Rapid Colorimetric Detection of Cartap Residues by AgNP Sensor with Magnetic Molecularly Imprinted Microspheres as Recognition Elements

The overuse of cartap in tea tree leads to hazardous residues threatening human health. A colorimetric determination was established to detect cartap residues in tea beverages by silver nanoparticles (AgNP) sensor with magnetic molecularly imprinted polymeric microspheres (Fe(3)O(4)@mSiO(2)@MIPs) as recognition elements. Using Fe(3)O(4) as supporting core, mesoporous SiO(2) as intermediate shell, methylacrylic acid as functional monomer, and cartap as template, Fe(3)O(4)@mSiO(2)@MIPs were prepared to selectively and magnetically separate cartap from tea solution before colorimetric determination by AgNP sensors. The core-shell Fe(3)O(4)@mSiO(2)@MIPs were also characterized by FT-IR, TEM, VSM, and experimental adsorption. The Fe(3)O(4)@mSiO(2)@MIPs could be rapidly separated by an external magnet in 10 s with good reusability (maintained 95.2% through 10 cycles). The adsorption process of cartap on Fe(3)O(4)@mSiO(2)@MIPs conformed to Langmuir adsorption isotherm with maximum adsorption capacity at 0.257 mmol/g and short equilibrium time of 30 min at 298 K. The AgNP colorimetric method semi-quantified cartap ≥5 mg/L by naked eye and quantified cartap 0.1–5 mg/L with LOD 0.01 mg/L by UV-vis spectroscopy. The AgNP colorimetric detection after pretreatment with Fe(3)O(4)@mSiO(2)@MIPs could be successfully utilized to recognize and detect cartap residues in tea beverages.