Quick determination of melamine in infant powder and liquid milk by Fourier transform infrared spectroscopy

A simple, cost-effective and environmentally friendly analytical method was developed for the quantification of melamine (MEL) in liquid milk and infant powder by using transmission Fourier transform infrared (FT-IR) spectroscopy. Standards and samples were analyzed in the form of a KBr pellet for recording FT-IR spectra. Partial least squares calibration was established in the FT-IR region, 851.62-798.39 cm(-1), with a linear range of 0.001-1%. An excellent coefficient of determination (R-2) of 0.9999 was achieved, with minimum errors in the root mean square error of calibration and the root mean square error of prediction, for which the values were 0.17 and 3.49, respectively. The accuracy of the calibration model was also verified using the root mean square error of cross-validation, which was found to be 2.25. The limit of detection and the limit of quantification of the method were 0.0001% (1 ppm) and 0.00035% (3.5 ppm), respectively. The method was successfully applied to liquid and infant powder milk samples and gave good recoveries (98.9-100.2%). The FT-IR method developed here is efficient, accurate and appropriate for MEL detection in the dairy industry, with a reduced cost and a short analysis time.