Determination of Macrolide Antimicrobials in Infant Formulas Using a Modified Alkaline QuEChERS and High-performance Liquid Chromatography Coupled to Tandem Mass Spectrometry

Macrolides are antimicrobials widely used in dairy farming, classified as critically important for human and animal health, and a priority for actions against antimicrobial resistance. Infant formula is used as a substitute for breast milk and should be safe to support child growth and development. In this context, the aim of this study was to validate an analytical method for macrolide analysis in infant formulas produced from bovine milk. The fast and practical method, based on a modified QuEChERS alkaline extraction and liquid chromatography-tandem mass spectrometry, was validated according to European Community guidelines and showed to be quantitative for erythromycin, spiramycin, oleandomycin, and tylosin, while qualitative for tilmicosin. Limits of detection (LODs) for ready-to-eat infant formulas ranged from 0.04 to 0.37 ng mL −1 and limits of quantification (LOQs) from 0.15 to 1.22 ng mL −1 . LODs were sufficiently low to detect residues of at least one of the assessed antimicrobials in 76.7% of the samples analyzed by the validated method.