Ionic liquid-based miniature electrochemical sensors for the voltammetric determination of catecholamines

Screen-printed electrodes modified with carbon paste that consisted of graphite powder dispersed in ionic liquids (IL) were used for the electrochemical determination of dopamine, adrenaline and dobutamine in aqueous solutions by means of cyclic voltammetry. The IL plays a dual role in modifying compositions, acting both as a binder and chemical modifier (ion-exchanger); ion-exchange analyte pre-concentration increases analytical signal and improves the sensitivity. Calibration graphs are linear in concentration range 3.9 x 10(-6) to 1.0 x 10(-4) M (dopamine), 2.9 x 10(-7) to 1.0 x 10(-4) M (adrenaline) and 1.7 x 10(-7) to 1.0 x 10(-4) M (dobutamine); detection limits are (1.2 +/- 0.1) x 10-6, (1.3 +/- 0.1) x 10(-7) and (5.3 +/- 0.1) x 10(-8) M, respectively. Using an additive of Co (III) tetrakis-(tert-butyl)-phthalocyanine leads to the increase of signal and lowering detection limit. Some practical advises concerning both the sensor design and selectivity of catecholamine determination are provided. (c) 2008 Elsevier B.V. All rights reserved.