Simplified quantitative determination of plasma phenytoin: on-line pre-column high-performance liquid immunoaffinity...

A method for on-line high-performance liquid immunoaffinity chromatographic analysis of 5,5-diphenylhydantoin (phenytoin) in human plasma is described. The technique is simple and does not require sample preparation or addition of an internal standard, and the phenytoin is eluted from the columns in 12 min. A phenytoin-specific polyclonal immunoglobulin was attached to an organic silane derivative on silica. The immunosorbent was packed into a short liquid chromatography column and installed in a modified high-performance liquid chromatography system for on-line sample pre-purification. Standard curve linearity of plasma phenytoin was obtained at concentrations up to 160 mumol/l. When compared to conventional high-performance liquid chromatography, plasma phenytoin levels gave a correlation coefficient of 0.993. The phenytoin is highly bound to plasma proteins (ca. 87%). When plasma is injected onto the pre-column, a dissociation and partition of phenytoin from plasma proteins to a complete association with on-column insolubilized antibodies results.