DETECTION OF MELAMINE IN PACKAGING MATERIALS USING TERAHERTZ TIME-DOMAIN SPECTROSCOPY

To detect melamine in packaging materials, terahertz time-domain spectroscopy (THz-TDS) was employed to measure the terahertz absorption spectra of melamine-polyethylene mixtures with varying mass ratios (1:0-3). The results revealed distinct characteristic absorption peaks of melamine at 2.0, 2.28, and 2.6 THz. Among these, the peak at 2.0 THz was the most prominent and remained clearly observable even within packaging materials. Several common packaging materials, including low-density polyethylene (LDPE), high-density polyethylene (HDPE), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS), polyethylene terephthalate (PET), and paperboard, were examined individually to assess their spectral interference. Characteristic melamine absorption peaks at 2.0 and 2.28 THz were used to establish a calibration model based on Gaussian distribution functions. Based on the International Union of Pure and Applied Chemistry (IUPAC) method, the limit of detection (LOD) and limit of quantification (LOQ) were calculated to be 15 and 80%, respectively. Even at a concentration close to the LOD (10%), the signal remained distinguishable (signal/noise (S/N) > 3). X-ray powder diffraction (XRD) was utilized as a complementary technique to confirm the presence of melamine in the transparent plastic zip bag. These results support the effectiveness of THz-TDS in detecting melamine through packaging materials and highlight its potential application for detecting specific molecules in packaging materials