Patent ID: 7476738

Claim:
A method for identifying a molecular weight of a phosphoric acid monoester compound, comprising steps of: (a) mixing a complex compound including a compound (I) having single kind of zinc isotopes and a sample in a solvent to obtain a solution, and then acquiring a mass spectrum of the solution, wherein R 1 to R 4 are identical to or different from each other, and are hydrogen atoms or substituents selected from a group consisting of a straight chain or a branched chain C1-C6 alkyl group, an amino group, a hydroxy group, a carbamoyl group, a straight chain or a branched chain C1-C6 alkoxy group, a halogen atom, a nitro group, a sulfonic acid group, a carboxyl group, a formyl group, an acyl group, a cyano group, an aminomethyl group, a hydroxymethyl group; (b) mixing a complex compound including a compound (I) having another kind of zinc isotopes and the sample in a solvent to obtain a solution, and then acquiring a mass spectrum of the solution; and (c) identifying the molecular weight of the phosphoric acid monoester compound by comparing the mass spectra.