This International Standard specifies a test method for the determination of the aqueous extractable content of the following preservative agents: 2-(thiocyanomethylthio)-benzothiazole (TCMTB); 4-chloro-3-methylphenol (PCMC); 2-phenylphenol (OPP); 2-octylisothiazol-3(2H)-one (OIT); in leather by liquid chromatography. This method can also be used to determine breakdown products of these preservative agents. Preservative agents are necessary to protect leather from microbiological attack. NOTE The preservative agents 4-chloro-3-methylphenol (PCMC) and 2-phenylphenol (OPP) can also be determined according to ISO 17070[1] and quantified by means of gas chromatography/mass spectroscopy (GC/MS).