Naphthalene-2,3-dicarboxaldehyde as a pulsed-post column derivatization reagent; comparison with two alternative o-phthalaldehyde based chemistries for the determination of histamine

In the present study, naphthalene-2,3-dicarboxaldehyde (NDA) was used in on-line post column derivatization (PCD) coupled to liquid chromatography under the new concept of Pulsed-PCD. In Pulsed-PCD, the reagents are introduced into the flowing stream of the mobile phase under precise timing overlapping the eluted analyte. The consumption of the reagents is minimized to a few microliters, resulting in a significant advantage, that is the use of expensive reagents in PCD. For this reason, NDA-CN chemistry was used for the determination of histamine in food samples, such as eggplant and spinach. Two additional methods were developed based on the reaction of histamine with o-phthalaldehyde (OPA), namely the classic OPA - nucleophilic compound reaction and the specific OPA - histamine reaction in alkaline medium. The chromatographic conditions and the Pulsed-PCD conditions were investigated, while the analytical figures of merit were satisfactory. In all three methods, a pulse of 50 & mu;L was used (OPA/NDA + Buffer), reducing dramatically the consumption of PCD reagents.

Automated summary

In this study, naphthalene-2,3-dicarboxaldehyde (NDA) was used in Pulsed-PCD, a new concept for on-line post column derivatization (PCD) coupled with liquid chromatography. The use of expensive reagents in PCD was minimized by introducing the reagents into the mobile phase flow at precise timing. NDA-CN chemistry was applied to determine histamine in food samples, while two additional methods based on histamine reactions with o-phthalaldehyde (OPA) were developed. The consumption of PCD reagents was significantly reduced by using a 50 μl pulse (OPA/NDA + Buffer) in all three methods.