Study On The Phthalate Contaminants In Food Package By Raman And Surface Enhancement Raman Spectroscopy

The harm of phthalate esters (PAEs), a kind of very common contaminants, isunneglected. Many governments have set laws and regulations to control the use andmigration of them. Because of health concerns and for the guarantee the product with worldstandards in quality, rapid detection technology of PAEs is in need. Surface-enhanced Ramanscattering (SERS) spectroscopy, a novel and ultra-sensitive vibrational spectroscopic method,has developed greatly in the field of environment, materials, and identification ofmicroorganism. Recent years, SERS is applied in food safety. The aim of this research is todevelop a rapid method to monitor contamination by phthalate esters (PAEs) in food and foodpackaging by surface-enhanced Raman scattering (SERS) spectroscopy.Firstly, analysis the ordinary Raman spectra of the six kinds of the PAEs-DibutylPhthalate (DBP), Di-2-Ethyl Hexyl Phthalate (DEHP), Butyl Benzyl Phthalate (BBP),Diisononyl Phthalate (DINP), Diisodecyl Phthalate (DIDP) and Di-n-Octyl Phthalate (DNOP),which are the most concerned by regulations. The main characteristic peaks at403、653、1043、1127、1167、1585、1605、1731cm-1as the fingerprint-like peaks of PAEs wereconformed.Secondly, the molecular structure and theoretical vibration frequency of dimethylphthalate (DMP) was studied by density functional theory (DFT) calculations. The structureof DMP with the dihedral angles of1C-6C-11C-13O and4C-3C-18C-20O being133.78°and-24.00°, respectively, has the lowest energy. The theoretical vibration frequency calculated byB3LYP method and6-31+G(d) basis set reached greatest agreement with the experimentalRaman spectrum of DMP. The vibration modes of the characteristic peaks of dimethylphthalate (DMP) were assigned with the result of theoretical vibration frequency calculation.And the molecular model of DEHP was also studied as the represent of PAEs, thecharacteristic peaks of PAEs were assigned.And then, the nanosubstrates to enhance the Raman signal of PAEs was investigated. It isdemonstrated that because hydrophobic property of PAEs and electrostatic interaction, the Agcolloid has no SERS activity for PAEs, although the process of clean or phase transfer. Thecommercial nanosubstrate-Klarite SERS-substrate was choosed. By the optimization of theparamenters, the Raman signal of PAEs was enhanced coupling with the Klarite SERS-substrate. The limit of detection (LOD) was0.1mg/L.Lastly, the SERS technology was applied in detecting trace PAEs contaminants in milkqualitatively. The results were agree with that by HPLC-UV method. It is demonstrated thatthe SERS technology is potential to apply in the rapid screening of trace PAEs contaminants.