930 (2001) 31–38 Journal of Chromatography A, www.elsevier.com / locate / chroma Determination of phenytoin in plasma by molecularly imprinted solid-phase extraction a, a a a b * ´ ´ Andrea Bereczki , Antal Tolokan , George Horvai , Viola Horvath , Francesca Lanza , b b ¨ Andrew John Hall , Borje Sellergren a Budapest University of Technology and Economics, Institute for General and Analytical Chemistry and Division of Chemical Information Technology, 1111 Budapest, Szt. Gellert ter 4, Hungary b Johannes Gutenberg University, Department of Inorganic Chemistry and Analytical Chemistry, Duesbergweg 10 –14, 55128 Mainz, Germany Received 7 June 2001; received in revised form 7 August 2001; accepted 8 August 2001 Abstract A molecularly imprinted polymer (MIP) using phenytoin as template and methacrylamide as the functional monomer was prepared. The selectivity was measured by comparing capacity factors of phenytoin and other structurally related compounds. The polymer was evaluated as a selective sorbent in molecularly imprinted solid-phase extraction (MISPE). Several washing solvents were tested to study their ability to disrupt the non-specific interactions occurring between the sample and the polymer matrix and the role of water in the recognition process was also investigated. It was shown that the key step of successful sample extraction is the right choice of the washing solvent. Plasma samples spiked with phenytoin were analyzed by the MISPE methodology developed in this work. Method validation (intra- and inter-day precision, recovery, specificity) was carried out. The calibration curve showed good linearity in the 2.5–40 mg / ml range corresponding to therapeutically relevant plasma levels. The intra- and inter-day precision values were below the 15% limit established for bioanalytical methods. The results showed that the method could be successfully applied for the determination of phenytoin in plasma samples.  2001 Elsevier Science B.V. All rights reserved. Keywords: Molecularly imprinted solid-phase extraction; Phenytoin 1. Introduction satility in measuring drugs and metabolites at the same time, has been established for determination of Phenytoin is one of the most commonly prescribed phenytoin [1–3]. The sample pretreatment in these anticonvulsant drugs in the treatment of epilepsy, cases is usually carried out by liquid–liquid ex- with a therapeutic concentration of 10–20 mg / ml. To traction or solid-phase extraction (SPE). The selec- avoid toxicity and ensure efficacy a continuous tivity of custom SPE sorbents is limited because they therapeutic monitoring is needed. The use of stan- differentiate only by some generic property like dard chromatographic techniques, due to their ver- hydrophobicity. In order to enhance the selectivity the use of molecularly imprinted polymers (MIPs) as selective sorbents is becoming increasingly popular *Corresponding author. E-mail address: bereczki.aak@chem.bme.hu (A. Bereczki). [4–13]. These are commonly highly reticulated 0021-9673 / 01 / $ – see front matter  2001 Elsevier Science B.V. All rights reserved. PII: S0021-9673(01)01190-6