On-line preconcentration strategy for the simultaneous quantification of three local anesthetics in human urine using...

The simultaneous determination of usually employed anesthetics (procaine, lidocaine, and bupivacaine) has been developed and validated using CE with ultraviolet detection at 212 nm. The separation of these three drugs has been achieved in less than 7 min, using a temperature of 25ºC and 25 kV, with a 150 mM citrate buffer (pH 2.5) as BGE. Field-amplified sample injection (FASI) has been used for on-line sample preconcentration. Ultrapure water and ACN 50/50 (v/v) mixture gave the greatest enhancement factor when it was employed as an injection solvent. Injection voltage and time were optimized, being 13 kV and 13 s, the optimum values, respectively. To avoid the possible irreproducibility associated with the electrokinetic injection, an internal standard such as tetracaine, was employed. The instrumental detection limits (LOD S/N = 3) for the compounds ranged between 2.6 and 7.0 μg L(-1) and the quantitation limits (LOQ S/N = 10) between 37.8 and 55.9 μg L(-1) . The detection limits obtained in real human urine samples ranged between 55.2 and 83.6 μg L(-1) and the quantitation limits between 196.0 and 276.0 μg L(-1) . The proposed method has demonstrated its applicability to the analysis of these local anesthetics in urine samples without any pretreatment, allowing the rapid determination of these target analytes.