Gas Chromatography Coupled With Flame Ionization Detector Research Articles

The importance of choosing the appropriate cholesterol quantification method: enzymatic assay versus gas chromatography

Cholesterol is a major lipid of the animal realm with many biological roles. It is an important component of cellular membranes and a precursor of steroid hormones and bile acids. It is particularly abundant in nervous tissues and dysregulation of cholesterol metabolism has been associated with neurodegenerative diseases such as Alzheimer's and Huntington's diseases. Deciphering the pathophysiological mechanisms of these disorders often involves animal models such as mouse and Drosophila. Accurate quantification of cholesterol levels in the chosen models is a critical point of these studies. In the present work, we compare two common methods, gas chromatography coupled to flame-ionization detection (GC/FID) and a cholesterol oxidase-based fluorometric assay to measure cholesterol in mouse brain and Drosophila heads. Cholesterol levels measured by the two methods were similar for mouse brain, which presents a huge majority of cholesterol in its sterol profile. On the contrary, depending on the method, measured cholesterol levels were very different for Drosophila heads, which present a complex sterol profile with a minority of cholesterol. We showed that the enzyme-based assay is not specific for cholesterol and detects other sterols as well. This method is therefore not suited for cholesterol measurement in models such as Drosophila. Alternatively, chromatographic methods, such as GC/FID, offer the required specificity for cholesterol quantification. Understanding the limitations of the quantification techniques is essential for reliable interpretation of the results in cholesterol-related research.

Analytical tools for monitoring glycol degradation

This paper aims to develop new methods for monitoring oxidative and thermal glycol degradation through solvent analysis. Methods for quantifying TEG, and for quantifying some degradation products (small glycols and acids), were successfully developed. The results were validated by applying two independent analytical methods for each compound monitored. The glycols were successfully quantified with gas chromatography coupled with flame ionization detection (GC-FID) and with quantitative carbon-13 nuclear magnetic resonance (13C NMR) spectroscopy. The acidic degradation compounds were successfully quantified with high-performance liquid chromatography coupled with ultraviolet detection (HPLC-UV) and heat-stable salt (HSS) analysis. The thermal stability of TEG decreased with the addition of impurities, especially formic acid. Some color changes were observed during the degradation, but they were not linked with the amount of TEG degraded. Finally, it was found that TEG samples have limited stability, even if stored cold.

Identification of Adulterants in Extra Virgin Olive Oil Using HS-SPME-GC-MS and Multivariate Data Analysis

Food fraud, such as the adulteration of extra virgin olive oil (EVOO), is found to cause substantial negative impacts on both the economy and the health of consumers. This work was aimed at evaluating 19 EVOO samples commercialized in Foz do Iguaçu, a frontier city located around the triple border of Brazil, Argentina, and Paraguay. To detect the presence of adulteration in EVOO samples, the present study employed gas chromatography coupled to flame ionization detector (GC-FID) and headspace solid phase microextraction with gas chromatography coupled to mass spectrometry (HS-SPME-GC-MS) in order to evaluate fatty acids composition and volatile organic compounds (VOCs), respectively. The quantitative results obtained from the analysis of fatty acids composition showed that 32% of the EVOO samples were adulterated, presumably with soy oil, due to the high levels of linoleic, linolenic, and myristic acids present in them. Principal component analysis (PCA) conducted using the complete chromatographic aroma profiles obtained from the VOCs helped distinguish authentic EVOO samples from adulterated ones and the country of origin of the samples. The following aromatic compounds were first described, as possible adulterant markers: 3,3-dimethylheptanoic acid, propyl pentanoate, methyl cyclohexanecarboxylate, ethyl cyclohexanecarboxylate, 2-phenylethyl acetate, 6,10,14-trimethylpentadecan-2-one, and 1,2-dimethoxy-4-methylbenzene.

Discrimination of Diptera order insects based on their saturated cuticular hydrocarbon content using a new microextraction procedure and chromatographic analysis.

The nature and proportions of hydrocarbons in the cuticle of insects are characteristic of the species and age. Chemical analysis of cuticular hydrocarbons allows species discrimination, which is of great interest in the forensic field, where insects play a crucial role in estimating the minimum post-mortem interval. The objective of this work was the differentiation of Diptera order insects through their saturated cuticular hydrocarbon compositions (SCHCs). For this, specimens fixed in 70 : 30 ethanol : water, as recommended by the European Association for Forensic Entomology, were submitted to solid-liquid extraction followed by dispersive liquid-liquid microextraction, providing preconcentration factors up to 76 for the SCHCs. The final organic extract was analysed by gas chromatography coupled with flame ionization detection (GC-FID), and GC coupled with mass spectrometry was applied to confirm the identity of the SCHCs. The analysed samples contained linear alkanes with the number of carbon atoms in the C9-C15 and C18-C36 ranges with concentrations between 0.1 and 125 ng g-1. Chrysomya albiceps (in its larval stage) showed the highest number of analytes detected, with 21 compounds, while Lucilia sericata and Calliphora vicina the lowest, with only 3 alkanes. Non-supervised principal component analysis and supervised orthogonal partial least squares discriminant analysis were performed and an optimal model to differentiate specimens according to their species was obtained. In addition, statistically significant differences were observed in the concentrations of certain SCHCs within the same species depending on the stage of development or the growth pattern of the insect.

Bioactive component analysis of aqueous seed extract of Aframomum melengueta

Objective: Aframomum melegueta Schum (Zingiberaceae) is widely cultivated for its valuable seeds in the tropical region of Africa. This study identified the bioactive components present in aqueous seed extract of Aframomum melengueta Methodology: Aqueous seed extract of Aframomum melengueta was qualitatively and quantitatively analyzed using Fourier-transform infrared spectroscopy (FTIR) and Gas chromatography coupled with flame ionization detector (GCFID). Result: FTIR identified twelve organic functional groups of –OH, -NH2, CH, -NH3+, -CH3, -OH, -N=C=O, -C≡N, -C=C=C, -NH, -CH3 and -1,3,5-trisubstituted benzenes. GCFID identified fifteen bioactive components namely kaemferol, naringenin, sapogernin, flavanones, anthocyanin, flavan-3-ol, cyanogenic glycoside, ribalinidine, rutin, catechin, resveratol, spartein, epicatechin, steroid and phytate. Conclusion: The highest concentration of bioactive components was sapogernin 23.1038µg/ml, while the lowest concentration 1.0565µg/ml consisted of Naringenin.

Influence of cooking methods on Oreochromis niloticus (Tilapia) oils antibacterial activity

The present study aimed to evaluate the influence of two cooking methods (boiling and microwave cooking) on antimicrobial activity of oil from Oreochromis niloticus as well as their interactions with some conventional antibiotics. Oils were extracted from raw, boiling and microwave cooked tilapia filet according to Bligh and Dyer method with chloroform/methanol/water mixture as solvent. The fatty acid profile of the crude samples was determined by gas chromatography coupled to flame ionization detector (GC-FID). The quality indices were determined by standard methods. The antibacterial activity on Gram positive and Gram negative bacteria as well as the influence on the activity of some classes of antibiotics were evaluated using the broth microdilution method. The GC-FID analysis showed that tilapia contains unsaturated fatty acids (55.64 %). The oil extracted from boiled tilapia was less oxidized compared to that obtained from the microwave cooked tilapia. The antibacterial assays revealed that all oil samples presented antibacterial activity with MIC varying from 32 to 256 mg/mL. The oil extracted from boiled tilapia was the most active over the fourteen tested bacteria. Tilapia oil was found to enhance the activity of Chloramphenicol, Ciprofloxacin, Erythromycin and Penicillin V. The overall results indicate that tilapia could be useful in preventing and improving the treatment of food-borne diseases.

Combination of Chemically-Characterized Essential Oils from Eucalyptus polybractea, Ormenis mixta, and Lavandula burnatii: Optimization of a New Complete Antibacterial Formulation Using Simplex-Centroid Mixture Design.

This study aims to identify the volatile profile of three essential oils obtained from Eucalyptus polybractea cryptonifera (EPEO), Ormenis mixta (OMEO), and Lavandula burnatii briquet (LBEO) and to examine their combined antibacterial activity that affords the optimal inhibitory ability against S. aureus and E. coli using simplex-centroid mixture design and checkerboard assay. Essential oils (EOs) were isolated by hydrodistillation and characterized using gas chromatography-mass spectrometry (GC-MS) and gas chromatography coupled with flame-ionization detector (GC-FID). The antibacterial activity was performed using disc diffusion and microdilution assays. The chemical analysis revealed that 1,8-cineole (23.75%), p-cymene (22.47%), and α-pinene (11.20%) and p-menthane-1,8-diol (18.19%), α-pinene (10.81%), and D-germacrene (9.17%) were the main components detected in E. polybractea and O. mixta EOs, respectively. However, L. burnatii EO was mainly represented by linalool (24.40%) and linalyl acetate (18.68%). The EPEO, LBEO, and OMEO had a strong antibacterial effect on S. aureus with minimal inhibitory concentrations (MICs) values ranging from 0.25 to 0.5% (v/v). Furthermore, the combination of 1/2048 MICEPEO + 1/4 MICLBEO showed a synergistic antibacterial effect on S. aureus with a FIC index of 0.25, while the formulation of 1/4 MICEPEO + 1/4 MICOMEO demonstrated an antibacterial synergistic activity on E. coli with a FIC index of 0.5. Moreover, the simplex-centroid mixture design reported that the most effective combinations on E. coli and S. aureus correspond to 32%/28%/40% and 35%/30%/35% of E. polybractea, O. mixta, and L. burnatii, respectively. Presented information highlights the action of antibacterial formulations of these EOs and suggests their potential applications as alternatives to commercialized drugs to contract the development of bacteria causing serious infections and food deterioration.

Influence of Native Saccharomyces cerevisiae Strains on Malvasia aromatica Wines.

In the search of tools to deal with climate change-related effects along with the aim of avoiding the loss of aromatic typicity in wine, two native yeasts strains of Saccharomyces cerevisiae (CLI 271 and CLI 889) were evaluated to determine their influence on white Malvasia aromatica wines aroma composition and sensory characteristics. The strains were tested versus a commercial yeast strain (LSA). The fermentations were performed on grape must of the Malvasia aromatica variety previously macerated. Wine quality was studied by analysis of oenological parameters together with volatile aroma components using gas chromatography coupled to flame ionization detector (GC-FID) to quantify major volatiles compounds and headspace-solid phase microextraction coupled with gas chromatography-mass spectrometry (HS-SPME/GC-MS) to determine terpenoids and C13-norisoprenoids. Sensorial analysis was also realized by an experienced taster panel. Wines from locally-selected yeasts strains used had lower volatile acidity levels and higher concentration of aromatic compounds compared to the commercial strain ones. The yeast strain S. cerevisiae CLI 271 provided wines with a higher concentration of esters related to fruity attributes, especially isoamyl acetate. The tasting panel highlighted the strong floral character of wines from S. cerevisiae CLI 889 fermentation. The use of microorganisms well adapted to climatic conditions can be used to produce quality wines of the Malvasia aromatica variety.

Extraction and Estimation of antistatic agent Glycerol Mono Stearate in Polypropylene by Gas Chromatography Coupled with Flame Ionisation Detector

A new method has been developed for the estimation of an antistatic agent Glycerol Mono Stearate (GMS) in Polypropylene (PP) over Gas Chromatography coupled with Flame ionization detector (GC-FID). In the present work, selection of suitable sample specimen, sample weight, solvent mixture, extraction time, and temperature have been identified for the extraction of GMS in the PP resin. In-house Polypropylene pellet has been used for study and the GMS extorted into n-hexane-Ethyl acetate and quantified using GC-FID over 100% Dimethylpolysiloxane column. The method limit of detection is 1 mg/L and the limit of quantification is 5-750 mg/kg in PP resin with a correlation coefficient greater than 0.999. This method is accurate and has not found any interference with other co additives used in the propylene.

A Rapid Procedure for the Simultaneous Determination of Eugenol, Linalool and Fatty Acid Composition in Basil Leaves.

Eugenol and linalool are often the most abundant volatile compounds found in basil (Ocimum basilicum L., Lamiaceae) leaves, and they are interesting for the aroma they provide and for their numerous beneficial bioactivities. Their determination is thus needed for several purposes. In the present study, to avoid the previous isolation of essential oil, the direct solvent extraction is proposed coupled with a transmethylation to convert acyl lipids into fatty acids methyl esters (FAMEs), thus assessing the possible simultaneous analysis of eugenol and linalool with FAMEs by gas chromatography coupled to flame ionization detector (GC-FID). The method has been validated and applied to ten basil leaves samples in which eugenol and linalool were found in mean concentrations of 2.80 ± 0.15 and 1.01 ± 0.04 g kg-1 (dry weight), respectively. FAMEs composition was dominated by linolenic acid (52.1-56.1%) followed by palmitic acid (19.3-22.4%) and linoleic acid (9.6-11.3%). The ratio of n6-polyunsaturated fatty acids (PUFAs)/n3-PUFAs was in the range of 0.17-0.20 in the investigated samples. The proposed method exploits a rapid procedure requiring 40 min, making use of a small amount of solvent and allowing the simultaneous determination of molecules contributing to assess the quality of this worldwide appreciated herb.

English

The chemical composition and seasonal variation of essential oils (EO) extracted from the aerial parts of the traditional medicinal plant Piper rivinoides were analyzed using gas chromatography (GC) coupled with mass spectrometry (MS) and GC coupled with flame ionization detector (GC-FID) technique, respectively. The wild plants were collected from two different sites in the Atlantic Forest. The analysis allowed us to identify 96.60 to 99.80% of the EO composition. The major compounds with the highest relative percentage for both specimens, regardless of the season, were the bioactive monoterpenes α-pinene and β-pinene, which ranged from 34.78 (summer) to 53.87% (winter) and from 15.24% (autumn) to 47.71% (winter), respectively. The seasonal stability of the major compounds in the two study specimens throughout the year indicates that the phenological cycle influences biosynthesis more than abiotic factors. This type of chemical phenotypic stability is rarely observed in species belonging to the Piperaceae family, which is characterized by high chemical variability. Furthermore, this stability is favorable, and P. rivinoides has the potential to be a source of bioactive compounds. Key words: -pinene, -pinene, Atlantic Forest, aromatic plant, volatile compounds.

Discrepancies between validated GC-FID and UHPLC-DAD methods for the analysis of Δ-9-THC and CBD in dried hemp flowers.

Herbal products for smoking containing cannabidiol (CBD) are available as "low-tetrahydrocannabinol cannabis products" in most EU countries. In Belgium, Δ9-tetrahydrocannabinol (THC) content of these products must be less than 0.2% w/w, which is also the limit for agricultural hemp. For agricultural hemp, the official and only valid method for European regulators is gas-chromatography coupled to flame ionization detector (GC-FID). There is no such method, for smoking products. Many of these herbal for smoking products are analyzed as part of their quality control and have certificate of analysis. During surveillance by official labs, discrepancies were seen between the official results and the certificate of analysis. In this study, a GC-FID method based on the European method and an ultra-high-performance liquid chromatography coupled to diode array detection (UHPLC-DAD) method were validated and applied for samples analysis in order to investigate these discrepancies. The GC-FID method shows better results for the validation parameters; notably, it has β-expectation tolerance limits within 10% with a β value of 95% while the validated UHPLC-DAD method has β-expectation tolerance limits within 15% with a β value of 90%. Furthermore, the other parameters evaluated are generally better with the GC-FID method. The statistic t test shows that the difference between both methods was significantly different for total-THC, but not significantly different for the total-CBD. The authors state that, as for agricultural hemp, the GC-FID method is to be preferred for the analysis of THC and CBD in products for smoking.

Phytochemical Analysis and Biological Activity of Three Stachys Species (Lamiaceae) from Romania.

Three species of Stachys genus (S. byzantina, S. officinalis, S. sylvatica) were investigated in the present study in terms of aromatic profile and total polyphenol content, as well as antibacterial activity and antioxidant capacity. Gas chromatography coupled with flame ionization detection (GC/FID) was used for exploration of the herbal alcoholic extracts. Using statistical analysis, volatile organic compounds (VOCs) and total phenolic chemical fingerprints were compared in order to describe differences and identify putative signature traits of the three Stachys species. The results showed that the analyzed Stachys extracts have a total polyphenol content being between 197 ± 0.27 mg GAE/g for S. sylvatica and 232 ± 43 mg GAE/g for S. officinalis. The antioxidant activity was between 444 ± 58 mM Trolox/g (S. sylvatica) and 602 ± 75 mM Trolox/g (S. officinalis). The volatile compounds identified were mostly sesquiterpenes, followed by monoterpenes and secondary compounds. The most abundant in all three species was germacrene D (21.9% 28–25.2%). The multivariate analysis demonstrated the potential of using plant tissue VOC profiles to discriminate between different Stachy species, with a total of 31 VOCs being identified from all three species. Although there were strong similarities among the three species’ VOC profiles, distinctions can be made using chemometric analysis. The microbiological results showed an antimicrobial capacity of all three extracts, especially on Gram-positive bacteria. In addition to increasing consumers’ understanding regarding the health benefits of these Stachy species, this investigation contributes to defining and preserving a precious genetic and cultural-historical biodiversity.

GC characterization and erectogenic enzyme inhibitory effect of essential oils from tangerine and lemon peels: A comparative study

AbstractThis study comparatively evaluated inhibitory effect of essential oils (EOs) from tangerine and lemon peels on some enzymes [angiotensin‐converting enzyme (ACE), acetylcholinesterase (AChE), arginase, monoamine oxidase (MAO), phosphodiesterase‐5 (PDE‐5), adenosine deaminase (ADA) and 5’‐nucleotidase] related to erectile dysfunction (ED), as well as thiobarbituric acid reactive species (TBARs) level in isolated Wistar albino rats’ penile homogenate. In addition, the chemical compositions of these EOs were characterized via gas chromatography coupled with flame ionization detector (GC‐FID). The result revealed that the studied EOs were able to inhibit these erectogenic enzymes and TBARs level in a dose‐dependent manner. The EOs were found to be rich in monoterpenes hydrocarbon. However, the major constituent in both oils was D‐limonene, 45.48% and 34.99% abundance in lemon and tangerine EOs, respectively. Other phytoconstituents detected in substantial amounts include the following: 4‐Vinyl‐2‐methoxyphenol (5.42% and 2.97%), N‐methyl‐D3‐Aziridine (6.58% and 10.01%) and Xanthotoxin (12.055 and 18.7%) for lemon and tangerine EOs, respectively. It is suggestive that these EOs owe their exceptional inhibitory capacities to the availability of these phytochemicals. Hence, their ability to inhibit ACE, AChE, arginase, MAO, PDE‐5, ADA and 5’‐nucleotidase activities, and TBARs level could be the possible mechanism by which the studied EOs exert their therapeutic potentials in the management of ED.

Raman spectroscopy in the detection of adulterated essential oils: The case of nonvolatile adulterants

AbstractEssential oils are liquid mixtures of volatile compounds extracted from plants. Their quality is usually controlled via gas chromatography (GC), although with limitations when adulterants are nonvolatile substances. The essential oils of lavender (Lavandula angustifolia Mill.), peppermint (Mentha piperita L.), patchouli (Pogostemon cablin Benth), and their adulterated versions were measured by GC coupled to flame ionization detector (GC‐FID) and Raman spectroscopy. Canola oil, a nonvolatile substance, was used as the adulterant. The adulterated essential oils contained 1%, 3%, 5%, 10%, 15%, and 20% (v/v) of canola oil. Chromatograms of the adulterated essential oils containing 20% (v/v) of canola oil showed decrements in peak areas of the essential oil components, compared with peaks of the pure essential oils. The highest decrements were observed for the adulterated essential oil of patchouli. In general, detection of adulterated essential oils by simple visual inspection of the Raman features was difficult, due to slight differences observed in the spectra. Principal Components Analysis (PCA) allowed achieving a good spectral discrimination between pure and adulterated essential oils. These results suggest that Raman spectroscopy can overcome limitations of GC‐based methods, thus becoming an interesting alternative and complementary technique for quality control of essential oils.

Persistence and ingestion characteristics of phytochemical volatiles as bio-fumigants in Sitophilus oryzae adults

Fumigant toxicity of phytochemical volatiles has been widely reported against stored product insect pests. Such volatiles are considered as natural fumigants and bio-fumigants in post-harvest food protection research. In the present study, persistence and ingestion of diallyl disulfide, citral, eucalyptol, eugenol and menthol were investigated in Sitophilus oryzae adults in comparison with fumigant toxicity and microstructural impact in elytra. The fumigant toxicity bioassay was performed with increasing concentrations of phytochemical volatiles at 25, 125, 250 and 500 μL/L air against S. oryzae adults in 50 mL glass vials. The phytochemical residues were examined from the treated adults by Gas Chromatography coupled with Flame Ionization Detector (GC-FID) and their pathological impacts on the elytral surface was observed under Scanning Electron Microscopy (SEM). After 72 h of fumigation, diallyl disulfide and eucalyptol were identified as potential fumigants with 5.24 and 8.30 μL/L air LC50 values, respectively. GC-FID analyses showed that diallyl disulfide and eucalyptol molecules persistence (1.29 and 2.60 ppb persistence with 0.94 and 0.90 r2 values respectively at 72 h exposure) on the body surface of weevil was positively correlated with the fumigation exposure and toxicity. Whereas, phytochemical molecules ingestion into the body of weevils was not directly linked with the insect mortalities. The SEM observations indicated that diallyl disulfide and eucalyptol molecules caused severe microstructural impacts on the elytra of weevils compared to other molecules. As a result, the present study suggested that phytochemical fumigants are persisted on the body surface and caused insecticidal toxicities in S. oryzae adults. In addition, it was predicted that persisted molecules might be entered into the body of weevils via cuticular penetration.

Assessement of Water Quality and Risk of Polyaromatic Hydrocarbons in Lungfish (<i>Protopterus annectens</i>) from Freshwaters of Ogba/Egbema/Ndoni, Rivers State, Nigeria

Water quality and health risk of polycyclic aromatic hydrocarbons in <i>P. annectens</i> from freshwaters of Egi, Egbema, and Omoku communities, in Ogba/Egbema/Ndoni local government area of Rivers State, Nigeria were examined. The PAHs were checked using gas chromatography coupled with flame ionization detector (GCFID), while the physicochemical parameters were done using standard methods. Summary of the results from the three communities indicates that TDS (Total Dissolved Solids) mean value was 98.1±16.88 mg/l, TSS (Total Suspended Solid) had an average value of 68.5±10.29 mg/l, turbidity and pH had averages of 1.6±0.011 Unit (NTU) and 7.4±1.05 respectively. The concentrations of tPAHs were 4.415±1.34 µg/kg, 4.634±0.59 µg/kg, and 4.859±0.69 µg/kg for Egi, Egbema, and Omoku communities. The major PAHs were Nap, Acn, and BbF. The cancer risk for children was 2.1E-3, 2.3E-3, and 9.5E-5 for Egi, Egbema, and Omoku while that for adults were 7.1E-4, 5.7E-4, and 2.6E-4 for Egi, Egbema, and Omoku respectively. The cPAHs with the most risk index were DbA, BaA, BaP, and BkF respectively. The risk indexes were higher than the USEPA criterion of 10^-6, indicating contamination of the fish species. It is recommended that monitoring of effluent should be done often and consumption of fish from polluted water sites should be avoided.

Cholesterol, fatty acids profile and the indices of atherogenicity and thrombogenicity of raw lamb and mutton offal

Dietary fats may affect blood lipid levels and the development of cardiovascular diseases. Offal, may contribute to food security in marginalised communities and information on the contribution to dietary fat intake is needed to inform dietary guidelines and recommendations and consumers. This study aimed to describe the fatty acid profile, cholesterol content and indexes of lipid quality. The fatty acid profile and cholesterol were determined by gas chromatography coupled with flame ionisation detection (GC-FID). To evaluate lipid quality the indices of atherogenicity (IA) and thrombogenicity (IT) were calculated. Offal products can contribute beneficial fatty acids to the diet, not only in terms of essential fatty acids such as linoleic (C18:2n-6) and alpha linolenic (C18:3n-3) acids, but also the polyunsaturated fatty acids, arachidonic (C20:4n-6) and eicosapentaenoic (C20:5n3) acids. The offal studied in the present work showed a P/S ratio of 0.04–0.12 and the n-6/n-3 ratio varied between 3.9 and 12.5.

Zeolite imidazolate framework nanocrystals electrodeposited on stainless steel fiber for determination of polycyclic aromatic hydrocarbons

New solid phase microextraction (SPME) coating was made by electrodeposition of zeolite imidazolate framework (ZIF-67) nanocrystals with the aid of polyaniline (PANI) on steel fiber. The SPME fiber was used to extract four polycyclic aromatic hydrocarbons (PAHs) from headspace (HS) of tea infusions and determined by gas chromatography coupled with flame ionization detector (GC-FID). The coating of the SPME fiber was characterized by Fourier transformed infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). Vital parameters affecting extraction performance, including desorption conditions, salt concentration, extraction time, and temperature, have been evaluated and optimized. The validated method was specific for the PAHs analysis, with the limit of detection (LOD) as low as 20.0 to 50.0 ng/L. The linear range was relevant to 70.0-180.0 ng/L with relative standard deviation (RSD) % of less than 12.8. The factor of enrichment was found to be 446.7-808.8. The synthesized coating was shown to be thermally and chemically stable. The recommended approach was successfully applied to quantify PAHs in some frequent tea infusions in the market. The fiber coating of ZIF-67 can be easily made and applied efficiently to detect PAHs pollution in the environment and food products.

Influence of Reaction Parameters on the Gelation of Silanised Linseed Oil.

The subject of this work was to characterize the catalytic course of the linseed oil silylation reaction with vinyltrimethoxysilane (VTMOS), carried out under elevated pressure and temperature conditions, and an explanation of the reasons for rapid gelation of the reaction product. To explain and describe the process, analytical methods were used, i.e., 1H and 13C NMR (nuclear magnetic resonance), GC-FID (gas chromatography coupled with flame ionisation detection), and GPC (gel permeation chromatography). Reaction products were monitored after 3, 6 and 12 h. The molar mass of the VTMOS-modified oil in only 3 h was comparable with the molar mass of the product obtained by conventional polymerisation. An increase in the reaction time resulted in further transformations resulting from the hydrolysis and condensation reactions taking place. In contrast to reactivity of soybean oil, the silanisation of linseed oil occurred much faster and without the need for cross-linking catalysts. The reason for the high reactivity of linseed oil to VTMOS and rapid gelation of the resulting product was primarily the amount of double bonds present in linseed oil and their high availability, in particular the double bond in the acid linolenic acid located at the C16 carbon.