A thin layer chromatographic method for high volume screening of urine for methylphenidate abuse

A thin layer chromatographic (TLC) method for the high volume screening of urine for methylphenidate (Ritalin) abuse is presented. The method utilizes charcoal extraction of ritalinic acid from urine and a simple test-tube methylation step for the conversion of the ritalinic acid to methylphenidate. The methylphenidate is then subjected to a routine TLC drug procedure for subsequent qualitative identification.