Direct analysis of anticonvulsant drugs in vitreous humour by HPLC using a column switching technique

A method is described for the rapid HPLC analysis of a number of anticonvulsant drugs in vitreous humour by injection directly onto a preconcentration column without the need for prior extraction. The conditions for optimum precision and accuracy were investigated and the method was subsequently applied to the analysis of phenytoin in a number of overdose cases. Sensitivity was 0.05 microgram/ml on a 0.5 ml vitreous sample. The mean blood/vitreous ratio for phenytoin was found to be 2.8 (range: 1.4-5.1). The relationship between blood and vitreous levels had a correlation coefficient of 0.85. Vitreous was found to be a very clean, stable sample, ideally suited to this technique.