Determination of diclofenac in pharmaceutical preparations by diffuse reflectance photometry

A quantitative analytical method for the determination of diclofenac in pharmaceutical preparations by diffuse reflectance in the visible region of the spectrum is presented. The color reaction is done directly in the measuring cell immediately after mixing, using small volumes of the analyte solution, of the reagent and of the buffer solutions. All reflectance measurements were carried out in a home made reflectometer equipped with a red LED as light source and a LDR as detector. The calibration curves were constructed from 1.0 to 18 mg mL⁻¹ (about 3.0 × 10⁻³ to 5.5 × 10⁻² mol L⁻¹) of sodium diclofenac or of potassium diclofenac in the analytical solution, with typical correlation coefficients equal to 0.999. The detection limit was estimated to be about 0.7 mg mL⁻¹ (2 × 10⁻³ mol L⁻¹). The method was applied to determine diclofenac in solid and liquid pharmaceutical preparations. The R.S.D. varied from 2% to 4% depending of the sample. The results were compared with those obtained with the HPLC procedure recommended by the United States Pharmacopoeia using the statistical Student's t-test procedure.     

稀疏降噪自编码结合高斯过程的近红外光谱药品鉴别方法

提出一种稀疏降噪自编码结合高斯过程的近红外光谱药品鉴别方法。首先对近红外光谱数据进行小波变换以消除基线漂移,然后用稀疏降噪自编码(SDAE)网络提取光谱特征并降维表示,最后采用高斯过程(GP)进行二分类,其中GP选用光谱混合(SM)核函数作为协方差函数,记此分类网络为wSDAG_SM。自编码网络具有很强的模型表示能力,高斯过程分类器在处理小样本数据时具有优势。wSDAG_SM网络通过稀疏降噪自编码学习得到维数更低但更有价值的特征来表示输入数据,同时将具有很好表达力的光谱混合核作为高斯过程的协方差函数,有利于更准确的光谱数据分类。以琥乙红霉素及其他药品的近红外光谱为实验数据,将该方法与经过墨西哥帽小波变换的BP神经网络(wBP)、支持向量机(wSVM), SDAE结合Logistic二分类(wSDAL)、SDAE结合采用平方指数(SE)协方差核的GP二分类(wSDAG_SE),以及未采用小波变换的SDAG_SM网络等方法进行对比。实验结果表明,对光谱数据进行墨西哥帽小波变换预处理能有效提升SDAG_SM网络的分类准确率和稳定性。wSDAG_SM方法无论从分类准确率还是分类结果稳定性方面,都优于其他分类器。     

Fracture propagation in brittle materials as a standard dissipative process: General theorems and crack tracking algorithms

The present work frames the problem of three-dimensional quasi-static crack propagation in brittle materials into the theory of standard dissipative processes. Variational formulations are stated. They characterize the three dimensional crack front “quasi-static velocity” as minimizer of constrained quadratic functionals. An implicit in time crack tracking algorithm that computationally handles the constraint via the penalty method algorithm is introduced and proof of concept is provided.     

Near-infrared spectroscopy-based methods for quantitative determination of active pharmaceutical ingredient in transdermal gel formulations

Abstract

Semi-solid pharmaceutical forms, like topical and transdermal products, are widely used for medical purposes since they provide convenient and pain-free treatment for patients. In this study, two transdermal gel formulations with different active pharmaceutical ingredients were analyzed with near-infrared spectrophotometers with three distinct optical arrangements (dispersive, Fourier transform, and diode-array spectrophotometers) for the measurement of active pharmaceutical ingredient concentration. The reference concentrations were measured with high-performance liquid chromatography methods.

The developing of calibration for reference concentrations based on near-infrared spectra was performed using partial least squares regression. The spectra from near-infrared spectrophotometer with diode-array optical arrangement presented the best root mean square error of cross-validation results with 0.045% and 0.144% for the two active pharmaceutical ingredients. The root mean square error of cross-validation using dispersive spectra were 0.125% and 0.193% and using Fourier transform spectra were 0.130% and 0.344% for the active pharmaceutical ingredients. The results of partial least squares regression were confirmed using simulated spectra based on the measured datasets.

Near-infrared spectroscopy can be used successfully for the quantitative measurement of active pharmaceutical ingredient concentration in transdermal gel formulations. The type of optical arrangements of spectrophotometers can influence the performance of calibrations and have to be optimized case by case.     

Efficiency of the medical care industry: Evidence from the Italian regional system

What might be the relation between clinical research and efficiency of medical care suppliers? Is the hypothesis of a positive relation consistent? Considering efficiency as the supplier’s ability to maximize the number of patients hospitalized in a mobility process among regions (i.e. mobility balance), this work aims at highlighting the existence of a positive externality of pharmaceutical clinical research on that kind of efficiency. In other words, an externality is able to affect the patients’ perception of good/bad quality of outputs supplied by the medical care industry, leading their mobility process. Taking Italy and the mobility of patients among regions into account, an Operational Research study will be performed in order to support this assumption.The goal of this work is to show an alternative way to increase the efficiency of medical care suppliers on the market of health care, that is to say, through their competitiveness on the market of human experimentation.     

Flow Injection Spectrophotometric Determination of Dipyrone in Pharmaceutical Formulations Using Fe(III) as Reagent

A flow injection spectrophotometric procedure with symmetric merging zones for dipyrone determination in pharmaceutical formulations is proposed. The determination is based on the formation of a blue complex (monitored at a wavelength of 642 nm) yield in the complexation reaction of dipyrone with Fe(III) in acid medium. Under optimum conditions, a calibration curve was obtained from 3.5 to 281 mg L^?1 with a detection limit of 2.8 mg L^?1 and the samples throughput was 80 h^?1. The analytical results obtained for commercial formulation samples by applying the proposed method were in good agreement with labeled values and those obtained by a comparative procedure at a 95% confidence level.     

Conductimetric,Potentiometric and Visual Titrimetric Methods for Analysis of Nadolol

Abstract

Nadolol, a beta-blocking agent, has been assayed in pure form and in pharmaceutical formulation by acidimetric titrations using visual, potentiometric and conductimetric methods for detecting the end point in aqueous as well as in non-aqueous media. The method of assay involves the determination of the amount of nadolol in a given weight of sample. Six samples were run for each method and the percentages of recovery of nadolol from its tablets were calculated. For aqueous titrations, the average percentages of recovery for the visual, potentiometric and conductimetric methods are 100.6 ± 1.0, 99.3 ± 1.9 and 100.1 ± 2.0 respectively. For the non-aqueous titrations, the average percentages of recovery are 98.6 ± 0.8, 99.5 ± 0.5 and 98.4 ± 1.3 for the visual, potentiometric and conductimetric methods respectively.     

Chemiluminescence Determination of Tetracyclines via Aluminum Sensitized Fluorescence

Tetracycline, oxytetracycline, doxycycline, and chlortetracycline have been determined by chemiexcitation of the corresponding Al(III) highly fluorescent complex from the permanganate or cerium(IV)-sulphite chemiluminogenic reactions. Limits of detection and ranges of linearity are equal to 0.024, 0.015, 0.014, and 0.050 µg mL^?1 and 0.067–3.20, 0.042–1.70, 0.042–3.00, and 0.103–2.80 µg mL^?1 for tetracycline, oxytetracycline, doxycycline, and chlortetracycline, respectively. Average recovery of tetracyclines from solutions of commercial formulations was equal to 99.8% and the procedure was successfully applied to the determination of tetracyclines in commercial products with mean relative error equal to 3.4% (range 1.4–5.0%).     

Cyclodextrin Enhanced Spectrofluorimetric Determination of Melatonin in Pharmaceuticals and Urine

ABSTRACT

Melatonin forms a 1:1 inclusion complex with methyl-β-cyclodextrin with an association constant of 139 ? 30 M^?1 at 20 °C. The effect of several cyclodextrins and derivatives on the fluorescence spectra of melatonin was studied with a great increase of fluorescence signal when methyl-β-cyclodextrin was employed. Optimal conditions of the method were: [methyl-β-cyclodextrin] = 0.01 M and temperature 20 °C; the pH does not affect the luminescence emission. The linear dynamic range (LDR) was 50-3000 ng ml^?1 and a limit of detection of 10 ng ml^?1 of melatonin was obtained with a relative standard deviation (RSD) of 0.77% (at 0.3 μg ml^?1 level). This simple method was satisfactorily applied to the determination of melatonin in pharmaceutical preparations and urine.