EVALUATION OF A NEW DISPOSABLE SCREEN-PRINTED SENSOR STRIP FOR THE MEASUREMENT OF NADH AND ITS MODIFICATION TO PRODUCE A LACTATE BIOSENSOR EMPLOYING MICROLITER VOLUMES

A combined sensor strip was fabricated by screen-printing a Meldola Bl ue modified carbon working electrode and a Ag/AgCl combined reference/ counter electrode alongside each other on a PVC substrate. This was in vestigated as an amperometric sensor for NADH, at an applied potential of 0 V, both in bulk solutions under hydrodynamic conditions and usin g 20 mu L volumes without agitation. The former technique gave linear responses in the range 3-60 x 10(-6) mol dm(-3) and the latter in the range 10-5 x 10(-4) mol dm(-3) of NADH. Further modification of the el ectrodes with NAD(+) and lactate dehydrogenase converted the device to a biosensor for lactate both in spiked phosphate buffer and bovine se rum. The sensors demonstrated good linear responses in the range 0-20 x 10(-3) mol dm(-3).