Formation Of Methyl Esters Research Articles

Direct Methane to Methanol Conversion: An Overview of Non-Syn Gas Catalytic Strategies.

Direct methane to methanol conversion is a dream reaction in industrial chemistry, which takes inspiration from the biological methanol production catalysed by methane monooxygenase enzymes (MMOs). Over the years, extensive studies have been conducted on this topic by bioengineering the MMOs, and tailoring methods to isolate the MMOs in the active form. Similarly, remarkable achievements have been noted in other methane activation strategies such as the use of heterogeneous catalysts or molecular catalysts. In this review, we outline the methane metabolism performed by methanotrophs and detail the latest advancements in the active site structures and catalytic mechanisms of both types of MMOs. Also, recent progress in the bioinspired approaches using various heterogeneous catalysts, especially first-row transition metal zeolites and the mechanistic insights are discussed. In addition, studies using molecular complexes such as "Periana catalyst" for methane to methanol conversion through methyl ester formation in the presence of strong acids are also detailed. Compared to the progress noted in the metal zeolites-mediated methane activation field, the utilisation of molecular catalysts or MMOs for this application is still in its nascent phase and further research is required to overcome the limitations of these methods effectively.

Synthesis and Binding Properties of High-Affinity Histidine-Bearing Polymers for Wood Lignin.

The pursuit of molecules capable of binding to wood lignin is pivotal for advancing lignin degradation technology, particularly when combined with lignin degradation catalysts. In this study, synthetic polymers bearing histidine moieties, demonstrating remarkable affinity for wood lignin are reported. These polymers, featuring varying degrees of histidine substitution in the form of histidine methyl esters, are synthesized through controlled radical polymerization of an activated ester-bearing monomer, employing a fluorescein-labeled chain transfer agent and subsequent postpolymerization amidation with histidine methyl ester. The binding properties of these histidine-bearing polymers with milled wood lignin under aqueous conditions are investigated. Qualitative assessment of lignin-binding capabilities involve spectroscopic analysis of changes in absorbance of visible light and fluorescence intensity. Furthermore, quantitative evaluation is conducted through surface plasmon resonance measurements to determine the binding parameters of the polymers with wood lignin. Notably, polymers with higher histidine substitution exhibit enhanced binding affinity compared to those with lower histidine substitution levels.

Transesterification of Azadirachta indica seed oil into biodiesel using MgO-supported tri-metallic catalyst– synthesis and characteristic evaluation

Environmentally sustainable biodiesel from non-edible waste Azadirachta indica (neem) seed oil provides an economical alternative to combat issues caused by fossil fuel combustion. The current study reports specifically a bi-functional trimetallic (Ca-Sr-Mo) catalyst delineated across MgO support synthesized via wet impregnation and green synthesis route using Cassia fistula extract. In FTIR analysis, peaks appeared at 992, 1390, 1424 cm−1 represent the C–O stretching, C–H deforming and M–O–M bending deformation vibrations, respectively. The diffraction peaks of all CaO, SrO, MoO2, and MgO in the XRD pattern represent the formation of catalysts. The prepared catalyst is employed in the transesterification reaction to convert A. indica oil into fatty acid methyl ester. The study used the response surface methodology to examine factors that could affect the conversion rate, including oil-methanol molar ratio, reaction time, and catalyst loading. The results were analyzed to determine the best combination of factors that yields the optimal catalytic transesterification process. The highest yield of 89.92 % was achieved under optimum conditions of methanol-to-oil (18:1), catalyst loading (5 wt%), and time (6 h). In FTIR analysis, the new peak appeared at 1160 cm−1, indicating the formation of methyl esters, while 1H NMR analysis confirmed the successful conversion of A.indica oil into FAMEs by the appearance of strong singlet at 3.66 ppm for methoxy proton.1H NMR also indicated a high yield (90.09 %) which is comparable to RSM obtained yield. Additionally, a reaction mechanism has been proposed. Specifically, GC-MS FAME profiles and physicochemical testing confirmed that biodiesel meets ASTMD6751 and EN14214 standards with key fatty acid methyl esters and desirable properties.

Influence of Solid Alkaline Photocatalysts Irradiated with UV Light on Fuel Properties of Palm Oil Biodiesel.

TiO2 nanoparticles are full of porosity that can be impregnated with a strong alkaline catalyst CH3ONa to form a TiO2/CH3ONa catalyst. TiO2 of the anatase phase, which is a semiconductor material, has been a prominent photocatalyst due to its excited photocatalyst activity, chemical and biological stability, and nontoxicity. The CH3ONa compound has been widely used as a catalyst for transesterification. Although the synthesized photocatalyst TiO2 powder with CH3ONa is anticipated to greatly enhance the transesterification efficiency, leading to improving biodiesel properties, relevant studies have not been found. After the photocatalyst was prepared, a reactant mixture of palm oil, methanol, and heterogeneous catalyst TiO2/CH3ONa was illuminated by ultraviolet (UV) light from light-emitting diode (LED) lamps. The experimental results revealed that the formation of fatty acid methyl esters was significantly increased to 98.4% with ultraviolet-light illumination for the molar ratio of methanol/palm oil equal to 6 and 3 wt % catalyst addition. The decrease of the catalyst amount to 2 wt % resulted in a slight decrease of the fatty acid methyl esters to 97.06 wt %. The lowest kinematic viscosity and acid value and the highest distillation temperature, heating value, and cetane index were observed under the above reaction conditions. The distillation temperature and cetane index were increased while the acid value was decreased under ultraviolet illumination on the reactant mixture. Consequently, the optimum preparing conditions for biodiesel production were 6 and 3 wt % for the molar ratio of methanol/palm oil and catalyst addition under UV-light irradiation.

Methyl Ester Production from Rice Bran Oil and Methanol with Calcium Carbonate Catalysts Using Esterification Method

Rice bran oil is a type of oil with high nutritional value from rice bran. However, the free fatty acid content in it can increase by more than 60% with sufficient storage time. Free fatty acids contained in rice bran have the potential to be produced into biodiesel (methyl ester). This research aimed to determine the effect of methanol volume and esterification process time on biodiesel yield and to compare methyl ester yield to standard biodiesel. This research was conducted in two stages, namely rice bran oil extraction and esterification. In the extraction stage, rice bran was extracted with n-hexane for 3 hours at an operating temperature of 65oC. The esterification process was carried out by mixing rice bran oil, methanol with a certain volume (100, 125, 150, 175, 200 mL), and calcium carbonate catalyst as much as 1% of the amount of methanol. Esterification was carried out with time variations of 1; 1.5; 2; 2.5 and 3 hours. The results in the form of rice bran oil were analyzed for the value of the biodiesel yield. The result of rice bran oil was analyzed for initial free fatty acid value. Pure biodiesel product in the form of methyl ester was obtained through separation with glycerol as a by-product. The optimum methyl ester yield was 81.70% at 175 ml methanol volume for 3 hours. The methyl ester results are in accordance with SNI biodiesel for density and kinematic viscosity values.

Hazardous waste management of novel non-edible Platycladus orientalis seed oil via recyclable yttria-based phyto-nanocatalyst: A practical approach towards sustainable bioenergy conversion

In current scenario of rising issues of economic crises, ecotoxicity and waste management, the search of novel, waste and non-food biomass for green energy production has become indispensable. This study is concerned with Platycladus orientalis, a novel feedstock with a seed oil concentration of 28 % (w/w), optimized via simulation-based response surface methodology (RSM) for biodiesel production. To enhance catalytic activity during transesterification, novel Yttria-based green metallic oxide, a phyto-nanocatalyst, was synthesized using Platycladus orientalis dried seed cones aqueous extract. The Yttria-based phytonanocatalyst was characterized using FTIR, XRD, SEM, and EDX that confirmed its structural and elemental composition with 12 nm nano-size and demonstrated the high catalytic efficiency. The optimal conditions for biodiesel synthesis were identified as methanol-to-oil ratio (7:1), catalyst concentration (0.14 wt%), reaction time (105 min), and reaction temperature (80 °C) with remarkable biodiesel yield (96 %). The reusability of the Yttria-based green nanoparticles was assessed over six reaction cycles. Methyl ester formation was validated through FTIR, GC–MS, and NMR analyses. The fuel properties were found to fall within the range recommended by the international biodiesel standards i.e. flash point of 90 °C, density of 0.614 kg/L, viscosity of 4.21 cSt, pour point of −8 °C, cloud point of −10 °C, total acid number of 0.124 mg KOH/g and sulfur content of 0.00002 wt%. With its prolific seed production and wide distribution, Platycladus orientalis is a highly recommendable species for sustainable and eco-friendly biodiesel production. This study contributes to the evolving field of green catalysis, offering a viable solution to environmental issues and waste management challenges in the biodiesel industry.

Maximizing Lipid Extraction from Chlorella pyrenoidosa: A Study on the Effectiveness of Cell Disruption Techniques

Microalgae are one of the most eco-friendly and promising raw material sources for the production of biofuel. Proteins, carbohydrates, lipids and nucleic acid are the major components of algal biomass depending upon the species. The present study aimed to determine the lipid extraction and transesterification from Chlorella pyrenoidosa microalgae. Different methods and solvents are used for the disruption of the cell-wall and extraction of lipid content. The methodology involved ultrasonication, microwave digestion, Soxhlet extraction and autoclave while using different solvents as methanol, chloroform, hexane, dichloromethane and heptane. We compared various cell disruption methods to improve lipid extraction yields and the highest lipid extraction yields were obtained using Soxhlet method with hexane. The obtained lipid converted into fatty acid methyl esters (FAMEs) through transesterification process. The identification of fatty acid was compared by retention time and individual pattern of use from caprylic acid (C8:0) to lignoceric acid (C24:0) in form of methyl ester. The Soxhlet method using methanol and chloroform and FAME analysis showed a highest percentage of palmitic acid (C16:0) and lowest percentage of myristic acid (C14:1).

Thin layer chromatography of methylated derivatives of sodium alkylbenzenesulfonates in water analysis by GC-MS

Sodium alkylbenzene sulfonates or linear alkyl benzene sulfonates (LAS) are the most common synthetic anionic surfactants and water pollutants. They can cause both acute and chronic toxic effects on water organisms. Selective determination of sodium alkylbenzene sulfonates as a separate class of anionic surfactants is possible using gas chromatography coupled with mass spectrometry (GC-MS) in the form of linear alkylbenzenesulfonic acid methyl esters (LABSA ME). In order to purify the extracts and concentrate the analytes, we studied the behaviour of these compounds by ascending high-performance thin-layer chromatography using Kieselgel 60 F254 and Sorbfil plates. A mixture of n-hexane and methanol solvents in a ratio of 23:1 (by volume) was used as the mobile phase. Under these conditions, sodium alkylbenzenesulphonates remain on the start line, while their derivatives (ME ABSC), obtained by methylation with trimethyl orthoformate in the presence of trifluoroacetic acid (with a yield of η=98%), form zones characterised by retention coefficient values of Rf = 0.62 and Rf = 0.71 on Kieselgel 60 F254 and Sorbfil plates, respectively. The repeatability of the Rf values was characterised by a standard deviation of 6.1 and 5.9 %, respectively (n=16). The completeness of extraction (95.0–100.0 %) of analytes from the plates by descending TLC with acetonitrile was noted. The applicability of the TLC method for the concentration of analytes and pretreatment of extracts on the example of real water samples was shown. Using GC-MS with electron impact ionisation, we determined the concentrations of sodium alkylbenzenesulphonates in water sampled in the southern basin of Lake Baikal from a depth of 400 m (0.24±0.02 µg/dm3) and in snowmelt water from the ice of the Krestovka River where it flows into Lake Baikal near the village of Listvyanka (31.1 ± 1.0 µg/dm3).

Analysis of biodiesel process from waste cooking oil using heterogeneous catalyst field snail shell (pila ampullacea)

Biodiesel is an alternative fuel in the form of Fatty Acid Methyl Ester (FAME) which can be renewed using vegetable oils and animal oils through esterification or transesterification processes. This study used waste cooking oil as a raw material for biodiesel with a CaO catalyst from the shells of field snails (Pila ampullacea) which were calcined for 4 hours at a temperature of 700°C. This experiment aim to study of the effect of temperature (55°C, 60°C, 65°C) and catalyst weight (4%, 6%, 8%), for 2 hours the transesterification process and the molar ratio of oil to methanol was 1:9. Crude Biodiesel from the transesterification process washed using dry washing method with activated coconut shell charcoal which has been activated using 1M H3PO4. Based on this research, the optimum yields about 91,5%-volume, were obtained in A2T2 with temperature 60°C and a catalyst weight of 6% with a biodiesel yield of 91.5%. The characteristics of the biodiesel produced were kinematic viscosity 3.32 cSt, density 863 Kg/m3, acid number 0.543%, iodine number 14.3%-mass, methyl ester content 169.12% and cetane number 43.28%-mass.

Two-stage co-pyrolysis of Kraft lignin and palm oil mixture to biofuels: The role of lignin as a methylation agent for methyl ester formation

In this work pyrolysis of palm oil and lignin has been investigated using a two-stage process at 550 °C, with a first step configuration of continuous condensation for vapors and separation of gases, and a second step with distillation of vapors. Experiments were realized as pyrolysis of palm oil, palmitic acid, and Kraft lignin, as well as co-pyrolysis of palm oil/lignin, palmitic acid/lignin and palmitic acid/guaiacol. It has been shown that the addition of lignin improves the quality of palm oil pyrolysis bio-oil, thanks to the conversion of fatty acids coproduct to fatty acid methyl esters (FAME). The production of methyl esters in the reaction environment using palm oil and lignin was studied by conducting experiments with palmitic acid and lignin, as well as palmitic acid and guaiacol (the main product obtained from lignin pyrolysis). The results highlighted that during pyrolysis, the production of FAME is a consequence of a direct esterification reaction on palmitic acid. The formation of FAMEs during pyrolysis presents a promising avenue to optimize the utilization of palm oil by generating FAMEs as supplementary fuel products, Furthermore, it is possible to consider the application of the studied process for the conversion of free fatty acids into FAME.

Saccharomyces cerevisiae cellular engineering for the production of FAME biodiesel

The unsustainable and widespread utilization of fossil fuels continues to drive the rapid depletion of global supplies. Biodiesel has emerged as one of the most promising alternatives to conventional diesel, leading to growing research interest in its production. Microbes can facilitate the de novo synthesis of a type of biodiesel in the form of fatty acid methyl esters (FAMEs). In this study, Saccharomyces cerevisiae metabolic activity was engineered to facilitate enhanced FAME production. Initially, free fatty acid concentrations were increased by deleting two acetyl-CoA synthetase genes (FAA1, FAA4) and an acyl-CoA oxidase gene (POX1). Intracellular S-adenosylmethionine (SAM) levels were then enhanced via the deletion of an adenosine kinase gene (ADO1) and the overexpression of a SAM synthetase gene (SAM2). Lastly, the S. cerevisiae strain overproducing free fatty acids and SAM were manipulated to express a plasmid encoding the Drosophila melanogaster Juvenile Hormone Acid O-Methyltransferase (DmJHAMT). Using this combination of engineering approaches, a FAME concentration of 5.79 ± 0.56 mg/L was achieved using these cells in the context of shaking flask fermentation. To the best of our knowledge, this is the first detailed study of FAME production in S. cerevisiae. These results will provide a valuable basis for future efforts to engineer S. cerevisiae strains for highly efficient production of biodiesel.

Formation of ketoprofen methyl ester artifact in GC–MS analysis of basic drugs in horse urine using alkaline liquid-liquid extraction

This study investigates the unexpected formation of ketoprofen methyl ester (KME) during the routine alkaline liquid–liquid extraction (LLE) process for analyzing basic drugs in horse urine samples using GC–MS analysis. An unidentified peak in the GC–MS chromatogram was observed in certain horse urine samples, identified as KME through mass spectral comparison with in situ synthesized KME. Since the KME is not a metabolite of ketoprofen present in urine, it is proposed that its formation occurs during the LLE process due to the reaction between ketoprofen contained in the urine and methanol used as the solvent of the spiked internal standard. Surprisingly, no artifact was detected when negative quality control horse urine samples (absence of ketoprofen) even when spiked with standard ketoprofen and methanol. Further investigation indicated that the presence of lipase enzymes from bacteria in specific urine samples is the key factor in the formation of the KME artifact. This hypothesis was confirmed when negative quality control horse urines were spiked with ketoprofen, methanol, and a lipase enzyme and the KME artifact was detected. Additionally, the formation of a methyl ester artifact was also detected for flunixin, a carboxylic acid NSAID drug, when negative quality control horse urines were spiked with the drug, methanol, and lipase enzyme. These findings will be valuable for scientists analyzing drugs in urine.

Analisa % FFA, PH dan Massa Jenis pada Campuran Minyak Jelantah dan Minyak Kelapa

The increase in population and increasing human needs along with the times has resulted in an increasing need for non-renewable energy. To reduce dependence on petroleum fuels, one way is to produce biodiesel fuel whose raw materials are obtained from plants. Biodiesel is a fuel that contains ester compounds from plants and animal fats and can be used as an alternative fuel with great potential as a substitute for diesel. This form of methyl ester or ethyl ester compound is environmentally friendly, non-toxic and economical. Coconut (Cocos nucifera) is a type of plant that has one glycerin unit and a number of fatty acids in every coconut oil molecule. Coconut oil has the potential to produce Coco methyl ester which can be used as a raw material for biodiesel. Used cooking oil is used oil from household (domestic) fryers whose remaining frying results or waste is immediately thrown into the environment. According to research from Kumar, the use of coconut oil as a raw material for making biodiesel is able to streamline time and the use of chemicals as solvents in the transesterification process. Before carrying out this research, a preliminary test should be carried out, by testing the %FFA, pH and density of the mixture of used cooking oil and coconut oil. This was done as a reference for further research. The %FFA in the mixture of used cooking oil and coconut oil was the highest at a ratio of 75: 25 (MJ: MK) %FFA value: 4.4%. The pH of the mixture between used cooking oil and coconut oil has the same value, namely: 5 and the specific gravity obtained is: 0.8 gram/ml
 
 Keywords: of used cooking oil, coconut oil, % FFA, pH and Specific gravity

Optimization of Methyl Ester Through Simultaneous Esterification –Transesterification Reactions Using Waste Cooking Oil as Raw Material

The increasing need for fossil energy does not equal the availability of alternative energy sources as a substitute generating new problems. In addition to decreasing availability, fossil energy harms the environment by producing dangerous gases from combustion such as carbon dioxide, sulfur, and nitrogen. These factors increasingly encourage researchers to create renewable energy sources with the same performance but are environmentally friendly. Biodiesel or Methyl Ester commonly called Fatty Acid Methyl Ester (FAME) is a renewable alternative energy produced from various raw materials such as animal, vegetable, or other oils. In this study, the methyl ester made from waste cooking oil was processed through two stages of esterification and transesterification using the addition of methanol with different catalysts, H2SO4 and NaOH relying on the reaction step. The research aimed to determine the optimal results from variations in the concentration of the acid catalyst used. From FTIR characterization found that functional groups indicating the formation of methyl esters have been identified at wave numbers 1800-1700 cm-1 with functional groups of -C=O ester the presence of FAME. Meanwhile, to determine the optimum methyl ester caloric value using Bomb Calorimetry according to ASTM D6751 standard. The caloric value was obtained at 9,572.58 Cal/g with catalyst 0,5% H2SO4. The methyl ester content was identified using GC-MS, and the results obtained for ME1, ME2, and ME3 are 74.90%, 77.15%, and 71.98%, respectively. From this study, it can be found that the methyl ester can be produced with esterification-transesterification reactions simultaneously.

Hazardous waste management (Buxus papillosa) investment for the prosperity of environment and circular economy: Response surface methodology-based simulation

Dealing with the current defaults of environmental toxicity, heating, waste management, and economic crises, exploration of novel non-edible, toxic, and waste feedstock for renewable biodiesel synthesis is the need of the hour. The present study is concerned with Buxus papillosa with seeds oil concentration (45% w/w), a promising biodiesel feedstock encountering environmental defaults and waste management; in addition, this research performed simulation based-response surface methodology (RSM) for Buxus papillosa bio-diesel. Synthesis and application of novel Phyto-nanocatalyst bimetallic oxide with Buxus papillosa fruit capsule aqueous extract was advantageous during transesterification. Characterization of sodium/potassium oxide Phyto-nanocatalyst confirmed 23.5 nm nano-size and enhanced catalytic activity. Other characterizing tools are FTIR, DRS, XRD, Zeta potential, SEM, and EDX. Methyl ester formation was authenticated by FTIR, GC-MS, and NMR. A maximum 97% yield was obtained at optimized conditions i.e., methanol ratio to oil (8:1), catalyst amount (0.37 wt%), reaction duration (180 min), and temperature of 80 °C. The reusability of novel sodium/potassium oxide was checked for six reactions. Buxus papillosa fuel properties were within the international restrictions of fuel. The sulphur content of 0.00090% signified the environmental remedial nature of Buxus papillosa methyl esters and it is a highly recommendable species for biodiesel production at large scale due to a t huge number of seeds production and vast distribution.

EFFECT OF INTERMEDIATE ESTERS TOWARDS BOUNDARY LUBRICITY OF PALM METHYL ESTER

Mechanism of methanolysis, using vegetable oil, methanol, and base-catalyze, is generally used to produce methyl ester. This method is also utilized for the kinetic study of the transesterification process based on the formation of fatty acid methyl esters to differentiate among the intermediate esters (e.g., triglyceride, diglyceride, monoglyceride, methyl esters). In the present study, the effect of intermediate ester content of palm oil transesterified with methanol, using potassium hydroxide as base-catalyze, was investigated. The operating conditions of transesterification used were the molar ratio of oil to methanol (1:7), the concentration of catalysis (1.0 wt% based on palm oil) with fixed reaction temperature of 55°C at reaction times of 0.5 and 60 minutes. A kinetic model was then adopted to determine the concentra tion of each intermediate esters. Boundary frictional analyses were conducted using lateral force microscopy (LFM) with different tip sliding velocities and applied normal loads. The experimental results obtained demonstrated that high triglyceride content exhibited better boundary frictional properties across tested tip sliding velocities and normal loads.

Innovative magnetic catalyst facilitates biodiesel production via transesterification of sunflower and waste cooking oils

ABSTRACT The surging global demand for biofuels, precipitated by concerns regarding fossil fuel limitations and their associated environmental consequences has thrust biodiesel into the spotlight as a promising alternative of energy source. In this research endeavor, a novel magnetic catalyst, denoted as K compounds/Fe3O4, was developed by incorporating potassium into the magnetite structure via sol–gel method. This catalyst was applied in the transesterification reaction to convert sunflower and waste cooking oils to biodiesel. It was found that the most effective catalyst for biodiesel production was synthesized by using potassium nitrate at a concentration of 1 M and calcination temperature of 550°C in the catalyst preparation stage. The K compounds/Fe3O4 catalyst was characterized by XRD, XRF, FTIR, SEM, ASAP, and VSM techniques. SEM images demonstrated the porous structure of the catalyst. The GC-mass analysis confirmed the formation of fatty acid methyl esters. The effects of the operating conditions including reactor temperature (55 to 75°C), catalyst dosage (2.5 to 12.5 wt.%), methanol to oil molar ratio (9:1 to 18:1), time (4 to 14 h) were investigated. The best operating conditions were selected inclusive of temperature 65°C, catalyst dosage 5 wt.%, methanol-to-oil ratio 12:1, and time 8 h, and at these operating conditions, biodiesel production efficiencies of 96.28% and 84.05% were obtained for sunflower and waste cooking oils, respectively. The reusability and regeneration of the K compounds/Fe3O4 were studied for five cycles.

Development and validation of a HPLC-MS/MS method for the analysis of fatty acids - in the form of FAME ammonium adducts - in human whole blood and erythrocytes to determine omega-3 index

Recent scientific studies in the field of health and nutrition have unanimously affirmed the importance of consuming the omega-3 fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), because of their cardioprotective properties. Fatty acid profiling in erythrocyte membranes allows the omega-3 index, which is a recognized indicator of the risk of developing cardiovascular disease, to be calculated. One consequence of the upward trend in healthy lifestyles and longevity is an increase in the number of studies into the omega-3 index, which requires a reliable method for the quantitative analysis of fatty acids. This article describes the development and validation of a sensitive and reproducible liquid chromatography tandem mass spectrometry (HPLC-MS/MS) method for the quantitative analysis of 23 fatty acids (in the form of fatty acid methyl esters, FAMEs) in 40 µl of whole blood and erythrocytes. The list of acids includes saturated, omega-9 unsaturated, omega-6 unsaturated and omega-3 unsaturated fatty acids as well as their trans-isomers. The limit of quantitation was 250 ng ml−1 for C12:0, C16:0 and C18:0; and 62.5 ng ml−1 for other FAMEs, including EPA, DHA and trans-isomers of FAME C16:1, C18:1 and C18:2 n-6. Sample preparation for fatty acid (FA) esterification/methylation with boron trifluoride-methanol (BF3) has been optimized. Chromatographic separation has been carried out on a C8 column in gradient mode using a mixture of acetonitrile, isopropanol and water with the addition of 0.1% formic acid and 5 mM ammonium formate. As a result, the problem of separating the cis- and trans-isomers of FAME C16:1, C18:1 and C18:2 n-6 has been solved. The electrospray ionization mass spectrometry (ESI-MS) detection of FAMEs, in the form of ammonium adducts, has been optimized for the first time, which has made the method more sensitive that when the protonated species are used. This method has been applied to 12 samples from healthy subjects that consumed omega-3 supplements and has proven to be a reliable tool for determining the omega-3 index.

Controlling Helical Asymmetry in Supramolecular Copolymers by In Situ Chemical Modification.

Amplification of asymmetry in complex molecular systems results from a delicate interplay of chiral supramolecular structures and their chemical reactivity. In this work, we show how the helicity of supramolecular assemblies can be controlled by performing a non-stereoselective methylation reaction on comonomers. By methylating chiral glutamic acid side chains in benzene-1,3,5-tricarboxamide (BTA) derivatives to form methyl esters, the assembly properties are modulated. As reacted comonomers, the methyl ester-BTAs induce a stronger bias in the screw-sense of helical fibers predominantly composed of stacked achiral alkyl-BTA monomers. Hence, applying the in situ methylation in a system with the glutamic acid-BTA comonomer induces asymmetry amplification. Moreover, mixing small quantities of enantiomers of glutamic acid-BTA and glutamate methyl ester-BTA in the presence of the achiral alkyl-BTAs leads to deracemization and inversion of the helical structures in solution via the in situ reaction toward a thermodynamic equilibrium. Theoretical modeling suggests that the observed effects are caused by enhanced comonomer interactions after the chemical modification. Our presented methodology enables on-demand control over asymmetry in ordered functional supramolecular materials.

Efficient and green esterification approach for determining of sodium alkylbenzene sulfonates in dry extracts

Linear alkylbenzenesulfonate is an anionic surfactant widely used in detergents and cleaners, both in industrial and household applications as well as a component of pesticides and fertilizers. In this work, the universal effective green approach for sodium alkylbenzenesulfonate esterification to determine these substances in a form of their volatile derivatives by gas chromatography coupled with electron ionization mass-spectrometry (GC–MS) is presented. The approach provides a simple conversion of sodium alkylbenzene sulfonates to a form of alkylbenzenesulfonic acid methyl esters in 98% yield for 20 min at 24 °C. The yield was estimated using high performance liquid chromatography-ultraviolet detection. Trimethyl orthoformate (125 µl) was used as low toxicity alkylation reagent. The obtained volatile derivatives might be redissolved in n-hexane and analyzed by GC–MS in selective ion monitoring mode. The limit of quantification of 20 alkylbenzenesulfonate isomer sum was estimated as 25 ng μL–1 of the analyzed extract. The approach might be applied to food, environmental and biological objects contaminated with alkylbenzene sulfonates. The applicability of the method is shown using dry solvent-free extracts of snow, river sediments, freshwater branching sponge Lubomirskia baikalensis, the whole blood, and widely cultivated plants such as spinach Spinacia oleracea and cucumber Cucumis sativus. The presence of sodium alkylbenzene sulfonates in snow (31.1 ± 1.0 µg L–1) and sediments (208±7 µg g–1 of d.w.) of the world's deepest Lake Baikal tributaries as well as in freshwater sponge (33.6 ± 1.1 µg g–1 of d.w.) was found. The repeatability of measurement is characterized by RSD = 2.24%.