Several carbonyl compounds are important because of their irritant and toxic properties, mutagenicity and carcinogenicity. Therefore, they are regulated in korean odor emission standard. In this study, atmospheric pressure ionization-mass spectrometry(API-MS) is used for the analysis of carbonyl compounds after derivatization with 2, 4-dinitrophenylhydrazine (DNPH) and liquid chromatographic separation. In the negative ion mode, the $[M-H]^-$ pseudomolecular ions are most abundant for the carbonyls. Analytical parameters such as linearity, repeatability and minimum detection limit were evaluated. The linearities ($r^2$) for carbonyls were $0.9977{sim}0.9999$ when analyte concentration ranges from $25;to;250{mu}g/L$(n=6). The relative standard deviations (%RSD) for carbonyls were $0.55{sim}3.51%$ for concentration of $100{mu}g/L$(n=5). The minimum detection limit (MDL) was $1.88{mu}g/L$(0.27 ppb) for i-valeraldehyde. It was shown that LC-MS method has a great potential for carbonyl compounds analysis.