Development of Colorimetric Method for the Assay of N-acetylcysteine in Dosage Forms using 2, 6-Dichloroquinone-4-Chlorimide

ABSTRACT A simple colorimetric method was developed for the determination of N-acetylcysteine (NAC) in pharmaceutical preparations. The method is based on the coupling N-acetylcysteine with 2,6-dichloroquinone-4-chlorimide (DCQ) in dimethylsulphoxide to give a yellow colored product absorbing at 438 nm. The absorbance-concentration plot was rectilinear over the range of 10-50 μg/mL with minimum detection limit (LOD) of 0.769 μg/mL .The recovery results (100.90 ± 0.00%, n=3) reflected no interference by the formulation excipients. The different experimental parameters affecting the development and stability of the color were carefully studied and optimized. The developed method was successfully applied to the analysis of NAC in injection and capsule dosage forms. The results obtained were statistically compared with those of the official titrimetric methods. A pathway for the reaction of NAC with DCQ was suggested

Simultaneous Determination and Stability Studies on Diminazene Diaceturate and Phenazone Using Developed Derivative Spectrophotometric Method

This work presents UV first derivative spectrophotometry as a precise, accurate, and feasible method for simultaneous determination of diminazene diaceturate and phenazone in bulk and dosage forms. The absorbance values of diminazene diaceturate and phenazone aqueous mixture were obtained at 398 nm and 273 nm, respectively. The developed method was proved to be linear over the concentration ranges (2–10) μg/mL and (2.496–12.48) μg/mL for diminazene diaceturate and phenazone, respectively, with good correlation coefficients (not less than 0.997). The detection and quantitation limits were found to be (LOD = 0.63 and 0.48 μg/mL; LOQ = 1.92 and 1.47 μg/mL, resp.). The developed method was employed for stability studies of both drugs under different stress conditions. Diminazene diaceturate was prone to degrade at acidic pH via first-order kinetics. The degradation process was found to be temperature dependent with an activation energy of 7.48 kcal/mole. Photo-stability was also investigated for this drug

Spectrophotometric Determination of Tranexamic Acid in Bulk and Dosage Forms Using Ascorbic Acid

A simple spectrophotometric method for the determination of tranexamic acid (TA) in pure form and pharmaceutical preparations was developed.  The method is based on coupling tranexamic acid with ascorbic acid (AA) in dimethyl sulfoxide (DMSO) to produce a colored product which absorbs maximally at two wavelengths (λmax) 390nm & 530nm. The molar ratio of tranexamic acid: ascorbic acid is 1:2. Beer’s law is obeyed in the concentration range 10-25µg/ml of tranexamic acid with molar absorbtivity of 2.4×103 L mol-1cm-1(λmax390nm) and 0.73×103 L mol-1cm-1 (λmax530nm). Different experimental parameters affecting the development and stability of the color were   studied and optimized. The proposed method was validated against an adopted B.P formal titration method.  The mean percentage recovery obtained for the assay of commercial capsules was found to be 99.77±1.02 (λmax390nm) and 101.01±0.97 (λmax530nm)

Derivative Spectrophotometric Methods for the Analysis and Stability Studies of Colistin Sulphate

Simple spectrophotometric methods were developed for the quantitative determination of colistin sulphate in bulk and dosage forms. The methods were based on the measurement of first and second derivative spectra of colistin sulphate at 298 nm and 318 nm, respectively. Beer's law was obeyed in the concentration range 800-4000 IU/mL with good correlation coefficient (not less than 0.998) for both methods. The developed first derivative spectrophotometric method was then selected to study the degradation behavior of colistin sulphate in alkaline media at different temperatures as the second derivative method failed to give reproducible results for the stability study. The pH-rate profile indicates a first-order dependence of the degradation rate on [OH − ] at pH ranging between 8 and 11. The obtained results for the photochemical study reflected photostability of colistin sulphate

Determination of Antioxidant Flavonoids in Sudanese Honey Samples by Solid Phase Extraction and High Performance Liquid Chromatography

Flavonoids were extracted by solid phase extraction (SPE) from seven floral honey samples of different botanical origin from different regions of Sudan. The flavonoids were determined by high performance liquid chromatography (HPLC) technique using photo diode array detector (PDA). An isocratic and gradient systems for the resolution, identification and quantification of five flavonoids, namely; quercetin, kaempferol, apigenin, hesperetin and isorhamnetin, were developed. Although the isocratic system resolved the five compounds, however it suffered from interference by the complex mixture of honey samples. The gradient system resolved three of five flavonoids, namely, quercetin, kaempferol, and isorhamnetin, without interference by the complex honey matrix. Two flavonoids, apigenin and hesperetin, were observed to elute at close retention times, which lead to their interference with each other when injected in a mixture; however, absorption wavelength selection was found indicative of the presence or absence of either compound. The quantification of these flavonoids was done through the calibration curves of their standards. The obtained results were compared with reported results

Kinetic Determination of Tobramycin In Drug Formulations

ABSTRACT A kinetic method for the accurate determination of tobramycin has been developed. A solution of tobramycin is heated with 6x10 -2 which the reaction is quenched by cooling and the absorbance of the colored product is measured at 390nm and 532nm. The following equations were used for calculating unknown concentrations of tobramycin at 390nm and at 532nm respectively: A= 0.027 + 0.019 C A= 0.009 + 0.006 C The method was applied for the determination of tobramycin in drug formulation and a statistical comparison with the BP biological assay method was made. The determination of tobramycin by the fixedconcentration method is feasible with the calibration equations obtained but the fixed time method has been found to be more applicable

Simultaneous Determination and Stability Studies on Diminazene Diaceturate and Phenazone Using Developed Derivative Spectrophotometric Method

This work presents UV first derivative spectrophotometry as a precise, accurate, and feasible method for simultaneous determination of diminazene diaceturate and phenazone in bulk and dosage forms. The absorbance values of diminazene diaceturate and phenazone aqueous mixture were obtained at 398 nm and 273 nm, respectively. The developed method was proved to be linear over the concentration ranges (2-10) g/mL and (2.496-12.48) g/mL for diminazene diaceturate and phenazone, respectively, with good correlation coefficients (not less than 0.997). The detection and quantitation limits were found to be (LOD = 0.63 and 0.48 g/mL; LOQ = 1.92 and 1.47 g/mL, resp.). The developed method was employed for stability studies of both drugs under different stress conditions. Diminazene diaceturate was prone to degrade at acidic pH via first-order kinetics. The degradation process was found to be temperature dependent with an activation energy of 7.48 kcal/mole. Photo-stability was also investigated for this drug

Synthesis and investigation of novel shelf-stable, brain-specific chemical delivery system

1Department of Pharmaceutical Chemistry. 2Department of Pharmacology, College of Pharmacy, King Saud University, P.O. Box 2457, Riyadh-11451, Saudi Arabia. *To whom correspondence should be addressed. E-mail: [email protected] 1,4-dihydropyridine pyridinium salt type redox system is described as a general and flexible method for site-specific and sustained delivery of drugs into the brain. Monoamine oxidase inhibitors (MAOIs) were used as a model example to be delivered into the brain. Chemical and biological oxidations of these compounds were investigated. The prepared 1,4-dihydropyridines were subjected to various chemical and biological oxidation to evaluate their ability to cross blood brain barrier (BBB), and to be oxidized biologically into their corresponding quaternary compounds. 1-(Ethoxy-carbonylmethyl)-3,5-bis[N-(2-fluorobenzylideneamino) carbamoyl]-1,4-dihydropyridine (31) proved to cross BBB in adequate rate and converted by the oxidizing enzymes into the corresponding quaternary salt N-(ethoxycarbonylmethyl)-3,5-bis[N-(2-fluorobenzylideneamino)carbamoyl]pyridinium bromide (20). Stability studies of the synthesized chemical delivery systems (CDSs) at various pH values and temperatures showed that the shelf life time of a solution containing compound 31 is 20.53 days at 5°C, which recommend a lower storage temperature for such solutions. The prepared CDSs proved to be fairly stable for powder form storage. The stability of the prepared compounds is attributed to the conjugation of the two carboxylic functions at C3 and C5 of the pyridine ring with their adjacent double bonds. These results are in consistency with the original rationale desig