[The quantitative analysis of amide local anesthetics using high pressure liquid chromatography and ultraviolet...

This study was undertaken to develop a time- and cost-effective method for the detection of lidocaine, mepivacaine, prilocaine, bupivacaine, and etidocaine by HPLC/UV. The chromatographic system consisted of a C18-column (300 x 3.9 mm) for reversed-phase chromatography and a mobile phase of 30% acetonitrile and 70% 0.05 M sodium phosphate buffer. For the analysis of lidocaine, mepivacaine, and prilocaine, the buffer was adjusted to pH 5.8. The buffer for the analysis of bupivacaine and etidocaine was adjusted to pH 3.5. The flow rate was 1 ml/min. UV detection took place at a wavelength of 210 nm. All blood samples were taken from a central venous line. After plasma separation, 1 microgram (100 microliters) of internal standard was added to 1 ml plasma. The samples were alkalized and extracted with ether, followed by the extraction of the organic phase in 250 microliters 0.05 N sulphuric acid; 50 microliters of this solution was injected into the system. The chromatographic system allowed the separation of bupivacaine and etidocaine (pH 3.5) as well as lidocaine and mepivacaine or prilocaine (pH 5.8). Separation of prilocaine and mepivacaine in one run was not satisfactory. Recovery rates for all local anesthetic substances were about 90%, standard variations below 3%, and coefficients of variation below 2%. The detection limit was about 30 ng/ml. The method is suitable for clinical practice. Only minor methodological modifications are necessary for the detection of the amide local anesthetics in current clinical use.