A SIMPLIFIED ROUTINE ASSAY FOR URINARY 3-METHOXY-4-HYDROXYPHENYLGLYCOL

Urinary 3-methoxy-4-hydroxyphenylglycol (MHPG) level may provide us wi th a biochemical index for central noradrenergic activity. Previous me thods for assaying MHPG ill urine often lacked specificity, sensitivit y, cost-effectiveness or convenience. We now describe a simplified rou tine assay for urinary MHPG by high-pressure liquid chromatography usi ng electrochemical detection. For convenience and cost-effectiveness w ithin a typical batch assay of total MHPG, 0.5 mL of urine sample, 50 mu L of glusulase and 4 mu g iso-vanillyl alcohol (internal standard) were used to hydrolyze conjugated MHPG at 37 degrees C overnight. Alte rnatively, for a same-day operation, it is efficient to hydrolyze the sample at 50 degrees C for 3 hours. Each sample was separated isocrati cally on a reversed-phase column (Ultracarb 5 ODS) at 25 degrees C wit h the flow rate at 1 mL/min. Intra- and inter-assay coefficients of va riation were found to be 4.0% (n = 10) and 5.0% (n = 27), respectively , for MHPG at a mean concentration of 1.9 mg/L. Sulfatase or glucuroni dase can be substituted for glusulase to obtain either sulfate- or glu curonide-conjugated MHPG. This procedure requires smaller sample amoun ts and less preparation time without compromising sensitivity and repr oducibility.