Combination of Gold‐Modified Electrode and α‐Amyloglucosidase for Simultaneous Determination of Starch and Glucose

Abstract

The electrocatalytic activity of copper‐modified gold electrodes has been investigated for the simultaneous detection of glucose and starch using α‐amyloglucosidase in solution. The amperometric response of glucose at the modified gold electrode was monitored for different copper loadings (0.04, 0.1, 0.2, and 0.3 mg cm⁻²), that of 0.2 mg cm⁻² deposited on the electrode surface being chosen for further investigation. The surface characteristics were confirmed by the electrochemical impedance spectra. The oxidation of glucose and starch was studied by linear sweep voltammetry (LSV) in order to determine the best applied potential for measuring glucose in the presence of starch, a value of +0.4 V vs. SCE being selected. The glucose detection limit at +0.4 V is equal to 0.64 mg L⁻¹ in the absence of starch. The same detection limit was found after adding 200 mg L⁻¹ starch to the cell. The properties of the copper‐deposited films were investigated in 0.15 M NaOH solution for the determination of α‐amyloglucosidase enzyme activity. The enzymatic reaction conditions were optimized. Conversion of starch into glucose was found to be around 89% by using α‐amyloglucosidase (2970 mUI) at 55°C for 30 min.

Keywords:

• Gold‐modified electrode
• Copper
• Starch
• Glucose
• α‐Amyloglucosidase

Acknowledgments

The authors acknowledge financial support from the Scientific and Technical Cooperation Agreement Portugal–Morocco (GRICES–CNRST, 2002–2003), and from ICEMS, Coimbra, Portugal (Research Unit 103).