A large peak of FMOC-OH is present in the chromatogram (see also Fig. 1) and possibly interferes with amino acids derivates. It is often advantageous to reduce or eliminate the reagent peak by extracting with pentane (Bank et al., 1996) or adding 1-adamantanamine (ADAM) or heptylamine to avoid the loss of derivates resulting from the extraction step (Molna´ r-Perl, 2011). Another disadvantage of FMOC-Cl is the formation of monoand di-substituted derivates of amino acids with more than one functional group such as tyrosine and histidine which might complicate the quantification.