Amperometric L-Lactate Biosensors: 1. Lactic Acid Sensing Electrode Containing Lactate Oxidase in a Composite Poly-L-lysine Matrix
✍ Scribed by Emmanuel I. Iwuoha; Armin Rock; Malcolm R. Smyth
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 125 KB
- Volume
- 11
- Category
- Article
- ISSN
- 1040-0397
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✦ Synopsis
A lactic acid biosensor was prepared with lactate oxidase (LOD) from Pediococcus species, which was immobilized in a polyion membrane containing poly-L-lysine and poly(4-styrenesulfonate). Bifunctional poly(ethyleneglycol)(400)diglycidyl ether cross-linked the polyion to a glassy carbon (GC) electrode surface modi®ed with cobalt phthalocyanine layer. Hydrogen peroxide produced by the reaction of lactate and LOD was detected on the cobalt phthalocyanine-modi®ed GC electrode operated at a potential of 600 mV (vs. Ag/AgCl). The response time of the sensor to 10 mmol dm À3 lactate was 1 s, and it required 45 s to give a 100% steady-state response of ca. 10 nA. The detection limit estimated from signal to noise ratio was 0.5 mmol dm À3 . The LOD/polyion biosensor exhibited electrochemical Michaelis-Menten kinetics and gave an average apparent Michaelis-Menten constant, K H M , value of 0X88 AE 0X07 mmol dm À3 over a storage period of 18 days. Using lower molecular weight poly-L-lysine, resulted in 10 times decrease in ascorbic acid interference in lactate sensing. The polyion matrix can be constructed to be an ultra®ltration membrane to exclude electroactive compounds that interfere with lactic acid determinations in analytical samples.