Determination of melamine in rat plasma, liver, kidney, spleen, bladder and brain by liquid chromatography–tandem mass spectrometry

In this study, we describe a method for the analysis of melamine in rat plasma, liver, kidney, spleen, bladder, and brain using trichloroacetic acid precipitation with mixed-mode cation-exchange solid-phase extraction and hydrophilic interaction chromatography coupled to tandem mass spectrometry detection. Method validation was investigated completely, including linearity, precision, accuracy, matrix effect, extraction recovery, and carryover for the determination of melamine. The method exhibited a good linear range covering 20–500 ng/mL, and the overall precision ranged from 1.6 to 16.3%, with the accuracy varying from −7.9 to 15.1%. The mean matrix effects of melamine in rat plasma, liver, kidney, spleen, bladder, and brain ranged from 66.2 ± 6.7 to 95.5 ± 13.2%, and the mean recoveries for melamine varied from 79.8 ± 8.2 to 113.0 ± 9.6%. Rat kidney showed the highest level among the organs (192.5% of the plasma melamine level), and the average concentration of melamine in the brain was only 7.5% of the plasma melamine concentration. This work has pointed out that even with the application of two popular preparation procedures (acid precipitation and solid-phase extraction) of melamine, the matrix effect in analyzing biological samples still exists in certain kinds of matrices.