New Stable Isotope Labeling Strategy in Quaternary Ammonium–Functionalized Magnetic Nanoparticles for the Analysis of Perfluorocarboxylic Acid in Cod Liver Oil.

Perfluorocarboxylic acids (PFCAs) in cod liver oil was analyzed for the first time using newly designed and synthesized quaternary ammonium–functionalized magnetic nanoparticles (Fe₃O₄@SiO₂@QTA). Fe₃O₄@SiO₂@QTA was characterized by TEM, IR, and magnetic hysteresis curve. It can interact with perfluorocarboxylic acids through electrostatic interactions, hydrogen bonding, and hydrophobic effect. Stable isotope labeling (SIL)–assisted liquid chromatography tandem mass spectrometry (LC-MS/MS) was used to evaluate the adsorption efficiency. The obtained recoveries for all compounds were in the range of 85.0–98.5%, with relative standard deviations of less than 8.1%. The sorbent amount was 20 mg. Desorption conditions were as follows: sample pH 5–7.0; desorption time, 5 min; and elution volume, 1.0 mL. The limits of detection were in the range of 1.5–20 ng/L, while the limits of quantitation were in the range of 5.0–70 ng/L. The proposed method was successfully applied to the selective adsorption of PFCAs from cod liver oil with no matrix effect observed because of the double assurance of selective adsorption and high accurate SIL strategy. [ABSTRACT FROM AUTHOR]