Gas Chromatography Instrument Research Articles

Unveiling Hidden Insights in Gas Chromatography Data Analysis with Generative Adversarial Networks

The gas chromatography analysis method for chemical substances enables accurate analysis to precisely distinguish the components of a mixture. This paper presents a technique for augmenting time-series data of chemicals measured by gas chromatography instruments with artificial intelligence techniques such as generative adversarial networks (GAN). We propose a novel GAN algorithm called GCGAN for gas chromatography data, a unified model of autoencoder (AE) and GAN for effective time-series data learning with an attention mechanism. The proposed GCGAN utilizes AE to learn a limited number of data more effectively. We also build a layer of high-performance generative adversarial neural networks based on the analysis of the features of data measured by gas chromatography instruments. Then, based on the proposed learning, we synthesize the features embedded in the gas chromatography data into a feature distribution that extracts the temporal variability. GCGAN synthesizes the features embedded in the gas chromatography data into a feature distribution that extracts the temporal variability of the data over time. We have fully implemented the proposed GCGAN and experimentally verified that the data augmented by the GCGAN have the characteristic properties of the original gas chromatography data. The augmented data demonstrate high quality with the Pearson correlation coefficient, Spearman correlation coefficient, and cosine similarity all exceeding 0.9, significantly enhancing the performance of AI classification models by 40%. This research can be effectively applied to various small dataset domains other than gas chromatography data, where data samples are limited and difficult to obtain.

The formulation of moisturizing and hydrating cream based on natural ingredients such as chitosan

The purpose of this work is to make moisturizing and hydrating cream for the skin. the ingredients of moisturizing and hydrating cream are based on natural polysaccharides, such as chitosan and extracted from aquatic organisms such as shrimp.Physical and chemical analysis, identification test of the oils in the cream based on gas chromatography instrument have been done in the reference laboratory of Food and Drug Organization of Iran country. Also, non-sensitizing test of the formulated cream have been done by the rabbit at department of pharmaceutics, school of pharmacy, Shahid Beheshti University of Medical Sciences in Irancountry.

The interhemispheric gradient of SF6 in the upper troposphere

Abstract. Anthropogenic trace gases often exhibit interhemispheric gradients because of larger emissions in the Northern Hemisphere. Depending on a tracer's emission pattern and sink processes, trace gas observations can thus be used to investigate interhemispheric transport in the atmosphere. Vice versa, understanding interhemispheric transport is important for interpreting spatial tracer distributions and for inferring emissions. We combine several data sets from the upper troposphere (UT) to investigate the interhemispheric gradient of sulfur hexafluoride (SF6) covering latitudes from ∼ 80∘ N to ∼ 60∘ S: canister sampling based measurements from the IAGOS-CARIBIC infrastructure and data from the in-flight gas chromatography instruments GhOST (Gas chromatograph for Observational Studies using Tracers) and UCATS (Unmanned aircraft systems Chromatograph for Atmospheric Trace Species). The interhemispheric gradient of SF6 in the UT is found to be weaker than near the surface. Using the concept of a lag time removes the increasing trend from the time series. At the most southern latitudes, a lag time of over 1 year with respect to the northern mid-latitude surface is derived, and lag times decrease over the period 2006–2020 in the extra-tropics and the southern tropics. Observations are compared to results from the two-dimensional Advanced Global Atmospheric Gases Experiment (AGAGE) 12-box model. Based on Emissions Database for Global Atmospheric Research (EDGAR 7) emissions, fair agreement of lag times is obtained for the Northern Hemisphere, but southern hemispheric air appears too “old”. This is consistent with earlier findings that transport from the northern extra-tropics into the tropics is too slow in many models. The influence of the emission scenario and the model transport scheme are evaluated in sensitivity runs. It is found that EDGAR 7 underestimates emissions of SF6 globally and in the Southern Hemisphere, whereas northern extra-tropical emissions seem overestimated. Faster southward transport from the northern extra-tropics would be needed in the model, but transport from the southern tropics into the southern extra-tropics appears too fast.

IDSL.CSA: Composite Spectra Analysis for Chemical Annotation of Untargeted Metabolomics Datasets.

Poor chemical annotation of high-resolution mass spectrometry data limits applications of untargeted metabolomics datasets. Our new software, the Integrated Data Science Laboratory for Metabolomics and Exposomics─Composite Spectra Analysis (IDSL.CSA) R package, generates composite mass spectra libraries from MS1-only data, enabling the chemical annotation of high-resolution mass spectrometry coupled with liquid chromatography peaks regardless of the availability of MS2 fragmentation spectra. We demonstrate comparable annotation rates for commonly detected endogenous metabolites in human blood samples using IDSL.CSA libraries versus MS/MS libraries in validation tests. IDSL.CSA can create and search composite spectra libraries from any untargeted metabolomics dataset generated using high-resolution mass spectrometry coupled to liquid or gas chromatography instruments. The cross-applicability of these libraries across independent studies may provide access to new biological insights that may be missed due to the lack of MS2 fragmentation data. The IDSL.CSA package is available in the R-CRAN repository at https://cran.r-project.org/package=IDSL.CSA. Detailed documentation and tutorials are provided at https://github.com/idslme/IDSL.CSA.

Untargeted Screening and Identification of Contaminants Using Gas Chromatography Coupled to High-Resolution Accurate Mass–Mass Spectrometry: Novel Solutions for Applied Testing Laboratories

The combination of gas chromatography (GC) instruments with quadrupole-based mass spectrometers is a common analytical setup for the detection of a broad range of volatile and semivolatile contaminants. GC–mass spectrometry (MS) (nominal mass) instruments are well known for their robustness and ease of use. However, they have some important limitations. Single quadrupole instruments can perform full scan analysis, but their sensitivity and selectivity in this mode are limited. Triple quadrupole (GC–MS/MS) systems are limited to a targeted acquisition within a specified compound list. High-resolution accurate mass (HRAM) mass spectrometry can overcome these limitations.

An Overview of VOC Sampling and Detection Techniques

Volatile Organic Compounds (VOCs) are the key air pollutants that act as precursors to major secondary pollutants including tropospheric ozone and secondary organic aerosols (SOA) and various health issues. Therefore, there is a need to have a simple, portable, reliable sampling method to quantify VOCs. This study reviews VOC sampling techniques based on feasibility, the material used, sensors and gas chromatographic instruments. A particular highlight on VOC sensors concerning their sensitivity, detection limit, response time and robustness has also been done. Also, the study focuses on critical aspects of VOC characterisation in ambient air along with the advantages and challenges of the methods. Around 65% of researchers have used the gas chromatography-based FID technique (GC-FID) for VOC characterisation in India. The typical sampling methods used in India are sorbent tubes or cartridges, air sample bags (commonly Tedlar bags), glass air sampling units and canisters. The portable real-time method is also used. The most common sampling method is passive sampling with sorbent tubes with activated carbon. However, extensive research is required on more sophisticated and world-class sensors, sampling and detection techniques to reach safe and recommended targets.

Teaching Analytical Instrumentation Through Remote Access – A Gas Chromatography Perspective

An approach to online laboratory exercises for analytical chemistry students with demonstrated practical exercises through the use of remote-controlled gas chromatography (GC) instrumentation is discussed. The approach allows for a practical-based learning activity to be carried out by students who are unable to attend in-person laboratory exercises and was conducted during the COVID-19 pandemic. Learning activities focused on the operation of GC instrumentation were completed prior to a research-based analysis activity being conducted by students. At the end of this experiment, the students are expected to understand, independently operate, and learn how to achieve better separation through the manipulation of GC settings, such as split/splitless injections, carrier gas flow rate, and oven temperature, and apply principles of GC to a practical application. Additional flexibility from this approach could also be beneficial during postpandemic and/or in the circumstance where students cannot physically attend the class.

Overview of Recent Development of Needle-Trap Devices for Analysis of Volatile Compounds

Needle-trap devices (NTDs) are another sorbent-based tool in the haystack of methods used in analytical extractions. Syringe needles, similar to those used for gas chromatography (GC) injection, can be partially filled with suitable sorbents and are used for extracting and collecting volatile organics, followed by injection into a GC instrument via thermal desorption. Although NTDs share many similarities and advantages of solid-phase microextraction (SPME), the larger sorbent bed provides robustness and offers potentially exhaustive extractions. This month, we take a look at the principles and applications of NTDs, and recent developments in their use.

Attractiveness preferences of Elaeidobius kamerunicus Faust. to different composition volatile organic compounds of female inflorescence on clay, sandy, and peat soil type

Preference of pollination insect Elaeidobius kamerunicus Faust. to the female inflorescence of oil palms influenced by volatile organic compounds (VOCs) emitted from the receptive flowers. VOCs, one factor of the pollination process, need more intensive research to escalate the production value of oil palm, such as fruit set. However, some cases occur in the suboptimal area where pollination is un-optimal. This research aims to study the E. kamerunicus preferences for different VOCs composition from female inflorescence on clay, sandy, and peat soil type. This study used a modified olfactometer as the test equipment. The extraction VOCs of female inflorescence on three different soil types used the maceration method and was analyzed by Gas Chromatography and Mass Spectrometry (GC-MS) instrument. The percentage of attraction E. kamerunicus preference to female inflorescence on clay, sandy, and peat soil types were 40%, 33%, and 24%. GC-MS analysis results showed that VOCs were only detected on clay soil types with a content of 1.11%, known as an attractant, namely Benzene, 1-methoxy-4 (2-Propenyl). It can affect the variation of preference of E. kamerunicus to the female inflorescence.

The Impact of Greenhouse Density on Cognitive Function in Primary School Children Using the WISC Method

Exposure to pesticides is associated with various health concerns and may also be related to impaired cognitive function. This study investigated the relationship between greenhouse density and cognitive function in primary school children using Wechsler Intelligence Scale for Children-Fourth Edition (WISC-IV) and environmental sampling. This study was conducted on 128 children (6–9 years old) in Ebrahimabad village, Ashkezar, Yazd, Iran in 2019, and 10 students were excluded from the study after filling consent form. The WISC-IV measured children’s cognitive function, and a flame ionization detector for gas chromatography (GC-FID) instrument was used to detect environmental exposure to pesticides. There was a significant inverse relationship between greenhouse density in children’s homes and cognitive function scores with verbal thinking scores (P value=0.003) and the total scale (P value=0.0001) on the WISC. Further, the results showed that the obtained verbal thinking scores are significantly related to their fathers’ education (P value=0.008) and occupation (P value=0.014). Moreover, the results of environmental exposure measurement confirmed the presence of malathion, ethion, chlorpyrifos, dieldrin, and oxadiazine with a maximum concentration of 183 µg/m3 in response to malathion. The present study indicated that increasing the density of the greenhouse reduces children’s cognitive functions. The results of ambient air analysis confirmed the environmental exposure to pesticides as well. Due to long-term chemical effects, management measures such as public education, substituting crop types, and the use of eco-friendly methods are unavoidable.

Valve-based comprehensive two-dimensional gas chromatography with quadrupole mass spectrometry detection using a porous layer open tubular column in the first dimension

A comprehensive two-dimensional gas chromatography instrument with quadrupole mass spectrometry (GC×GC-qMS) is developed and evaluated, by retrofitting a commercial GC-qMS instrument with a high temperature diaphragm valve (HT-DV) modulator. A porous layer open tubular (PLOT) column in the first dimension (1D), and a more polar wall coated open tubular (WCOT) column in the second dimension (2D) were used. The HT-DV can modulate analytes of any volatility and the combination of the PLOT and WCOT columns provides ample separation selectivity for samples containing an extended range of volatility from highly volatile analytes to analytes of more moderate volatility. In addition to instrument development, we describe data visualization considerations when upgrading from GC-qMS to GC×GC-qMS. Unlike time-of-flight mass spectrometry (TOFMS), the mass spectrum cycle time for qMS (defined as the sum of scan time and interscan delay) is a linear function of the range of mass channels (m/z) analyzed. If the cycle time does not divide evenly into the modulation period, PM, visual distortions will appear in the GC×GC chromatogram. We present two approaches to address this GC×GC chromatogram distortion issue. The first method does not require post-run computations; however, care must be taken in selecting an appropriate mass range to minimize the visual distortion issue. A half of the modulation period of total shift in the 2D separations with a PM of 2 s was determined tolerable for a 15 min separation, with 44 mass ranges (and their accompanying scan rate) deemed suitable out of 350 possible mass ranges. Also, a computational “resampling” method, which can be used to correct any qMS scan rate used was implemented. Figures-of-merit for the HT-DV modulated GC×GC-qMS instrument were also examined. Reproducible peak height (average RSDheight = 9.2%, s = 3.5%) and areas (average RSDarea = 9.3%, s = 2.8%) were obtained with low LODs (average LOD = 4.2 mg/L, s = 2.5 mg/L).

Quantitative Comparison of Tree Ensemble Learning Methods for Perfume Identification Using a Portable Electronic Nose

Perfume identification (PI) based on an electronic nose (EN) can be used for exposing counterfeit perfumes more time-efficiently and cost-effectively than using gas chromatography and mass spectrometry instruments. During the past five years, decision-tree-based ensemble learning methods, also called tree ensemble learning methods, have demonstrated excellent performance when solving multi-class classification problems. However, the performance of tree ensemble learning methods for the EN-based PI problem remains uncertain. In this paper, four well-known tree ensemble learning classification methods, random forest (RF), stagewise additive modeling using a multi-class exponential loss function (SAMME), gradient-boosting decision tree (GBDT), and extreme gradient boosting (XGBoost), were implemented for PI using our self-designed EN. For fair comparison, all the tested classification methods used as input the same feature data extracted using principal component analysis. Moreover, two benchmark methods, neural network and support vector machine, were also tested with the same experimental setup. The quantitative results of experiments undertaken demonstrated that the mean PI accuracy achieved by XGBoost was up to 97.5%, and that XGBoost outperformed other tested methods in terms of accuracy mean and variance based on our self-designed EN.

Study of Properties of Local Polypropylene Compared to International Standard Properties

This study was conducted in the Khartoum refinery in Algylee to study the properties of polypropylene (grade 113 &114) which are produced by the addition technique; they used refined propylene from Liquefied Petroleum Gas and Ziegler-Natta catalyst. The samples were taken from samples which are produced in (1-15)/08/2010 in three features (powder, granulates, and specimens). Both grades are homopolymer and isotactic polypropylene. They checked the component of liquefied petroleum gas by using a gas chromatography instrument and determination of thermal, mechanical, and physical properties. From the result, both grades differed in their properties according to molecular weight. Grade 113 has a large molecular weight which is suitable for the extrusion process while grade 114 has a small molecular weight which is suitable for the injection molding process. Each grade of polypropylene is within the standard range but they contain a slight amount (˂0.5ppm) of sulfur and moisture (49.1ppm) which are affecting product quality. However, if there is no separation unit the product will become yellowish and toxic.

Saturated And Unsaturated Fatty Acids Contents Analysis in Nasi Padang Chicken Gulai and Nasi Kandar Chicken Curry

Nasi Padang chicken gulai and Nasi Kandar chicken curry are traditional dishes made with coconut milk, thick sauce, and creamy gravy due to their lengthy processing. Chicken curry has a slightly spicy flavor, a reddish yellow sauce color, and a stronger aroma due to the addition of spices and herbs during the cooking process. This study aims to determine the saturated fatty acid and unsaturated fatty acid content in chicken gulai and chicken curry. The data of chicken gulai’s and chicken curry’s fatty acid was collected using Shimadzu’s GC (Gas Chromatography) instrument. As this study used an experimental research design, then T-test was employed in the data analysis process. The analysis results indicated that the saturated fatty acid content of chicken gulai and chicken curry was identical, as both were prepared using the same heated coconut milk. However, for an extended period, the saturated fatty acid content of chicken gulai and chicken curry increased, while the unsaturated fatty acid content remained unchanged, owing to the high spice content from some ingredients used in their processing. Besides, essential oils were also found in spices.

The concentration of BTEX in selected urban areas of Malaysia during the COVID-19 pandemic lockdown

Volatile organic compounds (VOCs) such as benzene, toluene, ethylbenzene and xylene (BTEX) are air pollutants that harm human health. This study aims to identify BTEX concentrations before the lockdown known as the Movement Control Order was imposed (BMCO), during the implementation of the Movement Control Order (MCO), and then during the Conditional Movement Control Order (CMCO). These orders were introduced during the COVID-19 pandemic in Malaysia. The study utilised data measured by the continuous monitoring of BTEX using online gas chromatography instruments located at three urban area stations. The results showed that the BTEX concentrations reduced by between −38% and −46% during the MCO compared to the BMCO period. The reduction of human mobility during the MCO and CMCO influenced the lower BTEX concentrations recorded at a station within the Kuala Lumpur area. The results of the BTEX diagnostic ratios and principal component analysis showed that the major source of BTEX, especially during the BMCO and CMCO periods, was motor vehicle emissions. Further investigation, using correlation analysis and polar plots, showed that the BTEX concentrations were also influenced by meteorological variables such as wind speed, air temperature and relative humidity.

Application of MXene as a new generation of highly conductive coating materials for electromembrane-surrounded solid-phase microextraction

Abstract For the first time, highly conductive thickly layered two-dimensional titanium carbide (MXene) was applied as a new coating agent for electromembrane-surrounded solid-phase microextraction (SPME) of triadimenol and iprodione as two model analytes. Preparation of the desired coated electrode was carried out using electrophoretic deposition of MXene on the surface of platinum electrode. Characterization of the prepared coated electrode was conducted using scanning electron microscopy and energy-dispersive X-ray spectroscopy. The coated electrode was located inside a hollow fiber membrane impregnated by 2-nitrophenyl octyl ether as the supported liquid membrane (SLM), while an aqueous solution was injected inside the hollow fiber lumen. Separation and quantification of the analytes were carried out using a gas chromatography instrument equipped with mass spectrometric detection. The effective parameters of the microextraction procedure comprising pHs of sample solution and the acceptor phase, composition of the SLM, extraction time, and the applied voltage were optimized using one-variable at-a-time method. Under the optimal conditions, the calibration curves of the analytes were linear (R 2 > 0.9973) in the range of 0.3–250.0 and 0.5–250.0 ng mL−1 for triadimenol and iprodione, respectively. The limit of detections was determined to be 0.10 and 0.15 ng mL−1 for triadimenol and iprodione, respectively. Repeatability and reproducibility of the method were evaluated by the calculation of intra-day and inter-day relative standard deviations (%). The applicability of the method was evaluated by quantitative analysis of the model analytes in environmental water samples. Relative recoveries in the range of 87.31–102.7% confirmed that the prepared coated electrode can be considered a reliable option in electromembrane-surrounded SPME techniques.

On the determination of the distillation curve of fatty acid methyl esters by gas chromatography

Given the increased concern for environmental protection and the need for finding viable alternatives for replacing fossil fuels in internal combustion engines, the research carried out in the recent past on the use of biodiesel has increased.Out of the physico-chemical characteristics of fuels, the volatility has a great influence on the combustion process. It is therefore important to accurately obtain all the data related to the volatility of the fuels. A way to assess the fuel’s volatility is the distillation curve (DC). The simplest way to determine DC is at atmospheric pressure. However, for low volatility fuels such as biodiesel, atmospheric distillation is not indicated, therefore, using of alternative methods is needed. One method that can be used in this case is the determination of the boiling range distribution by gas chromatography (GC). The GC equipment used for this purpose is specifically designed for this aim, meaning that the determination of DC by the GC itself is a given or standard feature of the equipment. However, in many labs, such specifically designed GC equipment is not available.In this context, the paper aims at providing a GC based method for finding the boiling points of fatty acid methyl-esters (FAME) on standard FID based GC instrument for those researchers wishing to add new capabilities to their existing GC instruments. To validate the method, five different samples of pure biodiesel were analyzed, and the results obtained by applying this method were confirmed by comparison with the distillation curve obtained via vacuum distillation.

Petroleum Hydrocarbon Quarterly Boiling Range Distribution of Iraqi Crude Oil by Simulated Distillation Method

This study includes analysis of different crude oil stock for various field Iraqi oil by gas chromatography instrument, using simulated distillation technique for determining the initial and final boiling point distribution and specified compound distillation information (normal paraffins) (Recovery W/W) for (nC5 – nC44), ASTM-D5307 becomes the analytical method. This method need tow samples; the first one spiked with internal standard and the second without internal standard. This analysis for quantitative and qualitative oil characterization which is often useful for evaluating the range of hydrocarbons in crude oil using Simulated Distillation. The study was performed using:
 
 Quarterly analysis of SIMDIS GC Distillation for three field (East Baghdad, Badra, Amara)
 Comparison of analyzes of SIMDIS GC Distillation with Different API (light, intermediate, heavy) with Initial boiling point (IBP).
 Finding experimental relationship between API and Initial boiling point (IBP):
 
 
 The result of this study shows that the boiling point increase as the number of carbon is increase, the values of n-Pentane (nC5) to n- Tetratetracontane (nC44) (w/w) changes from winter and summer (difference in temperatures), Positive correlation between C6 and C5 with API, where their percentages increase with increasing API for crude oil and C6 and C5 are lower in summer than in winter due to the evaporation of light components of the samples in summer. Initial boiling point increase as the API is decrease that mean in crude oil have heavy component increases and light component decrease (inverse relationship).

Incorporating Sulfur Atoms into Palladium Catalysts by Reactive Metal–Support Interaction for Selective Hydrogenation

Incorporating Sulfur Atoms into Palladium Catalysts by Reactive Metal–Support Interaction for Selective Hydrogenation

Development of an in situ dual-channel thermal desorption gas chromatography instrument for consistent quantification of volatile, intermediate-volatility and semivolatile organic compounds

Abstract. Aerosols are a source of great uncertainty in radiative forcing predictions and have poorly understood health impacts. Most aerosol mass is formed in the atmosphere from reactive gas-phase organic precursors, forming secondary organic aerosol (SOA). Semivolatile organic compounds (SVOCs) (effective saturation concentration, C*, of 10−1–103 µg m−3) comprise a large fraction of organic aerosol, while intermediate-volatility organic compounds (IVOCs) (C* of 103–106 µg m−3) and volatile organic compounds (VOCs) (C* ≥ 106 µg m−3) are gas-phase precursors to SOA and ozone. The Comprehensive Thermal Desorption Aerosol Gas Chromatograph (cTAG) is the first single instrument simultaneously quantitative for a broad range of compound-specific VOCs, IVOCs and SVOCs. cTAG is a two-channel instrument which measures concentrations of C5–C16 alkane-equivalent-volatility VOCs and IVOCs on one channel and C14–C32 SVOCs on the other coupled to a single high-resolution time-of-flight mass spectrometer, achieving consistent quantification across 15 orders of magnitude of vapor pressure. cTAG obtains concentrations hourly and gas–particle partitioning for SVOCs every other hour, enabling observation of the evolution of these species through oxidation and partitioning into the particle phase. Online derivatization for the SVOC channel enables detection of more polar and oxidized species. In this work we present design details and data evaluating key parameters of instrument performance such as I/VOC collector design optimization, linearity and reproducibility of calibration curves obtained using a custom liquid evaporation system for I/VOCs and the effect of an ozone removal filter on instrument performance. Example timelines of precursors with secondary products are shown, and analysis of a subset of compounds detectable by cTAG demonstrates some of the analytical possibilities with this instrument.