Comparative study of spectrophotometric and spectrodensitometric techniques for the estimation of riociguat in tablets

The present research paper includes the development, validation, and comparison of three analytical methods including spectrofluorimetric, ultraviolet (UV)-spectrophotometric, and spectrodensitometric methods based on high-performance thin-layer chromatographic (HPTLC) technique for the estimation of riociguat in tablet dosage form. The estimation was performed at wavelength maxima of 322 nm for UV-spectrophotometry, and for spectrofluorimetric method, excitation wavelength was 300 nm and emission wavelength was 465 nm. Quantification by HPTLC method was carried out at wavelength maxima of 323 nm using aluminum-backed pre-coated silica gel 60 F254 as the stationary phase and ethyl acetate–methanol–glacial acetic acid (8:2:0.3, v/v) as the mobile phase. The methods were validated according to the International Council for Harmonization (ICH) Q2(R1) guideline, where the limits of detection and quantification were found to be 0.240 and 0.728 μg/mL, 0.193 and 0.586 μg/mL, and 3.35 and 10.15 ng/band for spectrofluorimetric, UV-spectrophotometric, and HPTLC method, respectively. The developed methods were successfully applied for quantification of the content of active ingredient and content uniformity. Statistical comparison was done by ANOVA and paired t test showing no significant difference between the three methods. The proposed methods were successfully applied for content uniformity test of riociguat in its tablet dosage form.