A NEW SOLID-PHASE EXTRACTION METHOD FOR H UMAN URINARY 3-METHOXY-4-HYDROXYPHENYLETHYLENEGLYCOL

A new solid-phase extraction procedure for urinary 3-methoxy-4-hydroxy -phenylethyleneglycol (MHPG) was established. Sep-Pak Diol cartridge w as used, because MHPG is a neutral and alcoholic compound. Aqueous sam ples were adsorbed to the cartridge, then MHPG was eluted by the addit ion of ethyl acetate. After the eluate was evaporated, the residuum wa s dissolved with HPLC mobile phase and injected into HPLC. The extract ion procedure was highly specific to MHPG, and none of other acidic ca techolamine metabolites, such as vanillylmandelic acid (VMA), homovani llic acid (HVA) and 3,4-dihydroxy-phenylacetic acid (DOPAC), was extra cted. The recovery of MHPG using this method was over 90% and higher t han those using previously described methods such as liquid-liquid ext raction with ethyl acetate. Of the three vanillyl alcohol isomers, iso vanillyl alcohol was the most suitable as an internal standard for the correction of column-to-column variation of the recovery. Human urina ry unconjugated MHPG extracted by the new procedure could be measured by HPLC with a fluorescence detection. Further complicated derivatizat ion and more sensitive detection systems, such as GC-MS and HPLC-elect rochemical detector (ECD), were not needed due to high selectivity and high recovery of the extraction procedure. In addition, the urinary t otal (conjugated plus unconjugated) MHPG content could also be determi ned by the same procedure after an enzymatic hydrolysis of conjugated MHPG. The newly developed extraction procedure was simple, rapid and h ighly specific, and might be applicable to the analysis of MHPG in var ious body fluids.