A novel simple and selective electrochemical procedure is utilized for the determination of Dinoprostone (DIN) in drug substance and pharmaceutical preparation with good recovery and without interference with other excipient. Herein, the electrochemical sensing platform based upon preparing gold nanoparticle sensor on silica modified carbon paste electrode. The surface morphology of the modified electrode was characterized by scanning electron microscope. Different experimental conditions, including electrode composition, effect of pH and scan rate were estimated carefully by cyclic voltammetry to obtain the highest electrochemical response. By using square wave voltammetry a good linear response was obtained in the range of, 2 x 10-5-4 x10-4 mol L-1, and 2 x 10-7-1.6 x 10-4 mol L-1, with low detection limit of 5 x 10-6 mol L-1, and 4.9 x 10-8 mol L-1 by CPE and GNP/SMCPE respectively. The obtained results are in good agreement with those obtained by official method. No electrochemical method was reported before for determination of DIN. The developed method was simple, rapid, economic and challenging to green analytical chemistry.

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Simple, sensitive and accurate stability-indicating densitometric RP-TLC and RP HPLC-UV methods were developed and validated for analysis of Bimatoprost (BMT). Stress stability studies were performed using hydrolytic (acid & alkai) and oxidative degradation products and conformed using LC-MS. Structure elucidation and pathway of degradation were presented. Both methods were based on reversed phase thin-layer and liquid chromatographic separation of BMT from hydrolytic and oxidative degradation products. Acetonitrile, water and 33% ammonia (4:5:1, by volume) and acetonitrile –water (40:60, v/v) at 30◦C were used as mobile phases for separation of BMT from degradation products using RP TLC and HPLC methods respectively. Quantification was achieved at 220 nm for both methods. The linear ranges were 0.5-6.0 μg/band and 5 – 100 μg /mL with mean recoveries ± RSD%, of 98.72 ± 0. 31% and 99.25 ± 0.59% for the two methods respectively. The specificity of HPLC method was further assured by peak purity. The proposed methods are rapid with retention time less than 6 min. The methods met ICH regulatory requirements. The two methods were successfully applied for the quantification of BMT in drug substance and ophthalmic solution with acceptable accuracy and precisions; the label claim percentages were 93.145 ± 0.89 and 95.35 + 0.65 for densitometric RP-TLC and RP HPLC-UV methods respectively. The research work has a great value for quality control and stability studies of BMT.

Fluorescence study on inclusion interaction of bimatoprost in absence and presence of β-cyclodextrin shows significant increase in native fluorescence of bimatoprost in the presence of β-cyclodextrin. Fluorescence spectroscopy of host-guest interaction between bimatoprost and β-cyclodextrin shows formation of inclusion complex with 1:1 stoichiometric ratio. The changes of native fluorescence of bimatoprost on inclusion in the hydrophobic β-cyclodextrin cavity is used to calculate the association constant.The fluorimetric method was used for determination of bimatoprost in absence and presence of 1% (w/v) β-cyclodextrin. The studied drug shows native fluorescence at λem 285 after excitation at λex 217 nm in water. The quantum yield [QY] was calculated in absence and presence of β-CD and it was found to be increased from 0.26 to 0.31. The different experimental parameters affecting the fluorescence of the drug was carefully studied and optimized. Linearity was over the range of 25 – 250 ng/mL and 5 – 50 ng/mL in absence and presence of β-CD, respectively with detection limits of 0.05 and 0.006 ng/mL, and quantitation limits of 0.18, and 0.02 ng/mL in absence and presence of β-CD, respectively. The proposed methods were validated as per ICH guidelines, and were effectively applied to analysis of studied drug in its ophthalmic formulation. The results obtained were statistically compared with the reported method revealing high accuracy and good precision. The proposed methods are challenging to green. Qualitative and quantitative metrics revealed excellent eco-friendly fluorimetric method for application in QC laboratories.