A novel approach to determine the tyrosine concentration in human plasma by DART-MS/MS

Abstract

A novel method for determining the tyrosine (Tyr) concentration in human plasma using direct analysis in real time mass spectrometry (DART-MS/MS) was developed. DART-MS/MS was performed in the positive ionization mode with multiple reaction monitoring (MRM) while using the ion transitions at m/z of 182.2/136.2 (Tyr). The experimental conditions and the sample preparation method were optimized to maximize the signal intensity. The linear range was determined to be 2–50 μg mL⁻¹ from the calibration curve. The limit of quantification (LOQ) was 2 μg mL⁻¹. The intra- and inter-day precisions did not exceed 15%, and the accuracies were less than ±15% for the 4, 18 and 38 μg mL⁻¹ quality control (QC) samples. In addition, the extents of the matrix effects for the QC samples were also evaluated. Using the proposed method, samples could be analyzed simultaneously. The proposed DART-MS/MS-based method is not only rapid and simple with a high throughput but is also economical, as a mobile phase is not used. Furthermore, the method was used successfully to determine the Tyr levels in the plasmas of healthy volunteers and liver cancer patients. The proposed method should also be theoretically suitable for screening newborn babies for the hereditary tyrosinemia.