	US 7,485,436 B2
	Method of stabilizing oxidation color former
Yuji Yagi, Kyoto (Japan); and Tsuguki Komori, Gifu (Japan)
Assigned to Arkray, Inc., Kyoto (Japan)
Appl. No. 10/483,574 PCT Filed Oct. 09, 2002, PCT No. PCT/JP02/10465 § 371(c)(1), (2), (4) Date May 28, 2004, PCT Pub. No. WO03/033601, PCT Pub. Date Apr. 24, 2003.
Claims priority of application No. 2001-314219 (JP), filed on Oct. 11, 2001.
Prior Publication US 2004/0205900 A1, Oct. 21, 2004
Int. Cl. C12Q 1/26 (2006.01)

U.S. Cl. 435—25

25 Claims

1. A method of storing N-(carboxymethylamninocarbonyl)-4,4′-bis(dimethylamino)diphenylamine sodium salt stably in a state where the N-(carboxymethylaminocarbonyl)-4,4′-bis(dimethylamino)diphenylamine sodium salt is dissolved in a solution, comprising:

preparing a solution by dissolving N-(carboxymethylaminocarbonyl-4,4′-bis(dimethylamino)diphenylamine sodium salt as well as a fructosyl amino acid oxidase and/or a peroxidase and in an aqueous solvent; and

storing the solution at a temperature in a range from 0° C. to 40° C. for at least one day;

wherein a degree of spontaneous color development of the solution stored for at least one day is suppressed to ½ or smaller relative to a case where neither the fructosyl amino acid oxidase nor the peroxidase is contained, so that the solution stored for at least one day is usable as a reagent of an oxidation color former.