An NMR buffer solution was prepared at 400 mM of dibasic potassium phosphate ([K.sub.2]HP[O.sub.4]) in deuterium oxide ([D.sub.2]O) at pH = 7 using deuterium chloride (DCl) solution.
UV-Vis spectra were obtained at 0.75 [micro]M eosin Y and mixtures of 0.75 [micro]M eosin Y and caffeine at various concentrations (from 0.42 mM to 11.25 mM) in 400 mM dibasic potassium phosphate solution are shown in Figure 11.
The buffer was prepared 0.025 M dibasic potassium phosphate and 0.005 M hexane sulphonic acid sodium salt in 1000 ml water, adjust the pH with phosphoric acid to 3.0 [+ or -] 0.1 .The flow rate of mobile phase was 1.0 ml/min.
The pH 3.0 of the buffer and C18 bonded stationary phase has played key role in achieving the peak shape of metformin HCl and degradation product using a mobile phase containing a 0.025 M dibasic potassium phosphate and 0.005 M hexane sulphonic acid sodium salt with ratio of acetonitrile 93:7 as a mobile phase stressed samples of bulk were injected onto the above chromatographic system.
The chemical structure is given in fig.1 HPLC grade acetonitrile (Ranbaxy fine chemicals, India) dibasic potassium phosphate, hexane sulphonic acid sodium salt and orthophosphoric acid was purchased from Merck (Darmstadt.