A sensitive and validated HPLC method for the determination of cyromazine and melamine in herbal and edible plants using accelerated solvent extraction and cleanup with SPE.

A highly sensitive method was developed for the determination of the residues of cyromazine (CYR) and its metabolite, melamine (MEL), in herbal and edible plant samples by using reversed phase high-performance liquid chromatography-diode-array detection (RP-HPLC-DAD) with accelerated solvent extraction and solid phase extraction cleanup. The conditions of separation and detection were investigated and optimized. A Waters C18 column (250 × 4.6 mm i.d., 5 µm) was used for the RP-HPLC, with a mobile phase composed of 0.1% trifluoroacetic acid solution and methanol (85:15, v/v, pH 2.6). Under the optimized conditions, good linearity was achieved with a correlation coefficient of 0.9998. The limits of quantification of the method were 2.15 µg/kg for CYR and 2.51 µg/kg for MEL, which are maximum residue limits as low as three orders of magnitude. The recovery values at three spiked concentrations were in the range of 96.2-107.1% with relative standard deviations (RSDs) of 1.1-5.7% for CYR, and 92.7-104.9% with RSDs of 1.7-6.1% for MEL. The proposed method allows detection at levels as low as µg/kg levels for CYR and MEL. The method was validated by liquid chromatography-tandem mass spectrometry, and can be used for the routine determination of CYR and MEL in herbal and edible plant samples with the characteristics of speed, high sensitivity and accuracy, and low consumption of reagents.