Determination of amoxycillin in pharmaceutical forms by visible spectrophotometry and HPLC

Two rapid assay procedures based on visible spectrophotometry and high performance liquid chromatography (HPLC) have been developed for amoxycillin (AMX) in bulk drug and in dosage forms. Spectrophotometric method is based on the formation of a charge-transfer (CT) complex between chloranilic acid (CAA) as a pi-acceptor and amoxycillin (AMX) as an n-donor in acetonitrile solvent, the absorbance of the complex being measured at 520 nm. Beer's law is obeyed for 10-200 mu g mL(-1) with an apparent molar absorptivity of 1.3 x 10(3) L mol(-1) cm(-1) and a Sandell sensitivity of 0.2741 mu g cm(-2). The HPLC determination was performed on a reversed phase column (Hypersil C(18) 5 mu m; 250x4.6 mm i.d) using a mobile phase (1 mL min(-1)) consisting of acetonitrile-0.1% ortho phosphoric acid (pH 3.0)-60:40 (v/v) with UV-detection at 230 nm. A rectilinear relationship between mean peak area and concentration of AMX was observed in the range 7.2-396 mu g mL(-1) with a detection limit of 1.5 mu g mL(-1) and a quantitation limit of 4.5 mu g mL(-1). Intra-day and inter-day precision, and accuracy of the methods have been established according to the current ICH guidelines. The methods have been successfully applied to the assay of AMX in preparations and the results were statistically compared with those of the reference method by applying Student's t-test and F-test