Abstract: A fluid collection, filtration, and storage device is described. The device has a first tube with a closed first end, an open second end, inner tube-wall surfaces, and an internal diameter; a second tube with a first end porously closed by a filter and an open second end and having an external diameter smaller than the internal diameter of the first tube, the second tube slidably contacting the inner tube-wall surfaces of the first tube at the first end of the second tube when the second tube is inserted in the first tube; and a cap adapted to seal the open second end of the first tube and the open second end of the second tube in a single closing operation while the second tube is inserted into the first tube. The kit is particularly adapted for collecting and storing viscous biologic samples, such as saliva, in the inner tube after the sample has been mixed with a preservative or other substance initially located in the filter.

Abstract: A quantitative assay for creatinine has been developed in which creatinine is reacted with 3,5-dinitrobenzoate under alkaline reaction conditions to produce a fluorophore product which has excitation and emission maxima near 410 nm and 475 nm, respectively. Alternatively, 3,5-dinitrobenzoyl chloride or methyl-3,5-dinitrobenzoate may be employed as reagents. The chemical reactions proceed in the presence of Group IA bases and/or quaternary alkyl ammonium hydroxides under aqueous, nonaqueous and mixed solvent conditions. Detection limits for creatinine are well below one micromole per liter. Conversely, the reactivity of creatinine and/or base with 3,5-dinitrobenzoate may be employed to quantify 3,5-dinitrobenzoate by fluorescence intensity measurements. The chemical assay is readily adaptable to reagent pad and dry-layered coating technologies employing fluorescence detection/quantitation.