Rapid determination of melamine in soil and strawberry by liquid chromatography-tandem mass spectrometry

A fast and sensitive method to determine melamine in soil, strawberry fruit and plant materials using dispersive solid phase extraction (DSPE), and liquid chromatography-electrospray tandem mass spectrometry (LC-ESI-MS/MS) was developed. Validation parameters, including method precision, accuracy, and matrix effect were evaluated. The extraction solvent composition, clean-up adsorbents, and LC-ESI-MS/MS conditions were optimized such that this methodology can be adopted to monitor melamine residue concentration in both environmental, crop and food samples. This method exhibits good linear range from 5 to 500 μg/L (γ > 0.999) with an overall precision between 4 and 7%, 7-10% and 4-8% for soil, strawberry and plant materials, respectively. The mean method recovery varied from 92 to 96% for soil, 87-89% for strawberry, and 76-104% for strawberry plant materials. The limit of detection (LOD) and the limit of quantification (LOQ) for these matrices ranged from 0.2 to 1.3 μg/kg and 0.8-4.4 μg/kg, respectively. The applicability of this melamine residue analytical method was successfully demonstrated using field samples collected from an outdoor field trial.