Photometric determination of tetracycline based on surface plasmon resonance of silver nanoparticles

We report on a simple and sensitive method for the determination of tetracycline based on its reducing action on AgNO₃ in alkaline medium containing ammonia and sodium hydroxide at 65°C. As a result of this reaction, silver nanoparticles (AgNPs) are formed. The AgNPs are stabilized in solution by adding poly(vinyl pyrrolidone) as a capping agent. The formed AgNPs were identified by surface plasmon resonance absorption spectrum and transmission electron microscopy image. The plasmon absorption peak at 411 nm is proportional to the concentration of tetracycline. The calibration graph is linear in the concentration range of 0.05–5.0 mg/L with a detection limit of 0.013 mg/L. This method was applied to the determination of tetracycline in pharmaceutical products.