2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane modified glassy carbon electrodes as selective and sensitive voltammetric sensors. Selective detection of dopamine and uric acid

2,2-bis(3-Amino-4-hydroxyphenyl)hexafluoropropane (BAHHFP) was electro-polymerized oxidatively on glassy carbon by cyclic voltammetry. The activity of the modified electrode towards ascorbic acid (AA), uric acid (UA) and dopamine (DA) was characterized with cyclic voltammetry and differential puls voltammetry (DPV). The findings showed that the electrode modification drastically suppresses the response of AA and shifts it towards more negative potentials. Simultaneously an enhancement of reaction reversibility is seen for DA and UA. Unusual, selective preconcentration features are observed for DA when the polymer-modified electrode is polarized at negative potential. In a ternary mixture containing the three analytes studied, three baseline resolved peaks are observed in DPV mode. At physiological pH 7.4, after 5 min preconcentration at -300 mV, peaks positions were -0.073, 0.131 and 0.280 V (vs. Ag/AgCl) for AA, DA and UA, respectively. Relative selectivities DA/AA and UA/AA were over 4000:1 and 700:1, respectively. DA response was linear in the range 0.05-3 muM with sensitivity of 138 muA muM(-1) cm(-2) and detection limit (3sigma) of 5 nM. Sensitive quantification of UA was possible in acidic solution (pH 1.8). Under such conditions a very sharp peak appeared at 630 mV (DPV). The response was linear in the range 0.5-100 muM with sensitivity of 4.67 muA muM(-1) cm(-2) and detection limit (3sigma) of 0.1 muM. Practical utility was illustrated by selective determination of UA in human urine.