ABSTRACT
A pre-column derivatization and ultra-high performance liquid chromatography quadrupole time-of-flight mass spectrometry (UHPLC-QTOF-MS/MS) method was developed for qualitative and quantitative determination of medium- and short-chain fatty acids in mice feces, and was further applied to evaluate variations in the feces of mice before and after antibiotic treatment. This animal experiment had been approved by Animal Experimental Ethics Committee of Jiangsu Province Academy of Traditional Chinese Medicine. By optimizing the derivatization conditions and UHPLC-QTOF-MS/MS parameters a new UHPLC-QTOF-MS/MS method with 3-nitrophenylhydrazine as the derivatization reagent was developed for simultaneous determination of 16 medium- and short-chain fatty acids. Validation studies showed that the linearity of the calibration curves was good (R2>0.99), the RSD of intra-day and inter-day precision was less than 10%, the repeatability RSD was less than 6%, the recovery rate was between 80% - 120% at three spiked levels, and the stability RSD was less than 7% within 36 h. The types and amounts of the detected medium- and short-chain fatty acids in feces significantly changed after the mice were treated with antibiotics. The content of formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, and lactic acid decreased, whereas that of heptanoic acid and succinic acid increased significantly. All these results suggest that the newly established method is accurate and reliable, and can be used for determination of medium- and short-chain fatty acids in feces.