Quantitative analysis of seven free short-chain fatty acids in infant formula using GC–MS/MS

Free short-chain fatty acids (FSCFAs) are recognized as essential nutrients in infant formula. This study aims to develop a rapid, sensitive, and efficient method for analyzing seven FSCFAs in infant formula. The sample preparation process utilized an acetonitrile-anhydrous magnesium sulfate system for the FSCFAs extraction. The enriched FSCFAs were derivatized using butanol-acetyl chloride to enhance stability and chromatographic separation. Analysis of the resulting fatty acid butyl esters (FABEs) was performed using gas chromatography-tandem mass spectrometry (GC–MS/MS). Under optimized conditions, the chromatographic method achieved baseline separation of seven FABEs within 14.8 min, demonstrating excellent linearity and reproducibility. The limits of detection and quantification ranged from 12.0 to 34.9 ng/g and 40.0 to 116.5 ng/g, respectively. In the tested real samples, six FSCFAs were successfully detected. These findings provide a scientific basis for optimizing the nutritional composition of infant formula and improving its similarity to human milk.