Assessment of variants of solid-phase extraction in quantitative analysis of caffeine

Caffeine was recovered for anal. purposes from its aq. solns. by solid-phase extn. in presence of MeOH, MeCN and Me2CO. The apparent recovery degrees were higher than 100% because the signal of high performance chromatog. was disturbed by signals of interfering substances flushed from the column. MeOH was the most appropriate solvent for the recovering caffeine.