Rapid and inexpensive nylon-66-filter solid-phase extraction followed by gas chromatography tandem mass spectrometry for analyzing perfluorinated carboxylic acids in milk

In this study, a new rapid and inexpensive filter solid-phase extraction method (FSPE) was developed for the extraction and separation of five perfluorinated carboxylic acids (PFCAs) (namely, perfluorooctanoic acid, perfluorononanoic acid, perfluorodecanoic acid, perfluoroundecanoic acid, and perfluorododecanic acid) from milk samples. Commercial nylon 66 syringe filters were used as adsorbents without additional modification. The proposed method could achieve the fast adsorption of analytes by benefitting from the advantages of using the nylon 66 filter membrane on PFCAs with multiple adsorption interactions, namely, hydrophobic interactions and hydrogen bonds. The FSPE was designed to achieve the rapid isolation of analytes based on the rapid solid-liquid separation while using the solid-phase extraction disk. PFCAs residues in milk were extracted by first flowing the samples through a nylon 66 syringe filter from top to bottom. Double contact desorption with methanol was then accomplished by pulling and pushing the syringe, followed by derivatization with acetyl chloride-methanol. Finally, the extracted PFCAs residues were monitored using gas chromatography-tandem mass spectrometry (GC-MS/MS) quantification. Under optimal conditions, the established method presented good linearity (correlation coefficient ≥ 0.9996), precision (relative standard deviation ≤ 13%), accuracy (81–105%), sensitivity (limits of quantification: 4–18 ng kg −1 ) and extraction performance (10 min).