Determination of Dopamine and Its Metabolites in Mice Striatum by Ultra-High Performance Liquid Chromatography Tandem Mass Spectrometry

A method was proposed for the simultaneous determination of dopamine (DA) and its metabolites of high protocatechuic acid (DOPAC) and high vanillic acid (HVA) in mice striatum by ultra-high performance liquid chromatography tandem mass spectrometry. About 10 mg of mice striatum was extracted with 200 μL of 2% (volume fraction) formic acid solution and centrifuged. The supernatant (80 μL) was taken and 10 μL of 40 μg·L^-1 isoproterenol (internal standard) solution and 10 μL of methanol solution containing 0.1% (volume fraction, the same below) acetic acid were added. After vortex mixing, 100 μL of methanol was added, followed by vortex mixing and centrifugation. The DA and its metabolites in the supernatant were separated on a Gemini NX-C₁₈ column using a mixture of 0.1% acetic acid solution and methanol solution containing 0.1% acetic acid at different volume ratios as the mobile phase for gradient elution. And the mass spectrometry analysis was performed by electrospray ion source with positive and negative ion modes, and scanned by selective reaction monitoring (SRM) mode. As shown by the results, the three targets could be determined within 7.00 min. The linear ranges of the standard curves for DA, DOPAC and HVA were 0.05-100, 0.5-1 000, 0.25-500 μg·L^-1, and the detection limits were 0.015, 0.150, 0.075 μg·L^-1, respectively. According to the standard addition method, the recoveries of the three targets ranged from 84.4%-117%. RSDs of the determined values of tests for intra-day precision and inter-day precision were less than 15%. The determined values of the relative error for the three targets in quality control samples stored in an autosampler for 8 h, at 4℃ for 24 h and at -80℃ for 30 d were not more than 20%, indicating good sample stability.