Direct amperometric determination of lactate at a carbon fiber bundle microdisk electrode by capillary zone electrophoresis

Capillary zone electrophoresis was employed for the determination of lactate using end-column amperometric detection at a carbon fiber bundle microdisk electrode. The optimum conditions of separation and detection are 3.6×10−3 mol/l Na2HPO4–1.4×10−3 mol/l NaH2PO (pH 7.2) for the buffer solution, 18 kV for the separation voltage and 1.60 V versus the saturated calomel electrode for the detection potential. The limit of detection is 7.6×10−7 mol/l or 1.7 fmol (S/N=3) and the linear range is 1.7×10−6–8.2×10−4 mol/l for the injection voltage of 6 kV and injection time of 5 s. The RSD is 1.8% for the migration time and 3.3% for the electrophoretic peak current. The method was applied to the determination of lactate in human saliva. The recovery of the method is between 95 and 109%.