Determination of nicotinamide by stopped-flow injection method in pharmaceutical formulations

A simple stopped-flow injection system with spectrophotometric detection was proposed for the determination of nicotinamide (NAM) in pharmaceutical formulations. In this system cyanogen chloride formed from the combination of an acidic KSCN with the NaClO streams reacts with injected NAM to form glutaconic aldehyde. Then the product of these three components was coupled with another buffered (pH 3.5) stream of barbituric acid and directed towards the detector. A 45 s after sample injection the pump was stopped for 130 s. During this time the reactants in the flow cell were provided with the required temperature (40 °C) by placing the cell in a home made cell jacket to increase the yield of the polymethine dye product. Eventually, the absorbance of the formed pink color dye was monitored spectrophotometrically at 560 nm and NAM in the concentration range of 1.0–25.0 μg/mL (R = 0.9974 and D.L = 0.5 μg/mL) was determined. The results obtained by this method were compared statistically and agree with those obtained by the method described in the British Pharmacopoeia.     

Adaptive quasi-likelihood estimate in generalized linear models

This paper gives a thorough theoretical treatment on the adaptive quasi-likelihood estimate of the parameters in the generalized linear models. The unknown covariance matrix of the response variable is estimated by the sample. It is shown that the adaptive estimator defined in this paper is asymptotically most efficient in the sense that it is asymptotic normal, and the covariance matrix of the limit distribution coincides with the one for the quasi-likelihood estimator for the case that the covariance matrix of the response variable is completely known.     

Expansion of analytic functions in q-orthogonal polynomials

A classical result on the expansion of an analytic function in a series of Jacobi polynomials is extended to a class of q-orthogonal polynomials containing the fundamental Askey–Wilson polynomials and their special cases. The function to be expanded has to be analytic inside an ellipse in the complex plane with foci at ±1. Some examples of explicit expansions are discussed.      

Development and validation of a HPLC method for the determination of buprenorphine hydrochloride, naloxone hydrochloride and noroxymorphone in a tablet formulation

A simple isocratic reversed-phase high-performance liquid chromatographic method (RP-HPLC) was developed for the simultaneous determination of buprenorphine hydrochloride, naloxone hydrochloride dihydrate and its major impurity, noroxymorphone, in pharmaceutical tablets. The chromatographic separation was achieved with 10 mmol L⁻¹ potassium phosphate buffer adjusted to pH 6.0 with orthophosphoric acid and acetonitrile (17:83, v/v) as mobile phase, a C-18 column, Perfectsil Target ODS3 (150 mm × 4.6 mm i.d., 5 μm) kept at 35 °C and UV detection at 210 nm. The compounds were eluted isocratically at a flow rate of 1.0 mL min⁻¹. The average retention times for naloxone, noroxymorphone and buprenorphine were 2.4, 3.8 and 8.1 min, respectively. The method was validated according to the ICH guidelines. The validation characteristics included accuracy, precision, linearity, range, specificity, limit of quantitation and robustness. The calibration curves were linear (r > 0.996) over the concentration range 0.22-220 μg mL⁻¹ for buprenorphine hydrochloride and 0.1-100 μg mL⁻¹ for naloxone hydrochloride dihydrate and noroxymorphone. The recoveries for all three compounds were above 96%. No spectral or chromatographic interferences from the tablet excipients were found. This method is rapid and simple, does not require any sample preparation and is suitable for routine quality control analyses.     

Antioxidant Activity Degradation,Formulation Optimization,Characterization, and Stability of Equisetum Arvense Extract Nanoemulsion

Equisetum arvense supercritical CO₂ extracts (EAE) contained an initial antioxidant activity of 10.3 mM TEAC that suffered a sharp first order kinetics decay characterized by half-life time (t_1/2) of 1.05 ± 0.03 and 0.86 ± 0.03 weeks at 25 and 4°C, respectively. The aim of the present work was to develop a nanoemulsion formulation for providing EAE protection against deleterious environmental factors and extending its shelf-life functionality. The nanoemulsion area was identified by constructing pseudoternary phase diagrams and response surface methodology was used to optimize the preparation conditions. The best formulation achieved an EAE encapsulation efficiency of 97.5 ± 0.5% and antioxidant activity half-life time (t_1/2) was extended to 12.32 ± 0.40 and 14.56 ± 0.60 weeks at 25 and 4°C, respectively.      

Copolymeric nano/microgels of N-isopropylacrylamide and carboxyalkyl methacrylamides: Effect of methylene chains and the ionization state of the weak acids on size and sensitivity to pH and temperature

ABSTRACT

We prepared nano/microgels by precipitation copolymerization of N-isopropylacrylamide (NIPAAm), and one of three different carboxyalkyl methacrylamides [methacryloylamido hexanoic acid (M₅), 8-methacryloylamido octanoic acid (M₇), and 11-methacryloylamido undecanoic acid (M₁₀)], either in the acid forms or as carboxylates (potassium salts). The hydrodynamic diameter (Dh) of the nano/microgels prepared with the carboxylates was smaller (≈100 nm for M₁₀ copolymers), compared to the size of homopolymeric NIPAAm microgels prepared by dispersion polymerization (around 600 nm), indicating that the carboxylates act as surfactants reducing the size of the seeds during the polymerization process. These materials presented a swollen-shrunken transition temperature (T _tr) similar to the T _tr of the homopolymeric NIPAAm microgels, without pH sensitivity. On the other hand, the copolymeric microgels prepared from the acid form of the comonomers have a similar or bigger size than NIPAAm microgels. For these copolymers, the T _tr can be tuned by the type and proportion of acid comonomer used and present pH sensitivity. This is important for biomedical applications such as positive temperature control release. Polyelectrolyte titration demonstrates that the nano/microgels prepared with the carboxylates behave as hard spheres, while the microgels prepared with the weak acid behave as porous materials.     

Synthesis and Characterization of Dual Acidic Ionic Liquids

Novel ionic liquids with dual acidity, of which the cation contains Brφnsted acidity and anions contain Lewis acidity were synthesized. These ionic liquids obtained were identified by NMR, FF-IR, SDT and FAB-MS. Their acidities were determined by pyridine probe on IR spectrography.     

配糖蛋白B肠溶微胶囊的研究

采用双乳液法研制配糖蛋白Ｂ的肠溶微胶囊，考察了微胶囊的形态、粒径及其分布，在摸拟肠液的缓冲液中进行溶解释放试验。配制了两种口服微胶囊混悬制剂，并考察了它的稳定性。     

A common fixed point theorem for compatible quasi contractive self mappings in metric spaces

A common fixed point theorem for weakly commuting quasi contractive self mappings with contracting orbital diameters in metric spaces [V. Berinde, A common fixed point theorem for quasi contractive type mappings, Ann. Univ. Sci. Budapest. 46 (2003) 81-90] is extended to the more general class of compatible quasi contractive self mappings. Our result does extend and generalize numerous related results in literature.