A composition, method, and device for quantitatively determining the concentration of a dialdehyde in a sample are disclosed. The device includes a test pad having a suitable carrier matrix incorporating an indicator reagent composition capable of interacting with a dialdehyde to produce a detectable and measurable response for dialdehyde concentration over a range of 0% to about 20%, by weight of the sample. An indicator reagent composition contains: (a) a diamino carboxylic acid, (b) an optional polymer and (c) a carrier. An indicator reagent composition is incorporated into a carrier matrix to provide a test pad useful in a dry phase dialdehyde assay of a sample, especially for samples containing a high concentration of glutaraldehyde.
