Two simple, accurate, precise and economic spectrophotometric methods have been developed for simultaneous determination of Atorvastatin calcium (ATR) and Ezetimibe (EZ) in their bulk powder and pharmaceutical dosage form. Method (I) is based on dual wavelength analysis while method (II) is the mean centering of ratio spectra spectrophotometric (MCR) method. In method (I), two wavelengths were selected for each drug in such a way that the difference in absorbance was zero for the second drug. At wavelengths 226.6 and 244 nm EZ had equal absorbance values; therefore, these two wavelengths have been used to determine ATR; on a similar basis 228.6 and 262.8 nm were selected to determine EZ in their binary mixtures. In method II, the absorption spectra of both ATR and EZ with different concentrations were recorded over the range 200–350, divided by the spectrum of suitable divisor of both ATR and EZ and then the obtained ratio spectra were mean centered. The concentrations of active components were then determined from the calibration graphs obtained by measuring the amplitudes at 215–260 nm (peak to peak) for both ATR and EZ. Accuracy and precision of the developed methods have been tested; in addition recovery studies have been carried out in order to confirm their accuracy. On the other hand, selectivities of the methods were tested by application for determination of different synthetic mixtures containing different ratios of the studied drugs. The developed methods have been successfully used for determination of ATR and EZ in their combined dosage form and statistical comparison of the developed methods with the reported spectrophotometric one using F and Student's t-tests showed no significant difference regarding both accuracy and precision.

& Accurate, sensitive, and precise stability indicating TLC-Densitometric method was developed and validated for determination of chlorpropamide and its main degradation product and related impurity; 4-Chlorobenzenesulphonamide. The method is based on chromatographic separation on silica gel 60 F 254 TLC plates using chloroform: ethyl acetate: triethylamine: glacial acetic acid (70:30:3:1, by volume) as a developing system followed by densitometric measurements at 230 nm. Chlorpropamide was subjected to acid and alkaline hydrolysis, oxidation, and photodegradation. Method validation was carried out according to ICH guidelines and the proposed method was successfully applied to the analysis of chlorpropamide in pharmaceutical dosage form where no interference from additives has been found. Results obtained by the proposed method was statistically compared with those obtained by the reported RP-HPLC method and no significant difference.

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Sensitive, selective, precise and economic TLC-Densitometric method has been developed for determination of two binary mixtures containing the antihyperlipidemic Ezetimibe (EZ) in its combination with Atorvastatin calcium (AT) [mixture I] and with Simvastatin (SIM) [mixture II].In the developed TLC-Densitometric method EZ, AT and SIM were quantitatively separated on 60F 254 silica gel plates using ethyl acetate: hexane: glacial acetic acid (5.5:4.5:0.1 by volume) as a developing system with UV detection at 254 nm. Factors affecting the chromatographic separation have been studied, moreover the method has been validated as per ICH guidelines and it has been successfully applied for determination of the studied drugs in their different dosage forms without interference from excepients. Results obtained by the developed TLCDensitometric method were statistically compared with those obtained by the reported spectrophotometric method and no significant difference was found between them.