Spectrophotometric determination of acrivastine in urine and capsules

Three sensitive and accurate spectrophotometric methods are presented for the determination of the antihistaminic acrivastine (ACR) in capsules and urine. The first method utilizes the reaction of 2-nitrophenylhydrazine hydrochloride in presence of dicyclohexylcarbodiimide and pyridine. The violet colour of the resulting acid hydrazide is measured at 550 nm. The second method is based on alkaline oxidation of the drug with potassium permanganate and subsequent measurement of the formed manganate ion at 608 nm. The third method uses derivative spectrophotometry for the determination of ACR. The last method is extended to the in vitro determination of the drug in urine. All methods gave a relative standard deviation of less than 2%.     

Densitometric Kinetic Stability Studies of Some Plant Extracts Using Different Regression Methods

JPC – Journal of Planar Chromatography – Modern TLC -     

Spectrophotometric Determination of Ternary Mixtures by the Derivative Ratio Spectrum-Zero Crossing Method

Abstract

A new spectrophotometric method is introduced for the assay of ternary mixtures with overlapping spectra. The method is based on the use of the first derivative of the ratio spectra and measurements of zero-crossing wavelengths. The ratio spectra were obtained by dividing the absorption spectrum of the mixture by that of one of the components. The concentration of the other components are then determined from their respective calibration graphs treated similarly. The method has been applied for the resolution of two ternary mixtures, namely, dipyridamole, aspirin and salicylic acid (I) and dipyridamole, oxazepam and 2-amino-5-chlorobenzophenone (II). Salicylic acid and benzo-phenone derivative are the degradation products of aspirin and oxazepam, respectively. The proposed method was applied for the assay of these combinations in synthetic mixtures and in commercial dosage forms. The results obtained were precise and accurate.     

Diode array detection for stability assessment and evaluation of degradation kinetics of newly introduced sacubitril in its supramolecular complex (LCZ696) with valsartan

A newly FDA-approved heart failure therapy (LCZ696, supramolecular complex of sacubitril (SAC) and valsartan (VAL), Entresto?) is analyzed with a stability indicating HPLC–DAD method. For the newly introduced drug, SAC, there is no sufficient information about its stability under various stress conditions. The proposed chromatographic method was applied to the kinetic investigation of the acidic, alkaline, and oxidative degradation of SAC with the estimation of its activation energy and half-life at room temperature by the aid of Arrhenius plots. Kinetic investigation was conducted using either different strengths of HCl, NaOH, and H₂O₂ at one selected temperature or different temperature degrees at one selected reagent strength, for the acidic, alkaline, and oxidative stress conditions. It was found that the pseudo-first-order kinetics was followed at each case. The half-lives at room temperature using 0.1?M HCl, 0.01?M NaOH, and 15% H₂O₂ were found to be 20.50, 2.76, and 51.58?hr. The chromatographic method was achieved using Zorbax Eclipse plus-C18 (4.6?×?250?mm, 5?µm) with isocratic elution of mobile phase composed of acetonitrile and 0.025?M phosphate buffer (pH3) in a ratio of 60:40 (v/v).     

Extraction-spectrophotometric determination of phenytoin in capsules and plasma using potassium permanganate/dicyclohexano-24-crown-8

An extraction-spectrophotometric method for the determination of phenytoin in capsules and plasma is presented. The method is based upon oxidation of phenytoin using alkaline potassium permanganate solubilized in chloroform/cyclohexane (1:1) after crowning with dicyclohexano-24-crown-8 (DC-24-C-8). The formed benzophenone being soluble in the oxidation reaction medium was directly measured at 238 nm. The optimum conditions for the reaction were studied and the detection limit was found to equal 1.2 mg/100 ml. The developed method was applied to the determination of the drug in capsules and plasma. The method is simple, accurate and avoids laborious multistep extraction procedures.     

Spectroscopic Investigation of the Antazoune-p-chloranilic Acid Reaction Product

Spectroscopic studies on the reaction of p-chloranilic acid with antazoline base are reported. These include UV/VIS and IR spectrophotoraetry, electron spin resonance (ESR) and nuclear magnetic resonances (¹H-NMR & ¹³C-NMR). The results reveal that the antazoline-p-chloranilic acid product is an ion pair salt rather than a charge-transfer complex.     

Green chemistry: Analytical and chromatography

Nowadays, the environment protection and the personal health and safety are given more consideration in the field of chemistry, thus resulting in an increased number of published researches about how to work according to green instructions, to follow up the recommendations of environmental agencies and to obtain better clean handling of chemistry. In this review, green chemistry definition, importance, principles, and some recent applications in the field of green chemistry were discussed. In addition, the review summarizes the evolution of green analytical chemistry (GAC) with its specific principles and how to make the analytical process more environmentally benign with special emphasis on recent applications of GAC. Moreover, the green chromatography, its methods, and some of its applications were outlined. Finally, different techniques available up till now for the assessment of greening of the methods were also presented.     

Colorimetric determination of p-aminophenol in the presence of paracetamol with 3-cyano-N-methoxypyridinium perchlorate

Two simple and sensitive calorimetric procedures for the determination of p-aminophenol with 3-cyano-N-methoxypyridinium perchlorate are presented. One is based on reaction in methoxyethanol in presence of sodium acetate, with direct measurement at 410 nm. The reaction product obtained by this procedure has been separated and identified. The other is based on reaction in methoxyethanol in presence of chloramine-T and direct measurement at 448 nm. The method has been applied to the determination of p-aminophenol in pure form and as an impurity in paracetamol and paracetamol- containing tablets, with a coefficient of variation less than 2%.