Journal
CENTRAL EUROPEAN JOURNAL OF CHEMISTRY
Volume 10, Issue 1, Pages 157-164Publisher
SCIENDO
DOI: 10.2478/s11532-011-0118-3
Keywords
Biosensor; Malic acid; Nanocomposite; Enzyme; Wine analysis
Categories
Funding
- Slovak Research and Development Agency [VMSP-P-0073-09]
- Agency of the Ministry of Education, Science, Research and Sport of the Slovak Republic of EU [ITMS 26240220040]
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Amperometric biosensors based on a gold planar electrode and on two types of nanocomposite electrodes consisting of multi-walled carbon nanotubes for the determination of L-malic acid designed for wine-makers were developed. The biosensors designed for wine-makers were constructed by immobilization of L-malate dehydrogenase and diaphorase within chitosan layers on the surface of the electrodes. The coenzyme NAD+ and the electrochemical mediator ferricyanide were present in the measuring solution. The current resulting from re-oxidation of produced ferrocyanide was measured at a working potential of +300 mV against an Ag/AgCl reference electrode. The biosensor based on a gold electrode showed linearity over the range 10-520 A mu M with a detection limit of 5.41 A mu M. Calibration curves for biosensors utilizing nanocomposites were obtained both with the linear range of 10 to 610 A mu M. The detection limits were 1.57 and 1.77 A mu M, respectively. The biosensors showed satisfactory operational stability (no loss of sensitivity after 30 consecutive measurements) and storage stability (90% of the initial sensitivity after one year of storage at room temperature). The results obtained from measurements of wine samples were in a good correlation with the standard HPLC method. Satisfactory biosensor sensitivity, specificity and stability allowed their successful commercialization.
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