Separation and determination of n-alkylamines by reversed-phase high-performance liquid chromatography coupled with merging zone derivatization to water-soluble Schiff bases

Abstract

Separation and determination of n-alkylamines were investigated with anionic aldehydes to form water-soluble Schiff bases by using reversed-phase high-performance liquid chromatography (RP-HPLC). Two labeling reagents of salicylaldehyde-5-sulfonate (SAS) and 4-(4-sulfophenylazo)-1-hydroxy-2-naphthaldehyde (SPAHNA) were investigated. Sample solution containing the analytes and reagent solution were simultaneously injected and merged in the flow line, and water-soluble Schiff bases were formed in the reaction tube with its length of 5 m and at 70°C. The Schiff bases were resolved with water-methanol eluent on a reversed-phase column and photometrically detected. The entire analysis time including on-line derivatization, column separation and detection was accomplished within 25 min with SAS and 18 min with SPAHNA. The determination range for the n-alkylamines are 0∼50 μM with the limit of detections at 0.5∼1.0 μM for SAS and 0.08∼0.20 μM for SPAHNA.