Development of membrane electrodes for the selective determination of hyoscine butylbromide.

Four polyvinyl chloride (PVC) membrane sensors for the determination of hyoscine butylbromide are described and characterized. The sensors are based on the use of the ion association complexes of hyoscine cation with ammonium reineckate counter anions as ion exchange sites in the PVC matrix. The membranes incorporate ion association complexes of hyoscine with dibutylsebathete (sensor 1), dioctylphthalate (sensor 2), nitrophenyl octyl ether (sensor 3) and beta-cyclodextrin (sensor 4). The performance characteristics of these sensors were evaluated according to IUPAC recommendations, which reveal a fast, stable and linear response for hyoscine over the concentration range of 10(-5)-10(-2)M for sensors 1 and 2 and 10(-6)-10(-2) for sensors 3 and 4 with cationic slopes of -53.19, -55.17, -51.44 and -51.51mV per concentration decade for the four sensors, respectively. The direct potentiometric determination of hyoscine butylbromide using the proposed sensors gave average recoveries % of 99.92+/-1.11, 99.93+/-1.00, 99.94+/-1.18 and 99.87+/-1.39 for the four sensors, respectively. The sensors are used for determination of hyoscine butylbromide in laboratory prepared mixtures, pharmaceutical formulations in combination with ketoprofen and in plasma. Validation of the method shows suitability of the proposed sensors for use in the quality control assessment of hyoscine butylbromide. The developed method was found to be simple, accurate and precise when compared with a reported HPLC method.

Application of new membrane selective electrodes for the determination of drotaverine hydrochloride in tablets and plasma.

The construction and electrochemical response characteristics of poly vinyl chloride (PVC) membrane sensors for the determination of drotaverine hydrochloride were described. The sensors are based on the use of the ion association complexes of drotaverine cation with sodium phosphotungestate (Dro-PTA) or ammonium reineckate (Dro-R) counter anions as ion exchange sites in the PVC matrix. The performance characteristics of these sensors, which were evaluated according to IUPAC recommendations, reveal a fast, stable and linear response for drotaverine over the concentration range 10(-5) to 10(-2) M with cationic slopes of 49.55 and 51.36 mV per concentration decade. The direct potentiometric determination of drotaverine hydrochloride using the proposed sensors gave average recoveries of 99.95+/-0.71 and 100.04+/-0.60 for Dro-PTA and Dro-R, respectively. The sensors are used for determination of drotaverine hydrochloride in tablets, in its mixture with caffeine and paracetamol and in plasma. Validation of the method shows suitability of the proposed sensors for use in the quality control assessment of drotaverine hydrochloride. The developed method was found to be simple, accurate and precise when compared with a reported HPLC method.

Stability-indicating spectrophotometric and densitometric methods for determination of aceclofenac.

Three methods were developed for the determination of aceclofenac in the presence of its degradation product, diclofenac. In the first method, third-derivative spectrophotometry (D3) is used. The D3 absorbance is measured at 283 nm where its hydrolytic degradation product diclofenac does not interfere. The suggested method shows a linear relationship in the range of 4-24 micrograms mL-1 with mean percentage accuracy of 100.05 +/- 0.88. This method determines the intact drug in the presence of up to 70% degradation product with mean percentage recovery of 100.42 +/- 0.94. The second method depends on ratio-spectra first-derivative (RSD1) spectrophotometry at 252 nm for aceclofenac and at 248 nm for determination of degradation product over concentration ranges of 4-32 micrograms mL-1 for both aceclofenac and diclofenac with mean percentage accuracy of 99.81 +/- 0.84 and 100.19 +/- 0.72 for pure drugs and 100.17 +/- 0.94 and 99.73 +/- 0.74 for laboratory-prepared mixtures, respectively. The third method depends on the quantitative evaluation of thin-layer chromatography of aceclofenac using chloroform:methanol: ammonia (48:11.5:0.5 v/v/v) as a mobile phase. Chromatograms were scanned at 274 and 283 nm for aceclofenac and diclofenac, respectively. The method determined aceclofenac and diclofenac in concentration ranges of 2-10 and 1-9 micrograms spot-1 with mean percentage accuracy of 100.20 +/- 1.03 and 100.14 +/- 0.98 for pure drugs and 99.77 +/- 0.74 and 100.07 +/- 0.78 for laboratory-prepared mixtures, respectively. This method retains its accuracy in the presence of up to 80% degradation product for the studied drug. The suggested procedures were checked using laboratory-prepared mixtures and were successfully applied for the analysis of their pharmaceutical preparation. The validity of the proposed methods was further assessed by applying a standard addition technique. The obtained results agreed statistically with those obtained by the reported method.

Stability indicating methods for assay of mequitazine in presence of its degradate.

Six procedures have been suggested for the determination of the antihistaminic agent, mequitazine, in the presence of its degradate. Mequitazine, having a phenothiazine group, undergoes peroxide oxidation and the corresponding sulphone is produced. Its identity was confirmed by IR and MS. The first procedure is based on determination of mequitazine by HPLC with UV detection at 256 nm. The mobile phase used is acetonitrile, ortho phosphoric acid (50:50) using caffeine as an internal standard. Linearity range is 1.00-9.00 microg/ml. The second determination is a densitometric procedure based on the determination of mequitazine in the presence of its degradate at 256 nm using the mobile phase, chloroform:methanol:ammonia (50:18:3). Linearity range is 1.25-7.50 microg per spot. The third procedure is spectrophotometric, where a mixture of mequitazine and its degradate are resolved by first derivative ratio spectra. Linear calibration graphs of first derivative values at wavelengths 210.2, 247 and 259.8 nm are obtained. On carrying out measurements at the three mentioned wavelengths, the linearity range is found to be 1.00-10.00 microg/ml. The fourth procedure is based on first derivative spectrophotometry, where D(1) measurements are carried out at 290 nm. Linearity range is 1.00-10.00 microg/ml. The fifth procedure is based on the reaction of mequitazine with 3-methyl-2-benzothiazolinone hydrazone (MBTH) in the presence of ferric chloride. A stable violet colored oxidative coupling product is formed, which is measured spectrophotometrically at 685 nm. The optimum experimental parameters for the reaction have been studied and assigned. Linearity range is 1.00-16.00 microg/ml. The sixth procedure is based on the reaction of mequitazine in the presence of its degradate with 2,6-dichloroquinone-4-chloroimide (Gibbs reagent) in aqueous methanolic medium. The reddish-brown colored condensation product is measured at 405 nm. The optimum experimental conditions for the reaction have been studied. Linearity range is 50.00-600.00 microg/ml. The validity of the described procedures was assessed by applying the standard addition technique. Statistical analysis of the results has been carried out revealing high accuracy and good precision. The suggested procedures could be used for the determination of mequitazine, both in pure and dosage forms, as well as in the presence of its degradate.

Stability indicating method for determination of nortriptyline hydrochloride using 3-methyl-2-benzothiazolinone hydrazone (MBTH).

A spectrophotometric procedure is described for determination of nortriptyline hydrochloride in pure and dosage form as well as in the presence of its degradate. 3-Methyl-2-benzothiazolinone hydrazone (MBTH) has been used as the chromogenic reagent, where aqueous solutions of the drug and reagent are treated with cerium(IV) ammonium sulphate in an acidic medium. Nortriptyline hydrochloride reacts to give a blue coloured product having two absorption maxima at 619 and 655 nm. Various parameters affecting the reaction have been studied. Beer's law is obeyed in the concentration range of 24-216 microg ml(-1) of nortriptyline hydrochloride, with mean percentage recoveries of 100.22+/-0.870 and 100.66+/-0.642% for both maxima, 619 and 655 nm, respectively. Results were statistically analyzed and compared with those obtained by applying the British Pharmacopoeia (1993) method.

Stability-indicating methods for the spectrophotometric determination of norfloxacin.

Two spectrophotometric procedures for the selective determination of norfloxacin (NF) in the presence of its decarboxylated degradant are described. The first depends upon measurement of the pH-induced absorbance difference (delta A) of the drug solution between 0.1 N HCl and 0.1 N NaOH at 280 nm. The second involves chelation of the intact drug with iron (II) in acetate buffer solution (pH 5.7 +/- 0.1) to form a yellow-coloured chelate which absorbs at 358 nm. The two procedures are applied successfully for the determination of the intact drug both in pure form and in tablet form. The two methods retain their accuracy in the presence of up to 62% and 76% degradants, respectively.

Determination of quaternary ammonium surfactants in pharmaceutical formulations by the hypochromic effect.

A spectrophotometric procedure for determination of the quaternary ammonium salts cetrimide (N,N,N-trimethyl-l-hexadecylammonium bromide), cetylpyridinium chloride (l-hexadecyl-pyridinium chloride) and sapamine [N-(2-dimethylaminoethyl)oleamide acetate] in bulk form and some pharmaceutical formulations, such as eye-drops, disinfectant solutions, creams and tablets, is described. Following TLC separation when necessary, addition of an aqueous solution of the active surfactant to a standard amount of Bromothymol Blue, buffered at pH 7.5, leads to an equivalent decrease of the absorbance at 610 nm, which can be taken as an analytical measure of the drug concentration. Good mean recoveries have been obtained for standard additions of these analytes to pharmaceutical formulations containing them.