A new flow-injection determination of glucose based on the redox reaction of hydroquinone with iron(III) in the presence of 1,10-phenanthroline

A new spectrophotometric flow-injection (FI) method is proposed for the determination of glucose based on the redox reaction of hydroquinone with iron(III). When a glucose solution containing quinone is passed through the immobilized glucose oxidase column introduced in FI system, quinone is reduced to hydroquinone by glucose. In the presence of 1,10-phenanthroline (phen), iron(III) is then quantitatively reduced by hydroquinone to iron(II) followed by the formation of iron(II)-phen complex (λmax=510 nm). An FI peak observed at 510 nm corresponds to the concentration of glucose. The wide dynamic range for glucose was obtained in the range of 1×10−6–1×10−3 mol l−1 at a sampling rate of 24 h−1 and the detection limit (S/N=3) was 5×10−7 mol l−1. Relative standard deviations were 0.78, 0.44 and 0.23% (n=5) for 5×10−6, 5×10−5 and 5×10−4 mol l−1 of glucose, respectively. The proposed method was successfully applied to the determination of glucose in control blood sera, human blood plasma and wine.