Development and validation of a reversed-phase liquid chromatographic method for the assay of lidocaine in aqueous humour samples.

A simple, fast and reliable reversed-phase liquid chromatographic method was developed for the assay of lidocaine in human aqueous humour samples. The samples were analysed without any preliminary treatment on a C8 column with UV detection at 225 nm. The mobile phase consisted of methanol/sodium dihydrogen phosphate (30 mM) containing sodium pentansulphonate (10 mM) adjusted to pH 2.5 with phosphoric acid (50:50 v/v). Validation of the method showed it to be precise, accurate and linear over the concentration range of analysis with a limit of detection of 0.2 microgml(-1). The limit of quantitation was 2.5 microgml(-1) with a relative standard deviation of 2.5%. Linear regression analysis in the range 2.5-60 microgml(-1) gave correlation coefficients higher than 0.999. No interference from three commonly co-administered drugs was observed. The method developed was applied to the analysis of lidocaine in aqueous humour samples in order to evaluate and compare the efficacy of two different forms of administration of lidocaine for topical anaesthesia in cataract surgery.