A MULTICHANNEL IMMUNOCHEMICAL SENSOR FOR DETERMINATION OF 2,4-DICHLOROPHENOXYACETIC ACID

A disposable multichannel immunochemical sensor based on the electrochemical transducer is reported. The basic sensor consists of the array of 8 working electrodes (gold) and one common reference electrode (silver) placed at a ceramic substrate. On top, a piece of plastic plate with drilled holes is sealed to obtain 8 microwells with electrodes at their bottoms. An electronic computer-controlled switch is constructed which enables to use the multichannel sensor together with a usual amperometric measurement system. To prepare an immunochemical biosensor, circular pieces of nitrocellulose membrane with adsorbed antibodies against the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) are inserted into the microwells. For the competitive immunochemical assay of 2,4-D, the 2,4-D molecule conjugated to horse radish peroxidase is used as a tracer. The amount of bound tracer is determined amperometrically using hydrogen peroxide and hydroquinone as substrates for peroxidase. The detection limit for free 2,4-D in water is 0.1 mu g/l, the total time of analysis being less than 1 h. The multichannel sensor is potentially suitable for analysis of several samples and standards using one biorecognition system, moreover, different biospecific layers may be used to determine several different analytes in the same sample using only one multichannel sensor.