In our laboratory we needed to investigate a method in order to replace the liquid-liquid extraction of serum samples for clozapine determination

We took advantage of the newly available Strata X SPE columns (Phenomenex, CA, USA). We changed and optimised the suggested procedure in the following way: a) the sample loading and elution were performed strictly by gravity; b) the columns was washed with a strenghter eluent; c) no drying of the SPE column was needed before the final elution; c) we discarded the first 200 microlitres of eluent and held the next 500. Afterwards we submitted the reconstituted extract to HPLC under the following conditions: UV detector was set at 241 nm; the mobile phase was 15% Acetonitrile in Phosphate/Trietylamine buffer pH 2.1. We found this method easy to perform and reliable for routine analysis, and it allows us avoiding manipulation of volatile organic solvents.