A flow injection (FI) biosensor system for pentachlorophenol (PCP) using asubstrate recycling scheme

A flow injection (FI) biosensor system has been designed for the analysis o f pentachlorophenol (PCP) using a substrate recycling scheme comprising imm obilized bilirubin oxidase (BOX) in the presence of excess of NADH. PCP was efficiently converted to tetrachloro-p-benzoquinone (1,4-TCHQ) and then te trachloro-p-hydroquinone (1,4-TCHQ) by bis(trifluoroacetoxy)iodobenzene (BT FAIB) and zinc powder, respectively. BOX immobilized on aminopropyl glass b eads rapidly oxidized 1,4-TCHQ to 1,4-TCBQ, which in turn was readily reduc ed back to 1,4-TCHQ in the presence of excess NADH. This recycling scheme e nabled one molecule of PCP to consume several NADH molecules leading to enh anced sensitivity. tinder optimized conditions the rate of NADH uptake meas ured as the absorbance decrease at 340 nm yielded a detection limit for 1,4 -TCHQ or oxidized PCP of 250 nM. The detection limit was improved to 25 nM for both analytes using a fluorescence detector with excitation and emissio n wavelengths of 345 and 450 nm, respectively. The PCP level in contaminate d soil samples was measured using the Fl biosensor system, and the results obtained compared well with capillary zone electrophoresis (CZE) analysis.