Neocuproine and bathocuproine as new reagents for the spectrophotometric determination of certain proton pump inhibitors

Simple, sensitive and selective spectrophotometric methods were developed for the determination of five antiulcer drugs namely, omeprazole (OMZ), lansoprazole (LNZ), pantoprazole (PNZ), rabeprazole (RBZ) and esomeprazole (EMZ) using neocuproine or bathocuproine as reagents. The reaction is based on the reduction of copper(II) to copper(I) by OMZ, LNZ, PNZ, RBZ and EMZ which subsequently reacts with neocuproine or bathocuproine in neutral medium to produce yellow or orange-red coloured complex with maximum absorbance at 460 or 480 nm, respectively. Beer\'s law was obeyed in the concentration range 0.2-4.0 μg mL-1 with a relative standard deviation ranging between 0.5-1.0 and 0.5-1.1 for the drugs with neocuproine and bathocuproine, respectively. The limits of detection were found to be 0.007-0.024 and 0.01-0.026 μg mL-1 and the limits of quantification ranged between 0.019-0.067 and 0.026-0.062 µg mL-1 with neocuproine and bathocuproine, respectively. The optimum assay conditions were investigated and the accuracy was found to be 99.3-100.5 % and 99.1-100.7 %, while the correlation coefficients ranged between 0.9830-1.0213 and 0.9896-0.9981 with neocuproine and bathocuproine, respectively. The colour developed was stable for 24 h at room temperature (~ 27 oC). The commonly encountered excipients and additives did not interfere in the determination. Results obtained by this method for the pure drugs and commercial tablets agreed well with those obtained by reported method