Simple and convenient chemiluminescence method for the determination of melatonin

A simple and convenient chemiluminescence (CL) method for the determination of melatonin is reported. It is based on the observation that melatonin can greatly enhance the ultra-weak CL between H₂O₂ and acetonitrile in alkaline solution. Light emission is intense and long-lived, and even with a simple setup, a high sensitivity could be achieved. The log-log linear range was 250 nM-250 μM with a 3σ detection limit of 100 nM. Singlet oxygen is suggested to be produced by the reaction between H₂O₂ and acetonitrile and is responsible for the CL of melatonin. As a preliminary application, this simple method has been successfully applied into the determination of melatonin in health-foods.