Gas Chromatographic-mass Spectrometric Method Research Articles

Phytochemical composition, in vitro cytotoxicity, and in silico docking properties of Tamarix tetragyna L.

Tamarix tetragyna is a plant grows in Mediterranean area and some Arab countries. It possesses numerous medicinal values. Purpose of our study is to explore biological activity of tamarix tetragyna extracts of both leaves and stem with investigating their phytochemical composition. The investigated extracts’ phyto-constituent composition was determined using gas chromatographic-mass spectrometric method. In addition, in vitro cytoxicity activity versus cancer cell lines such MCF-7, HepG-2, HCT-116, and A-549 was examined by MTT assay method, together with exploring its apoptosis effect by flow cytometry and western blot analysis techniques. Moreover, some phytochemical compounds were identified, and in-silico evaluated against anticancer molecular targets. Plant extracts showed good cytotoxic activity against both A-549 and HCT-116 cancer cell lines. With an IC50 value of 23.90 µg/ml that led to apoptosis and G2/M-phase arrest in A-549 cells, cytotoxicity data demonstrate leaves’ extract effectiveness against these cells. Upon GC-MS analysis, it revealed presence of some bioactive components such as Stigmast-5-en-3-ol and 2-methoxy-4-vinyl phenol, which are known for their cytotoxic activity. Our findings suggest that methanolic extracts of Tamarix tetragyna parts may have potential therapeutic uses as anticancer against A-549 cells, which opens up further avenues for investigation into its industrial applications.

Nanomaterial-based magnetic surface molecularly imprinted polymers for specific extraction and efficient recognition of dibutyl phthalate.

A rapid and selective sorbent for the enrichment of dibutyl phthalate (DBP) from water and Chinese Baijiu samples was established using magnetic surface molecularly imprinted polymers (MSMIPs) combined with gas chromatography-mass spectrometer (GC-MS). The MSMIPs were synthesized using a magnetic nanosphere material with silica layer, increasing the polymer surface area as a carrier. Compared with the traditional methods, the addition of magnetic microspheres simplified the process of food substrate purification and significantly shortened the pre-concentration time. The MSMIPs adsorption conforms to the Freundlich isotherm model as multilayer adsorption on an inhomogeneous surface and the pseudo-second-order model. The developed MSMIPs combined with GC-MS method showed good linearity in DBP concentration range of 0.02-1.0mg L-1 with low LOD (0.0054mg L-1) and LOQ (0.018mg L-1), and obtained good recoveries in real samples (95.2-97.2%) with RSD<5.0% (n=9), which were consistent with those from Chinese national standard method.

Development of analytical method for illegal substances in sweat and comparison of the effectiveness of sweat collection materials

PurposeSweat analysis can yield valuable information in forensic investigations, diagnosis and treatment. The purpose of this study was to develop a validated gas chromatography–mass spectrometric method for the detection of illegal substances in sweat after optimizing the method by chemometric approach. This study also investigated the effectiveness of alternative sweat-collecting materials. MethodsPlackett-Burman screening design was employed to determine the effect of seven process factors on this new method. Then, central composite design (CCD) was used to optimize the method. The method was validated according to the international guidelines. The effectiveness of alternative sweat-collecting materials (cosmetic pads and swabs) was compared with a commercially available collecting device (DrugWipe5A). ResultsSample pH, ultrasonic bath time, and liquid–liquid extraction (LLE) shaking time were determined as the most significantly effective three parameters with the Plackett– Burman screening design. The validation procedure was successfully performed after optimizing this method. The comparison study demonstrated that cosmetic pads, swabs, and DrugWipe5A can be used interchangeably. ConclusionsOur results suggested that the statistical optimum strategy was an effective tool for the optimization of process parameters. Combined with the sensitivity and selectivity of our method, the analysis of sweat collection materials proved to be a useful tool for physicians and health care professionals.

Gastro-protective Effect of Carica papaya Leaf Extracts on Ethanol-Induced Gastric Ulcer in Rats

Carica papaya leaves are commonly used traditionally to treat many diseases, including peptic ulcers; however, these pharmacological claims and safety issues of the leaves have not been adequately resolved. The present study aims to evaluate the possible gastro-protective potential of Carica papaya aqueous and methanol leaf extracts on ethanol-induced ulcers. Aqueous and Methanol extracts of C. papaya were prepared by percolation method and screened for phytochemicals using conventional method and Gas Chromatography-Mass spectrometric methods. The gastro-protective effects of the extracts were determined using thirty (30) rats weighing 180 and 250 g were randomly divided into five groups. Group 1 served as the normal control (distilled water), groups 2 served as the (negative control), group 3 received 25mg/kg Omeprazole (standard drug) group 4 and 5 received 300 mg/kg and 600 mg/kg of aqueous and methanol extracts of Carica papaya. Two weeks after the oral administration, gastric ulcer was induced in all rats with 95% ethanol (2 mL). The aqueous and methanol leaf extract of C. papaya showed a significant (p&lt;0.05) dose-dependent protection against peptic ulcer. The effects produced by the methanol leaf extract of C. papaya were comparable to those of the standard drugs (Omeprazole). Phytochemical analysis of the aqueous and methanol leaves extracts of C. papaya revealed the presence of flavonoids, tannins, alkaloids, terpenoids, cardiac glycosides, reducing sugar and saponins, some of which have been reported to elicit cytoprotective effect. Gas chromatographic analysis showed the presence of cytoprotective agents. These findings show that aqueous and methanol extracts of the leaves of C. papaya possess potent antiulcer properties; hence justifies the traditional usage of this plant for ulcer treatment.

Qualitative screening analysis of urine samples by GC-MS method: Application in forensic toxicology

Toxicological screening is used to identify the ingested toxic in order to confirm or to refute a possible cause of toxic death. A gas chromatography–mass spectrometric (GC-MS) method allows toxicological screening of drugs and pesticides when the toxic is unidentified. The purpose of this study is to describe the data and the results of the screening analyses in forensic toxicology carried out by GC-MS at the toxicology laboratory of Annaba University Hospital. Toxicological screening has been realized following the suspicion of a toxic death, in the context of chemical submission (CS) and for drivers involved in traffic accidents. Analyses were performed on urine samples by GC-MS (a GC-Perkin Elmer, Clarus® 680 coupled to a Perkin Elmer mass spectrometer, Clarus® SQ8T) after a liquid-liquid extraction using tetrazepam as internal standard. Between May 2018 and March 2019, sixteen cases were included. The average age of the cases was 31.62 ± 12.55 years. The sex ratio (M/F) was 07. The requests were mainly from the forensic medicine service of Annaba University Hospital (31.25%) followed by forensic medicine service of SOUK AHRAS, EL KALA and EL BESBES with a rate of 18.75% and last and in the same rank the forensic medicine service of Guelma and the police department with a rate of 6.25%. Among these sixteen cases, the number of positive cases was 14 (87.50%), represented mainly by tobacco markers, and at a rate of 71, 42% followed by drugs, caffeine and cocaine, with a rate of 25%, 23.81% and 4.76%, respectively. The toxicological screening confirmed and identified the presence of urinary drugs and different molecules belonging to various drug classes in a forensic toxicology context.

Amphetamine or skin cream? The impact of the sampling site on the concentration of controlled substances: a case report

This case report demonstrates the impact of different sampling sites on the quantification of narcotic substances. In 2020, officers secured a syringe containing a light-yellow paste-like substance, for which a drug pre-test indicated a positive result for amphetamine, inducing subsequent analyses of the sample by means of a gaschromatographic-mass spectrometric method (GC–MS) and liquid chromatography–(tandem) mass spectrometry (LC–MS/MS). Depending on the sample location, different results were obtained, with amphetamine not being detected in each sample. Amphetamine was particularly found at the outlet of the syringe, while amphetamine detection on the inside of the syringe at the plunger seal was only possible occasionally and, moreover, in lower concentrations. Based on this and with regard to the comparatively small amphetamine concentrations, contamination of the syringe (especially on the tip of the syringe) was assumed. Hence, the results strengthened the importance of the implication of different sampling sites, when either homogenization of the sample is not feasible or is not performed for reasons of plausibility checks concerning possible contamination of the sample.

The Impact of Type of Brandy on the Volatile Aroma Compounds and Sensory Properties of Grape Brandy in Montenegro.

This paper presents the results of a study that examined the impact of grape variety on the volatile aroma compounds and sensory properties of standard and Muscat grape brandy produced in the Podgorica sub-region (Montenegro) in vintages 2011, 2012, and 2013. The brandies were prepared by the distillation of crushed grapes, from the autochthonous varieties of Vranac and Kratošija, and Muscat grapes, in a traditional copper alembic, under the same conditions. The gas chromatographic-mass spectrometric (GC/MS) method of 82 volatile aroma compounds that belong to the group (alcohols, volatile acids, volatile esters, terpenes, volatile aldehydes, acetals, ethers, ketones, and alkanes) and an evaluation of the sensory properties of brandies were carried out to determine the typical characteristics of the examined brandies. Alcohols, fatty acid esters, and terpene compound contents were significantly more abundant in all Muscat grape brandies compared to the brandies from the Vranac and Kratošija wine varieties (Standard brandy). Research results revealed that variety had a significant impact on the volatile aroma compound and sensory properties of brandy. The varietal effect was also confirmed, by multivariate analysis, based on the aroma volatile composition, which showed a grouping by type of grape brandy (varietal origin). Sensory analyses showed that all the brandies belonged to the category of high-quality brandies.

An Improved GC-MS Method for Malondialdehyde (MDA) Detection: Avoiding the Effects of Nitrite in Foods.

Malondialdehyde (MDA) is one of the representative end products under lipid peroxidation, indicating the degree of lipid oxidation in foods. However, compounds in pickled products, especially the nitrite in salted lean pork can react with MDA under the acidic condition, leads to the loss of MDA and an underestimation on lipid oxidation through the conventional assay. In this study, the quantification for MDA in the sample containing sodium nitrite were found lacking accuracy by the thiobarbituric acid (TBA) assay and chromatography assay based on alkaline hydrolysis as the reaction between them were difficult to be completely inhibited. Among other trials, the improvement GC-MS analysis utilizing deuterium substituted MDA (MDA-d2) as an internal standard and applying perfluorophenylhydrazine (PFPH) as a derivative reagent can reduce the deviations from the presence of nitrite in the salted lean pork meat and the recovery is between 93.9% and 98.4% and coefficient of variation for the intermediate precision is between 1.1 and 3.5% using the method. The advanced gas chromatograph mass spectrometer (GC-MS) assay also has a very low detection limit (0.25 ng/mL) with both hydrolysis types.

Dissipation, decontamination, dietary, and ecological risk assessment of chlorantraniliprole in chilli fields

For quantification of the insecticide chlorantraniliprole in chilli and soil, an optimized gas chromatographic-mass spectrometric method is presented, with recoveries of 92–96%, and relative standard deviations of 1.4–2.7%. The limit of quantification is 0.01 mg/kg. Degradation of chlorantraniliprole follows first-order kinetics with half-lives between 1.6 and 1.8 days for chilli and soil. For earthworms and arthropods in the chilli field, the calculated risk quotient is found to be <1, as well as for consumers of chilli just after application of chlorantraniliprole. Residue concentrations in chilli fruit can be further reduced by 6–63% using different decontamination methods.

Adsorptive Cathodic Stripping Voltammetry for Quantification of Alprazolam.

A simple and highly sensitive electrochemical sensor was developed for adsorptive cathodic stripping voltammetry of alprazolam. Based on an electrochemically pretreated glassy carbon electrode, the sensor demonstrated good adsorption and electrochemical reduction of alprazolam. The morphology of the glassy carbon electrode and the electrochemically pretreated glassy carbon electrode were characterized by scanning electron microscopy/energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, cyclic voltammetry, and electrochemical impedance spectroscopy. The electrochemical behaviors of alprazolam were determined by cyclic voltammetry, and the analytical measurements were studied by adsorptive cathodic stripping voltammetry. Optimized operational conditions included the concentration and deposition time of sulfuric acid in the electrochemical pretreatment, preconcentration potential, and preconcentration time. Under optimal conditions, the developed alprazolam sensor displayed a quantification limit of 0.1 mg L−1, a detection limit of 0.03 mg L−1, a sensitivity of 67 µA mg−1 L cm−2 and two linear ranges: 0.1 to 4 and 4 to 20 mg L−1. Sensor selectivity was excellent, and repeatability (%RSD < 4.24%) and recovery (82.0 ± 0.2 to 109.0 ± 0.3%) were good. The results of determining alprazolam in beverages with the developed system were in good agreement with results from the gas chromatography–mass spectrometric method.

Dynamic Analyses of Transcriptome and Metabolic Profiling: Revealing Molecular Insight of Aroma Synthesis of Mango (Mangifera indica L. Var. Tainong).

This study aimed to evaluate the changes in aromatic components and other chemical properties of Tainong mango during fruit development, ripening, and storage. As the volatiles of Tainong mango and their related molecular mechanisms remain unclear, volatile profile, metabonomics, and transcriptome analyses were applied to investigate the molecular determinants of the synthesis of aroma components in mango during fruit development and storage. Total acids, total sugar, total carotenoids, enzyme activities of the mango pulp samples were also determined. Volatile components of the mango pulp samples were identified using a gas chromatography-mass spectrometric method. Ribonucleic acid (RNA) sequences of the samples were analyzed by real-time polymerase chain reaction. The results showed that 181 volatiles were isolated and identified in the fruit at seven stages. Compared to the other stages, mango collected on day 8 and day 12 had higher concentrations of 17 volatile components, especially (E,Z)-2,6-nonadienal, 53384 transcripts were also detected through RNA sequencing. The differentially expressed genes analyses included catalytic activity, transferase activity, adenosine diphosphate binding, transcription factor activity, and oxidoreductase activity. α-Pinene content and expression of the differentially expressed genes involved in terpenoid metabolism and enzyme activities in the terpenoid metabolic pathways gradually increased during the maturity of the fruit, and had maximum values at day 8 of storage. Moreover, the integrative analyses revealed potential molecular insights of mango development and aroma formation in the fruit.

Validated Stability-Indicating GC-MS Method for Characterization of Forced Degradation Products of Trans-Caffeic Acid and Trans-Ferulic Acid.

When dealing with simple phenols such as caffeic acid (CA) and ferulic acid (FA), found in a variety of plants, it is very important to have control over the most important factors that accelerate their degradation reactions. This is the first report in which the stabilities of these two compounds have been systematically tested by exposure to various different factors. Forced degradation studies were performed on pure standards (trans-CA and trans-FA), dissolved in different solvents and exposed to different oxidative, photolytic and thermal stress conditions. Additionally, a rapid, sensitive, and selective stability-indicating gas chromatographic-mass spectrometric method was developed and validated for determination of trans-CA and trans-FA in the presence of their degradation products. Cis-CA and cis-FA were confirmed as the only degradation products in all the experiments performed. All the compounds were perfectly separated by gas chromatography (GC) and identified using mass spectrometry (MS), a method that additionally elucidated their structures. In general, more protic solvents, higher temperatures, UV radiation and longer storage times led to more significant degradation (isomerization) of both trans-isomers. The most progressive isomerization of both compounds (up to 43%) was observed when the polar solutions were exposed to daylight at room temperature for 1 month. The method was validated for linearity, precision as repeatability, limit of detection (LOD) and limit of quantitation (LOQ). The method was confirmed as linear over tested concentration ranges from 1−100 mg L−1 (r2s were above 0.999). The LOD and LOQ for trans-FA were 0.15 mg L−1 and 0.50 mg L−1, respectively. The LOD and LOQ for trans-CA were 0.23 mg L−1 and 0.77 mg L−1, respectively.

Influence of pesticides on the biological activity of light chestnut soils in South-East Kazakhstan

The paper discusses the impact of pesticides on the biological activity of soils, as well as an environmental assessment of the state of light chestnut soils by the Kazakh Research Institute of Agriculture and Crop Production with the aim to es-tablish diagnostic indicators that reduce biological activity. The study covers physical, chemical and biological properties of soils under crops of winter wheat in the light chestnut soil in the South-East of the Republic of Kazakhstan. The content of pesticides in soil samples was determined using the gas chromatography mass-spectrometric method. The paper shows results of the chromatographic analysis of soil samples regarding the content of pesticides. The study of changes of light chestnut soil biological activity was conducted to determine their relative resistance to pesticide contamination. Data ob-tained revealed the degree of light chestnut soil resistance to pesticide contamination. The study also identified species of soil invertebrates, as well as soil enzymes that should be used as bioindicators for the monitoring of the contamination with pesticides. Results obtained expand knowledge about changes in the biological activity of light chestnut soils due to pesti-cide contamination in the ecosystems of South-East Kazakhstan. In contrast to abundance indicators, the results suggest that the species composition of soil organisms can be used as a criterion for a qualitative assessment of the soil exposure to pesticides.

Synthesis of N-Doped Magnetic WO3-x@Mesoporous Carbon Using a Diatom Template and Plasma Modification: Visible-Light-Driven Photocatalytic Activities.

Synthesis of three-dimensional photocatalysts offers great potential for chemical conversion and hydrogen generation as appropriate solutions for environmental protection and energy shortage challenges. In this study, the magnetic WO3-x@mesoporous carbon (M-WO3-x@MC) was synthesized through the evaporation-induced self-assembly method applying diatom frustules as a natural template. Then, plasma modification was used to prepare the N-doped M-WO3-x@MC (NM-WO3-x@MC) with enhanced photocatalytic activity and durable performance. The WO3-x was embedded in the conductive MC, which was also partially reduced by the carbon precursor within the heat-treatment procedure. The obtained M-WO3-x@MC was treated by the plasma under an N2 atmosphere for the production of the final photocatalyst containing both the N-doped WO3-x and MC. As a result, the NM-WO3-x@MC had larger surface area (208.4 m2 g-1), narrower band gap (2.3 eV), more visible light harvesting, and confined electron-hole pairs recombination. The H2 generation rates of net WO3 nanorods and NM-WO3-x@MC nanocomposite were estimated as 532 and 2765 μmol g-1 h-1, respectively. Additionally, more than 90% of antibiotics (cephalexin, cefazolin and cephradine) degradation and 76% of total organic carbon elimination were obtained after 120 and 240 min of photocatalytic process under visible light irradiation. Eventually, more than eight intermediates were detected for each antibiotic degradation using the gas chromatography-mass spectrometer method, and based on the obtained results, the possible degradation pathways were suggested.

Qualitative and Quantitative Comparison of Flavor Chemicals in Tobacco Heating Products, Traditional Tobacco Products and Flavoring Capsules

A gas chromatography-mass spectrometric (GC-MS) method was developed for the qualitative and quantitative analysis of flavor chemicals in tobacco heating products (THPs), traditional tobacco products (TTPs) and their flavoring capsules. A total of 247 compounds were identified through nontargeted analysis, 151 compounds were selected as target analytes, and the final 302 compounds were selected to develop an analytical method. The lower limits of detection (LOD) of analytes were 0.00074 to 12 mg/kg and their LOD range was wide depending on the presence or absence in the reference cigarette. The precision of the 302 compounds was less than 24.5%, and the accuracy ranged from 80.0-120%. A total 190 flavors and 5 contaminants were determined in 21 THP, 10 TTP, 8 THP capsules and 11 TTP capsules. When comparing the total flavor content of flavors per cigarette, it was in the order of THP capsule > TTP capsule ≫ THP ≫ TTP. The correlations between the 53 cigarette products and 190 flavor compounds were analyzed using PCA. It has been demonstrated that PCA results can be a useful tool in differentiating brands and manufacturers of tobacco products.

Effect of locust bean gum-sodium alginate coatings incorporated with daphnetin emulsions on the quality of Scophthalmus maximus at refrigerated condition

In this study, the microbiological, physicochemical, and flavor changes of turbot (Scophthalmus maximus) coated with a composite active coating of locust bean gum (LBG) and sodium alginate (SA) supplemented with daphnetin emulsions (0.16, 0.32, 0.64 mg·mL−1) were determined during 18 days of refrigerated storage (4 ± 1 °C). Results showed that LBG-SA coatings containing 0.32 mg·mL−1 daphnetin emulsions could significantly lower the total viable count (TVC), psychrophiles, Pseudomonas spp. and H2S-producing bacteria counts, and inhibit the productions of off-flavor compounds including the total volatile basic nitrogen (TVB-N), trimethylamine (TMA) and ATP-related compounds. 32 volatile compounds were identified by solid phase microextraction combined with gas chromatography-mass spectrometer method (SPME-GC/MS) during refrigerated storage and the treated turbot samples significantly lowered the relative content of fishy flavor compounds. Further, the LBG-SA coatings containing daphnetin could also delay the myofibril degradation of the turbot samples. These results indicated that the LBG-SA coatings with 0.32 mg·mL−1 daphnetin were a potential alternative way to improve the quality of turbot during refrigerated storage.

Composition of low molecular weight impurities in dimethylmethylpheylsiloxane rubbers with terminal hydroxyl groups

Synthesis of dimethylmethylphenylsiloxane rubbers with terminal hydroxyl groups by copolymerization of cyclosiloxanes can be accompanied by formation of low molecular weight compounds, impurities, which are difficultly removed (due to target product affinity) and can lead to rubber opalescence. Identification of the impurities (the content of each impurity ≥ 10 –4 wt.% in 1 μ l of the sample) can be carried out using a sensitive gas chromatography-mass spectrometric method. The method allows separation of the analyzed mixture into individual components on a capillary column. These components enter a mass analyzer and undergo electron ionization which leads to their dissociation into pairs «cation – neutral fragment». Only positively charged ions are observed in the mass spectra, which provides the possibility of predicting the structure of the analyzed siloxane impurities. Rearrangement of linear and cyclic molecules occurring upon mass spectrometric fragmentation result in their transformation into cyclic and bicyclic cations. The structure of the cations formed under ionization conditions depends on the number of silanol bonds and their location in the molecule. To prove the presence of compounds with hydroxyl groups in the composition of impurities and to demonstrate the effect of electron ionization on the fragmentation of compounds with silanol bonds, a sample of oligomethylsiloxane with terminal trimethylsiloxy groups was synthesized in a similar way using the copolymerization method. Compounds with silanol bonds present in the composition of the impurities appear as chromatographic asymmetric peaks with ascending and descending gently sloping zones. Those compounds are rearranged either when passing through a chromatographic column due to sorption-desorption and enter the detector in a modified form or drift through the column and undergo rearrangements already under conditions of electron ionization. The impurities contained linear and cyclic methylsiloxanes with silanol and phenyl bonds. The chromato-mass spectrometric method provide a reliable control of the composition and content of undesirable impurities which cause rubber opalescence.

Investigating the presence of pesticides in fruits and vegetables by the chromatographic techniques: A review

The intensive development of agriculture means more and more toxic and inorganic compounds are entering the environment. Because of their widespread use, stability, selective toxicity, and bioaccumulation, pesticides are among the most toxic substances contaminating the environment. They are particularly dangerous in fruits and vegetables, by which people are exposed to them. It is therefore crucial to monitor pesticide residues in fruits and vegetables using various analytical methods. This article reviews various stages in the determination of pesticide residues in fruits and vegetables. Here the target analyte has been isolated and then enriched before final determination which may be carried out either by Gas Chromatography-Mass Spectrometer (GC-MS) method or Liquid Chromatography-Mass Spectrometer (LC-MS) method. This review explores the analysis of multiple pesticide residues in spinach samples and walks through the step-by-step process of developing the analytical method, from sample preparation to analysis, best suited to the data requirements

Development of a solventless stir bar sorptive extraction/thermal desorption large volume injection capillary gas chromatographic-mass spectrometric method for ultra-trace determination of pyrethroids pesticides in river and tap water samples

AbstractStir bar sorptive extraction (SBSE) has been developed in 1999 to efficiently extract and preconcentrate volatile compounds, and many applications have been found after that. This technique conforms to the principles of green chemistry. Here, we used an autosampler with an online thermal desorption unit connected to CGC-MS to analyze pesticides. This study describes the development of a highly sensitive extraction method based on SBSE for simultaneous determination of ultra-trace amounts of four pesticides λ-cyhalothrin, α-cypermethrin, tefluthrin, and dimefluthrin in environmental water samples. This method was compared to the standard liquid–liquid extraction. In this study, a totally solventless SBSE was applied to river and tap water samples for the extraction and preconcentration of four pesticides. PDMS-coated SBSEs of 10 mm × 1 mm thickness were used for this purpose, and SBSEs were directly placed into a large-volume injector of a CGC-MS for thermal desorption of the analytes. In all extractions, deltamethrin was used as an internal standard. This method showed linearity in the range of 1.0–200.0 ng L−1 for cyhalothrin, tefluthrin, and dimefluthrin and 10.0–800 ng L−1 for cypermethrin. Preconcentration factors of 179, 7, 162, and 166 were obtained with very low limits of detection of 0.32, 3.41, 0.36m and 0.69 ng L−1 for cyhalothrin, cypermethrin, tefluthrinm and dimefluthrin, respectively. These detection limits are thousands of times lower than that of the standard method of liquid–liquid extraction. Reproducibility of the method, based on the relative standard deviation, was better than 7.5% and recoveries for spiked tap and river water samples was within the range of 87.83–114.45%. The application of PDMS-coated SBSE coupled with CGC-MS equipped with a large volume injector thermal desorption unit can be used for ultra-trace analysis of environmental water samples. Solventless SBSE offers several advantages over conventional traditional liquid–liquid extraction such as being very fast and economical and provides better extraction without requiring any solvents; so it can be considered as a green method for the analysis of pesticides.

Identification of Impurities of Unknown Composition in Insulating Oil by Gas Chromatography-Mass Spectrometry (GC-MS)

This paper presents the results of a study of the behavior of an antioxidant additive (ionol) in insulating oil from existing high-voltage equipment. Decomposition products of the inhibitor (ionol), the concentration of which changes as the oil ages, were found in the oil samples. These compounds can be attributed to impurity compounds, which can also serve as additional markers of aging of a liquid dielectric. The ionol degradation products were analyzed by gas chromatography with a flame-ionization detector (FID) and a mass spectrometric detector (MSD). The advantages of the gas chromatography-mass spectrometric method over gas chromatography with an FID are shown. Compounds that are formed as the oxidation inhibitor (ionol) is consumed are identified using chromatography-mass spectrometry. It has been found that the ionol concentration decreases as the mineral oil ages. At the same time, the concentration of ionol “metabolites” increases and becomes much higher than the concentration of the additive itself.