Flow Injection Amperometric Detection of Phenolic Compounds at Enzyme Composite Biosensors Application to Their Monitoring During Industrial Waste Waters Purification Processes

Abstract

Flow amperometric detection of phenolic compounds at graphite–teflon–tyrosinase and graphite–teflon–glucose oxidase–peroxidase composite electrodes is discussed. In this later design, the H2O2 needed for the enzyme reaction with the phenolic compound is generated “in situ” by the enzyme reaction of glucose oxidase with glucose added to the carrier. Flow injection amperometric responses at −0.15 V for the tyrosinase biosensor and at 0.00 V for the bienzyme electrode exhibited a good repeatability and stability of the baseline. The stability of such responses with time was evaluated when the carrier was continuously flowing and the detection potential was continuously applied. FI calibration plots for phenol, 2-chlorophenol, 4-chlorophenol, 4-chloro-2-methylphenol, and 3,4-dimethylphenol were constructed with the tyrosinase electrode, whereas calibration curves for the same compounds and 2,4,6-trichlorophenol were made at the bienzyme electrode. Dual detection was also performed with both electrodes in a parallel configuration and with a multichannel detector. Monitoring of phenolic compounds in waste waters from a refinery was carried out at two different stages in the water purification process. This monitoring needed the insertion of a styrene(divinylbenzene) copolymer cartridge in the FI system to remove the phenolic compounds from the sample, and the further use of this solution as the carrier. The results obtained were compared with those achieved using the colorimetric official method based on the reaction with 4-aminoantipyrine.