ABSTRACT
In this study, a capillary electrochromatography (CEC) method coupled either with UV or mass spectrometric detection was developed for the detection of trace-amounts of melamine and its related by-products (ammeline, ammelide, and cyanuric acid). A series of poly(divinyl benzene-alkene-vinylbenzyl trimethylammonium chloride) monolithic columns, which were prepared by a simple in situ polymerization with divinyl benzene (DVB), vinylbenzyl trimethylammonium chloride (VBTA) and different types of alkene monomers such as 1-octene, 1-dodecene or 1-octadecene were used as separation columns, with the poly(DVB-1-dodecene-VBTA) monolith as the optimal chromatographic material because it provided a better separation. The detection limits of four melamine derivatives were in the ranged of 0.6-2.18 mg L(-1) by the optimal CEC-UV mode, and were reduced from 2.2 to 19.4 µg L(-1) by the optimal CEC-MS mode. Finally, the proposed CEC methods successfully determined melamine contaminations (0.1 mg L(-1) per analyte) in several dairy products as test samples with analyte recovery range of 69-85% (intra-day) and 68-75% (inter-day), and with peak area reproducibility range of 4.3-8.6% and 8.7-15.6% for intra-day and inter-day, respectively. This is the first report for CEC separation coupled with MS detection applied in trace melamine residue analyses with a faster separation and comparable or even better detection ability than previous GC-MS, CE-MS, as well as LC-MS methods.
