Simultaneous detection of catechol and hydroquinone on Ni-Al layered double hydroxide/reduced graphene composite electrode modified with laccase

The fast detection of environmental contaminants catechol (CC) and hydroquinone (HQ) is of great importance to public health. In this research, a composite was firstly synthesised by a pre-exfoliation method, the components of which were Ni-Al-LDH and reduced graphene (rGO). This material was then utilised in the development of a highly sensitive biosensor for determining CC and HQ. The construction procedure involved modification of glassy carbon electrode (GCE) by the composite and laccase (LAC). Tests conducted by electrochemical methods showed the addition of laccase can greatly improve the response signal of electrochemical measurements on the composite modified GCE to CC and HQ. The electrochemical tests were performed by utilising 0.1 mol/L phosphate-buffer. When separately detected, the detecting linear range for CC by the biosensor was 0.009-0.58 and 0.95-4.4 mmol/L. When it comes to HQ, the range was 0.009-0.57 and 0.95-4.4 mmol/L on the composite/enzyme modified electrode. When the biosensor was used for detecting CC and HQ together, the linear ranges were both 0.019-0.56 and 1.0-4.4 mmol/L. The detection limits calculated for simultaneous detection were 0.75 and 0.47 mu mol/L, respectively. The sensor also possessed excellent sensitivity, selectivity and long stability. For applicability of the biosensor, it was used in analysing the two substrates in real water samples, and the recoveries were acceptable.