Colorimetric Assay of Unfractionated Heparins (UH) and Low Molecular Weight Heparins (LMWH).Chromogenic substrate CBS 31.39, ~13 æmoles/vial, freeze-dried; purified bovine ATIII, freeze-dried; purified bovine factor Xa, 45nKat/vial, freeze-dried; Tris buffer.