Chemical Science International Journal

This paper describes a batch(direct spectrophotometer) and flow injection spectrophotometric for indirect determination of amoxicillin (AMX). The method involves addition of a known excess of N-bromosuccinimde (NBS) to AMX in acidic medium, the residual amount of oxidant (NBS) reacted with indigo carmine which causes bleaching of its blue color. The absorbance was measured at 610 nm. In the batch method Beer’s law was obeyed in the concentration range (0.2 - 6.0 μg ml^-1) and detection limit of 0.1 μg ml^-1with a correlation coefficient (r) of 0.9945 and a molar absorptivity of 3.874x10⁴L mol^-1cm^-1. A simple FI-spectrophotometric system was applied for determination of AMX depending on the batch method. A calibration graph gives linear range of (2.0 - 14.0 μg ml^-1) AMX, with a detection limit of 1.8 μg ml^-1, a correlation coefficient (r) of 0.9965 and a sampling frequency of 48 S h^-1. Essential parameters such as accuracy and precision were studied for the two methods by calculation of (RSD %) and (E%) for two different levels of concentration. The method was relatively free from common excipients and it is applied successfully for the determination of AMX in pharmaceutical formulations.