1. Instruments and medicines
High performance liquid chromatography: Shimadzu NexeraXR, pump: LC-20ADXR, autosampler: SIL-20ACXR, column oven: CTO-20A. Mass spectrometer: ABSCIEXAPI4000, centrifuge: ThermoSORVALLST8R.
Pure L-Tyrosine was purchased from China National Institute of Inspection and Quarantine, and the isotope internal standard solution L-p-hydroxyphenylalanine-D2 was purchased from TLC Company.
2. Chromatographic detection conditions
Chromatographic column: ThermoC183um (2.1×100mm) chromatographic column, the mobile phase A is 0.1% (v/v) formic acid, the B phase is acetonitrile, the flow rate is 0.2-0.3ml/min, the column temperature is 40°C, and the injection volume is 5ul.
3. Preparation of Stock Solution
Preparation of Pure L-Tyrosine stock solution: Weigh 10 mg of p-hydroxyphenylalanine, add ultrapure water with an electric pipette to make the effective concentration 1 mg/ml, and mark it as stock1.
Preparation of L-p-hydroxyphenylalanine-D2 stock solution: Weigh 10 mg of L-p-hydroxyphenylalanine-D2, add ultrapure water with an electric pipette to make the effective concentration 1 mg/ml, and mark it as stock2.
4. Preparation of Standard Curve Solution
Dilute the stock solution stock1 with ultrapure water step by step to 2000ng/ml, 1000ng/ml, 500ng/ml, 100ng/ml, 50ng/ml, 10ng/ml, 5ng/ml, 1ng/ml, respectively take 190ul of the above-mentioned solutions of each concentration, add stock solution Stock210ul, mix well, and obtain the standard curve solution of p-hydroxyphenylalanine.
5. Preparation of urine samples to be tested
Take 1ml of human urine sample, centrifuge at 1500×g/min for 10-15min, take the supernatant, dilute it 50 times, pass through a 0.22um microporous membrane, take 190ul filtrate and add 10ul stock solution Stock2, mix well.
6. Linear analysis
Take the standard curve solution of p-hydroxyphenylalanine obtained in step 4 for liquid phase mass spectrometry detection, and use liquid chromatography-mass spectrometer for detection. The chromatographic detection conditions of Pure L-Tyrosine are the conditions described in step 2. Linear regression analysis was performed with the theoretical value of the corrected concentration in the standard curve as the abscissa and the area ratio of p-hydroxyphenylalanine to the isotope internal standard as the ordinate. The regression curve equation is y=4.31e+003x+1.53e+004 (r=0.9991), and the weight coefficient is 1/x2.
7. Testing of urine samples to be tested
Select 200 urine samples prepared in step 5 for liquid chromatography-mass spectrometry detection, and use liquid chromatography-mass spectrometry for detection. The detection results are brought into the standard curve equation in step 6 to obtain the content of p-hydroxyphenylalanine in the urine sample. Among them, the maximum value is 39407ng/ml; the minimum value is 1260ng/ml; the average value is 11088ng/ml, and the positive rate is 6%.