Abstract
HPLC with electrochemical and spectrophotometric detection (ED/UV) after solid phase extraction (SPE) was used for determination of vanillylmandelic acid in human urine. HPLC-ED was performed at a glassy carbon electrode in a "wall-jet" arrangement in acetate-phosphate buffer at pH = 2.5 and gradient elution (increasing content of acetonitrile from 5 to 25% in 10 minutes) was used.
Optimized parameters were following: flow rate of mobile phase 1 mL min(-1), detection potential +1.1 V, detection wavelength 279 nm, injected volume 20 mu L. Dependence of the peak current on the analyte concentration was linear in the concentration range from 10 to 150 mu mol L-1, with obtained limits of detection 2.6 mu mol L-1 (calculated from peak height) and 1.9 mu mol L-1 (calculated from peak area) for HPLC-ED, and 11.0 mu mol L-1 (calculated from peak height) and 9.8 mu mol L-1 (calculated from peak area) for HPLC-UV.