Activity and stability of horseradish peroxidase in hydrophilic room temperature ionic liquid and its application in non-aqueous biosensing

The activity and stability of horseradish peroxidase (HRP) were investigated in a hydrophilic room temperature ionic liquid 1-butyl-3-methylimidazolium tetrafluroborate ([bmim][BF4]) by electrochemical methods. Although no detectable activity exhibited in anhydrous [bmim][BF4], HRP was active in the presence of a small amount of water (4.53%, v/v). And its activity can be improved by immobilization in agarose hydrogel. The immobilized HRP possesses excellent activity at 65 °C. It remained 80.2% of its initial activity after being immersed for 10.5 h in an aqueous mixture of [bmim][BF4] with some hydrogen peroxide (H2O2) under room temperature, implying extremely high stability. Moreover, the immobilized HRP was found to be very sensitive and stable in H2O-containing [bmim][BF4] for the detection of H2O2, with a wide linear range of 6.10 × 10−7 to 1.32 × 10−4 mol l−1 and low detection limit of 1.0 × 10−7 mol l−1.