Application of a chemometric method for simultaneous determination of acetaminophen and diclofenac in content-uniformity and drug-dissolution studies

A new, repeatable, and rapid method has been developed for resolution of binary mixtures of acetaminophen and diclofenac with minimum sample pretreatment and without separation of the analytes. The method, based on the PLS1 processing of absorbance data in the UV region, was successfully used for quantification of the drug content of three tablet preparations. The results obtained were in good agreement with HPLC recovery data. The method also enabled determination of drug-dissolution profiles of these commercial tablets, by simultaneous determination of both analytes during the dissolution test.     

Enhanced ethanol sensing properties of WO3 modified TiO2 nanorods

Pristine and WO₃ decorated TiO₂ nanorods (NRs) were synthesised to investigate n-n-type heterojunction gas sensing properties. TiO₂ NRs were fabricated via hydrothermal method on fluorine-doped tin oxide coated glass (FTO) substrates. Then, tungsten was sputtered on the TiO₂ NRs and thermally oxidised to obtain WO₃ nanoparticles. The heterostructure was characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX) spectroscopy. Fabricated sensor devices were exposed to VOCs such as toluene, xylene, acetone and ethanol, and humidity at different operation temperatures. Experimental results demonstrated that the heterostructure has better sensor response toward ethanol at 200 °C. Enhanced sensing properties are attributed to the heterojunction formation by decorating TiO₂ NRs with WO₃.     

Phenolic compounds,essential oil composition,and antioxidant activity of Angelica purpurascens (Avé-Lall.) Gill

In this study, methanol extracts (MEs) and essential oil (EO) of Angelica purpurascens (Avé-Lall.) Gill obtained from different parts (root, stem, leaf, and seed) were evaluated in terms of antioxidant activity, total phenolics, compositions of phenolic compound, and essential oil with the methods of 2,2-azino-bis(3ethylbenzo-thiazoline-6-sulfonic acid (ABTS•⁺), 2,2-diphenyl-1-picrylhydrazil (DPPH•) radical scavenging activities, and ferric reducing/antioxidant power (FRAP), the Folin–Ciocalteu, liquid chromatography−tandem mass spectrometry (LC−MS/MS), and gas chromatography-mass spectrometry (GC−MS), respectively. The root extract of A. purpurascens exhibited the highest ABTS•⁺, DPPH•, and FRAP activities (IC₅₀: 0.05 ± 0.0001 mg/mL, IC₅₀: 0.06 ± 0.002 mg/mL, 821.04 ± 15.96 µM TEAC (Trolox equivalent antioxidant capacity), respectively). Moreover, EO of A. purpurascens root displayed DPPH• scavenging activity (IC₅₀: 2.95 ± 0.084 mg/mL). The root extract had the highest total phenolic content (438.75 ± 16.39 GAE (gallic acid equivalent), µg/mL)). Twenty compounds were identified by LC−MS/MS. The most abundant phenolics were ferulic acid (244.39 ± 15.64 μg/g extract), benzoic acid (138.18 ± 8.84 μg/g extract), oleuropein (78.04 ± 4.99 μg/g extract), and rutin (31.21 ± 2.00 μg/g extract) in seed, stem, root, and leaf extracts, respectively. According to the GC−MS analysis, the major components were determined as α-bisabolol (22.93%), cubebol (14.39%), α-pinene (11.63%), and α-limonene (9.41%) among 29 compounds. Consequently, the MEs and EO of A. purpurascens can be used as a natural antioxidant source.     

PLS and first derivative of ratio spectra methods for determination of hydrochlorothiazide and propranolol hydrochloride in tablets

Two new analytical methods have been developed as convenient and useful alternatives for simultaneous determination of hydrochlorothiazide (HCT) and propranolol hydrochloride (PRO) in pharmaceutical formulations. The methods are based on the first derivative of ratio spectra (DRS) and on partial least squares (PLS) analysis of the ultraviolet absorption spectra of the samples in the 250–350-nm region. The methods were calibrated between 8.7 and 16.0 mg L⁻¹ for HCT and between 14.0 and 51.5 mg L⁻¹ for PRO. An asymmetric full-factorial design and wavelength selection (277–294 nm for HCT and 297–319 for PRO) were used for the PLS method and signal intensities at 276 and 322 nm were used in the DRS method for HCT and PRO, respectively. Performance characteristics of the analytical methods were evaluated by use of validation samples and both methods showed to be accurate and precise, furnishing near quantitative analyte recoveries (100.4 and 99.3% for HCT and PRO by use of PLS) and relative standard deviations below 2%. For PLS the lower limits of quantification were 0.37 and 0.66 mg L⁻¹ for HCT and PRO, respectively, whereas for DRS they were 1.15 and 3.05 mg L⁻¹ for HCT and PRO, respectively. The methods were used for quantification of HCT and PRO in synthetic mixtures and in two commercial tablet preparations containing different proportions of the analytes. The results of the drug content assay and the tablet dissolution test were in statistical agreement (p < 0.05) with those furnished by the official procedures of the USP 29. Preparation of dissolution profiles of the combined tablet formulations was also performed with the aid of the proposed methods. The methods are easy to apply, use relatively simple equipment, require minimum sample pre-treatment, enable high sample throughput, and generate less solvent waste than other procedures. Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users.     

Multivariate Optimization and Validation of a CZE Method for the Analysis of Pridinol Mesylate and Meloxicam in Tablets

A capillary zone electrophoresis method for the simultaneous determination of pridinol mesylate (PRI) and meloxicam (MEL) employing epinastine hydrochloride and piroxicam as internal standards, was developed and optimized employing experimental design and response surface methodologies. The separation was optimally achieved in less than 2 min at 30 kV in an uncoated fused-silica capillary (41.4 cm × 75 ??m I.D.), employing an 18 mmol L^?1 sodium phosphate buffer solution (pH 5.90) at 25 °C. Samples were injected in hydrodynamic mode (50 mbar, 5 s) and the analytes were spectrophotometrically detected at 200 nm. Method robustness was demonstrated by ANOVA of determinations performed under conditions slightly different from the optimum. The method was validated regarding separation selectivity (peak purity factors > 0.99), linearity and range (PRI = 17.6?C31.4 mg L^?1; MEL = 66.5?C122.5 mg L^?1), accuracy (PRI = 100.2?C101.9%; MEL = 98.9?C100.7%) and precision. The RSD values obtained were ??1.3% for injection repeatability and ??1.9% for intra-day precision. The limits of detection (1.0 and 0.9 mg L^?1) and quantification (3.3 and 16.5 mg L^?1) of PRI and MEL, respectively, were also determined. The method was successfully applied to the determination of both drugs in three brands of tablet formulations. No statistically significant differences were observed when these results were compared with those of a RP-HPLC method.     

CHARACTERIZATION OF NANOSTRUCTURES:TOOLS AND CHALLENGES

Apart from long-known and applied nanostructures like carbon black for tyres or pigments for coatings nanotechnology has created highly sophisticated structures used for nano/molecular electronics,diagnostics,drug delivery, UV-absorbers etc.Often the main question to be solved analytically is the local determination of tiny amounts of chemicals resulting in an ever increasing need for highly sensitive as well as locally resolved techniques.Applications of techniques like mass spectroscopy,transmission el...     

Photochromic and fluorescence properties of coumarin fulgimides

Four new fulgimides possessing a fluorescent coumarin unit were synthesized from the corresponding fulgides, and their photochromic as well as fluorescence properties were investigated. The open-ring forms of coumarin fulgimides were found to exhibit fluorescence in the visible region. Upon exposure to UV light, the fulgimides were transformed into the nonfluorescent closed-ring forms, which can be reverted to the initial fluorescent open-ring forms on exposure to visible light. The efficiency of quenching of fluorescence was as high as 95% at the photostationary state of UV irradiation.     

掺杂Eu2O3的SrTiO3及SnO2光致发光

用具有大能隙的本征半导体(SrTiO₃及SnO₂)粉末作本体,分别掺杂1%(原子百分数)的Eu₂O₃;所得物质表现出Eu³⁺离子的线发射光谱特性,但相对发光强度及光谱形状有相当大的变化。X射线衍射结构分析显示Eu³⁺在SrTiO₃晶格里是处在间隙位置,而它在SnO₂晶格里则形成新物相Eu₂Sn₂O₇。     

FLUORESCENCE ENERGY TRANSFER BETWEEN DIMETHYLDIAZAPEROPYRENIUM DICATION AND ETHIDIUM INTERCALATED IN POLY d(A-T)

Dimethyldiazaperopyrenium is one of the largest known DNA intercalators. Fluorescence energy transfer occurred between dimethyldiazaperopyrenium (donor) and ethidium (acceptor) when these dyes were bound to a double-stranded polynucleotide such as poly d(A-T). The addition of increasing amounts of ethidium bromide led to a marked shortening of the fluorescence lifetime of the donor, whereas the excited state of the acceptor was progressively populated via energy transfer from the donor. Critical Förster distance between these two chromophores was calculated to be 3.8 nm. The observed transfer efficiency was lower than that calculated on the basis of this critical distance and a statistical distribution of bound drugs. These results are discussed taking into account the conformational change induced by intercalation of dimethyldiazaperopyrenium in the double-stranded polynucleotide.