Determination of Rutin in Flos Sophorae by Molecular Imprinted Paper Chip Based on Digital Imaging Method

Based on digital imaging method, a molecular imprinted paper chip with high selectivity for rutin was prepared, and used to determine rutin in Flos sophorae. The microfluidic channels with diameter of 6 mm were printed on filter paper by laser printer, and the paper chip containing hydrophilic and hydrophobic areas was obtained after heating at 170 ℃ for 1.5 h. The prepolymer solution was obtained after ultrasonic polymerization for 45 min with rutin as template, acrylamide as functional monomer, ethylene glycol dimethacrylate as cross-linker and azodiisobutyronitrile as initiator. The prepolymer solution (14 μL) was dropped onto the hydrophilic area, and 0.01 mol·L^-1 sodium hydroxide solution was used for soak and elute, and then the rutin molecular imprinted paper chip was preparaed. Flos sophorae (2.00 g) was extracted twice with 10 mL of 4 g·L^-1 boiling borax solution, and the filtrates were combined and diluted with water to obtain rutin solution for test. The 5 μL of rutin solution above and 5 μL of 10% (mass fraction) aluminum chloride solution were dropped onto the detection area of rutin molecular imprinted paper chip, and the reaction was carried out for 40 min at room temperature. The fluorescence image was taken by mobile phone under 365 nm of UV light, and the image was processed by Adobe Photoshop software to obtain R (red), G (green) and B (blue) values. It was shown that linear relationship between the mass concentration of rutin and the sum of R, G and B values was kept in the range of 0.0100-0.2000 g·L^-1, with detection limit (3s/k) was 0.007 9 g·L^-1. Test for recovery was made on actual sample at 3 concentration levels, giving results in the range of 82.6%-105%. This method was applied to analysis of 3 Flos sophorae samples, and the mass fractions of rutin were in the range of 6.07%-6.53%, with RSDs (n=5) of the determined values ranged from 3.1% to 5.2%.