Analysis of free amino acids in green coffee beans. I. Determination of amino acids after precolumn derivatization using 9-fluorenylmethylchloroformate.

For the determination of free amino acids in green coffee beans, 9-fluorenylmethylchloroformate was applied successfully as the precolumn derivatization agent. The separation of the 27 free amino acids of green coffee as yet identified or quantitatively determined is almost complete. The paper describes in detail the conditions of extraction, derivatization and resolution and presents reproducible data of standard curves and of quantitative results. It has been demonstrated that by applying the extraction procedure described, 99.8% of the free amino acids detectable by this method are extracted. On principle, Arabica and Robusta coffees contain the same main and minor amino acids. It was possible for the first time to determine the free amino acids ornithine, beta-alanine and pipecolic acid quantitatively in Arabica and Robusta coffees as well as hydroxyproline in Arabica coffees.