A simple and highly sensitive HPLC method with fluorescent detection for determination of pipecolic acid in mouse brain areas.

A simple and highly sensitive high-performance liquid chromatography method for the determination of pipecolic acid in mouse brain areas was developed. After homogenization of brain and pretreatment with o-phthalaldehyde, the pipecolic acid and (2S,3S)-3-methylpyrrolidine-2-carboxylic acid (internal standard) were derivatized with 4-(5,6-dimethoxy-2-phthalimidinyl)-2-methoxyphenylsulfonyl chloride at 70 °C for 15 min in basic medium (pH 9.0). The fluorescent derivatives of pipecolic acid and internal standard were separated on a reversed-phase column by stepwise elution using acetic acid (30 mM)-acetonitrile at 50 °C and detected by fluorescence measurement at 316 nm (excitation) and 403 nm (emission). The detection limit (signal-to-noise ratio=3) of pipecolic acid was 13 fmol per injection. The recovery was about 106.7%. The precision (relative standard deviation) was 3.2%.