Abstract: It is known that chromogenic materials which yield a color reaction when in the presence of a peroxide of the formula ROOR' which decomposes to yield ROR' and oxygen are unstable when in the form of working solutions for use in chromogenic reactions. Such compositions which also contain the peroxide required for such reactions are also unstable, leading to premature appearance of color. Stable chemical compositions are disclosed herein containing chromogenic materials and containing mixtures of chromogenic materials and peroxides, which can be used in chromogenic reactions after having been stored for long periods of time. Stabilizing chemical compositions and methods are also disclosed for obtaining such stable compositions.

Abstract: Peroxidatively active enzyme assays have a variety of clinical and industrial applications. Such assays are based on color development resulting from the addition of the appropriate substrate to the enzyme-containing medium. The stability of the said substrate and the extent of appearance of color are two serious limitations in enzyme assays. A method is disclosed herein for carrying out peroxidatively active enzyme assays when the enzyme is in free solution or in cell-bound form. Stable chemical compositions are also disclosed for use as substrates for carrying out such method.