Spectrophotometric Determination of Carbimazole and Its Major Impurity, Degradation Product and Metabolite: Methimazole -=SUP=-*-=/SUP=-

The present research work was carried out in order to develop simple, accurate and precise UV sprctrophotometric methods having comparable sensitivity as that of sophisticated chromatographic techniques. Two methods were developed namely first derivative spectrophotometry and ratio spectra derivative spectrophotometry for accurate determination of specified impurity methimazole (imp A) in presence of drug carbimazole. First derivative spectrophotometric method involves recording of zero order spectra of both the drugs carbimazole and methimazole and its mixture in the range of 200-400 nm and subsequent conversion of these spectra into first derivative spectra. The drugs carbimazole and methimazole were determined by using zero crossing wavelengths of 227 and 260 nm respectively. In the second approach, ratio spectra were recorded for carbimazole and methimazole by selecting appropriate divisor concentration and converted into first derivative spectra. The determination of carbimazole and methimazole were carried out at wavelength 226.2 and 257 nm, respectively. Both the methods were validated as per ICH guideline. The drugs carbimazole and methimazole showed linear response with good correlation coefficient and exhibited specificity, accuracy and precision within acceptable range. The second method of ratio spectra derivative spectrophotometry was found more sensitive as compare to first derivative spectrophotometry in detecting level of impurity methimazole up to 0.5% as per official specification. Hence, these developed methods can be used as alternative to sophisticated chromatographic technique for determination of assay and related impurity in bulk drug and formulation. Keywords: carbimazole, methimazole, first derivative spectrophotometry, ratio spectra derivative spectrophotometry.

SIMULTANEOUS ESTIMATION OF ASPIRIN AND OMEPRAZOLE IN LABORATORY SAMPLE BY DIFFERENT UV SPECTROPHOTOMETRIC TECHNIQUES

The aim of the present work was to develop simple, precise and economic UV- spectrophotometric methods for the simultaneous estimation of aspirin and omeprazole in a laboratory sample. The absorbance maxima (λmax) for detection of aspirin and omeprazole were selected as 274 nm and 302 nm, respectively, for simultaneous equation method while wavelength range for detection of aspirin and omeprazole were selected as 270 nm - 276 nm and 300 nm - 305 nm, respectively for area under curve method. Absorbance ratio method uses the ratio of absorbances at two selected wavelengths, one which is an isoabsorptive point and other being the λ max of one of the two components. From the overlay spectra of two drugs, it is evident that aspirin and omeprazole show an isoabsorptive point at 238.6 nm. In zero crossing first derivative spectrophotometry, aspirin showed zero crossing point at 301nm and omeprazole showed zero crossing point at 274nm. Linearity for aspirin was between 25- 125 μg/mL and omeprazole it was 3-15 μg/mL. These methods were successfully applied for estimation of aspirin and omeprazole in the laboratory sample.

Determination of Rhodamine B and Rhodamine 6G dyes in Various Ink Samples by Zero Crossing Method: First Derivative Spectrophotometry

A simple spectrophotometric method has been developed for resolving binary mixtures of Rhodamine B and Rhodamine 6G dyes of red ballpoint pen ink using the first-derivative spectra with measurements at zero-crossing wavelengths. Calibration graphs were linear up to 8 mg L-1 for Rhodamine B and 10 mg L-1 for Rhodamine 6G. This method was successfully applied for the quantitative determination of dyes having overlapping spectra in their bi-component mixtures. The applied derivative method is practical, simple, rapid, inexpensive and suitable for quantitative analysis of bi-component dye solutions in the ballpoint pen ink.

Derivative Spectrophotometric Determination For Simultaneous Estimation Of Isoniazid And Ciprofloxacin In Mixture And Pharmaceutical Formulation

A simple analytical method was used in the present work for the simultaneous quantification of Ciprofloxacin and Isoniazid in pharmaceutical preparations. UV-Visible spectrophotometry has been applied to quantify these compounds in pure and mixture solutions using the first-order derivative method. The method depends on the first derivative spectrophotometry using zero-cross, peak to baseline, peak to peak and peak area measurements. Good linearity was shown in the concentration range of 2 to 24 μg∙mL-1 for Ciprofloxacin and 2 to 22 μg∙mL-1 for Isoniazid in the mixture, and the correlation coefficients were 0.9990 and 0.9989 respectively using peak area mode. The limits of detection (LOD) and limits of quantification (LOQ) were measured with first derivative method. The LOD and LOQ were found as 0.45 μg∙mL-1 and 1.50 μg∙mL-1 for Ciprofloxacin and 0.68 μg∙mL-1 and 2.28 μg∙mL-1 for Isoniazid, respectively. Accuracy and precision were determined by measuring the relative standard deviation and recoveries. The results also showed that the proposed method was successfully applied for direct analysis of ciprofloxacin and isoniazid in the tablet samples.

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.

Zero crossing and ratio spectra derivative spectrophotometry for the dissolution tests of amlodipine and perindopril in their fixed dose formulations

Dissolution tests of amlodipine and perindopril from their fixed dose formulations were performed in 900 mL of phosphate buffer of pH 5.5 at 37°C using the paddle apparatus. Then, two simple and rapid derivative spectrophotometric methods were used for the quantitative measurements of amlodipine and perindopril. The first method was zero crossing first derivative spectrophotometry in which measuring of amplitudes at 253 nm for amlodipine and 229 nm for perindopril were used. The second method was ratio derivative spectrophotometry in which spectra of amlodipine over the linearity range were divided by one selected standard spectrum of perindopril and then amplitudes at 242 nm were measured. Similarly, spectra of perindopril were divided by one selected standard spectrum of amlodipine and then amplitudes at 298 nm were measured. Both of the methods were validated to meet official requirements and were demonstrated to be selective, precise and accurate. Since there is no official monograph for these drugs in binary formulations, the dissolution tests and quantification procedure presented here can be used as a quality control test for amlodipine and perindopril in respective dosage forms.