0 5 10 15 Retention time (min)
figure 9.11 HPLC-chromatogram of plum leaf extract purified with Dowex 50W-X8 cation exchange resin. Concentration of polyamines: putrescine-0.9 nmol, spermidine-1.6 nmol and spermine-0.2 nmol. (Reproduced with permission from Wehr, J. B. J. Chromatogr. A, 709, 241-247, 1995. Copyright 1995, Elsevier Science.)
nonfluorescent, reacts with primary amines to form an intensely fluorescent isoindole with an absorption maximum at 430 nm, but its use, particularly in a precolumn, is somewhat restricted by its sensitivity to auto-oxidation and attack by light and acids. NDA also forms a more stable isoindole derivative than OPA product from a primary amine. The improvement in stability results, in part, from the use of cyanide instead of a thiol as a nucleophilic reagent, resulting in substitution of a nitrile group instead of a thiol group on the isoindole ring.
The determination of primary and secondary amines in foodstuffs was carried out by Pfundstein et al.59 by gas chromatography with a modified thermal energy analyzer, operated in nitrogen mode. A few samples were subjected to mineral oil vacuum distillation, then the isolated amines were derivatized with BSC to form the corresponding sulfonamides which were fractionated to yield primary and secondary derivatives using a modified Husberg procedure. The choice of BSC derivatives for amine analyses by GC has two major advantages over other commonly used derivatization techniques. The identification of unknown compounds is simplified, as fractionation using a modified Husberg method immediately allows the distinction between primary and secondary amines. Further, benzene sulfonamides have very characteristic mass spectral fragmentation patterns of ion masses (if m/c 77 and 141) relating to the structure of the derivatization reagent, which can be easily located using GC-MS-SIM for gaining structural information on the suspected
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