Determination of melamine in dairy products using electromembrane–LPME followed by HPLC

Abstract

This study presents the application of electromembrane microextraction technique combined with HPLC-UV detection for fast extraction–preconcentration and determination of melamine in dairy products. It is based on the extraction of charged melamine molecules migrated from 6.5mL feed solution through a liquid membrane immobilized in the pores of a hollow fiber into 20μL of the acceptor solution. The best performance was achieved by using 2-nitrophenyloctylether, tris-(2-ethylhexyl) phosphate (10%) and di-(2-ethylhexyl)phosphate (10%) as the extraction solvent; application of a potential of 90V as the driving force and by adjusting the pH of feed and receiving phases at 5.5 and 1, respectively. The working range was 7–8000ngmL−1, with detection limit of 2.0–5.8ngmL−1. The enrichment factor was in the range 82–192. Intra- and inter-day relative standard deviations were less than 6.6%. Extraction and relative recoveries for different samples were between 25–59% and 85–95%, respectively.