Improved host–guest electrochemical sensing of dopamine in the presence of ascorbic and uric acids in a β-cyclodextrin/Nafion®/polymer nanocomposite†
A voltammetric analytical method based on a combination of β-cyclodextrin (CD), Nafion® (NF) and a gold electrode modified with poly(3,4-ethylene-dioxythiophene) (PEDOT) has been successfully developed (Au/PEDOT/NF/CD) for the determination of dopamine (DA) in the presence of ascorbic acid (AA) or uric acid (UA). Optimization of the sensor was conducted, including variables such as the type of substrate, concentration of each modifier, pH of the electrolyte, method of deposition of the polymer and immobilization of CD, and also the time for accumulation of the compound at the modified surface. The synergistic effect of the high conductivity of PEDOT and NF, in addition to the pre-concentrating effect of CD, its different host–guest inclusion complexes and its formation of hydrogen bonds with each compound, was used to construct a stable electrochemical sensor for the determination of these compounds. Under optimized conditions a linear calibration curve was obtained for the determination of dopamine in urine within the range 0.6–320 μmol L−1, with a correlation coefficient of 0.996 and detection limit of 5.84 nmol L−1. The proposed sensor was successfully used for the determination of tertiary mixtures of DA, AA and UA, of DA, AA and acetaminophen (APAP), and of binary mixtures of DA and serotonin (ST). It has been demonstrated that Au/PEDOT/NF/CD can be used as a sensor with excellent reproducibility, sensitivity and stability.