Cucurbit[8]uril-based electrochemical sensors as detectors in flow injection analysis. Application to dopamine determination in serum samples

The results of the development of cucurbit[8]uril (CB[8]) electrochemical sensors and their performance as electrochemical transducers in a flow injection analysis (FIA) system are described. Two electrodes were designed, using either PVC or Nafion, to immobilise the macrocyclic receptor on a glassy carbon electrode (GCE) surface and used for dopamine (Dop) determination. 1H NMR and MS experiments were conducted to corroborate the formation of the CB[8]–Dop complex formation. Once all of the experimental variables were optimised, the developed methodologies achieved Dop detection limits of as low as 9.9 × 10−8 M in the case of the Nafion-CB[8] based electrode and 2.6 × 10−8 M for the case of the PVC-CB[8] electrode. For both sensors, the relative error values, Er (%), were lower than 13.9% and the relative standard deviation, RSD (%), ranged from 1.0% to 9.3% across the concentration range assayed, indicating that the methods proposed under flow conditions were of acceptable accuracy and precision. The electrodes were sufficiently durable to be used under flow conditions with no loss of reproducibility for approx. 85 successive analyses. Under optimised conditions, we were able to obtain sampling frequencies of 55 and 72 samples h−1 for the Nafion-CB[8] and PVC-CB[8]-modified electrodes, respectively. The elimination of any interference from ascorbic acid (Asc) in the Dop analysis demonstrates that the use of CB[8] leads to an additional selectivity in the method.