Identification and quantification of cereulide in cow's milk using liquid chromatography-tandem mass spectrometry.
In this study, the presence of cereulide in cow's milk was identified and quantified using our validated method with liquid chromatography-tandem mass spectrometry. Cereulide was concentrated using protein acid-precipitation and extracted from the precipitate by using acetonitrile twice. The combination of protein acid-precipitation and extraction sufficiently eliminated the matrix compounds from the milk and a further clean-up step utilising solid-phase extraction could be omitted. For robustly measuring the samples and keeping the MS devices clean, the extraction solution was diluted 10-fold using methanol. Owing to the minimisation of the interferences caused by fragmentation patterns, multiple reaction monitoring information-dependent acquisition-enhanced product ion spectra enabled the characterisation and identification of cereulide. Besides the matrix effect (-4%), an external solvent calibration curve was adapted for accurate quantification. The method was validated using fortified recovery tests, at two concentrations (10 and 50 µg kg-1), using three samples daily on five different days based on the Japanese guidelines. This new method exhibited good accuracy ranging from 91% to 94%. The relative standard deviations of repeatability ranged from 2% to 5%, and the relative standard deviation of within-laboratory reproducibility ranged from 5% to 6%. These standard deviations satisfied the criteria for the Japanese validation guidelines. The limit of quantification (LOQ) was estimated to be 2 μg kg-1. On the product ion spectra at the LOQ level, the library match was satisfactory with a purity fit value of >70%. The method was applied to 14 raw milk and three milk samples pasteurised using the low-temperature, long-time process and collected in Tokyo. None of the samples was found to contain the target toxin.
['Koike|Hiroshi|H|', 'Kanda|Maki|M|', 'Hayashi|Hiroshi|H|', 'Matsushima|Yoko|Y|', 'Ohba|Yumi|Y|', 'Nakagawa|Yukiko|Y|', 'Nagano|Chieko|C|', 'Sekimura|Kotaro|K|', 'Hirai|Akihiko|A|', 'Shindo|Tetsuya|T|', 'Kamiie|Junichi|J|', 'Sasamoto|Takeo|T|', 'Hashimoto|Tsuneo|T|']
D000818:Animals D002138:Calibration D002417:Cattle D002851:Chromatography, High Pressure Liquid D047630:Depsipeptides D005506:Food Contamination D008892:Milk D053719:Tandem Mass Spectrometry
Cereulide liquid chromatography-tandem mass spectrometry product ion spectra external solvent calibration curve cow’s milk