Preparation of molecularly imprinted polymer based on the magnetic multiwalled carbon nanotubes for selective separation and spectrophotometric determination of melamine in milk samples

A new molecularly imprinted polymers coated on magnetic multiwalled carbon nanotubes (MIPs/MMWCNTs) was synthesized. Synthesized sorbent were characterized by scanning electron microscopy, X-ray diffraction, FTIR spectroscopy and via adsorption kinetics and adsorption isotherms. The application of this sorbent was investigated in preconcentration and determination with a simple and selective spectrophotometric determination of melamine (MEL) by charge transfer complexation. The method is based on the adsorption of MEL on MIPs/MMWCNTs and subsequent reaction of desorbed MEL with tetrachloro-p-benzoquinone (TCBQ) reagent for final spectrophotometric detection. The effect of experimental parameters affecting separation efficiency and spectrophotometric detection were investigated and optimized. Under optimum conditions, the calibration curve for MEL determination showed a good linearity in the range of 10.0-600.0 ng mL(-1) (R-2 = 0.999) and the limit of detection (S/N = 3) was estimated to be 3.0 ng mL(-1). The intra-day and inter-day precision (RSD%) of MEL were in the range of 2.8-3.9%. This method was successfully applied to determination of MEL in milk and milk powder samples. The good spiked recoveries ranging from 94.6 to 102.3% were obtained.