Determination of aromatic amines in food products and composite food packaging bags by capillary electrophoresis coupled with transient isotachophoretic stacking.

A capillary electrophoretic method was explored to assay aromatic amines in food samples. With an inline-coupled transient isotachophoretic stacking approach, the method has yielded about 200-fold improvement of sensitivity in UV detection of three primary aromatic amines and melamine. By using K(+) as a leading ion and Tris(+) as a terminating ion, a plug of 10 cm (equivalent to 0.44 microL) sample solution was allowed to introduce into a 60 cm (50 cm effective) capillary for separation, giving limits of detection down to 2.0 x 10(-8)M. Baseline separation was achieved within 10 min, with relative standard deviation of 0.41-0.75% (intra-day) or 1.2-1.5% (inter-day) for migration time and 3.8-4.3% (intra-day) or 5.2-6.7% (inter-day) for peak area. The method was directly applicable to assaying the melamine in powder milk samples, with recovery in between 92.0% and 107.1%. The method could also be applied to the analysis of trace primary aromatic amines migrating from composite food packaging bags after combination of a 10-fold off-line concentration step, with limit of detection down to less than 1 microg/L. By this method, 4,4'-diaminophenylmethane and 2,4-diaminotoluene were thus found in three types of composite food packaging bags.