Mj. Lobocastanon et al., A BIENZYME-POLY-(O-PHENYLENEDIAMINE)-MODIFIED CARBON-PASTE ELECTRODE FOR THE AMPEROMETRIC DETECTION OF L-LACTATE, Analytica chimica acta, 346(2), 1997, pp. 165-174
A reagentless lactate amperometric biosensor, constructed by immobilis
ing the enzymes glutamic pyruvic transaminase (GPT) and L-lactate dehy
drogenase (LDH) together with its cofactor nicotinamide adenine dinucl
eotide (NAD(+)) in carbon paste using an electropolymerised poly(o-phe
nylenediamine) (PPD) film, is described. The response of the electrode
is based on the electrocatalytic oxidation, at low applied potentials
, of the enzymatically produced NADH by the PPD conducting film. This
sensor construction was optimised, the final biosensor contained 80 un
its of LDH, 5 units of GPT and 0.1 mg of NAD(+) mg(-1) of carbon paste
. Interference by direct electrochemical oxidation of easily oxidizabl
e substances such as uric acid, L-ascorbic acid, L-cysteine, glutathio
ne and paracetamol, are drastically reduced by covering the PPD-modifi
ed electrode with a second electrochemically synthesized, non-conducti
ng poly(o-aminophenol) film. The bienzyme-double polymeric layer-modif
ied electrode at an applied potential of 0 V (vs. Ag/AgCl), gives a li
near response for lactate in the range 6x10(-7) M8.5x10-5 M and a resp
onse time of 80 s. This sensor was used for the quantification of lact
ic acid in cider. Results compared favourably with a standard spectrop
hotometric method.