A reagentless amperometric electrode based on carbon paste, chemically modified with D-lactate dehydrogenase, NAD+, and mediator containing polymer for D-lactic acid analysis. I. Construction, composition, and characterization

✍ Scribed by Hun-Chi Shu; Bo Mattiasson; Björn Persson; Geza Nagy; Lo Gorton; Suresh Sahni; Lin Geng; Leonid Boguslavsky; Terje Skotheim

• Publisher: John Wiley and Sons
• Year: 1995
• Tongue: English
• Weight: 944 KB
• Volume: 46
• Category: Article
• ISSN: 0006-3592
• DOI: 10.1002/bit.260460310

✦ Synopsis

A reagentless carbon paste electrode was designed for o-lactic acid analysis in a flow injection system for the monitoring of the production of D-lactate in a batch fermentation. o-Lactate dehydrogenase, nicotinamide adenine dinucleotide (NAD+), a synthetic redox polymer containing covalently attached toluidine blue 0 as mediator, graphite powder, and paraffin oil were used for the construction of the modified carbon paste electrode. o-Lactate selectivity was indicated by insignificant responses from a variety of possible interferences including L-lactate. The electrodes gave a linear response in the range between 0.05 and 5 m M D-lactate, with a detecting limit of 30 pM, allowing a sample throughput of 20 h-'.

Preliminary investigations were made by covering the electrode surface with electropolymerized membranes. Satisfactory stability was observed, indicated by a reproducibility of 3.3% relative standard deviation (RSD, n = 31), with a non-membrane-covered electrode for the analysis of D-lactate in fermentation broth. A long-term stability (230 broth samples) was proven, suggesting the electrodes to have a good potential for use in on-line monitoring of fermentation processes.