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Amperometric L ‐Lactate Biosensors: 1. Lactic Acid Sensing Electrode Containing Lactate Oxidase in a Composite Poly‐ L ‐lysine Matrix
Author(s) -
Iwuoha Emmanuel I.,
Rock Armin,
Smyth Malcolm R.
Publication year - 1999
Publication title -
electroanalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.574
H-Index - 128
eISSN - 1521-4109
pISSN - 1040-0397
DOI - 10.1002/(sici)1521-4109(199905)11:5<367::aid-elan367>3.0.co;2-0
Subject(s) - chemistry , biosensor , lactic acid , ascorbic acid , detection limit , nuclear chemistry , bifunctional , electrochemistry , chromatography , electrode , organic chemistry , biochemistry , catalysis , genetics , food science , bacteria , biology
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 modified with cobalt phthalocyanine layer. Hydrogen peroxide produced by the reaction of lactate and LOD was detected on the cobalt phthalocyanine‐modified GC electrode operated at a potential of +600 mV (vs. Ag/AgCl). The response time of the sensor to 10 μmol dm –3 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 μmol dm –3 . The LOD/polyion biosensor exhibited electrochemical Michaelis‐Menten kinetics and gave an average apparent Michaelis‐Menten constant,K′ M , value of 0.88 ± (0.07 mmol dm –3 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 ultrafiltration membrane to exclude electroactive compounds that interfere with lactic acid determinations in analytical samples.