Microwave-assisted Hydrolysis Research Articles

Microwave-assisted hydrolysis: efficient synthesis of α-substituted cysteines on multi-gram scale

A microwave-assisted hydrolysis of thiazolidines was developed for the synthesis of enantioenriched α-alkylcysteines. Under optimized conditions, the efficiency of the reaction can be considerably improved and the scope significantly broadened as compared to previously described processes. This approach is shown to be applicable to the multi-gram scale using a high-throughput microwave system.

Microwave-assisted hydrolysis of phosphonate diesters: an efficient protocol for the preparation of phosphonic acids

A new highly efficient method for the hydrolysis of acyclic nucleoside phosphonate diesters (or generally of any organophosphonates) to the corresponding phosphonic acids has been developed. This novel methodology employs inexpensive hydrochloric acid in equimolar amounts to the number of ester groups present in the molecule and thus, avoids using trimethylsilyl halogenides, the standard reagents for these types of transformations. Moreover, simple and easy work-up of the reaction mixture affords very clean products in high yields (usually 77–93%). Another advantage of the described hydrolysis of phosphonate diesters is the fact that the course of the reaction can be instantly monitored through pressure changes in the reaction vessel. This ‘green’ method has also been successfully used for the preparation of otherwise synthetically difficult to access (phosphonomethoxy)ethyl (PME) derivatives of guanine (PMEG) and hypoxanthine (PMEHx), and furthermore, the method gains access to important novel acyclic nucleoside phosphonates derived from 2-chlorohypoxanthine and from xanthine (e.g. PMEX).

Improvement of microwave-assisted hydrolysis of cassava pulp and tapioca flour by addition of activated carbon.

The superior effects of addition of activated carbon were evidenced for microwave assisted hydrolysis of starches in cassava pulp and tapioca flour under hydrothermal conditions varying irradiation temperature (160-230°C at 5min), duration of heating time (5-18min at 210°C) and amount of activated carbon at 0.5-2.0:1:20 of activated carbon:solid:liquid ratio. The presence of 1.0g/g in microwave-assisted hydrolysis gave much improved glucose yields (44.49% for cassava pulp and 71.93% for tapioca flour) at lower heating temperature (220°C and 200°C, each for 5min) with suppressed formation of secondary decomposed compounds than those without addition of activated carbon (32.41% in cassava pulp at 230°C and 55.11% in tapioca flour at 240°C, each for 5min). The highest glucose yield from cassava pulp (52.27%) was obtained after heating at 210°C for 15min.

Coupling Oxygen Ion Conduction to Photocatalysis in Mesoporous Nanorod-like Ceria Significantly Improves Photocatalytic Efficiency

The mesoporous nanorod-like ceria with high BET surface area of 121 m2/g is prepared by a facile method, microwave-assisted hydrolysis of Ce(NO3)3·6H2O in presence of urea. As compared to bulk ceria, its absorption edge significantly shifts to the visible region with a band gap of as low as 2.75 eV due to the presence of Ce3+. A novel strategy of significantly improving its photocatalytic efficiency is developed by coupling oxygen ion conduction to photocatalysis in the mesoporous nanorod-like ceria, in which UV–visible photons and thermal energy from a Hg lamp were integrated. Under such photothermocatalytic oxidation conditions, the mesoporous nanorod-like ceria exhibits much higher photothermocatalytic activity for the gas-phase minerlization of organic contaminants than corresponding alone thermocatalytic and photocatalytic activity and good photothermocatalytic stability. The significantly enhanced mobility of oxygen ions with increasing temperature raised by thermal energy from the Hg lamp greatly i...

Microwave-assisted hydrolysis of lutein and zeaxanthin esters in marigold (Tagetes erecta L.)

Saponification of lutein and zeaxanthin was performed by microwave-assisted hydrolysis (MAH) and analysed by ultra performance liquid chromatography. The optimal condition of MAH was studied, and the degradation or isomerization of lutein and zeaxanthin were estimated under MAH. The concentrations of lutein and zeaxanthin in 20 marigold samples were assessed by saponification using traditional heater and MAH, the regression coefficient of lutein obtained by two methods was 0.9688 and that of zeaxanthin was 0.9527. The limit of detection for lutein and zeaxanthin was 0.05 and 0.1 μg/ml, respectively, and the limit of quantification for lutein and zeaxanthin was 0.05 mg/100 g and 0.1 mg/100 g, respectively.

Ionic liquid aqueous solvent‐based microwave‐assisted hydrolysis for the extraction and HPLC determination of myricetin and quercetin from Myrica rubra leaves

An ionic liquid aqueous solvent-based microwave-assisted hydrolysis (ILAS-MAH) approach was proposed for the rapid extraction and accurate determination of myricetin and quercetin from Myrica rubra (M. rubra) leaves for the first time. The effects of the ionic liquid class and concentration, liquid-solid ratio, hydrolysis temperature and time were investigated to obtain the optimal ILAS-MAH conditions. The optimized conditions were 2.0 mol/L [bmin][HSO4] or 2.5 mol/L acidified [bmin]Br solution, liquid-solid ratio 30:1 (mL : g), hydrolysis temperature 70°C and hydrolysis time 10 min. Under these conditions, the recoveries of myricetin and quercetin were in the range of 86.3-107.3% with relative standard deviation lower than 5.8%. Compared with conventional heating hydrolysis and regular MAH, the proposed approach reduced hydrolysis time and improved yields. The mechanism of ILAS-MAH was also investigated.

Microwave-assisted hydrolysis and extraction of tricyclic antidepressants from human hair

The objective of this research was to develop, optimize, and validate a modern, rapid method of preparation of human hair samples, using microwave irradiation, for analysis of eight tricyclic antidepressants (TCADs): nordoxepin, nortriptyline, imipramine, amitriptyline, doxepin, desipramine, clomipramine, and norclomipramine. It was based on simultaneous alkaline hair microwave-assisted hydrolysis and microwave-assisted extraction (MAH–MAE). Extracts were analyzed by high-performance liquid chromatography with diode-array detection (HPLC–DAD). A mixture of n-hexane and isoamyl alcohol (99:1, v/v) was used as extraction solvent and the process was performed at 60°C. Application of 1.0 mol L−1 NaOH and microwave irradiation for 40 min were found to be optimum for hair samples. Limits of detection ranged from 0.3 to 1.2 μg g−1 and LOQ from 0.9 to 4.0 μg g−1 for the different drugs. This enabled us to quantify them in hair samples within average therapeutic concentration ranges.

Development and validation of a spectrophotometric method for soil adsorption study of malathion on three Indian soils

In view of the widespread use of pesticides in agriculture and its associated toxic effects on environment and human beings, the fate of these chemicals in soil is of major concern. The pesticide adsorption process is one of the major factors affecting its persistence and movement in the soil. With a view of studying the fate of malathion in soil, the adsorption of this insecticide was studied on three Indian soils by using batch equilibrium method. To carry out the adsorption study, a new simple, sensitive, and rapid method was developed, based on microwave-assisted alkaline hydrolysis of insecticide to the dimethyl dithiophosphate and its subsequent reaction with copper(I) perchlorate in acetonitrile. On mixing the reagents, a yellow color developed, which was stable for 120 min and was measured at 419 nm. The adsorption of malathion was studied by using Freundlich's adsorption equation and n f values were observed less than 1 in all the soils. The leaching behavior of the insecticide was studied in terms of ground ubiquity score, which was below 1.8, classifying malathion as non-leacher pesticide, and hence it is not hazardous.

Microwave-assisted hydrolysis of nitroglycerin (NG) under mild alkaline conditions: New insight into the degradation pathway

Nitroglycerin (NG), a nitrate ester, is widely used in the pharmaceutical industry and as an explosive in dynamite and as propellant. Currently NG is considered as a key environmental contaminant due to the discharge of wastewater tainted with the chemical from the military and pharmaceutical industry. The present study describes hydrolytic degradation of NG (200 μM) at pH 9 using either conventional or microwave-assisted heating at 50 °C. We found that hydrolytic degradation of NG inside the microwave chamber was much higher than its degradation using conventional heating. Products distributions in both heating systems were closely related and included nitrite, nitrate, formic acid, and the novel intermediates 2-hydroxypropanedial (O CHCH(OH)HC O) and glycolic acid (CH 2(OH)COOH). Two other intermediates glycolaldehyde (CH 2(OH)CHO) and glyoxylic acid (CHOCOOH) were only detected in the microwave treated samples. The molar ratio of nitrite to nitrate in the presence and absence of microwave heating was 2.5 and 2.8, respectively. In both microwave assisted and conventional heating a nitrogen mass balance of 96% and 98% and a carbon mass balance of 58% and 78%, respectively, were obtained. The lower C mass recovery might be attributed to further unknown reactions, e.g., polymerization of the aldehydes CH 2(OH)CHO, CHOCOOH and O CHCH(OH)HC O. A hydrolytic degradation pathway for NG was proposed involving denitration (loss of 2 NO 2 - ) from the two primary carbons and the loss of one nitrate from the secondary carbon to produce 2-hydroxypropanedial.

Microwave-assisted hydrolysis of crystalline cellulose catalyzed by biomass char sulfonic acids

Download options Please wait... Supplementary files Titration method of every functional group over the BC-SO 3H samples; XRD pattern of BC-SO 3H-1 (Fig. S1); FT-IR spectra of BC-SO 3H-1 (Fig. S2); XPS spectra of BC-SO 3H-1 (Fig. S3); TGA curves of the BC-SO 3H samples (Fig. S4) PDF (558K) Article information DOI https://doi.org/10.1039/B917807D Article type Paper Submitted 01 Sep 2009 Accepted 21 Nov 2009 First published 24 Feb 2010 Download Citation Green Chem., 2010,12, 696-700 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions Microwave-assisted hydrolysis of crystalline cellulose catalyzed by biomass char sulfonic acids Y. Wu, Z. Fu, D. Yin, Q. Xu, F. Liu, C. Lu and L. Mao, Green Chem., 2010, 12, 696 DOI: 10.1039/B917807D To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Social activity Tweet Share Search articles by author Youyu Wu Zaihui Fu Dulin Yin Qiong Xu Fenglan Liu Chunli Lu Liqiu Mao

Solid acid and microwave-assisted hydrolysis of cellulose in ionic liquid

Solid acid-catalyzed hydrolysis of cellulose in ionic liquid was greatly promoted by microwave heating. H-form zeolites with a lower Si/Al molar ratio and a larger surface area showed a relatively higher catalytic activity. These solid catalysts exhibited better performance than the sulfated ion-exchanging resin NKC-9. Compared with conventional oil bath heating mode, microwave irradiation at an appropriate power significantly reduced the reaction time and increased the yields of reducing sugars. A typical hydrolysis reaction with Avicel cellulose produced glucose in around 37% yield within 8 min.

Anomalous Photocathodic Behavior of CdS within the Urbach Tail Region

A series of cadmium sulfide materials have been prepared using microwave-assisted hydrolysis of cadmium−thiourea complexes in water and nonaqueous solvents. Materials are characterized using X-ray diffraction, scanning electron microscopy, diffuse reflectance spectroscopy, and various photoelectrochemical techniques. Sulfur-doped samples of CdS exhibit a pronounced photoelectrochemical photocurrent switching effect within low-energy tails of their absorption spectra. A mechanism of the photocurrent switching process is presented on the basis of experimental investigations and quantum−chemical calculations.

Elucidating the Structure of Cyclotides by Partial Acid Hydrolysis and LC−MS/MS Analysis

We describe here a rapid method to determine the cyclic structure and disulfide linkages of highly stable cyclotides via a combination of flash partial acid hydrolysis, LC-MS/MS, and computational tools. Briefly, a mixture of closely related cyclotides, kalata B1 and varv A purified from Viola yedoensis was partially hydrolyzed in 2 M HCl for 5 min by microwave-assisted hydrolysis or for 30 min in an autoclave oven (121 degrees C and 15 psi). The partially hydrolyzed peptide mixture was then subjected to LC-MS/MS analysis, with the disulfide linked-peptides fragmented by collision activated dissociation (CAD). A computer program written in-house (available for download at http://proteomics.sbs.ntu.edu.sg/cyclotide_SS ) was used for interpreting LC-MS/MS spectra and assigning the disulfide bonds. Time-point analysis of single-disulfide fragments revealed that nonrandom acid catalyzed fragmentation mostly occurred at the turns which are solvent-exposed and often contain side chain functionalized amino acids such as Asx/Glx and Ser/Thr. In particular, the most susceptible bond for acid hydrolysis in kalata B1 and varv A was found to be the highly conserved N25-G26 which is also the head-to-tail ligation site of the linear precursor proteins, indicating that formation of the three disulfide bonds might precede cyclic structure closure by N25-G26 ligation. This observation is consistent with the recent report that the N25-G26 bond formation is the last step in the cyclotide biosynthetic pathway. The process demonstrated here can potentially be a high throughput method that is generally applicable to determine disulfide bonds of other relatively low-abundance cyclotides.

Study of the microwave-assisted hydrolysis of nitriles and esters and the implementation of this system in rapid microwave-assisted Pd-catalyzed amination

Microwave-assisted hydrolysis of benzonitriles and methyl benzoates has been studied using a toluene/concd aq KOH two phase system in the presence and absence of phase transfer catalyst. Conditions to allow and avoid smooth hydrolysis could be identified. Based on the latter, the first microwave protocol which allows the rapid Pd-catalyzed amination of aliphatic amines with chlorobenzenes containing sensitive functional groups has been developed.

Rapid Microwave-Assisted Hydrolysis for Determination of Ginkgo Flavonol Glycosides in Extracts of Ginkgo biloba Leaves

A rapid microwave-assisted hydrolysis (MAH) method is presented for the sample pretreatment of the determination of ginkgo flavonol glycosides in extracts of Ginkgo biloba L. (EGb). By this method, flavonol glycosides can be completely hydrolyzed within 2 min. After investigating the effects of solvents, acidity, microwave power, and microwave radiation time on hydrolysis, the optimal hydrolysis conditions are as follows: 300 W of microwave power, 2 min of hydrolysis time, 5.7% of hydrochloric acid in the hydrolysis solution, and n-propanol as the hydrolysis solvent. After MAH of the samples, three flavonol aglycones, such as quercetin, kaempferol, and isorhamnetin are analyzed by high-performance liquid chromatography. Compared with conventional reflux hydrolysis, this method owns offers several advantages: it saves time, costs less, and is environmentally friendly.

Effect of microwave irradiation on the molecular and structural properties of hyaluronan

Hyaluronan (Na+ salt of hyaluronic acid, HA) was extensively depolymerised by HCl-catalyzed hydrolysis at pH 3 for up to 500min under temperature-controlled microwave irradiation. The effects of microwave heating on the hydrodynamic properties of the polysaccharide were determined by SEC-MALLS and viscometry. The weight-average molecular mass (Mw) of HA decreased from 1.44×106 to ∼5000, reaching the region of higher oligosaccharides. The scission of HA chains was found to proceed randomly during the whole degradation process. Treatment of the Mw and intrinsic viscosity data according to the Mark–Houwink equation, [η]=k×Mwα suggested three relationships with α1=0.46 for Mw>500,000, α2=0.84 for Mw between 500,000 and 50,000, and α3=1.13 for Mw<50,000. The results revealed that HA with Mw>10,000 adopts a stiffish coil conformation in solution. As monitored by FT-IR and NMR spectroscopic techniques, the primary structure of the HA chains was maintained during the microwave-assisted hydrolysis at pH 3 at 105°C. At reaction times larger than 240min, uv spectroscopy suggested the depolymerisation of HA was accompanied by formation of by-products produced by side reaction.

Structural Analyses of Carbohydrate Moieties of Glycoproteins by Microwave-Assisted Partial Acid Hydrolysis and Mass Spectrometry

Characterization of carbohydrate moieties of glycoproteins using microwave-assisted partial acid hydrolysis (MAPAH) and mass spectrometry (MS) are described in this review. Acids including hydrochloric acid (HCl), trifluoroacetic acid (TFA), and phosphoric acid (H3PO4) can be used to induce partial hydrolysis of the carbohydrate moieties of glycoproteins in as short as 30 s of microwave exposure. High resolving power of MS allows distinction between different glycopeptide fragments. Several glycoproteins including bovine pancreatic ribonuclease B (RNase B, MW ∼15 kDa), egg white avidin (MW ∼16 kDa), human serum α1-acid glycoprotein (α1-AGP, MW ∼36 kDa), horseradish peroxidase (HRP, MW ∼44 kDa), fetal calf serum fetuin (BSF, MW ∼45 kDa), and glucose oxidase from Aspergillus niger (GO, MW ∼75 kDa), are used to demonstrate this technique. Information of the sugar composition and/or arrangement of the carbohydrate moieties can be readily obtained either from glycoproteins directly or digested glycopeptides of the glycoproteins. This method is fast, sensitive, and a reliable technique. Challenges when working on larger and heavily glycosylated glycoproteins are discussed.

Analysis of Phenacylester Derivatives of Fatty Acids from Human Skin Surface Sebum by Reversed-Phase HPLC: Chromatographic Mobility as a Function of Physico-Chemical Properties

A set of 13 fatty acids was transformed into their phenacyl esters by reaction withphenacyl bromide in acetonitrile using 18-crown-6 as phase-transfer catalyst. Conditions forthe RP-18 HPL chromatographic separation of most of the esters has been worked out.Using this standard the fatty acid spectra from skin surface sebum lipids of 17 test personswas taken after microwave-assisted hydrolysis, neutralization and extraction with n-hexane.Quantitative evaluation of the chromatograms exhibits that oleic acid predominates in thesebum of all test persons. In the second part of the work the chromatographic mobility (REvalues) of fatty acid phenacyl esters is correlated with calculated physico-chemicalparameters of the corresponding acids. The best linear correlation was found between the REand the logP values. This is helpful for the structural elucidation of un-identified fatty acidsin a chromatogram.

HPLC for Simultaneous Quantification of Total Ceramide, Glucosylceramide, and Ceramide Trihexoside Concentrations in Plasma

Simple, reproducible assays are needed for the quantification of sphingolipids, ceramide (Cer), and sphingoid bases. We developed an HPLC method for simultaneous quantification of total plasma concentrations of Cer, glucosylceramide (GlcCer), and ceramide trihexoside (CTH). After addition of sphinganine as internal calibrator, we extracted lipids from 50 microL plasma. We deacylated Cer and glycosphingolipids by use of microwave-assisted hydrolysis in methanolic NaOH, followed by derivatization of the liberated amino-group with o-phthaldialdehyde. We separated the derivatized sphingoid bases and lysoglycosphingolipids by HPLC on a C18 reversed-phase column with a methanol/water mobile phase (88:12, vol/vol) and quantified them by use of a fluorescence detector at lambda(ex) 340 nm and lambda(em) 435 nm. Optimal conditions in the Solids/Moisture System SAM-155 microwave oven (CEM Corp.) for the complete deacylation of Cer and neutral glycosphingolipids without decomposition were 60 min at 85% power, fan setting 7. Intra- and interassay CVs were <4% and <14%, respectively, and recovery rates were 87%-113%. The limit of quantification was 2 pmol (0.1 pmol on column), and the method was linear over the interval of 2-200 microL plasma. In samples from 40 healthy individuals, mean (SD) concentrations were 9.0 (2.3) micromol/L for Cer, 6.3 (1.9) micromol/L for GlcCer, and 1.7 (0.5) micromol/L for CTH. Plasma concentrations of GlcCer were higher in Gaucher disease patient samples and of CTH in Fabry disease patient samples. HPLC enables quantification of total Cer, GlcCer, and CTH in plasma and is useful for the follow-up of patients on therapy for Gaucher or Fabry disease.

A Microwave-Assisted Alternative Synthesis of 8-Amino-2-methyl-3,4-dihydroisoquinoli­n-1-one

A shorter, alternative synthesis of 8-amino-2-methyl-3,4-dihydroisoquinolin-1-one is described in 32% overall yield, over three steps starting from commercially available 2-methyl-6-nitrobenzonitrile. The synthesis includes two ‘one-pot’ procedures in which the key process involves the microwave-assisted hydrolysis of a nitrile group followed by lactamization under elevated temperatures.