〔Abstract〕 To establish a method for measuring major organic acids in the tricarboxylic acid cycle using a high-performance liquid chromatography-tandem mass spectrometry ( HPLC-MS/MS) system , and to investigate the changes in six tricarboxylic acid cycle organic acids ( fumaric acid , malic acid , succinic acid , α-ketoglutaric acid , cis-aconitic acid , and citric acid) in the serum , liver , and placenta of mice exposed to di(2-ethylhexyl) phthalate (DEHP) during pregnancy . Methods The serum , liver and placental samples from pregnant mice were processed and eluted through a Waters ACQUITY UPLC BEH Amide Column ( 130 ?，1 . 7 μm , 2. 1 mm × 150 mm ) using a gradient elution program . Mobile phase A comprised an aqueous solution of 10 mmol/L ammonium acetate and 5 μmol/L methanephosphonic acid , while mobile phase B consisted of a 90% acetonitrile aqueous solu- tion containing 10 mmol/L ammonium acetate and 5 μmol/L methanephosphonic acid , with a flow rate maintained at 0. 35 ml/min . The mass spectrometry detection system utilized an electrospray ionization technique with negative ion mode for multiple reaction monitoring. Results The correlation coefficients of the standard curves for the six tricarboxylic acid cycle organic acid metabolites were all above 0. 996 within the quantitative range . The method ’s accuracy ranged from 97. 14% to 108. 26% , with inter-day and intra-day precision relative standard deviation be- tween 1 . 35% and 6. 73% . The matrix effect was between 93 . 29% and 107. 47% , and the extraction recovery rate ranged from 94. 82% to 112. 57% . Analysis of six tricarboxylic acid cycle organic acids in the liver , serum , and placenta of DEHP-exposed mice during pregnancy showed significant reductions in fumaric acid , malic acid , α-ke- toglutaric acid , cis-aconitic acid , and citric acid compared to the control group ( P < 0. 05) . Conclusion The HPLC-MS/MS method established in this study for detecting six tricarboxylic acid cycle organic acids in the serum , liver , and placenta of DEHP-exposed pregnant mice is stable , highly sensitive and selective . Prenatal DEHP expo- sure induced alterations in the levels of tricarboxylic acid (TCA) cycle organic acid metabolites in the liver , ser- um , and placenta of mice , suggesting that DEHP exposure during pregnancy may interfere with mitochondrial TCA cycle processes . These findings indicate potential value in the diagnosis and treatment of diseases associated with prenatal DEHP exposure .