Electrochemical determination of electroinactive guests of ?-cyclodextrin at a self-assembled monolayer interface

Abstract

A novel determination method of electroinactive molecules by means of electrochemical technique is presented. A new self-assembled monolayer containing cyclodextrin (CD) is prepared with mono(6-o-p-tolylsulfonyl)- β -cyclodextrin. Although this derivatization process leads to a β -CD coverage of 10% of a full monolayer, this layer shows an effective host-guest response to ferrocene. The interfacial ferrocene complexation gives a response similar to that expected for a Langmuir adsorption isotherm yielding a stability constant of 4.2×10 4 mol -1 ·L and a maximum ferrocene coverage of 8.6´10 -12 mol/cm 2 . The redox peak currents of the surface-confined ferrocene decrease upon addition of competing β -CD guest species to the solution, such as m-toluic acid (mTA) and sodium dodecyl sulfonate (SDS). This principle has been used for the determination of the electroinactive molecules, mTA and SDS in the concentration ranges of 0.8—2.7 mmol/L and 5—100 nmol/L, respectively.