ECSpecifically, in the HPLC/EC, the oxidation potential wasadjusted to +1.1 V, and the concentration of the sodium dihydro-genphosphate solution was increased to 0.1 M, which gave thehighest response for LA. The mobile phase was degassed withhelium to remove oxygen, which can interfere with LA reduction.The LA peak presented a slight tail due the adsorption of LA onelectrode surface. This phenomenon did not impair the methodreliability and is in accordance with data reported previously [18].LA displayed linearity over a wide concentration range. Intra- andinter-day precision (coefficient of variation) was less than 6.5%. Theaccuracy of this method was greater than 90%, determined fromthe percentage recovery at 8, 2, 0.5 g/mL LA. The LLOD and LLOQvalues were determined to be 1.0 and 0.91 ± 0.05 g/mL, respec-tively. The chromatograms for standard solutions and LLOQ of LAdetermined by HPLC/EC are shown in Fig. 2A. Routine cleaning ofthe surface of the electrode was performed to maintain the sen-sitivity [19]. In this way, the results obtained from skin analysesare reproducible and accurate as reported for LA in plasma sam-ples [25]. Therefore, HPLC/EC may be applied to samples with lowconcentrations of LA.