Fe3O4 decorated single wall carbon nanotubes (Fe3O4/SWCNTs) composite and 1-ethyl-3-methyl imidazolium chloride (1E3MICl) were used for modification of carbon paste electrode (CPE) and fabricated sensor applied to the sensitive and convenient determination of xanthine (Xt). The carbon paste electrode amplified with 1E3MICl and Fe3O4/SWCNTs (CPE/1E3MICl/Fe3O4/SWCNTs) exhibit an anodic peak for Xt at potential similar to 830 mV that is about 135 mV less positive than detected potential for Xt at an unmodified CPE in the similar condition. In addition, the CPE/1E3MICl/Fe3O4/SWCNTs exhibit a potential ability for analysis of Xt in the presence of theophylline (Tp) with the separated potential 280 mV. The CPE/1E3MICl/Fe3O4/SWCNTs was used for determination of Xt and Tp in the concentration ranges of 4.0 nM-300.0 mu M and 0.1-300.0 mu M, respectively. The CPE/1E3MICl/Fe3O4/SWCNTs was used as a high performance sensor with good detection limit for determination of Xt in food samples such as fish meat, tea and soft drinks. (C) 2018 The Electrochemical Society.