Method and apparatus for analyzing compounds with amino group

A method for analyzing a compound with amino group comprising:

• (a) reacting a compound with amino group contained in a sample comprising the same with a derivatization reagent to generate a derivatized compound, wherein said derivatized compound is a compound of formula (I) or formula (II):
• wherein
• Ar1 denotes an optionally substituted hydrocarbon or a substituent comprising a carbocyclic or heterocyclic ring having an aromaticity, wherein the binding of Ar1 to the nitrogen atom may be (i) the binding of a carbon ring or heterocyclic ring having an aromaticity directly to the nitrogen atom, (ii) the binding via a carbonyl group or an amide group to nitrogen atom, or (iii) the nitrogen atom may compose a part of a carbon ring or heterocyclic ring,
• R1 denotes a hydrogen atom, an optionally substituted alkyl group, or a ring forming carbon atom, and
• R2 denotes an optionally substituted alkyl group, and
• wherein Ar1 and R1 or R1 and R2 may form a ring with each other,
• wherein
• Ar2 denotes a carbocyclic compound residue or a heterocyclic compound residue having an aromaticity,
• X denotes an oxygen atom or a sulfur atom,
• Y denotes an oxygen atom, a sulfur atom, a secondary amine, a tertiary amine, or an optionally substituted methylene group,
• R1 denotes a hydrogen atom, an optionally substituted alkyl group, or a ring forming carbon atom and
• R2 denotes an optionally substituted alkyl group, and
• wherein R1 and R2 may form a ring with each other;
• (b) eluting said derivatized compound by liquid chromatography via stepwise elution on a concentration gradient;
• and
• (c) detecting said derivatized compound eluted from said liquid chromatography by mass spectrometry.