Abstract
Urine is extracted with ethyl acetate at a highly acid pH. Hydrolysis of the aqueous phase by hydrochloric acid is followed by oxidation of the metanephrines to vanillin using sodium periodate at pH 10–11. After extraction in CH 2Cl 2, vanillin is estimated by gas chromatography as a trimethyl silyl (TMS) derivative. The ethyl acetate phase which contains among others, 4-hydroxy-3-methoxymandelic acid (VMA) is extracted by acetate buffer pH 6.2. VMA is oxidized to vanillin by sodium periodate at pH 11–12. After being extracted in CH 2Cl 2, vanillin is estimated by gas chromatography as a TMS derivative. Results obtained in the estimation of urinary metanephrines as well as VMA are compared with those of Pisano's spectrophotometric procedure.
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