We present a temperature-responsive spin column using an all-aqueous eluent. The method is intended as a simple sample preparation method for protein removal from serum, which is required for serum drug analysis. As packing materials for the spin column, we prepared two types of silica beads via surface-initiated radical polymerization. The large beads (diameter, 40–63 μm) were grafted with a temperature-responsive cationic copolymer, poly(N-isopropylacrylamide-co-N,N-dimethylaminopropyl acrylamide-co-n-butyl methacrylate) (P(NIPAAm-co-DMAPAAm-co-BMA)), and the small beads (diameter, 5 μm) were grafted with a temperature-responsive hydrophobic copolymer, P(NIPAAm-co-BMA). The beads were packed into the spin column as a double layer: P(NIPAAm-co-BMA) silica beads on the bottom and P(NIPAAm-co-DMAPAAm-co-BMA) silica beads on the top. The sample purification efficacy of the prepared spin column was evaluated on a model sample analyte (the antifungal drug voriconazole mixed with blood serum proteins). At 40 °C, the serum proteins and voriconazole were adsorbed on the prepared spin column via hydrophobic and electrostatic interactions. When the temperature was decreased to 4 °C, the adsorbed voriconazole was eluted from the column with the pure water eluent, while the serum proteins remained in the column. This temperature-responsive spin column realizes sample preparation simply by changing the temperature.
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