Determination of lidocaine by flow-injection analysis with electrochemical detection

A novel method for determining lidocaine using a flow-injection analysis system with electro-chemical detection (FIA-ECD) has been developed. The detection was based on the voltammetric oxidation prepeak of alpha-tocopherol, due to lidocaine, where the prepeak current was proportional to the concentration of lidocaine. Using FIA-ECD, the peak current height, which was proportional to the amount of lidocaine, ranged from 11.7 ng to 585 ng (r = 0.998). Standard lidocaine at 117 ng was determined ten times with a relative standard deviation (RSD) of 1.9%. The detection limit (S/N= 3) was 11.7 ng. To determine the purity of lidocaine in drugs listed in the Japanese Pharmacopoeia, the conventional titration method and the present method were used. Both analytical results were essentially identical. The presented method is useful for the determination of lidocaine, because it requires only one hundredth of the amount of lidocaine and one twentieth of the measuring time, and produces less waste compared to the titration method.