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 (lambda(max)=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 1x10(-6)-1x10(-3) mol l(-1) at a sampling rate of 24 h(-1) and the detection limit (S/N=3) was 5x10(-7) mol l(-1). Relative standard deviations were 0.78, 0.44 and 0.23% (n=5) for 5x10(-6), 5x10(-5) and 5x10(-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.