Ionic liquids impact on the catalysis of glucose oxidase and Cu/luminol/H2O2 system

The use of ionic liquids (ILs) as sensitivity enhancers and stabilizers in (bio)chemical assays is highlighted in this work. For that, the influence of several ILs on the copper-catalyzed chemiluminescence (CL) based on the oxidation of glucose by the system Cu/luminol/Glucose oxidase (Gox) was assessed. The evaluation of the effect of the ILs on the CL reaction was performed, in the presence and in the absence of enzyme, in an automated sequential injection analysis (SIA) system. The concentration of IL varied between 0.25 and 1.50 mol L−1, and its effect registered when mixed with the copper solution. The results evidenced that all the ILs of the imidazolium group enhanced the sensitivity of the CL reaction and the ILs with pyridinium and pyrrolidinium cations decreased it markedly, both in a concentration dependent mode. However, after joining the enzymatic reaction, the imidazolium ILs with anions tetrafluoroborate and 1-ethyl-3-methylimidazolium acetate caused a decreased of the chemiluminescence obtained. The most promising IL for this reaction showed to be the 1-ethyl-3-methylimidazolium trifluoromethanesulfonate. The results stress the usefulness of ILs to increase the analytical signal and point out to the necessity of evaluation of different cations and anions ILs moieties for each case.