Gas Chromatographic Method Research Articles

ADVANCES IN GAS CHROMATOGRAPHY FOR DETECTING PROCESS IMPURITIES: A COMPREHENSIVE REVIEW ON METHOD DEVELOPMENT, VALIDATION, AND SCALABILITY

Background:Gas chromatography (GC) remains a cornerstone in analytical chemistry, extensivelyemployed for the detection and quantification of process impurities, including volatile organic compounds (VOCs) and genotoxic impurities (GTIs) in pharmaceutical and industrial applications. Main Body:This review examines the evolution of conventional GC techniques with a focus on method development and validation in line with International Council for Harmonisation (ICH) guidelines. Special emphasis is placed on nitrosamines, scalability, cost-benefit analysis, and the integration of advanced technologies, as these aspects are pivotal in addressing modern analytical challenges.Nitrosamines, due to their carcinogenic potential, have become a focal point of regulatory scrutiny, demanding highly sensitive methods for trace-level detection. Scalability ensures that laboratory-developed GC methods can meet industrial-scale requirements efficiently. The cost-benefit analysis underscores the balance between analytical precision and economic feasibility, which is critical for widespread adoption. Additionally, the integration of advanced technologies such as sustainable practices not only enhances performance but also aligns with evolving environmental and industrial needs. Conclusion: By synthesizing recent advancements, this article highlights emerging challenges and future directions for GCs role in ensuring pharmaceutical quality and safety. Citations throughout emphasize the fields progress.

Pharmacognostic Study of the Leaves of Ptilostemon greuteri Raimondo & Domina, a Rare Sicilian Paleoendemic Species

Ptilostemon greuteri Raimondo & Domina is a rare Sicilian paleoendemic species. The aim of study was to investigate the micro-morphological features of leaves by light and scanning electron microscopy, to elucidate the phytochemical profile of essential oil (EO), n-hexane (HE) and hydroalcoholic extract (HAE) by gas and liquid chromatographic methods, and antioxidant and anti-inflammatory properties by in vitro assays. Leaves had a large lanceolate blade, dark green on the upper side and greyish on the lower one with a dense tomentum. Epidermis showed many protruding stomata. By lipid-specific dyes, lipophilic droplets within cells surrounding the secretory ducts and within palisade cells were detected, whereas the presence of polyphenols in the mesophyll was highlighted by toluide blue O. These observations have driven the subsequent phytochemical analyses. EO showed germacrene D (29.94%), carvacrol (14.3%) and eugenol (12.93%) as the most abundant compounds. In the HE, docosane, oleic and palmit acid, and lupeol were the predominant compounds, whereas caffeoylquinic acid and quercetin derivatives were the most common polyphenols in HAE. Considering the detected mean half-inhibitory concentrations (IC50), HAE showed predominant antioxidant activity (IC50 30.54 µg/mL), while EO showed predominant anti-inflammatory activity (IC50 397.59 µg/mL). Finally, HE, rich in medium-to-long fatty acids, showed the best protease inhibitory activity

Оцінка безпечності дієтичної добавки “Rheumacаre Ultra”, оптимізація дієтологічних умов для функціонування суглобів

In Ukraine, among chronic diseases, pathology of the musculoskeletal system is one of the most frequent problems, and about 3.5 million people have problems with the musculoskeletal system and its various complications, which require continuous therapy throughout life. Aim. Generalization of the results of a comprehensive sanitary and hygienic assessment of the safety for consumers of a dietary supplement created to support the normal functioning of joints; data analysis of electronic publishers Scopus, Web of Science, PubMed, other foreign and domestic sources of scientific information on the research topic. Materials and Methods. The dietary supplement "Rheumacare Ultra" has been tested for the content of heavy metals and pesticides for compliance with the State Sanitary Rules and Regulations of Ukraine. The microbiological safety of the dietary supplement was controlled by the content of mesophilic aerobic and facultative anaerobic microorganisms. The method of ultra-high-performance high-speed mass spectrometric liquid chromatography with electron spray ionization (UPLC-MC/MC, Waters, USA) and the gas chromatography method were used to determine the content of pesticide residues; the content of lead, cadmium, mercury was determined by the atomic emission method (instrument ‒ atomic emission spectrometer "SHIMADSU ICPE ‒ 9820"). Results. Based on expert assessment of documentation, analysis of data sources of scientific information, results of sanitarychemical, radiological and sanitary-microbiological studies, it was established that dietary supplement "Rheumacare Ultra" ("Rheumacare Ultra") is safe for the health of consumers and can be used for purpose: to promote the normalization of metabolism, optimization of the chemical composition of the diet, creation of optimal dietary conditions to support the normal functioning of the musculoskeletal system, in particular ‒ joints; to purposefully affect the growth of the level of adaptation capabilities of the human body in conditions of constantly increasing harmful effects of the environment. Conclusions. Assessing the safety of traditional Ayurvedic recipes is a difficult task due to the multicomponent composition of organic-mineral complexes and the lack of complete information on the chemical structure of biologically active components of endemic plants and their impact on human health. Keywords: dietary supplements, sanitary and hygienic assessment, musculoskeletal system, joints.

Манкоцеб: медико-санітарні нормативи, контроль харчової безпеки та запобігання технічним бар’єрам у торгівлі

Introduction. Mancozeb is a widely used synthetic fungicide from the group of dithiocarbamates. Numerous mancozeb preparations are used to protect many agricultural crops and obtain a significant number of products from them for consumption in Ukraine, as well as for export to other countries of the world. In accordance with Regulation (EC) No. 1107/2009, a decision was made concerning the «approval of the active substance mancozeb is not renewed». Therefore, it is necessary to reduce the parameters of the permissible exposure of mancozeb residues to its limit of quantification (LOQ), which is 0.01 mg/kg, and food products with higher levels of this substance have become non-compliant and, starting from January 2022, cannot be placed on the EU market. Purpose. To determine the limits of controlled values of mancozeb content in agricultural products of plant origin in accordance with EU requirements, considering the parameters of permissible exposure on human health and control over the use of mancozeb for plant protection in Ukraine. Materials and Methods. Preparations with the active substance (a.s.) mancozeb (from 302 to 800 g a.s./kg) in the form of wettable powder (WP) or water-soluble granules (WG) were used during state trials in Ukraine on grapes, potatoes, and tomatoes, onions, cucumbers, sugar beets and grain bread crops with the general rates of mancozeb consumption from 2.4 to 14.4 kg per year/ha. The content dynamics of residual amounts of mancozeb and its metabolite – ethylenethiourea (ETU) were studied by the methods of vapor phase gas chromatography and high-performance liquid chromatography, respectively. Evaluation of results and medical-sanitary standardization of mancozeb and ETU residues were performed in accordance with national and international documents. Results. Within the established waiting periods before harvesting of agricultural products the residual amounts of mancozeb/ETU were less than the LOQs of 0.05/0.005-0.05 mg/kg, respectively. The LOQs of mancozeb according to the official methods in force in Ukraine corresponded to the LOQs of the methods used in the EU until January 2022, but do not ensure control of mancozeb at the level of 0.01 mg/kg in accordance with the current requirements for placing products on the EU market, except for SSTU (State Standards of Ukraine) EN 12396-2:2003. The parameters of acceptable exposure to mancozeb and its metabolite ETU in Ukraine provided for a higher level of human health protection than the regulations adopted in the EU until January 2022. Conclusions. Adherence to the researched and approved application rates and waiting periods before harvesting in Ukraine ensures the absence of residual mancozeb amounts and ETU in plant origin agricultural products at the level of the LOQ and its compliance with the national parameters of permissible exposure on human health. If the EU requirements for the content of mancozeb in food products do not exceed the proposed LOQ of 0.01 mg/kg, domestic agricultural products of plant origin can be placed on the EU market. To prevent the appearance of technical barriers related to the reduction of LOQs of active substances of plant protection products (PPPs) in food raw materials and food products, residues determination methods should provide for LOQs of controlled substances not exceeding 0.01 mg/kg. Keywords: mancozeb, agricultural products, limit of quantification of residues, food safety, technical barriers.

Lomatium Species of the Intermountain Western United States: A Chemotaxonomic Investigation Based on Essential Oil Compositions.

Lomatium is a genus of 98 species, widely distributed in western North America. This work presents a chemometric analysis of the essential oils of seven species of Lomatium (L. anomalum, L. dissectum var. dissectum, L. multifidum, L. nudicaule, L. packardiae, L. papilioniferum, and L. triternatum var. triternatum) from the intermountain western United States (Oregon and Idaho). The essential oils were obtained by hydrodistillation and analyzed by gas chromatographic methods. Lomatium packardiae essential oil can be characterized as limonene-rich, L. anomalum is a species rich in sabinene and α-pinene, and L. multifidum essential oils were rich in myrcene, while L. dissectum var. dissectum essential oils were dominated by octyl acetate and decyl acetate, L. papilioniferum essential oils from western Idaho had high p-cymene and 2-methyl-5-(1,2,2-trimethylcyclopentyl)phenol concentrations, while those from Oregon had relatively high β-phellandrene and sedanenolide levels. The essential oils of L. triternatum var. triternatum were too variable to confidently assign a chemical type. The major components in the L. nudicaule essential oils were β-phellandrene (16.0-45.7%), (Z)-ligustilide (5.6-47.1%), (E)-β-ocimene (3.3-9.9%), and δ-3-carene (0.2-12.6%). The enantiomeric distributions of α-pinene, camphene, sabinene, β-pinene, limonene, and linalool were also utilized to discriminate between the Lomatium taxa. There are not enough consistent data to properly characterize L. triternatum var. triternatum or the Oregon L. papilioniferum essential oils. Additional research is needed to confidently describe the chemotype(s) of these species.

Leaf Essential Oil Compositions and Enantiomeric Distributions of Monoterpenoids in Pinus Species: Pinus albicaulis, Pinus flexilis, Pinus lambertiana, Pinus monticola, and Pinus sabiniana.

Members of the Pinus genus are well known for their medicinal properties, which can be attributed to their essential oils. In this work, we have examined the leaf essential oils of five understudied Pinus species collected from various locations in western North America. The essential oils were obtained by hydrodistillation and analyzed by gas chromatographic methods, including enantioselective gas chromatography. Pinus albicaulis was dominated by (+)-δ-3-carene; Pinus flexilis was dominated by α-pinene (mostly (+)-α-pinene) and (-)-β-pinene; Pinus lambertiana was dominated by (-)-β-pinene; Pinus monticola was dominated by (-)-β-pinene, (+)-δ-3-carene, and (-)-α-pinene; and Pinus sabiniana was rich in (-)-α-pinene and limonene. While this work adds to our knowledge of Pinus essential oils, additional research is needed to more fully appreciate the geographic and altitudinal variations in the volatile compositions of these Pinus species.

Assessment of heavy metals, PAHs, and pesticide levels in yerba mate on the European market.

Although yerba mate has been known and used for hundreds of years, not all of its properties have been fully understood yet. Yerba mate is a source of many desirable substances, but it may also contain toxic metals and other substances that are harmful to health. Fifteen samples of yerba mate tea from three South American countries were analyzed. The content of Cr, Ni, and Cd was determined using the AAS technique, while the PHA's content was determined with the gas chromatography method. Our studies show that some of the analyzed substances present in Ilex paraguariensis may exceed their acceptable levels specified in European standards established for the given substances. All analyzed samples contained the determined metals, where the concentrations of individual elements ranged from 1.92 ± 0.38 to 0.12 ± 0.05µg/g (for Cr), from 4.86 ± 0.28 to 1.72 ± 0.14µg/g (for Ni), and from 0.0008 ± 0.000 to 0.0695 ± 0.0745µg/g (for Cd). The total PAH content ranged from 0.064 to 0.585mg/kg. Yerba mate samples from Brazil were characterized by a lower PAH content (0.064-0.254mg/kg), compared with mate from Argentina and Paraguay (0.084-0.374 and 0.197-0.585mg/kg, respectively). Pesticide residues were found only in samples from Argentina and Paraguay, while samples from Brazil did not contain those compounds. Only four active substances belonging to the group of herbicides, fungicides, and insecticides were detected, two of them not approved for use in the EU: chlorpyrifos and fenbuconazole. The most frequently detected compounds in yerba mate samples were pendimethalin (in four samples), fluazifop-p-butyl and fenbuconazole (detected in two samples), and chlorpyrifos (in one sample).

(ECS Charles W. Tobias Young Investigator Award Address) Lithium Oxide Content in the Li Metal Anode Solid Electrolyte Interphase Drives High Coulombic Efficiency

Despite remarkable improvements in Li cycling Coulombic efficiency (CE) in recent years, Li anodes still cannot meet the >99.9% CE needed for >1,000 cycle life. This shortfall arises from uncontrolled reactivity at the solid electrolyte interphase (SEI) and its resulting properties, leading to inhomogeneous plating and stripping, continuous electrolyte consumption, and loss of active Li inventory. Despite progress in electrolyte design, the lack of precise SEI understanding hinders attempts to rationally design an improved interface towards bridging remaining gaps in CE.Recent advancement in quantitative chemical analysis of cycled Li anodes has enabled unprecedented understanding of the origin of capacity loss. Pioneering work by Meng et al. demonstrated the method of titration gas chromatography (TGC) for quantifying the amount of metallic Li0 which becomes entrapped in the electrode residuals over repeated cycling.1 The authors showed that Li0 is mainly responsible for capacity loss at intermediate values of CE, and decreasing Li0 is therefore effective for improving performance. As CE becomes very high, however, losses become dominated by the SEI formation itself.2 This talk will describe our efforts to build upon and advance chemical titration by coupling to gas chromatography (GC) and other liquid-phase assays, which has enabled tracking of an extended array of key SEI phases and their proportions over cycling. Beyond Li0, such methods enable accurate resolution of capacity loss as stranded phases to semicarbonates (ROCO2Li), lithium carbide (Li2C2), olefins (RLi), LiF, and P-containing phases, as well as total Li loss, which allow for compositional trends with CE to be revealed. In a prior work,3 we achieved chemical resolution of up to ~70% of the total capacity loss and ~33% of SEI phases, yet still with significant unknown phase contributions. Recently, we have further advanced these titration techniques to quantify an additional key SEI phase, lithium oxide (Li2O),4 which substantially improves upon these numbers. Statistical analysis of correlations between major ionic and organic phases and CE unambiguously reveal that Li2O content is the most strongly predictive of high CE, even moreso than LiF content—widely asserted to be a uniquely beneficial SEI component—or decreasing Li0. By designing several new O-rich and low-F or F-free electrolytes that achieve highly competitive CE breaching 99%, we reveal a compelling electrolyte design landscape based on oxygenation, rather than fluorination. Fang, J. Li, M. Zhang et al., Nature 2019,572, 511–515.M. Hobold, J. Lopez, R. Guo, et al., Nature Energy 2021, 6, 951-960.M. Hobold and B. M. Gallant, ACS Energy Letters 2022, 7, 3458-3466.M. Hobold, C. Wang, K. Steinberg et al., Nature Energy 2024 (published ASAP).

Development and validation of a gas chromatography method for quantifying metham sodium in diverse plant origin foods

To ensure food safety and public health, it is essential to establish dependable methods for the qualitative and quantitative analysis of pesticide residues in plant origin foods. This study developed and optimized a gas chromatographic method using the QuEChERS approach for detecting metham sodium residues in 22 plant origin foods. The method was refined by adjusting inlet temperature and transformation conditions to effectively convert metham sodium into its primary metabolite, methyl isothiocyanate. Furthermore, parameters such as the extraction solvent type, volume, and purifying agent were systematically optimized. The method achieved a limit of quantification (LOQ) of 0.05 mg/kg, with a linear range from 0.025 to 1.0 mg/L and determination coefficients (R²) from 0.9892 to 0.9999. Recovery rates ranged from 82 % to 102 %, with relative standard deviations (RSDs) between 0.3 % and 6.8 %. Inter-laboratory validation, in accordance with EU SANTE guidelines, confirmed the method's accuracy and reliability. Validation results passed Cochrane's and Grubbs' tests, with repeatability RSDs between 0.70 % and 5.28 % and reproducibility RSDs from 3.62 % to 21.89 %. This method provides a reliable and effective approach for determining metham sodium residues, and addresses a critical gap in current analytical techniques, offering significant contributions to residue monitoring and food safety regulations.

Ultrafast, simple, practical and environmental-friendly HS-UFGC-FID approach for furan and six alkylfurans determination in fruit juice samples

A simple, rapid, sensitive and robust gas chromatographic method was developed forthesimultaneous determination of seven furans in fruit juice samples. The target analytes were transferred directly from the headspace of incubated samples without any preparation step. Thedeveloped method exhibits satisfactory limits of detection (from 1.0 to 2.4 µg/L) and limits ofquantification (from 3.1 to 7.3 µg/L), and average recoveries between 86 % and 107 %. The developed procedure was used for furan and alkylfurans determination in the juices of different berries. During research, two types of juices were tested, namely store-bought and homemade juices. It should be noted that homemade elderberry juice contained the highest level of furans. The HS-UFGC-FID procedure was assessed for green and blue characters using AGREE and BAGI indexes.

Amino Acid Profile of Goat Milk Kefir with Lacticasei bacillus casei AP and Oat Milk during Storage

Background: Accurate and up-to-date information about amino acid profile is crucial in the production and promotion of dairy products and fermented milk because both components contribute to the nutritional and market value of the dairy products. Methods: This study aims to evaluate the amino acid profile of goat milk kefir supplemented with Lacticaseibacillus casei AP, oat milk or both during 14-day storage using the gas chromatography method. Result: The results demonstrated that Lacticaseibacillus casei AP and oat milk incorporated into kefir production significantly affected amino acids (aspartac acid, glutamic acid, tyrosine, valin, phenylalanine, ileusin and leucine).The dominant amino acids in the treatments were phenylalanine (46.66 ppm), glutamic acid (40.40 ppm) and lysine (23.91 ppm). The storage time only significantly reduced the amount of valine. Conclusively, incorporating Lacticaseibacillus casei AP, oat milk or both into goat milk kefir did not negatively affect the amino acid profile during storage time.

Solubilization of n-hexadecane by micellar solutions of trehalolipid - surfactants of biological origin

Objectives. To isolate biosurfactants of glycolipid nature produced by oil hydrocarbon degrading bacteria and to establish their ability to solubilize hydrophobic compounds in the case of n-hexadecane.Methods. Trehalolipids were isolated from bacteria Rhodococcus erythropolis X5 (VKM Ac-2532 D) and Rhodococcus erythropolis S67 (VKM Ac-2533 D) included in the MikroBak biopreparation for the bioremediation of oil-contaminated territories. The genome of R. erythropolis X5 is deposited in the National Center for Biotechnology Information database under GenBank accession numbers CP044283 and CP044284, BioSample – SAMN12818508, BioProject – PRJNA573614, and SRA – PRJNA573614. The content of trehalolipid biosurfactants was estimated by the amount of trehalose in aqueous solutions of biosurfactants using the phenolsulfur method. The surface tension of the obtained aqueous solutions of biosurfactants was determined by the du Noüy ring method using a Kruss K6 tensiometer (Kruss, Germany). The critical concentration of micelle formation was determined by the inflection point on the curves of surface tension dependence on the concentration of the biosurfactant solution. In order to establish the solubilizing ability of biosurfactants, the residual concentration of n-hexadecane in an aqueous sample of different concentrations was determined using a gas chromatographic method of analysis.Results. At a constant surface tension of 24.2 mN/m and 25.0 mN/m for R. erythropolis X5 and R. erythropolis S67, respectively, the critical micelle concentration for both strains was 33 mg/L (3.8 ∙ 10−5 mol/L). The solubilizing effect of Rhodococcus trehalolipid micellar solutions against hydrophobic n-hexadecane was demonstrated by gas chromatographic analysis. The solubilization process was characterized using molar solubilization capacity (Sm), molar solubilization ratio (MSR), micelle–water partition coefficient (Km), and solubilization energy 0 (ΔGS ). It was shown that the solubilization process of n-hexadecane proceeds spontaneously 0 (ΔGS = −35.5 kJ/mol) and more efficiently (Sm = 4.3 mol/mol, MSR = 4.7 mol/mol) than in comparison with other biosurfactants of glycolipid nature.Conclusions. Based on the value of the molar solubilization coefficient, it can be concluded that trehalolipids of the R. erythropolis X5 strain solubilize n-hexadecane in aqueous solutions to a greater extent than compared to other biosurfactants of a glycolipid nature, but are inferior to synthetic surfactants.

Trace-level quantification of NDMA in levosulpuride active pharmaceutical ingredient and tablet formulation Using UFLC-MS/MS

Nitrosamine impurities identified in several pharmaceuticals during recent times has raised concerns leading to product recalls worldwide and necessitating sensitive liquid and gas chromatographic methods for trace level detection of nitrosamine impurities. This study developed and validated a ultra-fast liquid chromatography-tandem mass spectrometry (UFLC-MS/MS) method for the quantification of NDMA in Levosulpuride drug substance and tablet formulation. Current method utilizes a triple quadrupole analyzer, atmospheric pressure chemical ionization (APCI) ionization source and multiple reaction monitoring (MRM) scan mode for the analysis. Chromatographic separation was achieved on a Gemini NX-C18 column (150 × 4.6 mm, 3 µm) maintained at 40 °C. The mobile phase consisted of a binary gradient of solvent A (0.1 % formic acid in water) and solvent B (methanol), with a total run time of 18 minutes. Current method achieved excellent linearity, recovery, precision, and sensitivity. Greenness of the developed method was evaluated using the GAPI, AGREE, and AES metrics. Current method is sensitive and selective for NDMA in levosulpuride drug substance and tablet formulations and can be employed for routine quality control analysis in pharmaceutical industry.

Fluxes of carbon dioxide gases (CO2) in the mangrove soil of Passo Village, Ambon City

Mangrove ecosystems play a significant role in carbon absorption. However, the accumulation of organic matter in mangrove sediments undergoes decomposition, which triggers the release of CO2 gas flux. This study aimed to analyze the CO2 gas flux in mangrove sediments of Negeri Passo, Ambon City. Gas data collection was performed using cylinder canopies at the three observation stations. Gas was passed through the syringe five times with an interval of 30s. Gas concentration analysis was carried out using the gas chromatography method, while CO2 flux was analyzed with flux equations referring to slope regression, volume and area of the scope, temperature, molecular weight of the gas, ideal gas settings, and time constants based on gas intake intervals. The results showed that the average CO2 concentration in St. 1 was 465.14 ± 96.52 ppm, and was the lowest compared to St. 2 and St. 3 with values of 638.60 ± 90.05 ppm and 630.98 ± 54.09 ppm, respectively. Meanwhile, the average CO2 flux was 50.44 mg/m2/hour. The largest CO2 gas flux was observed at St. 2 at 103.69 mg/m2/hour. Meanwhile, the lowest flux was found at St. 3, which was 16.24 mg/m2/hour. Based on this, it can be concluded that] the mangrove ecosystem in Negeri Passo has a higher concentration of CO2 gas than the average concentration of climate change stabilization scenarios. However, the CO2 flux was lower than that at other locations in the Ambon Dalam Bay area. In addition, the potential for significant carbon sequestration based on the Tier 1 model approach indicated that mangrove ecosystems in this location play an important role in climate change mitigation.

Fermented By-Products of Banana Wine Production Improve Slaughter Performance, Meat Quality, and Flavor Fingerprint of Domestic Chicken.

This study aimed to compare the effects of incorporating fermented feed into daily diets on the slaughter performance, meat quality, and flavor compounds of 120 domestic chickens over a 140-day period. A total of five groups (n = 24), including the control group (CK) of the Guangxi Partridge chickens received a standard base diet. The other four groups were provided with pellets that had been added with 10% fermented banana peel (Pe-10), 20% fermented banana peel (Pe-20), 10% fermented banana pulp residue (Pu-10), and 20% fermented banana pulp residue (Pu-20). The flavor compounds in the meat samples of the chickens in these groups were determined using the gas chromatographic method. The results demonstrated that the chickens in the Pe-10, Pe-20, Pu-10, and Pu-20 groups exhibited pectoral muscle percentages, thigh muscle percentages, and total fatty acid content of chest meat that were higher than those observed in the CK group. The moisture content, meat color, carcass weight, total net weight, and abdominal fat percentage of the meat samples in these experimental groups exhibited no notable differences. The flavor compounds in the meat samples of the chickens fed with the two concentrations of fermented banana peel and banana residue were found to be significantly different from those in the control group, with p-values less than 0.05. As the quantity of fermented banana peel incorporated into the daily ration was increased from 10% to 20%, a notable alteration in the flavor compounds present in the chicken samples was observed. The chickens that were provided with fermented banana peels and pulps in their diets exhibited superior slaughter performance and meat quality, particularly in the case of the Pu-10 group, in comparison to the control chickens.

End Column Reverse Chromatography as a Novel Approach for Enhanced Separation: A Pilot Study.

Currently, the most popular technique in gas chromatography (GC) is the "temperature programming", where the temperature increases from the start of the injection. This leads to faster elution of analytes compared to isothermal methods. However, isothermal methods are considered optimal for separating compounds with similar retention times. Another interesting technique that provides higher resolution is the dynamic thermal gradient gas chromatography (TGGC), where separations are achieved as a decreasing thermal gradient. This gradually decreases the positive gas velocity. Nevertheless, it was proven that GC techniques with negative velocity gradients don't improve the resolution of compounds with nearly identical retention times. Optimizing a new GC approach to combine both the short time from positive temperature ramps programming, and the enhanced separation of the negative ramps of the TGGC, a model under the name of "end column reverse chromatography". The process simply consists of two steps, the first is a normal positive ramp from the start of the injection, the second step is a negative thermal ramp at a time that is around the retention time of the first eluting peak. This will decrease the solute velocity almost solely for the second compound leading to relatively enhanced separation. Optimized ECRC method increased the resolution of two isomers (trans and cis chlordane) from 1 (slightly overlapping) in case of temperature programming to 2.78 as shown in this study. This comes in expense of the width and intensity of the peaks, where the intensity decreased about 17% and 12% for cis and trans chlordane, and the peak width increased with 37% and 77% for the same compounds respectively. ECRC is a novel model for enhanced separation that comes with some drawbacks. It can be an alternative approach to get a fast GC method with enhanced separation for isomers.

Reference Material for the Composition of Fuel Oil

Electrical transformers are a key element in the process of distributing electricity from the producer to the final consumer. The reliability of electrical transformers is ensured through systematic monitoring of the structural condition using chemical analysis of fuel (transformer) oil used for electrical insulation and cooling of transformers. The working life of energy oil and paper insulation can be assessed by evaluating the content of antioxidant additive (ionol) and furan derivatives (furfuryl alcohol, furfural, 2-acetylfuran and 5-methylfurfural). The article provides a critical analysis of methods for measuring ionol and furan derivatives in oils. In particular, it has been established that the most widely used methods for the identification of ionol and furan derivatives are liquid and gas chromatography methods with preliminary isolation of analytes based on the principles of liquid/solid-phase extraction. At the same time, the need for matrix reference materials with established metrological traceability was identified for metrological support of methods for measuring the content of ionol and furan derivatives in oils. Therefore, the purpose of this study was the development of a certified reference material (CRM) for the composition of fuel oil. The technology for producing such a CRM makes it possible to prepare the material with the required concentrations of analytes. The article describes the sequence of preparation of a CRM batch and presents the conclusions of studying the stability and between-bottle homogeneity of the material. The given calculation of the standard uncertainty for the certified value of the CRM from the characterization method, heterogeneity, and instability of the material in accordance with GOST ISO Guide 35–2015 deserves attention. The metrological traceability of certified values of the CRM to the unit of value «mass fraction of a component» reproduced by the State Primary Standard of units of mass (molar) fraction and mass (molar) concentration of organic components in liquid and solid substances and materials based on liquid and gas chromatography-mass spectrometry with isotope dilution and gravimetry (GET 208–2019). The competence of the study is confirmed by the fact that the CRM was recognized as GSO 12232–2023.

Oxidation of Geraniol on Vermiculite—The Influence of Selected Parameters on the Oxidation Process

Geraniol is a compound belonging to the group of monoterpenes that finds many applications in organic syntheses, medicine and cosmetics. The following properties of geraniol and its derivatives are of particular interest in medicine: its anti-inflammatory, antioxidant, antimicrobial and anticancer effects. The geraniol oxidation process was carried out using a mineral of natural origin—vermiculite. Vermiculite is a catalyst that perfectly fits into modern trends in the organic industry, where the aim is to use cheap, renewable and relatively easily available catalytic materials (vermiculite is found on continents including Africa, North America, South America, Australia and Asia). Preliminary studies on the oxidation process of geraniol on vermiculite was carried out in a glass apparatus using molecular oxygen supplied by means of a bubbler and magnetic stirrer with a heating function. During the oxidation process of geraniol on vermiculite, the influence of the following parameters was examined: the temperature, amount of catalyst and reaction time. The main parameters of the process, on the basis of which the most favorable process conditions were selected, were the selectivity of the transformation to 2,3-epoxygeraniol, citral and 2,3-epoxycitral, and the conversion of geraniol. The composition of the post-reaction mixtures was determined qualitatively and quantitatively using the gas chromatography method. In addition, vermiculite was subjected to instrumental tests, such as XRD, SEM, EDX, FTIR and UV-VIS. Moreover, the specific surface area, pore volume and pore volume distribution were estimated on the basis of N2 sorption at −196 °C and also the acid-site concentration in vermiculite was established.

Application of straw-derived biochar: a sustainable approach to improve soil quality and crop yield and reduce N2O emissions in paddy soil.

The burning of agricultural straw is a pressing environmental issue, and identifying effective strategies for the rational utilization of straw resources is decisive for achieving sustainable development. Owing to its high carbon content and exceptional stability, straw biochar produced via pyrolysis has emerged as a key focus in multidisciplinary research. However, the efficacy of biochar in mitigating nitrous oxide (N2O) emissions from paddy soils is not consistent. A 2-year field experiment was conducted and investigated the impact of biochar derived from two feedstocks (rice straw and wheat straw, pyrolyzed at 450°C) on N2O emissions, global warming potential (GWP), greenhouse gas intensity (GHGI), nitrogen use efficiency (NUE), crop yield, and soil quality. The static chamber technique was used for collecting N2O gas samples, and concentrations were analyzed through gas chromatography methods. The treatment combinations included BR0 (control), BR1 (NPK at the recommended dose, 120:60:40kgha-1), BR2 (wheat straw biochar, 5 t ha-1), and BR3 (rice straw biochar, 5 t ha-1). The results exhibited that cumulative N2O emissions from BR2 and BR3 treatments decreased by 10.55% and 13.75% respectively, compared to BR1. Lower GWP and GHGI were observed under both biochar treatments compared with BR1. The highest rice grain yield (3.48Mgha-1) and NUE (76.72%) were recorded from BR3, which also exhibitedthe lowest yield-scaled N2O emission. We observed positive correlations between soil nitrate, ammonia and water-filled pore spaces, while NUE showed negative correlations with N2O emissions. Significant (p < 0.05) improvements in soil quality were also detected in both the biochar treated plots, indicated by increased soil pH, water holding capacity, porosity, and nutrient contents. Overall, the results suggest that applying biochar at a rate of 5 t ha-1 in paddy soil is a viable nutrient management strategy with the potential to reduce reliance on inorganic fertilizers, mitigate N2O emissions, and contribute to sustainable food production.

Inter-laboratory study for extraction testing of medical devices

Biocompatibility evaluation of medical devices often relies on chemical testing according to ISO 10993–18 as a critical component for consideration. However, the precision associated with these non–targeted chemical characterization assessments has not been well established. Therefore, we have conducted a study to characterize intra–laboratory (repeatability) and inter–laboratory (reproducibility) variability associated with chemical testing of extractables from polymeric materials. To accomplish this, this study focused on two polymers, each with nine chemicals that were intentionally compounded into the materials. Eight different laboratories performed extraction testing in two solvents and subsequently characterized the extracts using gas chromatography and liquid chromatography methods. Analysis of the resulting data revealed the central 90 % range for the repeatability and reproducibility relative standard deviations are (0.09, 0.22) and (0.30, 0.85), respectively, for the participating laboratory methods. This finding implies that if the same sample was tested by two different laboratories using the same extraction conditions, there is 95 % confidence for 95 % of systems that the test results could exhibit differences up to 240 %. While the study was not designed to evaluate the relative impact of specific underlying factors that may contribute to variability in quantitation, the data obtained suggest the variability associated with analytical method alone is a substantial contribution to the overall variability. The relatively large reproducibility limits we observed may have significant implications where variability in extraction measurements can impact aspects of biocompatibility risk evaluation, such as exposure dose estimation and chemical equivalence assessments.