1. When determining endotoxin in blood, pay attention to the selection of methods and reagents.

2. Preparation of plasma or serum

As a common clinical sample, plasma is the main sample, and its utilization rate is more than 95%. Therefore, it is very important to prepare plasma as the main part of body fluid. According to Das, endotoxin is generally attached to platelets in addition to its free state, so it is more appropriate to use plasma containing a large number of platelets as a sample. When preparing human plasma or animal plasma, at present, in order to prevent cell damage, foreign countries mostly use low-temperature separation, using plasma samples containing a large number of platelets, that is, at 4 ℃ 1000gx10 minutes separation conditions, or 3000gx40 seconds separation conditions when there is no low-temperature centrifuge. It is not allowed to conduct high-speed and long-term separation under normal temperatures. In addition, when separating plasma or serum, bacterial contamination should be avoided.

Preparation of serum: use a syringe without anticoagulant to collect blood and transfer it into a centrifuge tube, and place it in an ice water bath for 30 minutes, at 4 ℃, 1000xg, 10 minutes for centrifugation.

After separation of plasma or serum, if not used temporarily, it can be frozen at - 80 ℃ and used within 1 month. Note In order to avoid the adsorption of endotoxin, please use a glass test tube for storage.

3. Types and effects of anticoagulants

During the preparation of plasma, due to the addition of certain anticoagulants, the type and amount of anticoagulants have a great impact on the recovery rate. Generally, commonly used anticoagulants mainly include heparin, sodium citrate, and EDTA, among which heparin is the most widely used. However, we know that a large amount of heparin will interfere with the endotoxin reaction, especially for the dilution heating method and chloroform extraction method, which will reduce the recovery rate, but have less impact on the PCA method, so the amount of heparin added and released during plasma preparation only needs 2~5 μ L/ml is enough.