Determination of patulin in apple juice by high-performance liquid chromatography-atmospheric pressure chemical ionization mass spectrometry

An HPLC-MS-MS method with selected reaction monitoring (SRM) for the determ ination of patulin in apple juice samples is described. Mass spectrometric detection was accomplished following atmospheric pressure chemical ionizati on (APCI) in both positive and negative ion modes. Collision induced dissoc iation (CID) of the protonated molecular ion led initially to the loss of H 2O (fragment m/z 137). At higher energies CO is lost from both the protonat ed parent molecule (fragment m/z 127) and the dehydrated molecular ion (fra gment m/z 109). In contrast, CID of the deprotonated molecular ion led init ially to the fragment at mit 109 corresponding to the loss of either CO, or acetaldehyde, followed at higher CID energy by the loss of H2O (fragment m /z 135) and CO (fragment m/z 125) from the deprotonated molecular ion. Dete ction in the negative ion mode proved superior and a linear response was ob served over the injected range from 6 to 200 ng patulin. Apple juice sample s spiked with patulin between 10 and 135 mug/l were analyzed following liqu id-liquid extraction with ethyl acetate and clean up with sodium carbonate. Utilizing reversed-phase HPLC with acetonitrile-water (10:90) at 0.5 ml/mi n, levels down to 10 mug/l were readily quantified and a detection limit of 4 mug/l was attainable at a signal-to-noise (S/N) ratio of 4. The MS data for the spiked samples compared well to the UV data and when plotted agains t each other displayed a correlation coefficient (R) of 0.99. (C) 2000 Else vier Science B.V. All rights reserved.