Adsorption of Amlodipine at the Surface of Tosyl─Carbon Nanoparticles for Electrochemical Sensing.

The adsorption processes of amlodipine onto hydrophilic carbon nanoparticles (Emperor 2000) are investigated. The significant increase in voltammetric responses for pre-adsorbed amlodipine compared with those for solution confirms high affinity of amlodipine to carbon nanoparticles (possibly due to π-π stacking interaction between aromatic rings of amlodipine and surface-sulfonated carbon nanoparticles). To obtain the optimum of adsorption conditions, the effects of pH, agitation rate, and adsorption time are investigated. Under differential pulse voltammetry conditions, the peak current for the oxidation of amlodipine shows two linear relationships with concentration in the range from 1000 μM to 10.0 μM and 10.0 μM to 10.0 nM. The limit of detection is estimated to be 1.0 nM. Determination of amlodipine in real samples such as human serum and commercial tablets is demonstrated.