Abstract: In pH=1.89 Briton-Robinson(BR) buffer, HAuCl4 can be reduced by amoxicillin to form gold nanoparticles, resulting in characteristic plasmon resonance absorption signals at 537 nm and 720 nm. The intensity at 537 nm is proportional to the amoxicillin concentration in a certain range, and amoxicillin can be detected based on the plasmon resonance absorption intensities of the gold nanoparticles. Under the optimized conditions(pH=1.89, reaction temperature is 65 ℃, reaction time is 40 min), amoxicillin can be detected in the range of 2.0×10-6~3.6×10-5 mol/L with the detection limit of 1.3×10-7 mol/L. This method has been used in the synthesized samples determination of amoxicillin with the recovery of 90.4%~103.2% and a relative standard deviation of less than 4.6%, then it is applied to the determination of amoxicillin in two commercial capsules with satisfied results compared with HPLC method.

Key words: amoxicillin, gold nanoparticles, plasmon resonance