Determination of a local anesthetic, lidocaine, in human whole blood by HPLC

A high-performance liquid chromatographic (HPLC) method for the determination of a local anesthetic, lidocaine, in human blood, human plasma and human serum albumin(HSA) solution was developed. Lidocaine extracted from blood was analyzed by the HPLC method on a reversed-phase column using an eluent consisting of 50 mM potassium dihydrogenphosphate-acetonitrile (3 : 1) and UV detection at 220 nm. Sample solution for HPLC was prepared as follows. Lidocaine in human whole blood (0.51 ml) was directly extracted with diethyl ether (5ml). The extract (3 ml of organic layer) was evaporated to dryness in a stream of nitrogen gas at 60°C. The dried residue was dissolved in 500μl of eluent and then 100μl of this solution was injected into the HPLC system through a disposable filter (pore size of 0.45μm). The calibration curves for the human whole blood, human plasma and HSA solution were linear (γ>0.9996) over the concentration range of 0.220μM of lidocaine. The lidocaine in human whole blood could be successfully determined from the calibration curve with a standard lidocaine solution. The recoveries of lidocaine from the solution of 10μM were almost 100% for human blood, human plasma and HSA solution. The relative standard deviation (%) was less than 4% in the concentration range of 220μM of lidocaine. No interference from other endogenous blood constituents was observed. This method was applied to determination of lidocaine in rabbit blood.