Abstract: The invention describes biological assays in which hydrogen peroxide is used as an oxidizing agent, or wherein hydrogen peroxide is used to oxidize a dye or other intermediate to generate a detectable species. The stability of the hydrogen peroxide in the presence of at least one other enzyme which decomposes hydrogen peroxide is enhanced by the addition of a suitable inhibitor for the enzyme and the inhibitor does not substantially inhibit enzymes used in the assay. When catalase is the enzyme to be inhibited, catalase inhibitors that can be used in the biological systems include hydroxylamine sulfate. The enzyme inhibitor can be incorporated in an integral analytic device.

Abstract: A dye is covalently bound to a polymeric film, especially a polyhydric polymer, for assays and other purposes. The dye may be one which, when it comes into contact with hydrogen peroxide, changes color to indicate the presence of hydrogen peroxide. This dyed film may be used in qualitative or quantitative assays. This method chemically immobilizes dyes on support matrices with much higher yields of immobilized dye than has heretofore been possible. The covalently immobilized dye may be immobilized on solid matrix particles and combined with a free-flowing dye component to form a two component dye system. By combining a dyed film-former with a film-opener, the amount of dye available for assay is greatly enhanced. This provides a dye system which can be used to detect and measure quantitatively, accurately and precisely high levels of hydrogen peroxide. These high levels of hydrogen peroxide may result from the enzyme-mediated decomposition of various analytes from undiluted whole blood samples.

Abstract: Sizing materials are applied to porous substrates to retain fluids in the substrate for a discrete period of time. After that time period, the fluid is substantially completely released from the porous substrate. Sizing materials include alkyl ketene dimers, fluorocarbon resins, and fatty acid chlorides.

Abstract: Low density lipoproteins are directly determined in fluid samples by selectively precipitating low density lipoproteins from the sample by forming clusters, selectively consuming the high density and very low density lipoproteins, and resolubilizing the low density lipoproteins for direct determination thereof. The clusters are formed by treating the fluid sample with a mixture of a polyanionic compound, a divalent metal, and a nucleating agent. The clusters are redissolved and assayed for low density lipoproteins.

Abstract: Low density lipoprotein are directly determined in body fluids by selectively precipitating very low density lipoprotein, forming clusters with low density lipoproteins, selectively consuming the high density lipoproteins, and resolubilizing the low density lipoproteins for direct determination thereof. The clusters are formed by treating the fluid sample with a mixture of a polyanionic compound, a divalent metal, and a nucleating agent.

Abstract: A stabilizer for maintaining a constant level of CO.sub.2 in coenzyme containing enzymatic CO.sub.2 diagnostic reagents is disclosed, comprising rate-limiting amounts of (a) the diagnostic reagents and (b) coenzyme-regenerating reagents, e.g., wherein (a) is malate dehydrogenase, phosphoenolpyruvate carboxylase and NADH, and (b) is glucose dehydrogenase and glucose, as are methods of use and kits containing a diagnostic reagent and stabilizer.

Abstract: An enzymatic reagent, kit and method for determining the concentration of monovalent anions, especially chloride, particularly in clinical samples, and especially in a single-reagent format suitable for automated clinical chemistry analyzers.