabolomics datasets validated the proposed method, demonstrating real-time peak/interferent identification.

Colorimetric Signal Readout for the Detection of Volatile Organic Compounds Using a Printable Glass-Based Dielectric Barrier Discharge-Type Helium Plasma Detector.

In this paper, we report on a printable glass-based manufacturing method and a new proof-of-concept colorimetric signal readout scheme for a dielectric barrier discharge (DBD)-type helium plasma photoionization detector. The sensor consists of a millimeter-sized glass chamber manufactured using a printable glass suspension. Plasma inside the chip is generated using a custom-built power supply (900 V and 83.6 kHz), and the detector uses ∼5 W of power. Our new detection scheme is based on detecting the change in the color of plasma after the introduction of target gases. The change in color is first captured by a smartphone camera as a video output. The recorded video is then processed and converted to an image light intensity vs retention time plot (gas chromatogram) using three standard color space models (red, green, blue (RGB), hue, saturation, lightness (HSL), and hue, saturation, value (HSV)) with RGB performing the best among the three models. We successfully detected three different categories of volatile organic compounds using our new detection scheme and a 30-m-long gas chromatography column: (1) straight-chain alkanes (n-pentane, n-hexane, n-heptane, n-octane, and n-nonane), (2) aromatics (benzene, toluene, and ethylbenzene), and (3) polar compounds (acetone, ethanol, and dichloromethane). The best limit of detection of 10 ng was achieved for benzene at room temperature. Additionally, the device showed excellent performance for different types of sample mixtures consisting of three and five compounds. Our new detector readout method combined with our ability to print complex glass structures provides a new research avenue to analyze complex gas mixtures and their components.

Characterization of the Volatile Profiles of Insect Flours by (HS)-SPME/GC-MS: A Preliminary Study.

The growing world population, combined with scarcities of agricultural land, water, forest, fisheries, and biodiversity resources, makes it necessary to search for alternative sources of nutrients. For this reason, in recent years, edible insects have been introduced into the diet, even in areas where entomophagy is not traditional. In light of this, the present study aims at characterizing the aromatic profile of three edible insects flours: cricket (Acheta domesticus, CP), buffalo worm (Alphitobius diaperinus, BW), and mealworm (Tenebrio molitor, MW). This goal has been achieved by means of an (HS)-SPME/GC-MS strategy. 67 compounds have been tentatively identified; of these, 27 are present only in the CP and BW flours, while 10 are common in all three flours. The compound with the highest peak's relative area in gas chromatograms of CP and BW flours is hexadecanoic acid, while in MW it is 1-heptylpyrrolidin-2-one. In general, we have observed that CP and BW flours have 37 compounds in common, and their volatile compositions along with their profiles are more similar to each other than to MW profile.

Mechanistic insight into efficient H2 generation upon HCOONa hydrolysis

Sodium formate (SF) is regarded as a technological additive to improve H2 generation upon HCOOH dehydrogenation. The development of SF as a hydrogen storage material is still a challenge. Herein, we report the design and synthesis of carbon nanosphere-stabilized Pd nanoparticles (Pd/CNS) for the direct H2 generation upon SF hydrolysis in the presence of Fe3+. The tandem reaction, isotopic mass spectrometry, and gas chromatograms result confirmed that SF hydrolysis generates H2 with one H atom provided by SF and other H by H2O. The kinetic study and detailed mechanistic investigations have demonstrated that the concerted process between the cleavage of O-H bond in H2O and -O2C-H bond oxidative addition is the rate-controlling step in SF hydrolysis. This work offers a new chemical hydrogen storage material (HCOONa) for the high-efficiency generation, transport, and storage of H2.

Incorporating Chemometric Methods in the Undergraduate Curriculum: A Problem Set Activity for an Upper-Level Analytical Elective Course

In this paper, a problem set activity focused on understanding and applying unsupervised and supervised chemometric methods for the analysis of biodiesel–diesel blended fuels is described. This problem set was utilized in two upper-level analytical elective courses aimed for junior and senior level students. The data set consists of peak areas taken from gas chromatograms comprising various biodiesel concentrations and feedstock types. Students are tasked with analyzing the data set using principal component analysis (PCA), hierarchical cluster analysis (HCA), and k-nearest neighbors (kNN). The primary purpose of this problem set is to gain hands-on experience manipulating and drawing conclusions about large data sets using chemometric methods. The problem set activity utilizes a large GCMS data set with many varieties of sample types and can be included at any institution with no need for a GCMS instrument on campus.

Two-step classification of highly mixed oil in the Qikou Sag (Bohai Bay Basin, China): Implications for origin, maturity, and biodegradation

Mixing of crude oil leads to unpredictable changes in the property and composition of mixtures, bringing uncertainties to petroleum production. Therefore, it is crucial to reveal the origin, maturity, and biodegradation of mixed oil during the exploration stage. Here we address these issues using the highly-mixed oil from the Qikou Sag (Bohai Bay Basin, eastern China) after a two-step classification. Firstly, the highly-mixed oil was classified into two groups (groups I and II) according to their physical property (API gravity and sulfur content), molecular composition, and gas chromatograms of saturated hydrocarbons. Secondly, the group I oil was further divided into two sub-groups (groups I-1 and I-2) based on the principal component analysis (PCA) and hierarchical cluster analysis (HCA) of biomarkers (including n-alkanes, isoprenoids, terpenoids, and steroids). The group I oil is non-biodegraded, in which the group I-1 oil from deep reservoirs is a mixture of hydrocarbons from three sets of source rock, whereas the group I-2 oil from shallow reservoirs is mixed by hydrocarbons from five sets of source rock. Maturity parameters of biomarkers suggest that the group I oil is thermally mature. The group II oil was slightly (PM 1–2) to severely (PM 4+) biodegraded, as indicated by low API gravity, high percentages of asphaltenes and NSO, high ratios of Pr/n-C17 and Ph/n-C18, and the assignment of UCM and 25-norhopane. The burial depth of reservoirs and secondary faults (formed after the Neogene) are the primary controlling factors for the biodegradation. Our results demonstrate that the two-step classification facilitates the grouping of highly mixed oil, which provides a basis for indicating their origin, maturity, and biodegradation. The results also provide guidance for regional petroleum exploration and production.