An immunomagnetic electrochemical sensor based on a perfluorosulfonate-coated screen-printed electrode for the determination of 2,4-dichlorophenoxyacetic acid.
A disposable immunomagnetic electrochemical sensor involving a magnetic particle-based solid phase and a Nafion film-coated screen-printed electrode (Nafion-SPE) stuck at the bottom of a polystyrene cylinder (microwell of 300 microL) was developed and evaluated in a competitive immunoassay of the widely used herbicide 2,4-dichlorophenoxyacetic acid (2,4-D). The competitive binding of 2,4-D and 2,4-D labled with alkaline phosphatase (AP) for a limited amount of polyclonal anti-2,4-D antibody-coated magnetic beads was monitored electrochemically by measuring the AP labled++ activity bound to the beads. The phosphoric acid ester of [[(4-hydroxyphenyl)amino]-carbonyl]cobaltocenium hexafluorophosphate was used as the AP substrate. This anionic substrate (S-) is enzymatically transformed at pH 9.0 into a cationic phenol derivative (P+) which can be easily accumulated in the polyanionic Nafion coating and determined by cyclic voltammetry. During the enzyme reaction, the AP-associated beads were localized on the surface of the Nafion-SPE with the aid of a magnet, thus effectively increasing the concentration of P+ in the Nafion-modified electrode vicinity. The enzyme generation of P+ close to the electrode surface, and thereby to the Nafion film, resulted in a high amplification of the response. A detection limit of 0.01 microgram L-1 2,4-D was thus achieved. The performance of the sensor was successfully evaluated on river water samples spiked with 2,4-D, indicating that this convenient and sensitive technique offers great promise for decentralized environmental applications.
Electrosynthèse et Electroanalyse Bioorganique, UMR CNRS 6504, Université Blaise Pascal de Clermont-Ferrand, Aubière, France.
M
M
Dequaire
C
C
Degrand
B
B
Limoges
D015084:2,4-Dichlorophenoxyacetic Acid / Q000032:analysis*; D004563:Electrochemistry; D004566:Electrodes; D005465:Fluorocarbon Polymers; D006540:Herbicides / Q000032:analysis*; D007120:Immunochemistry
D005465:Fluorocarbon Polymers; D006540:Herbicides; D015084:2,4-Dichlorophenoxyacetic Acid; C040402:perfluorosulfonic acid