Simple and rapid uv-spectrophotometric methods were investigated for pharmaceutical estimation of riociguat (RCG). RCG is a novel soluble guanylate cyclase (sGC) stimulator. We report here; zero order absorbance (Method I) and first order derivative UV-spectroscopy (Method II) for RCG. The analysis involved the use of methanol as solvent for determination of RCG using for both methods. The drug was found to be stable in aforementioned solvent for more than 72 hrs. Method I was executed by measuring absorbance at wavelength maximum of 321.45 nm while for Method II; post derivatization of zero order spectrum; the uniform area in between 329.00 - 346.60 nm was measured. The absorbance and the area were plotted against concentration respectively. The estimations obeyed the linearity range in between 5 - 25 microgram/ml. The mean correlation coefficient was found to be 0.999 after five replicate determinations of linearity of both developed methods. The non-interference of tablet excipients from the formulation (Rioteph) ensured the specificity for proposed methods. The accuracy of the methods was effectively reflected with a mean recovery of 99.70 (Method I) and 99.64 (Method II). The results for method precision were found to be within the specified limits; which is expressed as percentage RSD. The developed methods as based on measurement of both absorbance as well as the area after spectral derivatization found to be efficient. Both the developed methods were validated according to ICH guideline and proved statistically accurate, precise and sensitive; hence the studies can be extended effectively towards routine determination of RCG.
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