Ion-selective electrode for procainamide determination in blood serum

A procainamide-selective electrode was constructed and applied for the determination of procainamide concentration in blood serum. The detection limit was 1.5 μg ml−1, but determination down to 0.5 μg ml−1 was possible with an appropriate calibration. The results correlated well with those obtained by a fluorescence polarization immunoassay which is widely used for the determination of serum procainamide concentration. The present method is simple, rapid, economical and is unaffected by common cations present in blood and only slightly by N-acetylprocainamide, a metabolite of the drug. It is therefore useful for therapeutic drug monitoring in a clinical setting.