A Rapid, Precise, and Sensitive LC-MS/MS Method for the Quantitative Determination of Urinary Dopamine Levels via a Simple Liquid-liquid Extraction Technique

Objectives: Dopamine (DA) is a prominent biochemically complex neurotransmitter and immunomodulator. The quantification of DA could contribute to a better understanding of how endocrine system, cardiovascular and renal functions are regulated. The study aims to develop a rapid, precise, and extremely sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for routine clinical quantification of DA in urine. Materials and Methods: Urine samples were extracted via one simple and rapid liquid-liquid extraction technique; then analyzed using a sensitive LC-MS/MS method developed by multiple reaction monitoring mode. Results: DA and internal standard (IS) retention durations were found to be 2.28 min and 2.24 min, respectively. The mean extraction recovery of DA and DA-IS in urine was above 95.62%. DA calibration curve in urine was linear (r(2)>= 0.998) ranging from 20 ng/mL to 1000 ng/mL. The maximum intra-day and inter-day precisions were 5.87 and 2.81, respectively and coefficients of variation were 10.55% and 7.57%, respectively. Conclusion: A rapid, precise, sensitive and quantitative LC-MS/MS detection of DA without the use of derivatization, evaporation, reconstitution and ion-pairing reagents has been developed with a simple and non-invasive sample technique for clinical laboratory applications, basic neuroscience research and drug development studies.