Determination of urinary vanillylmandelic acid by liquid chromatography with electrochemical detection.

Abstract

Abstract We describe an improved method for the assay of urinary vanillylmandelic acid by "high-performance" liquid chromatography, with electrochemical detection. A 1-mL aliquot of urine is acidified and extracted with ethyl acetate, then the ethyl acetate extract is extracted with phosphate buffer, pH 8.5. An acidified aliquot of the phosphate extract is injected into a reversed-phase column and vanillylmandelic acid is detected electrochemically. The between-day CV is 5-6% for concentrations ranging from 10 to 75 mumol/L. We also discuss the critical steps for extraction and calibration.