Effective separation and simultaneous detection of cyromazine and melamine in food by capillary electrophoresis

A novel and simple method was, for the first time, developed for effective separation and sensitive detection of cyromazine (CM) and its metabolite melamine (MM) by CZE with DAD (CZE-DAD). Among different solvents, ACN containing 20% NH4OH was found to be the best one as an extractant of CM and MM in real samples. After centrifugation and filtering, the extract was analyzed by CZE-DAD directly. The linearity is good in the range of 0.7-50 mg/L With correlation coefficient (r) of 0.9998. Under the optimal conditions, the method LOQ for the two analytes was 0.38 mg/kg for feed samples and 0.42 mg/kg for egg and liquid milk samples. The peaks of MM and CM were identified by comparison of their migration times in real samples with that in standard solution and spiked sample. The effective baseline separation and high sensitivity of MM and CM were achieved. The proposed method has been applied successfully for the quantitative determination of CM and MM residues in real samples. The average total recoveries ranged from 92.5 to 97.4% with the RSD of 3.0-5.1% for CM and from 93.0 to 97.6% with the RSD of 2.8-4.9% for MM. The proposed method offers the effective separation selectivity of CZE as well as a quicker analysis time for simultaneous determination of CM and MM in feed, egg and liquid milk.