Stability of a calibrant as certified reference material for determination of trans-zearalenone by high performance liquid chromatography-diode array detection-triple quadrupole tandem mass spectrometry

In this study, a trans-zearalenone (trans-ZEN) calibrant in acetonitrile as certified reference material (CRM) was prepared and intensively investigated the stability by high performance liquid chromatography coupled diode array detection and triple quadrupole tandem mass spectrometry (HPLC-DAD-MS/MS). The photoisomerization and degradation of main component and related impurities in trans-ZEN calibrant CRM was studied in detail under different light conditions such as UV light (254 nm), sunlight, and visible light. Trans-ZEN in acetonitrile was confirmed a significant shift toward cis-ZEN up to a 52% cis-isomerization rate after exposing to UV light (254 nm) in transparent ampule for 1 day. The unsaturated double bond photosensitive groups of trans-ZEN and cis-ZEN will further undergo photoreaction to generate more isomers and related products with the increase of UV irradiation time. The calibrant in amber ampules was relatively stable after exposing to sunlight for 28 days, with only 0.35% cis-isomer observed. The results indicated that trans-ZEN solution calibrant should be packed in amber ampules to avoid UV rays. Thermal stability test exhibited this calibrant was stable over 6 weeks even at 60 °C. Trans-ZEN was found to be more stable in acetonitrile than in methanol since an unknown impurity was observed in methanol after 6 weeks placed at 25 °C. The stability study of trans-ZEN calibrant provided a basis for the usage, storage, and transportation of the CRM. A concentration and expanded uncertainty of the trans-ZEN calibrant CRM of 11.01 ± 0.18 µg/mL was developed.