Synthesis of Multisubstituted Pyrroles from Enolizable Aldehydes and Primary Amines Promoted by Iodine.

1,2,4-Trisubstituted pyrroles were synthesized from enolizable aliphatic aldehydes and primary aliphatic amines by using iodine as the dual Lewis acid/mild oxidant. In the presence of 3.0 equiv of TBHP, enolizable α,ß-unsaturated aldehyde, for example, cocal reacted with aromatic primary amines to form C2-iodized N-arylpyrroles. An acetal-containing pyrrole was successfully prepared from 4-aminobutyraldehyde diethyl acetal, which can be converted easily to 5,6,7,8-tetrahydroindolizine derivatives.

Ionic liquid-based headspace in-tube liquid-phase microextraction coupled with capillary electrophoresis for sensitive detection of phenols.

An ionic liquid-based headspace in-tube liquid-phase microextraction (IL-HS-ITLPME) in-line coupled with capillary electrophoresis (CE) is proposed. The method is capable of quantifying trace amounts of phenols in environmental water samples. In the newly developed method, simply by placing a capillary injected with IL in the HS above the aqueous sample, volatile phenols were extracted into the IL acceptor phase in the capillary. After extraction, electrophoresis of the phenols in the capillary was carried out. Extraction parameters such as the extraction time, extraction temperature, ionic strength, volume of the sample solution and IL types were systematically investigated. Under the optimized conditions, enrichment factors for four phenols were from 1510 to 1985. The proposed method provided a good linearity, low limits of detection (below 5.0 ng mL-1 ), and good repeatability of the extractions (RSDs below 6.7%, n = 6). This method was then utilized to analyze two real environmental samples of Xiaoxi Lake and tap water, obtaining acceptable recoveries and precisions. Compared with the usual HS-ITLPME for CE, IL-HS-ITLPME-CE is a simple, low-cost, fast and environmentally friendly pre-concentration technique. This article is protected by copyright. All rights reserved.

Engineering P-Fe2O3-CoP nanosheets for overall freshwater and seawater splitting.

Tailoring surface composition and coordinative environment of catalysts in a nano-meter region often influence their chemical performance. It is reported that CoP exhibits a low dissociation ability of H-OH, originating from the poor desorption of intermediate species. Herein, we provide a feasible method to construct P-Fe2O3-CoP nanosheets through a gas-phase phosphorization process. P doping induces the formation of interfacial structure between Fe2O3 and CoP and the generation of defective structures. The resulting P-Fe2O3-CoP nanosheets afford high freshwater/seawater oxidation activity (250/270 mV@10 mA/cm2) in 1 mol/L (M) KOH, which is even lower than commercial RuO2. Compared with CoP||CoP, P-Fe2O3||P-Fe2O3, and Co3O4||Co3O4, the assembled P-Fe2O3-CoP||P-Fe2O3-CoP exhibits the superior water/seawater electrolysis performance with 1.61/1.65 V@10 mA/cm2. The synergistic effect of P doping, defective structure, and heterojunction leads to high water oxidation efficiency and water splitting efficiency.

On-line concentration by field-enhanced sample injection with reverse migrating micelles in micellar electrokinetic capillary chromatography for the analysis of coumarins from traditional Chinese medicine and human serum.

In this work, a simple, reproducible and sensitive micellar electrokinetic chromatography method was developed for the separation and determination of three coumarins, imperatorin (IM), isoimperatorin (IO) and osthole (OS) from traditional Chinese medicine and human serum. Field-enhanced sample injection with reverse migrating micelles was used for on-line concentration of the coumarins. The optimum buffer contained 50 mM H(3)PO(4), 160 mM sodium dodecyl sulfate, 20% acetonitrile and 15% 2-propanol, and the pH of buffer was 2.0. The sample solution was diluted with water containing 5 mM sodium dodecyl sulfate and injected for 15 s with -8 kV after injection of 2 s water plug. The effects of concentrations of sodium dodecyl sulfate and organic modifier, the sample matrix, the injection time of water plug, the injection voltage and injection time of sample on the separation and stacking efficiency were investigated. Under the optimum conditions, the analytes were well separated and by optimizing the stacking conditions, about 93, 195 and 136 fold improvement in the detection sensitivity was obtained for IM, IO and OS. The contents of three coumarins in Angelica dahurica Benth, Radix Angelicae Pubescentis and Fructus Cnidii were successfully determined with satisfactory repeatability and recovery. The possibilities of using this method for the determination of three coumarins in spiked human serum were also tested.

Determination of fluoroquinolones in milk, honey and water samples by salting out-assisted dispersive liquid-liquid microextraction based on deep eutectic solvent combined with MECC.

A simple and sensitive salting out-assisted dispersive liquid-liquid microextraction method using deep eutectic solvent combined with back extraction and micellar electrokinetic capillary chromatography (SO-DLLME-DES-BE-MECC) was developed for the determination of fluoroquinolones in milk, honey and water samples. Several parameters affecting the extraction efficiency including DES volume, vortex time, centrifugation time, salt type and amount, sample pH and volume, etc. were investigated. Good linearity were obtained for fluoroquinolones in a range of 0.020-3.200 µg mL-1 and 0.030-4.800 µg mL-1 with LODs less than 0.010 µg mL-1. The recoveries were in the ranges of 95.0-104.9%, 90.1-110.2% and 87.8-114.1% for water, honey and milk samples, respectively. The relative standard deviations for reproducibility were all below 7.6%. Under the optimized conditions, the enrichment factors for analytes were achieved in the range from 531 to 858 folds. The presented method was successfully applied for the determination of fluoroquinolones in milk, honey and water samples.

Cancer cell-targeted nanoprobe for multilayer imaging of diverse biomarkers and precise photodynamic therapy.

A novel multifunctional nanoprobe was designed for cancer cell targeted multilayer imaging of two cancer biomarkers. Based on the proposed method, in situ imaging of membrane MUC1 mucin and cytoplasmic microRNA miR-21 coupled with precise photodynamic therapy was achieved.

Enhanced Photoelectrochemical Performance of WO3 -Based Composite Photoanode Coupled with Carbon Quantum Dots and NiFe Layered Double Hydroxide.

An attractive photoanode material, WO3 , has suffered from its limited visible-light absorption and sluggish surface reaction kinetics, as well as poor stability in neutral electrolytes. Herein, a NiFe/CQD/WO3 composite photoanode was designed and fabricated, with loading of carbon quantum dots (CQDs) and electrodeposition of NiFe layered double hydroxide. The NiFe/CQD/WO3 photoanode obtained a photocurrent density of 1.43 mA cm-2 at 1.23 V vs. reversible hydrogen electrode, which is approximately three times higher than that of bare WO3 . During the test period of 3 h, the stability of WO3 was improved substantially after the loading of cocatalysts. Furthermore, mechanistic insights of the favored band structure and beneficial charge-transfer pathway elucidate the high photoelectrochemical performance of the NiFe/CQD/WO3 composite photoanode.

FeO x Derived from an Iron-Containing Polyoxometalate Boosting the Photocatalytic Water Oxidation Activity of Ti3+-Doped TiO2.

The development of efficient and stable catalyst systems using low-cost, abundant, and nontoxic materials is the primary demand for photocatalytic water oxidation. Distinguishing the true active species in a heterogeneous catalytic system is important for construction of efficient catalytic systems. Herein, hydrothermally synthesized Ti3+ self-doped TiO2, labeled as Ti3+/TiO2, was first used as a light absorber in a powder visible light-driven photocatalytic water oxidation reaction. When an iron-containing polyoxometalate Na27[Fe11(H2O)14(OH)2(W3O10)2(α-SbW9O33)6] (Fe11) was used as a cocatalyst, an amorphous layer of active species was wrapped outside the initial Ti3+/TiO2 nanorod and the in situ formed composite was labeled as F/Ti3+/TiO2. When the composite F/Ti3+/TiO2 was tested as a photocatalytic water oxidation catalyst, dramatically improved oxygen evolution performance was achieved. The composite F/Ti3+/TiO2 showed an oxygen evolution rate of 410 µmol/g/h, which was about 11-fold higher than that of prism Ti3+/TiO2. After 24 h of illumination, an O2 yield of 36.4% was achieved. The contrast experiments, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy characterization demonstrated that FeO x is the true cocatalyst that enhanced the oxygen evolution activity of TiO2. A recycling experiment proved that the composite F/Ti3+/TiO2 has favorable stability in the oxygen production process.

Determination of kava lactones and flavonoid glycoside in Scorzonera austriaca by capillary zone electrophoresis.

A capillary zone electrophoretic method has been developed for the quantitative analysis of three active comppounds, 12-hydroxy-desmethoxyyangonin (HD), 12-beta-d-glucopyranoside-desmethoxyyangonin (GD) and luteolin 3'-(6-E-p-coumaroyl-beta-d-glucopyranoside) (LG) in Scorzonera austriaca with UV detection at 254 nm. The applied voltage was 25 kV and the capillary temperature was kept constant at 25 degrees C. The effect of buffer pH, the concentration of electrolyte and organic modifier on migration were studied systematically. Optimum separation was achieved with 20 mM borate buffer at pH 10.00 containing 10% (v/v) methanol. Daphnetin was used as internal standard for quantification. Regression equations revealed good linear relationship between the ratios of the peak area of each compound and its the ratios of concentration. All the correlation coefficients were higher than 0.9990. The relative standard deviations of migration time and the peak area were <1.46% and 5.13% (inter-day), and <1.65% and 5.16% (intra-day), respectively. The contents of the three compounds in S. austriaca were successfully determined with satisfactory repeatability and recovery.

Separation of plant hormones from biofertilizer by capillary electrophoresis using a capillary coated dynamically with polycationic polymers.

A new, simple and rapid capillary electrophoresis (CE) method, using hexadimethrine bromide (HDB) as electroosmotic flow (EOF) modifier, was developed for the identification and quantitative determination of four plant hormones, including gibberellin A3 (GA3), indole-3-acetic acid (IAA), alpha-naphthaleneacetic acid (NAA) and 4-chlorophenoxyacetic acid (4-CA). The optimum separation was achieved with 20 mM borate buffer at pH 10.00 containing 0.005% (w/v) of HDB. The applied voltage was -25 kV and the capillary temperature was kept constant at 25 degrees C. Salicylic acid was used as internal standard for quantification. The calibration dependencies exhibited good linearity within the ratios of the concentrations of standard samples and internal standard and the ratios of the peak areas of samples and internal standard. The correlation coefficients were from 0.9952 to 0.9997. The relative standard deviations of migration times and peak areas were < 1.93 and 6.84%, respectively. The effects of buffer pH, the concentration of HDB and the voltage on the resolution were studied systematically. By this method, the contents of plant hormone in biofertilizer were successfully determined within 7 min, with satisfactory repeatability and recovery.

Separation and determination of nitrofuran antibiotics in turbot fish by microemulsion electrokinetic chromatography.

A microemulsion electrokinetic chromatography (MEEKC) method has been developed for the determination of four nitrofuran antibiotics (furazolidone (FZD), furaltadone (FTD), nitrofurazone (NFZ) and nitrofurantoin (NFT)) in turbot fish. The effect of buffer the pH, the concentration of SDS and the concentrations of octane and butan-1-ol were studied systematically. With the optimized experimental conditions (octane, 0.82% (w/w); SDS, 3.48% (w/w); butan-1-ol, 6.48% (w/w); and 10 mM sodium tetraborate buffer (pH 9.70), with 30 kV as the applied voltage) all four analytes were baseline-separated within 8 min. Regression equations revealed a good linear relationship between the peak area of each compound and its concentration. The correlation coefficients of the four analytes were from 0.9945 to 0.9999. The relative standard deviations of the migration times and the peak areas were <1.84 and 5.16% (intra-day). The obtained recovery ranged between 97 and 104%. Moreover, the method was successfully validated and applied to the determination of nitrofuran antibiotics in contaminated fish.

Determination of six bioactive components of Saussurea katochaete by capillary electrophoresis.

The simultaneous determination of 3,4-dimethoxy-3'-hydroxy propiophenone, 5-hydroxy-7-methoxy coumarin, 7-hydroxy coumarin, 3',5'-dimethoxy apigenin, apigenin and 4-hydroxy cinnamic acid in the extract of S. katochaete has been investigated by capillary electrophoresis for the first time. The six active components were completely separated within 10 min in 20 mM Na(2)HPO(4) buffer at pH 11.00 with 10% (v/v) methanol and detected at 214 nm. The applied voltage was 15 kV and the temperature was kept at 25 degrees C. The effects of buffer pH, the concentration of Na(2)HPO(4) and the concentration of methanol on the separation efficiency were studied systematically. The regression equations revealed good linear relationships (correlation coefficients were 0.9987-0.9998) between the peak area of each analyte and its concentration. The relative standard deviations (RSD) of migration time and peak areas were <1.63 and <4.03%, respectively. The application of this method for the separation and determination of the six bioactive components in S. katochaete was reported. The contents of the six analytes ranged from 0.023 to 0.131 mg/g and recoveries ranged from 94.7 to 104.8%.

Application of 1-alkyl-3-methylimidazolium-based ionic liquids in separation of bioactive flavonoids by capillary zone electrophoresis.

Room-temperature ionic liquids (ILs) are liquids that are constituted entirely of ions and can provide a solvent environment quite unlike any other available at room temperature. They continue to attract considerable interest in the chemistry research community as they are good solvents for a wide range of both inorganic and organic materials. In this study, a CZE method has been established for resolving natural flavonoids, quercetin, kaempferol and isorhamnetin in the Chinese herbal extract from Hippophae rhamnoides and its medicinal preparation (Sindacon Tablet). In this method, 1-alkyl-3-methyl-imidazolium-based ILs are used as the additive, and the effects of the alkyl group, imidazolium counterion (anionic part), along with the concentration of IL are investigated and discussed. Baseline separation, high efficiencies and symmetrical peaks of the three flavonoids were obtained. The separation mechanism seems to be the hydrogen-bonding interaction between the imidazolium cations of IL and the flavonoids.

Simultaneous determination of noradrenaline and dopamine in Portulaca oleracea L. by capillary zone electrophoresis.

A simple and rapid capillary electrophoretic method was developed for the simultaneous determination of noradrenaline (NA) and dopamine (DA) in Portulaca oleracea L. The buffer solution used in this method was 40 mM tris (hydroxymethyl) aminomethane (Tris)-H3PO4 at pH 2.00 containing 15% methanol. The effects of pH value, organic modifier, and applied voltage were investigated. The linear ranges of NA and DA were 0.5-100 microg/mL (r=0.9952) and 6.25-200 microg/mL (r=0.9992), respectively. The relative standard deviations of the corrected peak area were 6.73% and 4.26%, respectively. NA and DA in Portulaca oleracea L. were simultaneous determined successfully within 5.6 min. In this way, the contents of NA and DA in different parts (stem, leaves, and seeds) of P. oleracea L. and in different extracts of leaves with different solvents (distilled water, 50% methanol, and methanol) were studied.

Separation and determination of coumarins from Cacalia tangutica by capillary zone electrophoresis.

Capillary zone electrophoresis (CZE), using a 20 mmol/L borate buffer at pH 10.5, was developed for the identification and determination of three coumarins--7-hydroxy-coumarin (HC), 7-hydroxy-8-methoxy-coumarin (HMC) and 7-O-beta-D-glucosyl-coumarin (GC)--in the extracts of the flower of Cacalia tangutica. Regression equations revealed linear relationships (correlation coefficient 0.9986-0.9990) between the corrected peak area (the ratio of peak area to migration time) of each constituent and its concentration. The relative standard deviations (RSD) of the migration time and peak area were 1.45-1.52 and 2.60-3.84% (intra-day), and 1.75-2.22 and 2.90-4.04% (inter-day), respectively. The recoveries of three constituents ranged between 94.5 and 105.6%. The effects of pH value, buffer concentration and applied voltage on the migration behavior of HC, HMC and GC were investigated. The contents of the three active constituents in the flower of Cacalia tangutica were successfully determined within 6 min under the optimum conditions chosen. Moreover, the dissociation constants for three coumarins were also determined by CE.

Fast determination of flavonoids in Hippophae rhamnoides and its medicinal preparation by capillary zone electrophoresis using dimethyl-beta-cyclodextrin as modifier.

A fast capillary zone electrophoresis (CZE) method, using dimethyl-beta-cyclodextrin (DM-beta-CD) as modifier, has been developed for the determination of three flavonoids (quercetin (QU), kaempferol (KA) and isorhamnetin (IS)) in the Chinese herbal extract from Hippophae rhamnoides and its medicinal preparation (Sindacon tablet). Optimum separation was achieved with 20mM borate buffer at pH 10.0 containing 5mgml(-1) of DM-beta-CD. The applied voltage was 15kV and the capillary temperature was kept constant at 25 degrees C. Regression equations revealed linear relationships (correlation coefficients: 0.9973, 0.9992 and 0.9996) between the peak area of each compound (QU, KA and IS) and its concentration. The relative standard deviations of migration times and peak areas were <1.53 and 4.14%, respectively. The effects of several CE parameters on the resolution were studied systematically. The contents of three flavonoids in H. rhamnoides were successfully determined with 4.5min, with satisfactory repeatability and recovery. It was also tested that the possibilities of using this method for the determination of flavonoids in Chinese medicinal preparation.