These authors identified the corresponding butyl and methyl esters of 6 low-molecular weight and 15 high-molecular weight organic acids. Also, according to Balzer (2001), several methods have been applied for organic acid determinations, e.g. GC–MS, CE and high performance liquid chromatography (HPLC)/ UV, but with green coffee samples or roasted coffee from only one or two geographic origins or types of coffee (robusta or arabica).