IMPROVACUTER® Gel & heparin tube is a kind of anti-coagulation tube with inert separation gel at the bottom of heparin tube. Through centrifugation, the separation gel can form a barrier between plasma and blood cell and prevent substance exchange between them, while keeping the original characters of plasma. Plasma specimen obtained is the best choice for electrolyte test, and is also used for plasma analysis in routine biochemistry and any emergent biochemistry. The specimen could be put into the equipment directly and kept stable in cold storage for 48 hours, which favors the specimen retest.