Flow injection analysis of L-lactate in milk and yoghurt by on-line microdialysis and amperometric detection at a disposable biosensor.
A disposable lactate biosensor able to operate in flow injection analysis is described and characterized. The biosensing layer, obtained by glutaraldehyde co-crosslinking of lactate oxidase with bovine serum albumin, was cast on an underlying electropolymerized layer of overoxidized polypyrrole. The resulting biosensor was interference-free and showed a K'M value of 2.4 mmol l-1 and a maximum current density of 440 microA cm-2. When integrated in a flow injection analysis system, a sensitivity of 300 +/- 10 nA mmol-1 l, a linear response up to 1 mmol l-1 and detection limits in the low micromolar range were obtained. The introduction of a microdialysis membrane-based sampler reduced the sensitivity to 7.9 +/- 0.2 nA mmol-1 l and extended the linear range up to 50 mmol l-1 lactate. The anti-interference characteristics of the biosensor permitted lactate determination in untreated milk and diluted yoghurt samples.
Palmisano
F
F
Dipartimento di Chimica, Università degli Studi di Bari, via Orabona, 4 70126 Bari, Italy. palmisano@chimica.uniba.it
Quinto
M
M
Rizzi
R
R
Zambonin
P G
PG
D000818:Animals; D002417:Cattle; D003956:Dialysis; D004563:Electrochemistry; D017022:Flow Injection Analysis; D007773:Lactates / Q000032:analysis*; D008892:Milk / Q000737:chemistry*; D015014:Yogurt / Q000032:analysis*
D007773:Lactates