FURTHER OBSERVATIONS ON GAS-CHROMATOGRAPHIC MEASUREMENT OF URINARY PHENOLIC AND INDOLIC METABOLITES

Previous gas-liquid Chromatographie (GLC) studies on urinary phenolic and indolic metabolites and accompanying extraction and preparative procedures have been extended. Whilst ethyl acetate and ether were both suitable for the extraction of phenolic compounds from urine, with a few exceptions, only the latter is recommended for indolic metabolites. Metabolites were selectively extracted into organic solvent by suitably adjusting the pH of the aqueous solution. Thus all acids were extracted at pH 2; between pH 3 and 5 only weaker acids were readily removed; at pH 8 neutral compounds were still extracted but acids now remained in the aqueous phase. Conditions have been devised to minimise O-methylation during the preparation of methyl ester derivatives. Quantitation has been improved; indolic compounds at concentrations present in normal urine may now be measured. Using the refined techniques for their estimation, the normal output (20 subjects) of the catecholamine metabolites, homovanillic acid, 4-hydroxy-3-methoxymandelic acid and 4-hydroxy-3-methoxyphenylglycol were (mean ± S.D.) 4.2 ± 1.5 mg/24h, 5.7 ± 1.3 mg/24hand 2.4 ± 0.8 mg/24 h respectively. © 1969.