Sodium citrate 9: 1 tube, cap color: blue, blood volume: 1.8ml-4.5ml, material: glass, plastic, double plastic, size: 13 * 75/13 * 100 mm for clinical examination Coagulation mechanism (PT, APTT, hemagglutination factor) test. Sodium citrate concentration of 109mmol / L., The exact ratio of blood and anticoagulant was 9: 1. The double-layer plastic pipe inner tube material is PP (polypropylene), which prevents the gradual evaporation of the liquid additive to ensure the long-term stability of the sodium citrate solution concentration. In addition, the dry surface is advantageous for obtaining accurate and reliable test results. The material of the outer tube is PET, which ensures the long-term stability of the vacuum during the shelf life. The PET and PP material can withstand 2500-3000 g of relative centrifugal force to obtain platelet-free plasma (PFP).