2- Sodium citrate is used in coagulation studies.Therefore, 3.2% sodium citrate tubes contain 3.2 grams of sodium citrate per 100 ml of solution, and this is the preferred concentration for conducting these coagulation studies such as: pT, APTT, also 3.8%, contains 3.8 sodium citrate per 100 ml of solution.Who have abnormal hematocrit levels.The most commonly used concentrations are 3.2% and 3.8%.