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Orthogonal design has been applied to the optimization of separation and determination of dauricine and daurisoline in Rhizoma Menispermi and its herbal medicine by micellar electrokinetic capillary chromatography. Operational variables, such as the voltage, micelle concentration, buffer concentration and pH were optimized. Their different effects on peak resolution were studied by the experimental design method. Optimized separation conditions were obtained and successfully applied to the separation and determination of dauricine and daurisoline in real samples. The proposed method allows alkaloids in real samples to be determined within 15 min using a buffer system composed of 25 mM HAc, 25 mM NaAc and 2% polyoxyethylene sorbitan monolaurate (Tween-20) (pH 4.5). In addition, a radial basis function neural network with a '4-18-1' structure was developed based on the experimental results of orthogonal design and uniform design, and applied to the prediction of peak resolution of dauricine and daurisoline under the optimum separation conditions given by orthogonal design. The predicted results were in good agreement with the experimental values, indicating that radial basis function neural network may be a potential method for the selection of separation conditions in capillary electrophoresis. Keywords: micellar electrokinetic capillary chromatography, experimental design, radial basis function neural network, Rhizoma Menispermi, dauricine, daurisoline DOI: 10.1134/S1061934813060166, Dauricine and daurisoline are two isoquinoline alkaloids existed in Rhizoma Menispermi, which are the main effective components in Rhizoma Menispermi and have been known to show many pharmacological activities and [...]

Highlights • A new water-soluble fluorescent silicon quantum dots (Si QDs) were synthesized by facile one-step strategy in water-bath. • A simple fluorescent method for detection of K 4 [Fe(CN) 6 ] in table salt and salted food was established. • Realized rapid, highly selective determination of K 4 [Fe(CN) 6 ] due to the synergistic effect of electrostatic interaction and statically quenching. • Analysis of K 4 [Fe(CN) 6 ] in food samples, the recoveries were ranged from 91.90% to 107.0%. • The Si QDs can also act as fluorescent nanosensors to monitor the pH change in wide range. Abstract The addition of potassium ferrocyanide (K 4 [Fe(CN) 6 ]) in table salt as anti-caking agent has a crucial role in preventing the formation of lumps. However, the excess of K 4 [Fe(CN) 6 ] and its decomposers are harmful to both human health and environment. To date, there are still lack of suitable methods for simple and rapid analysis of K 4 [Fe(CN) 6 ] in table salt and salted food. Herein, a novel fluorescent Si QDs probe for sensitive, selective and rapid detection of K 4 [Fe(CN) 6 ] was synthesized by facile one-step strategy. Notably, the fluorescence of Si QDs could be remarkably quenched by K 4 [Fe(CN) 6 ] via electrostatic interaction. Based on this phenomenon, a new method of determination of K 4 [Fe(CN) 6 ] was established. A wide linear range was obtained from 0.05 to 8.0 µg/mL with a detection limit of 30 ng/mL. The established fluorescent new method was suitable for detecting K 4 [Fe(CN) 6 ] in table salt and salted food samples with satisfactory results. [ABSTRACT FROM AUTHOR]

The importance of measuring the content of silver ions (Ag+) in aqueous solutions and biological samples has increased in recent years due to their very high toxicity to the environment and the human body. Orange-emissive carbon dots (CDs) were simply synthesized through the hydrothermal treatment of p-aminobenzoic acid and p-aminophenol. The obtained CDs display orange fluorescence and stability, including favorable photostability, salt tolerance and water solubility. Significantly, the fluorescence intensity of the CDs was quenched by the addition of Ag+via static quenching to form a nonfluorescent complex; thus a highly selective fluorescent method for the determination of Ag+ was developed. The present method showed a rapid response and excellent selectivity for Ag+ over other metal ions, and the relevant linear range and limit of detection were 5–100 μM and 1.4 μM, respectively. Furthermore, the practicability of this method was validated by the successful determination of Ag+ in water samples and a human serum sample. Compared with previous reports, this method showed rapid response and excellent selectivity, which present it as a valuable strategy in environmental protection and biological assays. [ABSTRACT FROM AUTHOR]

Silicon nanoparticles (SiNPs) have attracted increasing attentions due to their unique properties and related applications. However, previously reported SiNPs generally showed emission band only in the blue- or green-light regions, which limited their applications in biochemical samples. So far, synthesis of longer wavelength emissive SiNPs remains a challenge. In this paper, the yellow-emitting fluorescent SiNPs were prepared via a facile room temperature procedure, which avoided heating and pressurizing operation, multistep and time-consuming post-modified procedures. The obtained SiNPs displayed excellent water-solubility, pH-stability, salt-tolerance, and photo-stability. Significantly, the fluorescence of SiNPs could be remarkably quenched by crystal violet (CV) via synergistic effect of inner filter effect (IFE) and fluorescence resonance energy transfer (FRET). Based on this phenomenon, a method for the determination of CV was established. Under the optimum conditions, the method showed a wide linearity range from 0.075 to 15.0 μg/mL with a limit of detection of 25 ng/mL. Furthermore, the method was successfully applied to the analysis of CV in fish tissues samples. [ABSTRACT FROM AUTHOR]

A novel and effective ratiometric fluorescence strategy was developed for rapidly, sensitively and selectively probing sulfide anions (S2−). A dual-emission nanosensor was prepared by covalently attaching fluorescent carbon nanoparticles (CNPs) to gold nanoclusters (Au NCs), triggering the sensing mechanism of fluorescence resonance energy transfer (FRET) from CNPs (donor) to Au NCs (acceptor). Once S2− was added, considerable fluorescence recovery of CNPs and quenching of Au NCs were observed due to the inhibition of FRET progress via the formation of Au2S. The ratiometric probe showed good, specific S2− sensing behavior and high sensitivity with a detection limit of 18 nM. Significantly, the assay was successfully employed to determine the S2− content in biological and water samples, presenting immense promise in the biological and environmental fields. [ABSTRACT FROM AUTHOR]

In this work, it was reported that Cu-BTC (HKUST-1) can excellently catalyze the chemiluminescence (CL) reaction of luminol–H 2 O 2 system in an alkaline medium for the first time. Compared with the luminol–H 2 O 2 system, the CL intensity of luminol–H 2 O 2 –HKUST-1 system was enhanced significantly up to about 90-fold, which formed the sensitized CL system. The presence of dopamine (DA) inhibited the luminol–H 2 O 2 –HKUST-1 system, thus causing the changes in CL intensity (Δ I ). Based on this phenomenon, the excellent sensing platform for detection of DA was established. Under the optimized conditions, the Δ I was proportional to the concentration of DA in the range of 0.010–0.70 μM with the detection limit of 2.3 nM (3S/N). The proposed method was applied to the determination of DA in human plasma and urine samples with satisfactory results. Furthermore, the corresponding mechanism of such enhancement was investigated. The results indicated that the enhancement in CL intensity of the luminol–H 2 O 2 –HKUST-1 system originated from the catalysis of HKUST-1, which facilitated the radical generation and electron-transfer processes on its surface. [ABSTRACT FROM AUTHOR]

Highlights: [•] Potential toxicity of methyl-triclosan (MTCS) at the protein level was evaluated. [•] Binding mechanism of human serum albumin (HSA) with MTCS was discussed in detail. [•] Binding distance between MTCS and HSA was provided. [•] Visualized binding details were shown clearly by molecular simulation method. [Copyright &y& Elsevier]

Capillary electrophoresis (CE) has become one of the most useful tools in separation science because of its high separation efficiency, low cost, versatility, ease of sample preparation and automation. However, some limitations of CE, such as poor concentration sensitivity due to its lower sample loading and shorter optical path length, limits its further applications in separation science. In order to solve this problem, various on-line sample preconcentration techniques such as transient isotachophoresis preconcentration, field-enhanced sample stacking, micelle to solvent stacking, micelle collapse, dynamic pH junction, sweeping, solid phase extraction, single drop microextraction and liquid phase microextraction have been combined with CE. Recent developments, applications and some variants together with different combinations of these techniques integrating in CE are reviewed here and our discussions will be confined to the past three years (2008-2011). [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Iridoid glycosides and flavanoids are two main effective components of Lamiophlomis rotata (Benth.) kudo. However, there is no method for simultaneous analysis of iridoid glycosides and flavanoids in L. rotata and its pharmaceutical preparations. A simple and rapid capillary zone electrophoresis (CZE) method was developed and validated for simultaneous determination of two iridoid glycosides (8-O-acetylshanzhiside methylester and 8-deoxyshanzhiside) and three flavanoids (apigenin, quercetin and luteolin) in L. rotata. Operational variables, such as the voltage, buffer concentration and pH were optimized, the final optimum separation condition was 10 mM sodium tetraborate-20 mM NaH2PO4 (pH 8.5)-15% (v/v) methanol, 238 nm UV detection, 18 kV applied voltage. The linearity and the recovery of the proposed method were very satisfactory (correlation coefficients were 0.9994-0.9998 and the recoveries were 94.5-108.8% for the analytes) and the method allowed analytes in real samples to be determined within 9 min. The proposed CZE method can be used for quality control of iridoid glycosides and flavanoids in L. rotata and its herbal preparation. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: A novel procedure for in situ assembling a complex chiral selector, di-n-butyl l-tartrate–boric acid complex, by the reaction of di-n-butyl l-tartrate with boric acid in a running buffer was reported and its application in the enantioseparation of β-blockers and structural related compounds by chiral microemulsion electrokinetic chromatography (MEEKC) has been demonstrated. In order to achieve a good enantioseparation, the effect of dibutyl l-tartrate and sodium tetraborate concentration, surfactant identity and concentration, cosurfactant, buffer pH and composition, organic modifiers, as well as applied voltage and capillary length were investigated. Ten pairs of enantiomers that could not be separated with only dibutyl l-tartrate, obtained good chiral separation using the complex chiral selector; among them, seven pairs could be baseline resolved under optimized experimental conditions. The fixation of chiral centers by the formation of five-membered rings, and being oppositely charged with basic analytes were thought to be the key factors giving the complex chiral selector a superior chiral recognition capability. The effect of the molecular structure of analytes on enantioseparation was discussed in terms of molecular interaction. [Copyright &y& Elsevier]

Abstract: The logarithmic n-octanol/water partition coefficient (log K ow) is a very important property which concerns water-solubility, bioconcentration factor, toxicity and soil absorption coefficient of organic compounds. Quantitative structure–property relationship (QSPR) model for log K ow of 133 polychlorinated biphenyls (PCBs) is analyzed using heuristic method (HM) implemented in CODESSA. In order to indicate the influence of different molecular descriptors on log K ow values and well understand the important structural factors affecting the experimental values, three multivariable linear models derived from three groups of different molecular descriptors were built. Moreover, each molecular descriptor in these models was discussed to well understand the relationship between molecular structures and their log K ow values. The proposed models gave the following results: the square of correlation coefficient, R 2, for the models with one, two and three molecular descriptors was 0.8854, 0.9239 and 0.9285, respectively. [Copyright &y& Elsevier]

A nonaqueous capillary electrophoresis with laser-induced fluorescence detection method was developed for the quantification of ephedrine and pseudoephedrine after derivatization with 4-chloro-7-nitrobenzo-2-oxa-1, 3-diazol in nonaqueous media. The derivatization was made in off-line mode. By a series of optimizations, a derivatization buffer composed of 40 mm ammonium acetate and 20% acetonitrile and a running buffer composed of 80 mm ammonium acetate and 3% acetic acid were applied for the derivatization and separation of ephedrine and pseudoephedrine, respectively. Linear relationships for ephedrine and pseudoephedrine were obtained in the range 1.23-19.60 mg/L (correlation coefficients 0.9970 for ephedrine and 0.9994 for pseudoephedrine), and the detection limits for ephedrine and pseudoephedrine were 0.014 and 0.011 mg/L, respectively. The method was applied to the analysis of ephedrine and pseudoephedrine in four preparations with recoveries in the range 93.9-105.1%. Copyright © 2006 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract Co 3 O 4 nanoparticles - graphene oxide (Co 3 O 4 NPs - GO) nanocomposites with good solubility were successfully synthesized and well characterized. As a nanocatalyst with oxidase-mimicking activity, the nanocomposites can catalyze the oxidation of 3′,5,5′-tetramethylbenzidine (TMB) with high efficiency. The catalyzing reaction was rapid and no extra H 2 O 2 was needed compared with other similar TMB oxidation reactions. The catalyzing reaction mechanism of the system was investigated in detail. And it was demonstrated that the oxygen involved in the reaction came from the oxygen absorbed on the nanocomposites which oxidized TMB. Based on this reaction, a colorimetric system for vitamin C detection in vegetable and fruits was established. Under the optimum conditions, the detection can be achieved within 10 min and a linear relationship in concentration range of 2.5 × 10−6 to 1.8 × 10−5 M and 3.4 × 10−5 to 1.7 × 10−4 M was obtained with a detection limit of 7.0 × 10−7 M. The colorimetric system exhibited good selectivity, sensitivity and satisfactory recoveries ranged from 93.1% to 101.1%. [ABSTRACT FROM AUTHOR]

Abstract: A capillary zone electrophoresis method using only 1-alkyl-3-methylimidazolium-based ionic liquids as background electrolyte for the simultaneous determination of five anthraquinone derivatives including aloe-emodin, emodin, chrysophanol, physcion and rhein in Rhubarb species was described. Ion association constants, K ass, between anthraquinone anions and imidazolium cations were determined by analyzing the electrophoretic mobility change of anthraquinone anions using a non-linear least-squares method and factors contributing to ion associability were systematically clarified. For method optimization, several parameters such as ionic liquids concentration, background electrolyte pH and applied voltage, on the separation were evaluated and the optimum conditions were obtained as follows: 90mM 1-butyl-3-methylimidazolium tetrafluoroborate (pH 11.0) with an applied voltage of 20kV. Under these conditions, the method has been successfully applied to the determination of anthraquinones in extracts of two kinds of Rhubarb plants (R. palmatum and R. hotaoense) within 12min. The method proposed herein was shown to be much simpler than the previously reported methods. [Copyright &y& Elsevier]