Fast Determination of Sodium Monofluoroacetate in Liquid Milk and Dairy Powder by Hydrophilic Interaction Liquid Chromatography-Triple Quadrupole Mass Spectrometry

Manufactured sodium monofluoroacetate is a rodenticide with high acute toxicity. A fast and sensitive analytical method in liquid milk and dairy powder was developed both for routine analysis and for fast tackling the terrorist threat. Monofluoroacetate was extracted from liquid milk using acetonitrile and from dairy powder with water and acetonitrile, cleaned using a solid phase extraction (SPE) cleanup procedure with polymeric anion exchange (PAX) cartridge, and measured by hydrophilic interaction liquid chromatography-triple quadrupole mass spectrometry (LC-MS/MS). The conditions for the monofluoroacetate extraction, SPE cleanup, and instrument injection solvent were optimized. A BEH amide chromatographic column with hydrophilic interaction was used to directly separate monofluoroacetate under basic conditions. The limits of detection in liquid milk and dairy powder were 1 and 2 μg kg^-1, respectively. The recoveries at three spiking levels (10, 50, and 200 μg kg^-1) were 72.5–97.6 % with relative standard deviations (RSDs) of 4.7–5.9 % for liquid milk and 70.1–92.8 % with RSDs of 4.7–6.8 % for dairy powder. The method has been applied to analyze sodium monofluoroacetate in dairy products including infant formula.