Patent ID: 7727949

Claim:
A method comprising: adding a cleaner into water provided in a thermostatic water bath for preventing generation of microorganisms and generation and attachment of air bubbles on the outer wall of a reaction vessel in the thermostatic water bath, and for producing no substances having absorption in the wavelength range of 300 to 900 nm in the water provided in the thermostatic water bath, the cleaner comprising: a quaternary ammonium salt represented by the following general formula I and/or a preservative agent having amphoteric surface activity, and a surface active agent: wherein R 1 to R 4 are each independently an alkyl group, with the proviso that at least one of R 1 to R 4 is an alkyl group having 8 to 18 carbon atoms, and at least one of them is a lower alkyl group having 1 to 3 of carbon atoms; and X is an anion derived from a carboxylic acid having two or more carbon atoms.