Determination of Melamine by Differential Pulse Polarography/Application to Milk and Milk Powder

Melamine made headlines in September 2008 because it was found to be the contaminant responsible for the deaths of several infants and making many more sick. Determination of trace melamine is very important. Therefore, in this work a novel, sensitive and reliable method was developed using differential pulse polarography. The most suitable buffer system was found to be Britton-Robinson (B-R) buffer, pH 11.2. The melamine peak in this medium appeared at about -50 mV, it responded well to standard additions and high reproducibility was obtained. The calibration graph was linear in the concentration range of melamine from 1.0 to 66.4 mu M with a correlation coefficient of 0.999. The limit of detection (LOD) and limit of quantification (LOQ) were obtained as 0.3 and 1.0 mu M, respectively. The current was characterized as being adsorption-controlled process. The proposed method was successfully applied to the determination of melamine in spiked milk and milk powder. The linear dynamic ranges observed for melamine concentration in milk and milk powder samples were between 1-58 and 10-57 mu M, respectively. The sufficiently good recoveries and low standard deviations for the data reflect the high accuracy and precision of proposed differential pulse polarographic method.