Electrochemistry of hydrophobic Nafion gels Part 3. Preconcentration and electrochemical detection of cationic and neutral organic compounds in hydrophobic Nafion gels made from various n-alkylphosphates

Application of a Nafion-modified carbon paste electrode for the absorptive stripping voltammetric determination of fenoterol in pharmaceutical preparations and biological fluids

The preconcentration of fenoterol on a Nafion-modified carbon paste electrode and its subsequent determination using differential pulse voltammetry is described. The effect of pH and percentage Nafion concentration on the accumulation behaviour of fenoterol was studied, and accumulation curves, calibration graphs and reproducibility studies at two different Nafion concentrations have been carried out in the range 2.5 x 10(-8)-5.0 x 10(-7) M fenoterol. A limit of detection in aqueous solutions, calculated using a signal-to-noise ratio (S/N) of 3, was 9.0 x 10(-9) M. Application of the electrode to pharmaceutical preparations, without sample pretreatment, resulted in acceptable deviation from the stated concentration (RSD = +/- 3.81%, n = 4). For more complex matrices, a suitable extraction procedure was developed, resulting in recoveries of > 90% (urine) and > 75% (serum).