Uric acid was analyzed by paired-ion, reversed-phase HPLC
coupled with electrochemical detection by following the same
procedure described for vitamin C; an electrode potential of 0.6 V
was used, but the gain was set at 1 A. Uric acid was eluted as a
single peak with a retention time of 3.5 min. Peaks were integrated
with a ChemStation (Hewlett Packard). Uric acid concentrations
were calculated on the basis of a calibration curve and are
expressed as mol/L (33).