Quadruple-pulsed amperometric detection for simultaneous flow injection determination of glucose and fructose Original Research Article

A quadruple-potential waveform, at Edet1=−0.5 V (tdet1=240 ms), Edet2=+0.2 V (tdet2=180 ms), Eoxd=+1.0 V (toxd=180 ms), and Ered=−0.8 V (tred=300 ms) versus SCE, was employed at a Nafion-coated Au electrode for the simultaneous determination of glucose and fructose by flow injection analysis. Edet1 and Edet2 caused the oxidation of glucose and glucose and fructose, respectively. Hence, concentration subtraction could be used to determine both species. Using the FI-PAD, a linear response to glucose at Edet1 was obtained across the concentration range 5–60 mM, with a sensitivity of 2.34×10−7 A mM−1, and the limit of detection of 1.2 mM (S/N=3). Whereas at Edet2 scaled linearly with either glucose or fructose concentration in the range up to 60 mM, with a sensitivity of 7.50×10−6 A mM−1, and the limit of detection of 0.13 mM (S/N=3). Interference from other sugars, organic acids, and amino acids were studied. The method developed was used to analyze glucose and fructose contents in five different fruit samples; the method showed good agreement with the standard liquid chromatographic method.