Determination of taurine in plasma by high-performance liquid chromatography using 4-(5,6-dimethoxy-2-phthalimidinyl)-2-methoxyphenylsulfonyl chloride as a fluorescent labeling reagent.

A sensitive high-performance liquid chromatography method for the determination of taurine in human plasma was developed. Taurine and N-methyltaurine (internal standard) were derivatized with 4-(5,6-dimethoxy-2-phthalimidinyl)-2-methoxyphenylsulfonyl chloride to produce fluorescent sulfonamides. The labeling reaction was carried out at 70 degrees C for 20 min at pH 7.5. The fluorescent derivatives were separated on a reversed-phase column by a stepwise elution using (A) acidic phosphate buffer/acetonitrile (83/17) and (B) acetonitrile and detected by fluorescence measurement at excitation and emission wavelengths of 318 and 392 nm, respectively. The detection limit (signal-to-noise ratio=3) of taurine was 3 fmol per injection. The within-day and day-to-day relative standard deviations were 3.0-4.8 and 2.5-4.7%, respectively. The concentration (means) of taurine in normal human plasma was 48.9+/-7.5 microM.