Evaluation of plasma 3-methoxy-4-hydroxyphenylglycol.

A high-performance liquid chromatographic (HPLC) assay suitable for the evaluation of 3-methoxy-4-hydroxyphenylglycol (MHPG) in 1-ml aliquots of plasma is presented. Preparatory steps include extraction into ethyl acetate and minicolumn chromatography. Recoveries are monitored with [3H]MHPG. The HPLC procedure utilizes a C18 column, isocratic elution and amperometric detection. The assay was checked against a gas chromatographic-mass spectrometric procedure; the two procedures correlated well with a correlation coefficient of 0.99. Intra-assay reproducibility was 5.4%, inter-assay reproducibility 10.7%. Immediate changes in the orthostatic position did not affect the plasma MHPG concentration. Based on 22 normal controls the daytime plasma MHPG level was 2.98 +/- 0.66 ng/ml (mean +/- S.D.).