Novel Ce(OH)CO3/carbon nanotubes hybrid material towards a highly sensitive electrochemical dopamine determination in real urine samples

Abstract

Cerium hydroxycarbonate and multiwalled carbon nanotubes (Ce(OH)CO3/CNT), drop-casted onto a glassy carbon (GC) electrode and electrochemically treated (tCe(OH)CO3/CNT) has been obtained as a new hybrid material. tCe(OH)CO3/CNT was characterized through SEM, FT-IR, UV–Vis, and electrochemical techniques such as cyclic voltammetry (CV) with different redox couples as Fe2+/3+, Fe(CN)63-/4− or Ru(NH3)62+/3+and electrochemical impedance spectroscopy (EIS) measurements with Fe(CN)63-/4−. The charge transfer resistance (RCT) value of tCe(OH)CO3/CNT was up to two orders of magnitude lower than the RCT of bare GC electrodes and these results were confirmed by the effective heterogeneous electron transfer rate constant values (k°eff, 2.4 10−3 vs 7.0 10−4, respectively). The calibration curve of DA exhibits a linear response within the range of 0.1 and 70 μmol L−1 with a correlation coefficient (R2) of 0.987 (n = 3) and a limit of detection of 0.003 μmol L−1. Inorganic and organic interferents do not alter significatively the selectivity. The electrochemical treatment of Ce(OH)CO3 and CNT generates a modified electrode which successfully combines the selectivity of Ce towards catechol with the high conductivity of CNT presenting an ideal performance for the electrochemical DA determination in 5 real urine samples (1.94 μmol L−1 in a 1:20 dilution) using differential pulse voltammetry (DPV) with an RSD < 6.1 %.