Abstract: There is provided a stable cholesterol assay composition which comprises an aqueous solution of at least one bile acid or salt thereof being present in an amount of up to about 5 mM; a nonionic surfactant present in an amount of from about 0.15 to about 1.5 percent volume by volume; a buffer in a concentration of from 0 to about 65 mM; and cholesterol oxidase in a concentration of at least about 0.1 KIU/l. Solution pH is from about 5.5 to about 8.5. Addition of cholesterol esterase, phenol, peroxidase and 4-aminoantipyrine provides a total cholesterol chromogen system.

Abstract: There is provided an assay method for determining the concentration of magnesium ions in biological fluids. The method comprises the introduction of a sample of biological fluid to a magnesium-free assay solution containing at least one reactant and an enzyme capable of catalyzing a reaction with at least one reactant wherein the enzyme activity, and hence the rate of reaction, is partially or totally dependent on and correlatable to the concentration of magnesium that is present. The rate of reaction is measured by monitoring the loss of a detectable reactant or the formation of a detectable product.