The method used previously for the fluorodensitometric determination of compounds with an alcoholic hydroxyl group was examined for its applicability in high-performance liquid chromatography. The conversion of alcoholic substances into urethanes was performed with naphthyl isocyanate-Chloroform-benzene-ethanol and n-heptanediethyl ether, were used as eluents for the separation of urethanes of various polarity with silica gel columns. Reversed-phase material is also suitable. The detection limits ascertained by means of fluorescence detection are in the picomole range. INTRODUCIION Several workers have reported on the conversion of alcohols into urethanes with phenyl isocyanate and their high-performance liquid chromatographic (HPLC) I-' separation . Fluorescence detection of such compounds is not possible, however. Pn previous papers8sg we described the derivatization of substances with an alcoholic hydroxyl group using fluorescent isocyanates, followed by fluorodensitometric measurement_ Both naphthyl isocyanate (NI) and anthracene isocyanate (AQ can be used for the derivatization of many alcoholic compounds with different structures. owing to *he greater number of rings in the AI mokcule, its reactiviq is lower, especially with tertiary alcohols. This may be balanced by increasing the exc&s of the rea-gent_ However, it was found that this may lead to a complicated separation of the urethanes from the by-products_ This paper describes the use of NL, enabling smalkr amounts of reagent to be used in the determination of compounds with alcoholic hydroxyl groups by means of HPLC with fluorescence detection.