Fast Red is a widely used chromogen for immunohistochemical staining. When in the presence of alkaline phosphatase (AP) enzyme, intelliPATH FLX™ Fast Red produces a bright fuchsin-red precipitate that is insoluble in organic solvents—and can be coverslipped with a permanent mounting media. This product is available in a stable two-component system, consisting of Fast Red Chromogen and Buffer. When using an alkaline phosphatase system, tris buffer (pH 7.6) should be used as a rinsing buffer. PBS should never be used! Phosphates act as a competitive inhibitor to alkaline phosphatase enzymes. For optimum performance, use Immunocare TBS Wash Buffer with AP activator or TBS Wash Buffer, 20X.