Single Column HPLC Method for Drug Level Monitoring by Direct Plasma Sample Injection. Application to 6-Mercaptopurine, Theophylline and Chlorpromazine

An HPLC method with direct plasma sample injection onto a reverse phase column and stepwise elution was applied to the drug level monitoring of 6-mercaptopurine, theophylline and chlorpromazine by using spectrophotometric or electrochemical detection. The analysis of the drug spiked in human plasma was quantitative, and 100% of the drug was recovered regardless of the entity free or bound to plasma protein. Owing to a preliminary procedure of protein coating on the ODS silica gel the column characteristics were somewhat deteriorated, but accurate analyses could be achieved by a single column method including the simultaneous determination of some metabolites of the drug.