Quantification of ricinine in rat and human urine: a biomarker for ricin exposure.

Ricin is a toxalbumin derived from the castor bean plant, Ricinus communis. Ricinine is an alkaloid (3-cyano-4-methoxy-N-methyl-2-pyridone) that shares a common plant source with ricin, and its presence in urine infers ricin exposure. A new quantification method for ricinine was developed that uses solid-phase extraction to prepare 1-mL urine samples (81% recovery) for a 5-min, isocratic high-performance liquid chromatography method, followed by electrospray ionization tandem mass spectrometry.