Abstract: A test method and device is described for determining biguanides in aqueous fluids such as swimming pool water which involve contacting the fluid with a matrix incorporating a pH sensitive indicator material which exhibits the biguanide error effect. A buffer is advantageously used to maintain the test system within a defined constant pH range to eliminate the effect of pH changes on the test system.

Abstract: A colorimetric test reagent composition is presented for determining the amount of cyanuric acid in water. Cyanuric acid is added to outdoor swimming pool water to stabilize the chlorine added as a sanitizer. Basically the test composition utilizes melamine and an indicator material which responds to a change in pH of the test environment caused by the action of cynanuric acid on the reagent composition. Preferably the test composition is incorporated in a porous matrix which results in a convenient solid state test device.

Abstract: A novel test composition, device and method for determining the presence of urobilinogen in a test sample. The composition is capable of producing a detectable response, such as a change in color or change in light absorption, thus indicating the presence of urobilinogen, both on a qualitative and a semi-quantitative basis. Briefly, the composition comprises para-di(lower alkyl)aminobenzaldehyde as an indicator compound, a buffer substance capable of producing a pH of about 0.5 to 3, and a compound having the structure ##STR1## in which X is O or S, and in which R and R', same or different, are lower alkyl, or R and R' together are lower alkylene or ##STR2## wherein n is an integer of 1 to about 6. The device comprises a carrier matrix incorporated with the composition. The method of use comprises contacting a test sample with the composition or device and observing any detectable response formed therein.