Conventional Reflux Method Research Articles

OPTIMIZATION OF MICROWAVE- AND ULTRASONIC-ASSISTED EXTRACTION OF MAHKOTA DEWA (PHALERIA MACROCARPA [SCHEFF.] BOERL.) FRUIT PULP

Objective: This work aimed to determine the optimal extraction conditions of Mahkota dewa using different extraction methods: microwave-assistedextraction with ethanol (MAE-ethanol), ultrasonic-assisted extraction using a choline chloride natural deep eutectic solvent (UAE-NADES), andSoxhlet and reflux extractions.Methods: Experimental design was performed through Box-Behnken. The efficiency of the methods was evaluated based on the total phenolic content(TPC) and antioxidant activity. The presence of relevant compounds was qualitatively assessed by high-performance liquid chromatography (HPLC).Results: For the MAE-ethanol method, optimum extraction was achieved with 65% ethanol, in 1 min under 30% microwave power, and a 1:12 sample–solvent ratio, which yielded a TPC and antioxidant activity of 62.79±0.74 mg gallic acid equivalents (GAE)/g powder and 30.48±0.32%, respectively. InUAE-NADES, the optimal conditions were choline chloride: lactic acid ratio of 1:4 with a 50% water addition, 20 min extraction (TPC and antioxidantactivity of 65.25 mg GAE/g powder and 26.45±0.02%). The Soxhlet and reflux methods gave a TPC of 49.68±0.59 and 50.98±0.54 mg GAE/g powder,and antioxidant activity of 22.87±0.13% and 25.97±0.34%, respectively. Qualitative HPLC analysis showed the presence of quercetin, mahkoside A,4,6-dihydroxy-4-methoxybenzophenone-2-O-β-D-glucopyranoside, and mangiferin.Conclusion: MAE-ethanol was more efficient than the conventional Soxhlet and reflux methods and performed similarly to UAE-NADES in terms of TPC.

Identification of camellia oil using FT-IR spectroscopy and chemometrics based on both isolated unsaponifiables and vegetable oils.

Camellia oil is one of editable high-quality oils recommended by Food and Agriculture Organization. Thus the method to authenticate camellia oil is significant research. Saponification is one of the simple and inexpensive processes have been used to identify the adulteration in edible oil. At present, the saponification takes a long time, higher temperature and the isolation of unsaponifiables from saponifiables is tedious. In this research, the enriched saponification process has been developed using ultrasonication technique instead of a conventional reflux method. The process has been significantly reduced to 15min at 55 °C from the regular saponification which need about 2h by ISO 18609:2000. The special solid phase extraction (SPE) cartridge has been designed and prepared to separate the unsaponifiables, which separates the residual alkaline substance as well as absorbs water in the organic phase in a single cycle. PLS-DA is used to establish model I based on isolated unsaponifiables and model II based on of vegetable oils for identification of camellia oil. The combined FT-IR and chemometrics based on the isolated unsaponifiables was first used to authenticate vegetable oil. Model I had more sensitivity to discriminate adulterated camellia oils by adulterants whose fatty acid compositions similar to camellia oil such as hazelnut oil, soybean oil, corn oil and cheap mixed oil. On the contrary, model II had more sensitivity to discriminate adulterated camellia oils by adulterant whose fatty acid compositions were different from camellia oil such as palm oil. The results concluded that the FT-IR spectroscopy combined with chemometrics based on both isolated unsaponifiables and vegetable oils could be fast and effective to authenticate camellia oil.

Selective synthesis of pyrimidines from cinnamyl alcohols and amidines using the heterogeneous OMS-2 catalyst

Herein, an efficient aerobic oxidative synthesis of pyrimidines was carried out using cinnamyl alcohols and amidines catalyzed by manganese oxide octahedral molecular sieve (OMS-2). The heterogeneous catalytic method features base-/additive-free conditions, wide substrate scope, use of O2 as a green oxidant, and simple operation. Moreover, the OMS-2 catalyst prepared by the conventional reflux method demonstrates catalytic selectivity, activity, and excellent recyclability.

Synthesis, crystal structures, Hirshfeld surface analysis and spectroscopic studies of two Schiff bases of anisaldehyde and their urease and acetylcholinesterase inhibitory and antioxidant properties

The growing demand of pharmaceutical industry for more effective drugs requires new molecules with promising medicinal activities. In the present work, a natural product anisaldehyde was treated with hydrazine and 3,5-dichloroaniline to synthesize their Schiff bases, ASB1 and ASB2, which were assessed for various bioactivities. ASB1 was synthesized by conventional reflux method while ASB2 was synthesized by reflux as well as by mechanochemical grinding method which gave higher yield. The bases were recrystalised, and their structures were elucidated based on XRD and spectroscopic studies. Hirshfeld surface analysis was also carried out. They showed considerable urease inhibitory activity, almost comparable with the standard thiourea. The activity of ASB1 was much higher than ASB2. Acetylcholinesterase inhibitory activity of ASB1 was also higher than that of ASB2. The antioxidant activities were determined using DPPH, ABTS radical scavenging and total antioxidant capacity (TAC) assays. The bases were very poor scavengers of DPPH radical. However, they showed considerable anti-radical activity against ABTS radical, ASB2 being more active than ASB1, while ASB1 showed higher TAC than ASB2. In conclusion, the bases appeared to have good drugability as inhibitors of urease and acetylcholinesterase enzymes. They can be easily synthesized for possible large-scale applications. The grinding method proved to be more efficient than the reflux method.

Effect of enzyme pretreatment in the ultrasound assisted extraction of finger millet polyphenols

Polyphenols from plant sources are increasingly recognized as functional ingredients with multiple health benefits. Finger millet (Eleusine coracana), a major millet grown in Asia and Africa is a significant source of polyphenols. The extraction of polyphenols from millets which are under-utilized has received less research attention compared to other plant matrices. Therefore, the present study was carried out to identify an effective method of extracting the polyphenols from finger millet (v. GPU 28) seed coat (FMSC). Two eco friendly methods namely ultrasonication (UA) and enzyme treatment followed by ultrasonication (EUA) were compared with the conventional heat reflux method (HR). The polyphenolic profile and content along with the antioxidant potential of the extract were evaluated. Phenolic yield increased 2.3 fold using EUA with xylanase (XUA) compared to heat reflux extraction (HR). However, yield with UA was equivalent to the conventional method. Total flavonoids increased 1.4 fold in UA and 1.3 fold in XUA, similarly, tannins also showed a significant increase (1.1 fold in UA and 1.2 fold in XUA). FTIR spectra revealed the presence of all phenolic functional groups and ESI-MS showed 80% similarity in the individual polyphenols in the extracts. Catechins, luteolin and cyanidin were identified in the UA and XUA treated samples, whereas, shikimic acid derivatives- caffeoyl and di caffeoyl were present only in XUA extracts. This is the first report on enhanced extraction of polyphenols from FMSC using a combination of enzyme treatment and ultrasonication, providing a green technology for utilization of polyphenols in nutraceuticals and functional foods.

Decoration of Bi2Se3 nanosheets with a thin Bi2SeO2 layer for visible-light-driven overall water splitting

Exploring and developing novel semiconductor photo-catalysts for visible-light-driven water splitting are of great scientific significance to solve energy and environmental problems. Herein, Bismuth Selenide (Bi2Se3) nanosheets decorated with a thin layer of Bi2SeO2 to form Bi2Se3/Bi2SeO2 nanocomposites were successfully prepared using a conventional reflux and heating method. Fabricated Bi2Se3/Bi2SeO2 heterojunctions were characterized via X-ray diffraction, scanning electron microscopy, high resolution transmission electron microscopy and X-ray photoelectron spectroscopy. It has revealed that, the thickness of outer Bi2SeO2 layer can be tuned upon the annealing temperatures, which strongly influenced the performance of catalyst towards water splitting performances. Annealed at 200 °C, the Bi2Se3/Bi2SeO2 heterojunction with ∼5 nm of Bi2SeO2 layer yielded the highest hydrogen production rate of 136 μmol g−1 h−1. This enhanced photo-catalytic activity was ascribed to the synergy effect between the Bi2Se3/Bi2SeO2 layer, increased the visible light absorbance capacity, adjustment of the band gap and accelerate the electron-hole separation efficiency. The results represent a simply solution-based method towards a material with high photo-catalytic performance through the appropriate regulation of the oxidation degree of Bi2Se3 nanosheets, promising their industrial applications.

Synthesis, crystal structure, spectral and DFT studies of potent isatin derived metal complexes

The isatin-core in compounds offers exciting perspectives in medicinal and pharmacological research. The present study reports the successful development of new isatin-core transition metal based anti-bacterial complexes via conventional refluxing method. The bidentate nature of as-synthesized isatin-core ligand was confirmed using various analytical techniques such as FTIR, 1H NMR, 13C NMR, EIMS, and single crystal X-ray diffraction. The computed analysis i.e. IR, UV–Visible, NBO (Natural Bond Orbital) and FMO (Frontier Molecular Orbital) of crystalline isatin-core ligand reflect its dimer nature and predict the conjugative interaction among molecules. Moreover, metal complexes of isatin-core ligand using metallic salts of first transition series i.e. VO(IV), Cr(III), Mn(II), Fe(II), Co(II), Ni(II), Cu(II) and Zn(II) were prepared and further screened against bacterial strains. Octahedral geometry was proposed for all the complexes except vanadium which had square-pyramidal geometry. All the as-prepared metal complexes are found potentially active entities against both of the gram-positive and gram-negative bacterial strains. Additionally, the bacterial screened data revealed that metal complexes have better bactericidal activities compared to their parent ligand.

Comparative Study of Microwave Assisted and Conventional Synthesis of Tp*-Complexes

Cobalt, copper and nickel complexes with tris(3,5-dimethyl-1H-pyrazol-1-yl)hydroborate (Tp*) were synthesized by the reaction of potassium tris(3,5-dimethyl-1H-pyrazol-1-yl)hydroborate (KTp*) with the corresponding metal(II) chloride by using conventional reflux methods and microwave methods. The two methods were compared and the microwave method was found to be less time consuming and gave higher yields.

Fast cleavage of phycocyanobilin from phycocyanin for use in food colouring

Phycocyanins from cyanobacteria are possible sources for new natural blue colourants. Their chromophore, phycocyanobilin (PCB), was cleaved from the apoprotein by solvolysis in alcohols and alcoholic aqueous solutions. In all cases two PCB isomers were obtained, while different solvent adducts were formed upon the use of different reagents. The reaction is believed to take place via two competing pathways, a concerted E2 elimination and a SN2 nucleophilic substitution. Three cleavage methods were compared in terms of yield and purity: conventional reflux, sealed vessel heated in an oil bath, and microwave assisted reaction. The sealed vessel method is a new approach for fast cleavage of PCB from phycocyanin and gave at 120°C the same yield within 30min compared to 16h by the conventional reflux method (P<0.05). In addition the sealed vessel method resulted in improved purity compared to the other methods. Microwave irradiation increased product degradation.

High Electrocatalytic Activity of Pt/C Catalyst Promoted by TT‐Nb2O5 Nanoparticles under Acidic Conditions

AbstractMethanol electrooxidation activity of pseudohexagonal niobium pentoxide (TT‐Nb2O5) nanoparticles promoted Pt/C catalyst under acidic conditions is reported. The TT‐Nb2O5 nanoparticles (nano‐TT‐Nb2O5) with crystallite size ∼22 nm were prepared by sol‐gel approach and incorporated into Vulcan carbon by a solid state intermittent microwave heating method. Subsequently, Pt nanoparticles were deposited over the TT‐Nb2O5/C composite by conventional polyol reflux method. It is found that the TT‐Nb2O5 promotes Pt particle dispersion and the average size of Pt nanoparticles thus obtained is about 3.2 nm. The electrochemical methanol oxidation studies were performed on Pt/nano‐TT‐Nb2O5/C catalyst and compared with bulk‐orthorhombic niobium pentoxide (bulk‐T‐Nb2O5) promoted Pt/C as well as bare Pt/C catalysts. The electrooxidation results show that the nano‐TT‐Nb2O5 promoted Pt/C catalyst exhibits lower onset potential and higher current density compared to Pt/bulk‐T‐Nb2O5/C and Pt/C catalysts. Also, it has shown appreciable catalytic stability and improved antipoisoning ability during the methanol oxidation. The origin of higher electrocatalytic activity of Pt/nano‐TT‐Nb2O5/C catalyst is attributed to the large number of triple‐phase interface active centers on nano‐TT‐Nb2O5, which provide abundant hydroxide (OH–) species for effective oxidation of intermediates such as adsorbed carbon monoxide (COads) at lower potentials.

Mechanochemical and Conventional Synthesis of Zn(II)/Cd(II) Luminescent Coordination Polymers: Dual Sensing Probe for Selective Detection of Chromate Anions and TNP in Aqueous Phase.

Isostructural Zn(II)/Cd(II) mixed ligand coordination polymers (CPs) {[M(IPA)(L)]}n (CP1 and CP2) built from isophthalic acid (H2IPA) and 3-pyridylcarboxaldehyde nicotinoylhydrazone (L) were prepared using versatile synthetic routes: viz., diffusion of precursor solutions, conventional reflux methods, and green mechanochemical (grinding) reactions. Both robust CPs synthesized by different routes were characterized by various analytical methods, and their thermal and chemical stability as well as the phase purity was established. Crystallographic studies revealed that CP1 and CP2 are isostructural frameworks and feature a double-lined two-dimensional network composed of Zn2+/Cd2+ nodes connected through IPA and pillared by the Schiff base ligand L with a double-walled edge. The photoluminescent (PL) properties of CP1 and CP2 have been exploited as dual detection fluorosensors for hexavalent chromate anions (CrO42-/Cr2O72-) and 2,4,6-trinitrophenol (TNP) because it was observed that the emission intensity of aqueous suspensions of CPs selectively quenches by chromate anions or TNP among large pools of different anions or nitro compounds, respectively. Competitive experiments in the presence of interfering anions/other nitro compounds also revealed no major effect in the quenching efficiency, suggesting the selective detection of hexavalent chromate anions as well as TNP by the LCPs. The limits of detection by CP1 for CrO42-/Cr2O72- and TNP are 4 ppm/4 ppm and 28 ppb, respectively, whereas the limits of detection by CP2 for the same analytes are 1 ppm/1 ppm and 14 ppb, respectively. A probable mechanism for the quenching phenomena is also discussed.

A convenient solvothermal method to synthesize highly ordered mesoporous silica SBA-15 with high loading of amino groups

Developing a convenient method to prepare mesoporous silica with high loading of functional groups is vital for further applications. In this work, a convenient solvothermal method was employed to synthesize highly ordered mesoporous silica SBA-15 with high loading of amino groups. The properties of amino-functionalization SBA-15 obtained by conventional reflux and solvothermal method were compared. Furthermore, the effects of synthesis temperature and time on the amino content were investigated systematically. It was found that highly ordered SBA-15 with high loading of amino functional groups (up to 3.52 mmol g−1) can be synthesized through the post-grafting via solvothermal method at low temperature (80 °C) for short time (2 h). This convenient method can be extended to synthesize other functional materials.

Microwave assisted synthesis of zeolitic material from agricultural waste bagasse fly ash for the sorption of monocrotophos

The sorption of monocrotophos (MCP) from aqueous solution by native bagasse fly ash (BFA) and zeolitic material (MZBFA) synthesised by combined conventional and microwave reflux method was studied. These sorbents were characterised by XRF, PXRD, FTIR and SEM and were establish to have improved morphology with new crystalline phases. Batch sorption experiments for the removal of MCP by BFA and MZBFA were carried out to evaluate isotherm capacity and kinetics of sorption processes. The isotherm data proved to fit the Langmuir isotherm than that of Freundlich, Temkin and Dubinin-Radushkevich isotherms. The highest sorption capacity, calculated through the values of the isotherm constant Kf, was obtained for MZBFA. The kinetics data proved a closer fit to the pseudo-second order model. The kinetics data of intra particle diffusion confirmed that the sorption rate was controlled by film diffusion followed by pore diffusion.

Microwave assisted synthesis of zeolitic material from agricultural waste bagasse fly ash for the sorption of monocrotophos

The sorption of monocrotophos (MCP) from aqueous solution by native bagasse fly ash (BFA) and zeolitic material (MZBFA) synthesised by combined conventional and microwave reflux method was studied. These sorbents were characterised by XRF, PXRD, FTIR and SEM and were establish to have improved morphology with new crystalline phases. Batch sorption experiments for the removal of MCP by BFA and MZBFA were carried out to evaluate isotherm capacity and kinetics of sorption processes. The isotherm data proved to fit the Langmuir isotherm than that of Freundlich, Temkin and Dubinin-Radushkevich isotherms. The highest sorption capacity, calculated through the values of the isotherm constant Kf, was obtained for MZBFA. The kinetics data proved a closer fit to the pseudo-second order model. The kinetics data of intra particle diffusion confirmed that the sorption rate was controlled by film diffusion followed by pore diffusion.

A Vanadium(V) Oxide Nanorod Promoted Platinum/Reduced Graphene Oxide Electrocatalyst for Alcohol Oxidation under Acidic Conditions.

A Pt-V2 O5 /rGO ternary hybrid electrocatalyst was designed by using active vanadium(V) oxide (V2 O5 ) nanorods and reduced graphene oxide (rGO) components. The V2 O5 nanorods were synthesized by a simple polyol-assisted solvothermal method and were incorporated uniformly onto rGO sheets by intermittent microwave heating. Subsequently, Pt nanoparticles (2-3 nm in size) were deposited over the V2 O5 /rGO composite by the conventional polyol reflux method. The electrocatalytic performance of the Pt-V2 O5 /rGO ternary hybrid and bare Pt/rGO catalysts towards the oxidation of simple alcohols was evaluated in acidic media. The ternary hybrid catalyst exhibited higher electrocatalytic activity than bare Pt/rGO and also showed good stability. The higher electrocatalytic activity of the Pt-V2 O5 /rGO ternary hybrid was attributed to a synergistic effect among the Pt, V2 O5 , and rGO components. In addition, oxygen-containing species, such as OH groups, were generated on V2 O5 at lower potentials. These groups were able to scavenge intermediate species such as COads on the Pt surfaces and helped to regenerate the active sites on the Pt surface more effectively for the routine alcohol oxidation reaction.

Alternative mannosylation method for nanomaterials: application to oxidized debris-free multiwalled carbon nanotubes

Mannosylation is a method commonly used to deliver nanomaterials to specific organs and tissues via cellular macrophage uptake. In this work, for the first time, we proposed a method that involves the binding of d-mannose to ethylenediamine to form mannosylated ethylenediamine, which is then coupled to oxidized and purified multiwalled carbon nanotubes. The advantage of this approach is that mannosylated ethylenediamine precipitates in methanol, which greatly facilitates the separation of this product in the synthesis process. Carbon nanotubes were oxidized using concentrated H2SO4 and HNO3 by conventional reflux method. However, during this oxidation process, carbon nanotubes generated carboxylated carbonaceous fragments (oxidation debris). These by-products were removed from the oxidized carbon nanotubes to ensure that the functionalization would occur only on the carbon nanotube surface. The coupling of mannosylated ethylenediamine to debris-free carbon nanotubes was accomplished using n-(3-dimethylaminopropyl)-n-ethylcarbodiimide and n-hydroxysuccinimide. Deconvoluted N1s spectra obtained from X-ray photoelectron spectroscopy gave binding energies of 399.8 and 401.7 eV, which we attributed to the amide and amine groups, respectively, of carbon nanotubes functionalized with mannosylated ethylenediamine. Deconvoluted O1s spectra showed a binding energy of 532.4 eV, which we suggest is caused by an overlap in the binding energies of the aliphatic CO groups of d-mannose and the O=C group of the amide bond. The functionalization degree was approximately 3.4 %, according to the thermogravimetric analysis. Scanning electron microscopy demonstrated that an extended carbon nanotube morphology was preserved following the oxidation, purification, and functionalization steps.

Effect of microwave radiation on the morphology of tetragonal Cu3SnS4 synthesized by refluxing method

Tetragonal Cu3SnS4 nanostructures were synthesized in the solution precursors containing CuCl2·2H2O, SnCl2·2H2O and thiourea (NH2CSNH2) in ethylene glycol by conventional refluxing and microwave refluxing methods at an ambient condition. Cu(I)2Cu(II)Sn(IV)S4 of the as-synthesized products were detected by X-ray diffraction (XRD), selected area electron diffraction (SAED) and X-ray photoelectron spectroscopy (XPS). Scanning and transmission electron microscopy (SEM and TEM) revealed the gradual transformation of nanoparticles into curved nanoscales grown out of rods synthesized by conventional refluxing (CR) method, and into flower-like particles synthesized by microwave-assisted refluxing (MR) method. Prominent Raman peaks of CR and MR products were respectively detected at 316 and 318cm−1, including photoluminescence (PL) emission at 372nm and 367nm due to interband electron–hole recombination. Possible formation mechanism was also proposed according to the experimental results.

Comparison of conventional and ultrasound-assisted methods for extraction of nutraceutical compounds from Dendrobium candidum

The present study was conducted with the objective of developing efficient method of extraction of nutraceutical compounds from protocorms of Dendrobium candidum for the food industry. Conventional heat reflux method was compared with ultrasonic-assisted method for extraction of polysaccharides, polyphenolics and flavonoids. Methanol, ethanol, acetone, acetonitrile and water were used as solvents for heat reflux extraction. Parameters tested for the optimization were methanol concentration (20, 40, 60, 80 and 100%) and duration of treatment (30 min, 1, 2, 4, 6 h). The treatment of samples with 80% methanol for 2-h period proved to be most suitable procedure for extraction of bioactive compounds. Heat reflux method was found superior to ultrasonic-assisted method since it yields higher amounts of bioactive compounds (463.0 mg g−1 DW polysaccharides, 10.75 mg g−1 DW polyphenolics and 5.30 mg g−1 DW flavonoids) and extracts obtained from heat reflux method also showed optimal antioxidant activity.

Novel nanostructured CeO 2 as efficient catalyst for energy and environmental applications

We report here versatile methods to engineer the microstructure and understand the fundamental physicochemical properties of CeO2 to improve its catalytic viability for practical applications. In this context, different morphologies of CeO2 are synthesized using tailored homogeneous precipitation methods and characterized by XRD, BET, SEM and TPR methods. The shuttle-shaped CeO2 prepared under hydrothermal condition shows higher surface area and low-temperature reducibility. The 0.5 wt% Pt-impregnated shuttle-shaped CeO2 shows lower-temperature CO oxidation behaviour as compared to its bulk-like CeO2 (with 0.5 wt% Pt) counterpart, synthesized by conventional-reflux method. Further, nanorod morphology of CeO2 prepared with Cl− as counter ion shows lower-temperature oxidation of soot as compared to the mesoflower morphology of CeO2, prepared with NO\(_{3}^{-}\) as counter ion in the reaction medium. Further, linear sweep voltammetry, chronopotentiometry and CO-stripping voltammetry studies are performed to evaluate the promoting activity of CeO 2 to Pt/C for ethanol electro-oxidation reaction in acidic media. Results show that CeO2 provides active triple-phase-interfacial sites for suitable adsorption of OH species which effectively oxidize the COads on Pt/C. The results presented here are significant in the context of understanding the physicochemical fine prints of CeO2 and CeO2 based hetero-nanocomposites for their suitability to important catalytic and energy-related applications. CeO2 with engineered microstructure promotes CO oxidation, soot oxidation and alcohol electro-oxidation for energy and environmental applications

Sorption of phosphamidon onto microwave synthesized zeolitic material

Bagasse fly ash (BFA) a sugar industry waste had been collected and converted to zeolitic material (MZBFA) by combined conventional and microwave reflux method. The synthesized sorbent has been characterized using various techniques such as FTIR, XRD, and SEM. BFA and MZBFA were used for the removal of phosphamidon (PSM), an organophosphorus pesticide from aqueous solution. The PSM sorption capacities of MZBFA and BFA were determined by batch sorption technique. Langmuir, Freundlich, Dubinin Redushkwich, and Temkin isotherms were estimated for the sorption nature and efficiency of sorbents. The sorption kinetics is better reflected by pseudo second order model and thermodynamics parameters exhibited specified endothermic nature of sorption. The overall sorption was approximated well by film diffusion at lower concentrations and pore diffusion at higher concentrations simultaneously. From the results, it was observed that MZBFA exhibited higher removal capacity than BFA. © 2013 American Institute of Chemical Engineers Environ Prog, 33: 114–122, 2014