Development of gas chromatography tandem mass spectrometry as a candidate reference method for the accurate determination of fatty acid contents in infant formula

This study optimized the gas chromatography-mass spectrometry method for accurate fatty acid (FA) analysis in infant formula. The focus was on key factors such as derivatization methods, calibrant selection, calibration techniques, instrument settings, and matrix effects. Derivatization techniques examined included acetyl chloride and sodium methoxide for direct transesterification, as well as multi-step derivatization through acid and alkaline hydrolysis. The results showed that direct ester exchange with acetyl chloride was the most efficient derivatization method. Internal calibration using fatty acid methyl esters performed similarly to external calibration with triacylglycerols, providing valuable insights for calibration method selection. Matrix effects were minimized by using a direct dilution technique, ensuring reliable results. Based on these findings, an accurate analytical method was developed for quantifying 20 FAs in the infant formula. The method demonstrated excellent repeatability, with relative standard deviations below 3% for higher FA concentrations (> 1.0 g/100 g) and below 5.2% for lower concentrations (< 1.0 g/100 g). Validated with NIST SRM 1869, the method proved robust, highly accurate, and suitable for the value assignment of certified reference materials.