Ritalinic acid is an inactive, major metabolite of methylphenidate, a schedule II drug in the United States commonly used as a psychostimulant drugs methylphenidate and ethylphenidate. The elimination half-life of methylphenidate is relatively short (approximately 2 hours); therefore it is also available in extended release (ER) forms. The main metabolite is ritalinic acid, and the methylphenidate metabolites are mostly excreted in urine.

Racemic alpha-alkyl-alpha-amino-acids are difficult solutes to resolve on chiral chromatographic phases derived from proline or pipecolic acid-polyacrylamide. The use of L-3-carboxy-1,2,3,4-tetrahydroisoquinoline (L-porretine) as the chiral selector instead of the former alpha-amino-acids selectively resolves the alpha-alkyl-alpha-amino-acids.