H. G. Daabees

Selective Differential Spectrophotometric Methods for Determination of Niclosamide and Drotaverine Hydrochloride

ABSTRACT Differential (ΔA), second derivative (ΔD2) and third derivative (ΔD3) differential ultraviolet spectrophotometric methods have been presented for the quantitation of niclosamide and drotaverine hydrochloride in pure forms and in their pharmaceutical formulations. For niclosamide, the method is based on measuring ΔΔ A, Δ ΔD2, A ΔD3 of niclosamide in alkaline solutions against their neutral ethanolic solutions as blanks. For drotaverine hydrochloride, the acidic solutions of the drug are measured against their alkaline solutions as blanks. The proposed methods are sensitive, highly specific and advangageous over the conventional UV assays, since the interference of the excipients, impurities, degradation products or other accompanying drugs is nullified. Accuracy of the analysis with the proposed procedures is significantly greater than the classical spectrophotometric methods.

New simple spectrophotometric method for determination of the binary mixtures（atorvastatin calcium and ezetimibe;candesartan cilexetil and hydrochlorothiazide） in tablets

A new simple spectrophotometric method was developed for the determination of binary mixtures without prior separation. The method is based on the generation of ratio spectra of compound X by using a standard spectrum of compound Y as a divisor. The peak to trough amplitudes between two selected wavelengths in the ratio spectra are proportional to concentration of X without interference from Y. The method was demonstrated by determination of two drug combinations. The first consists of the two antihyperlipidemics: atorvastatin calcium (ATV) and ezetimibe (EZE), and the second comprises the antihypertensives: candesartan cilexetil (CAN) and hydrochlorothiazide (HCT). For mixture 1, ATV was determined using 10 μg/mL EZE as the divisor to generate the ratio spectra, and the peak to trough amplitudes between 231 and 276 nm were plotted against ATV concentration. Similarly, by using 10 μg/mL ATV as divisor, the peak to trough amplitudes between 231 and 276 nm were found proportional to EZE concentration. Calibration curves were linear in the range 2.5–40 μg/mL for both drugs. For mixture 2, divisor concentration was 7.5 μg/mL for both drugs. CAN was determined using its peak to trough amplitudes at 251 and 277 nm, while HCT was estimated using the amplitudes between 251 and 276 nm. The measured amplitudes were linearly correlated to concentration in the ranges 2.5–50 and 1–30 μg/mL for CAN and HCT, respectively. The proposed spectrophotometric method was validated and successfully applied for the assay of both drug combinations in several laboratory-prepared mixtures and commercial tablets.

Use of Differential Spectrophotometry for Determination of Cytarabine and Acyclovir in Their Dosage Forms

Abstract Differential (ΔA), first derivative- (ΔD1) and second derivative- (ΔD2) differential ultraviolet spectrophotometric methods have been presented for the quantitation of cytarabine and acyclovir in their pharmaceutical formulations such as injections and creams. The methods are based on measuring ΔA, ΔD1 and ΔD2 of the active ingredients in acidic solutions against their basic solutions as blanks. The proposed methods are sensitive, highly specific and advantageous over the conventional UV assays since all interferences of the excipients or irrelevant absorptions are nullified. Accuracy of the analysis with the proposed procedures is significantly greater than the classical spectrophotometry methods.

The use of derivative spectrophotometry for the determination of acyclovir and diloxanide furoate in presence of impurity or degradation product

Abstract Second (D2) and third (D3) derivatives spectrophotometry have been developed for the determination of acyclovir in the presence of guanine (its main impurity) and diloxanide furoate in the presence of diloxanide (its degradation product). The methods depend upon measuring D2 and D3 peak amplitudes at 269 and 262 nm for acyclovir and at 260 and 270 nm for diloxanide furoate in 0.1 N hydrochloric acid. Accuracy of analysis with the proposed derivative spectrophotometric procedure is significantly greater than the classical methods.

New Sensitive Method for the Analysis of Some Non UV Absorbing Quaternised Compounds

Abstract A rapid first derivative spectrophotometric assay of bretylium tosylate, hyoscine butylbromide, oxyphenonium bromide, cetrimide and benzalkonium chloride in pure and in pharmaceutical formulation is developed, The assay depends upon extracting the picrate salt of these quaternised compounds into chloroform from aqueous medium and measurement of peak amplitude at 430 nm or peak - trough amplitude at 365/330 nm. Linear correlation over the concentration range of 5–20 ug ml−1 of the investigated compounds is obtained. The recovery percentage of the pure compound varied from 99.5 to 100.6%. The developed method is simple, sensitive, accurate and suitable for routine analysis of these quaternised compounds in bulk powder and in pharmaceutical formulations.

Some spectrophotometric methods for determination of certain antipyretic and antirheumatic drugs

Heating paracetamol in strongly alkaline medium with 4-nitrosoantipyrine gives a red colour with maximum absorption at 515 nm. Mefenamic and flufenamic acids can be determined colorimetrically after extraction as ion-pairs with Methylene Blue.

A New Sensitive Spectrophotometry Method for the Analysis of Some Antihistamines

Abstract A simple and sensitive spectrophotometric method is developed for the assay of some antihistamines. The method is based on the interaction of these basic compounds with picrolonic acid in chloroform to give a yellow color exhibiting maximum absorption at 359 nm. The drugs determined are astemizoie, cinnarizine, mequitazine and terfenadine. Beers Law is valid for the investigated antihistamines. The drugs are determined either in pure form or in their pharmaceutical formulations. The sensitivity of the proposed procedure is discussed and the results are compared with reported ones.

Spectrophotometric determination of cefprozil in pharmaceutical dosage forms, in urine and in the presence of its alkaline induced degradation products

Four simple, rapid and accurate methods for spectrophoto-metric determination of cepfrozil are presented. Method I and II depend on measuring first derivative peak-trough amplitude of the drug in 0.1 N HCl (D1 a) and in phosphate buffer pH 7(D1 b), respectively. Method III and IV are based on measuring the absorbance difference (ΔA) and first derivative difference (ΔD1) of buffered cefprozil solutions against its acidic solutions as blanks. The proposed methods are applied for the determination of the drug in pure and dosage forms with good accuracy and precision. Among the previously mentioned methods; D1 a, D1 b and ΔD1 are used for the determination of cefprozil in urine. These methods have been successfully applied for the determination of cumulative amounts of cefprozil in urine following an oral dose of 500 mg to a human male volunteer. Moreover, by using D1 a method and applying the zero-crossing technique, both the intact drug and its alkaline induced degradation products could be determined in presence of each other without interference. The proposed methods proved to be accurate and reproducible.

Validated spectrofluorimetric determination of two pharmaceutical antihypertensive mixtures containing amlodipine besylate together with either candesartan cilexetil or telmisartan

Amlodipine besylate (AML) is available in fixed-dose combination tablets with either candesartan cilexetil (CAN) or telmisartan (TEL). This work describes a simple, selective and sensitive spectrofluorimetric method for analysis of AML/CAN and AML/TEL binary mixtures without prior separation. The method involves measurement of the native fluorescence of AML at excitation and emission wavelengths of 367 and 454 nm, respectively, in water without interference from either of the two drugs. By contrast, the intrinsic fluorescence of CAN was measured at excitation and emission wavelengths of 265 and 392 nm, respectively, in ethanol, while TEL was measured at 366 nm in 0.05 M sodium hydroxide solution using 294 nm as the excitation wavelength. The proposed spectrofluorimetric procedure was validated with respect to linearity, ranges, precision, accuracy, selectivity, robustness, detection and quantification limits. Regression analysis showed a good correlation between fluorescence intensity and concentration over the ranges 0.1-1.4, 0.025-0.25 and 0.0025-0.05 µg/mL for AML, CAN and TEL, respectively. Limits of detection were 0.034, 0.0063 and 0.0007 µg/mL for AML, CAN and TEL, respectively. The proposed method was successfully applied for the analysis of several synthetic binary mixtures of different ratios and laboratory-prepared tablets with good recoveries, and no interference from common pharmaceutical additives was observed.

Spectrophotometric Determination of Aminoglutethimide by Diazotization and Subsequent Coupling

Abstract Three simple and sensitive spectrophotometric methods for the determination of aminoglutethimide are described. The first method is based on the diazotization of the drug and the reaction product is quantified spectrophotometrically at 273 nm. The second and third methods involve coupling of the diazotized salt of the drug with either ethyl acetoacetate (EAA) in alkaline medium or N-(1-naphthyl)ethylenediamine hydrochloride (NED) in acid medium, to give colored reaction products measurable at 368 nm and 558 nm, respectively. The optimization of different experimental conditions is described. The proposed methods were applied successfully to the determination of amino-glutethimide in tablets with good accuracy and precision. The reliability of the developed methods were established by comparing the obtained results with those given by the official United States Pharmacopeial XXII methods.