The 500 µg purified IL-5 capture antibody is buffered in a preservative-free phosphate solution, pH 7.2, and the 100 µg purified IL-5 biotinylated detection antibody is buffered in a phosphate solution, pH 7.2, containing 0.09% sodium azide. Streptavidin alkaline phosphatase is supplied in a Tris Buffer, pH 8.0, containing 0.1 M sodium chloride, 1 mM magnesium chloride, 0.2% (w/v) BSA, 10% (w/w) glycerol, and 0.1% sodium azide.