Determination of Benzalkonium Homologues and Didecyldimethylammonium in Powdered and Liquid Milk for Infants by Hydrophilic Interaction Liquid Chromatography-Mass Spectrometry

In this study, a hydrophilic interaction liquid chromatography–\r\nmass spectrometry (HILIC-MS/MS) method for\r\nthe determination of benzalkonium (BAC) homologues and\r\ndidecyldimethylammonium (DDAC) was developed. A satisfactory\r\nchromatographic separation of BAC homologues and\r\nDDAC was achieved using, as mobile phase, acetonitrile–\r\naqueous 50 mM ammonium formate (pH 3.2) (93+7 v/v) at\r\n0.3 mL min−1. The elution order of BAC homologues was\r\nfrom benzyldimethylhexadecylammonium chloride (C16-\r\nBAC) to benzyldimethyldecylammonium chloride (C10-\r\nBAC), the exact opposite with respect to separation using\r\nreversed liquid chromatography. The instrumental method\r\nwas successfully applied to powdered and liquid milk for\r\ninfants (about 50 samples). From powdered milk samples,\r\nBAC and DDAC were extracted using 5 % formic acid in\r\nmethanol for 60 min at 60 °C in an ultrasonic bath; after\r\ndilution with water and 5 % NH4OH solution, a purification\r\nstep using a weak cationic exchange column was performed.\r\nSatisfactory limit of detections (LODs) were achieved, below\r\n1.0 μg kg−1 and 0.05 μg L−1 for powdered and liquid milk for\r\ninfants, respectively. No sample was free of BAC homologues\r\nand DDAC, and in one powdered milk sample, the contamination\r\nlevel exceeded 500 μg kg−1, the maximum level recommended\r\nby the Standing Committee on the Food Chain\r\nand Animal Health for food and feed.