Temperature and magnetic dual responsive restricted access material for the extraction of malachite green from crucian and shrimp samples

A new restricted access material (RAM) based on magnetic graphene oxide (MGO) and a temperature-response polymer brush was developed and used as an adsorbent for the magnetic solid-phase extraction (MSPE) of malachite green (MG). The adsorption and desorption of MG could be achieved on the obtained smart material only through changing the temperature of the solution. At 20 degrees C, lower than the lower critical solution temperature (LCST) of poly (N-isopropylacrylamide) (PNIPAAM), the temperature-response polymer chains are swollen and are in a hydrophilic state, which can improve mass transfer and binding capacity, and further enhance recognition capability and extraction efficiency for MG. When the temperature is above the LCST, the adsorbent shows hydrophilic to hydrophobic surface property alterations, leading to a gradually weakening interaction between MG and the adsorbent material, so the captured MG molecules were released. The smart material and aqueous solution achieve separation using a magnet within 2 min. The main parameters affecting the extraction efficiency were optimized. An effective analytical method for MG was developed by combining with a UV-Vis spectrophotometer. In real sample analysis, the average recoveries with their respective relative standard deviation (RSD%) for crucian and green shrimp were 79.7-90.1 (3.8-5.3%) and 73.6-81.2 (3.7-4.3%), respectively. It indicated that the new method can be applied in the determination of MG in complex real samples.