Determination of the aflatoxin M1 (AFM1) from milk by direct analysis in real time - mass spectrometry (DART-MS)

•Analytical method for determination of mycotoxin AFM1 from milk.•Utilizes direct analysis in real time - mass spectrometry for rapid, convenient determination.•Achieves sensitive, robust determination from a variety of milk products with good recovery.•Use of isotopic internal standards for AFM1 facilitates effective quantitation.

Certain fungi that grow on crops can produce aflatoxins, which are highly carcinogenic. One of these, aflatoxin B1 can be metabolized by mammals to aflatoxin M1, a form that retains potent carcinogenicity and which can be excreted into milk. Direct analysis in real time (DART) ionization coupled to a high resolution mass spectrometer (MS) was used for the rapid quantitative analysis of a common form of aflatoxin, AFM1, extracted from cow milk. Sample preparation procedure and instrument parameter settings were optimized to obtain sensitive and accurate determination of AFM1. The lowest calibration level (LCL) for aflatoxin AFM1 was 0.1 μg/kg. Quantitative analysis was performed with the use of matrix-matched standards employing a 13C-labeled internal standard for AFM1. DART-MS of spiked milk extracts gave linear response over the range of 0.1-2.5 μg/kg. Good recoveries (94.7-109.2%) and repeatabilities (RSD 13.5-9.6%) were obtained at spiking levels of 0.5 and 2.0 μg/kg. The results of the study further demonstrate the potential of ambient ionization-MS techniques for the sensitive, convenient and rapid quantitative determination of mycotoxins from difficult matrices.