Ultratrace analysis of uracil and 5‐fluorouracil by molecularly imprinted polymer brushes grafted to silylated solid‐phase microextraction fiber in combination with complementary molecularly imprinted polymer‐based sensor

Main inborn errors of metabolism diagnosable through uracil (Ura) analysis and the therapeutic monitoring of toxic 5‐fluorouracil (5FU) in dihydro pyrimidine dehydrogenase (DPD) deficient patients require a sensitive, reproducible, selective and accurate method. In this work, an artificial receptor in the format of molecularly imprinted polymer (MIP) brush ‘grafted to’ the surface of sol–gel immobilized on cost‐effective homemade solid‐phase microextraction (SPME) fibers, individually imprinted with either of Ura and 5FU, was used in combination with a voltammetric sensor duly modified with the same MIP. This combination provided up to 10‐ and 8.4‐fold preconcentrations of Ura and 5FU, respectively, which was more than sufficient for achieving stringent detection limits in the primitive diagnosis of uracil disorders and fluoropyrimidine toxicity in DPD‐deficient patients. The proposed method permits the assessment of Ura and 5FU plasma concentrations with detection limits pf 0.0245 and 0.0484 ng mL^?1 (RSD = 1.0–2.5%, S/N = 3), respectively, without any problems of non‐specific false‐positives and cross‐reactivities in complicated matrices of biological samples. Copyright © 2008 John Wiley & Sons, Ltd.