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

A quadruple-potential waveform, at E-det1 = -0.5 V (t(det1) = 240 ms), E-det2 = +0.2 V (t(det2) = 180 ms), E-oxd = + 1.0 V (t(oxd) = 180 ms), and E-red = -0.8 V (t(red) = 300 ms) versus SCE, was employed at a Nafion-coated An electrode for the simultaneous determination of glucose and fructose by flow injection analysis. E-det1 and E-det2 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 E-det1 was obtained across the concentration range 5-60 mM, with a sensitivity of 2.34 x 10(-7) A mM(-1), and the limit of detection of 1.2 mM (S/N = 3). Whereas at E-det2 scaled linearly with either glucose or fructose concentration in the range up to 60 mM, with a sensitivity of 7.50 x 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. (C) 2001 Elsevier Science B.V. All rights reserved.