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Background Stability indicating determination of pharmaceuticals is crucial, especially for drugs which have few published official analytical methods. Silodosin (SLD) is an FDA approved α1A-adrenoceptor blocker. Objective Efficient analytical methods were suggested, based on different instrumental techniques for quantification of SLD, besides conducting kinetic investigation of its degradation. Methods The first method is based on Reversed Phase High Performance Liquid Chromatography with Photodiode Array Detector (RP-HPLC-PDAD). Detection is done at wavelength 225 nm. The second method is focused on using High Performance Thin Layer Chromatography (HPTLC) and eluting the drug by solvent mixture followed by scanning at wavelength 270 nm. The third method depends on the First Derivative Synchronous Fluorescence Spectroscopy (1DSFS) for analysis of solutions of SLD and its acid and oxidative induced degradation products at Δλ = 90 nm, then determining the first derivative of the spectra and measuring peak amplitudes at 360 nm. Results Acceptable linearities were found in the concentration range of 0.50–90 μg/mL, 0.10–3.0 μg/band, and 0.05–0.50 µg/mL, for RP-HPLC-PDAD, HPTLC, and spectrofluorimetric methods, respectively. Conclusion Statistical analysis showed no significant difference between the suggested and the reported method. In monitoring the kinetics of SLD degradation, the order of reactions was determined and effects of degrading agent concentration and temperature on reaction rate were studied. Highlights Three analytical methods were developed for the determination of SLD based on RP-HPLC-PDAD, HPTLC, and 1DSFS in bulk and capsule dosage form. In addition, kinetic investigation of SLD degradation was performed using the developed RP-HPLC-PDAD method.

Two accurate, selective, and precise chromatographic methods, namely TLC-densitometric and reversed-phase (RP)-HPLC, were developed and validated for the simultaneous determination of nifuroxazide (NIF) and its four synthesized impurities, which are also reported to be its related substances in the range of 10-100 μg/band and 10-100 μg/mL for NIF in the TLC and RP-HPLC methods, respectively. The developed TLC-densitometric method depended on the separation and quantitation of the studied components on silica gel 60 F254 TLC plates. Ethyl acetate-acetone-methanol-ammonia (85 + 25 + 5 + 0.5, v/v/v/v) was used as the developing system, and the separated bands were UV-scanned at 230 nm. On the other hand, the developed RP-HPLC method depended on chromatographic separation using a C8 column at 25°C and an aqueous solution of 0.1% sodium lauryl sulfate-acetonitrile as the mobile phase delivered according to the gradient elution program. Factors affecting the developed methods were studied and optimized. Also, method validation was carried out according to International Conference on Harmonization guidelines. The proposed methods were successfully applied for the determination of the studied drug in its bulk powder and in its pharmaceutical formulation. The developed methods showed no significant difference when compared with the reported RP-HPLC one. Their advantage is being the first stability-indicating methods for NIF and its genotoxic impurities.

Three new, simple, sensitive, and accurate stability-indicating methods were developed for quantitative determination of bisacodyl in the presence of its degradation products, monoacetyl bisacodyl (I) and desacetyl bisacodyl (II), in enteric coated tablets, suppositories, and raw material. The first is a spectrodensitometric method in which the drug is separated from I and II on silica gel plates using chloroformacetone (9 + 1, v/v) as the mobile phase with ultraviolet detection of the separated bands at 223 nm over a concentration range of 0.2-1.4 g/band for bisacodyl with mean recovery 100.35 ± 1.923%. The second method is fourth derivative D4 spectrophotometry, which allows determination of bisacodyl in the presence of its degradation products in raw material at 223 nm using acetonitrile as the solvent with adherence to Beer's law over the concentration range 2-18 μg/mL with mean recovery 99.77 ± 1.056%. In the third method, the spectrophotometric data of bisacodyl, I, and II using absolute ethanol as solvent were processed by 3 chemometric techniques: classical least-squares, principal component regression, and partial least-squares. A training set consisting of 15 mixtures containing different ratios of bisacodyl, I, and II was used for construction of the 3 models. A validation set consisting of 6 mixtures was used to validate the prediction ability of the suggested models. The 3 chemometric methods were applicable over a concentration range between 2-14 μg/mL for bisacodyl with mean recovery of 99.97 ± 0.865, 100.01 ± 0.749, and 99.97 ± 0.616% for the 3 models, respectively. The proposed methods were checked using laboratory-prepared mixtures and were successfully applied to the analysis of raw material and pharmaceutical formulations containing bisacodyl, except for the second method that applies only for raw material. The validity of the suggested procedures was further assessed by applying the standard addition technique; the recoveries obtained were in accordance with those given by the reference method.

Three new, different, simple, sensitive, and accurate methods were developed for quantitative determination of nifuroxazide (I) and drotaverine hydrochloride (II) in a binary mixture. The first method was spectrophotometry, which allowed determination of I in the presence of II using a zero-order spectrum with an analytically useful maximum at 364.5 nm that obeyed Beer's law over a concentration range of 2-10 μg/mL with mean percentage recovery of 100.08±0.61. Determination of II in presence of I was obtained by second derivative spectrophotometry at 243.6 nm, which obeyed Beer's law over a concentration range of 2-10 μg/mL with mean recovery of 99.82±1.46%. The second method was spectrodensitometry, with which both drugs were separated on a silica gel plate using chloroformacetonemethanolglacial acetic acid (6 + 3 + 0.9 + 0.1) as the mobile phase and ultraviolet (UV) detection at 365 nm over a concentration range of 0.2-1 μg/band for both drugs, with mean recoveries of 99.99 0.15 and 100.00 0.34% for I and II, respectively. The third method was reversed-phase liquid chromatography using acetonitrilewate (40 + 60, v/v; adjusted to pH 2.55 with orthophosphoric acid) as the mobile phase and pentoxifylline as the internal standard at a flow rate of 1 mL/min with UV detection at 285 nm at ambient temperature over a concentration range of 2-10 μg/mL for both drugs, with mean recoveries of 100.24±1.51 and 100.08±0.78% for I and II, respectively. The proposed methods were checked using laboratory-prepared mixtures and were successfully applied for the analysis of pharmaceutical formulations containing the above drugs with no interference from other dosage form additives. The validity of the suggested procedures was further assessed by applying the standard addition technique which was found to be satisfactory, and the percentage recoveries obtained were in accordance with those given by the EVA Pharma reference spectrophotometric method.