High-performance liquid chromatography with ultraviolet or electrochemical detection for the determination of...

The high-performance liquid chromatographic (HPLC) analysis of dopazinol, an anti-Parkinsonian drug, using either ultraviolet (UV) absorbance detection at 282 nm or oxidative amperometric electrochemical detection at the glassy carbon electrode (+0.92 V vs. Ag/AgCl) is described and evaluated. The influence of such factors as mobile phase composition, pH and column temperature on the detection of dopazinol using both detectors is reported. The HPLC analysis of samples resulting from the development and evaluation of a pharmaceutical formulation demonstrated a precision of less than 2.5% (R.S.D.) in the working ranges of the UV and electrochemical detectors. The limits of detection were 100 ng/ml for the UV detector and 1 ng/ml for the electrochemical detector. The higher sensitivity of the latter makes its use appropriate for the analysis of samples with low concentrations of dopazinol. Studies to compare the UV and electrochemical detectors for the routine analysis of dopazinol in pharmaceutical formulations are presented.