Abstract: Liquid chromatography (LC) in hyphenation with mass spectrometry (MS) was applied to qualitative and quantitative analysis of sulfonated castor oil.SR-CN liquid chromatographic column (100 mm×4.6 mm,3.5 μm) was used as the stationary phase and a mixture of methanol and water mixed in the ratio of 1 to 1 was used as the mobile phase with flow-rate of 500 μL·min-1.Elaectrospray ionization negative ion collection mode and selective reaction monitoring were used in the MS determination.The quantification ion pair used was m/z 377/297.Detection limit of the method was found to be 0.1 mg·L-1.Linearity was held in the range from 0.4-400 mg·L-1.The proposed method was applied to the qualitative and quantitative analysis of an ink sample for the content of sulfonated castor oil.