Determination of local anaesthetics in body fluids by gas chromatography with surface ionization detection.

Ten local anaesthetics were tested for their detection by gas chromatography (GC)-surface ionization detection (SID). Lidocaine, mepivacaine and bupivacaine were detected with the highest sensitivity; their detection limit was 5-10 pg in an injected volume. The sensitivity of other drugs, such as procaine, dibucaine tetracaine and oxybuprocaine, was an order of magnitude lower than that of the above three local anaesthetics. A detailed procedure for isolation of local anaesthetics from human whole blood and cerebrospinal fluid (CSF) by the use of Sep-Pak C18 cartridges, before the GC-SID, is also presented. The recovery of lidocaine, mepivacaine and bupivacaine, which had been added to 1 ml of whole blood or CSF, was close to 100%.