For research use only. The Rox Factor IX kit if for the determination of Factor IX (FIX) activity in FIX preparations, including potency assignment of FIX concentrates. FIX activity is determined in a chromogenic method, in which human FIX is activated by bovine FXIa and where formed FIXa activates human FX in the presence of human FVIII, calcium ions and phospholipid. Similar to in vivo conditions, FVIII is activated by thrombin which is generated during the incubation. The amount of FXa formed is determined from the hydrolysis of a chromogenic FXa substrate. The FIX activity of the sample is assigned vs. a FIX concentrate standard with FIX potency expressed in International Units (IU).