Substances: 2 -2 -Difluorodeoxyuridin (FIRDBEQIJQERSE-QPPQHZFASA-N) 5-Fluorouracil (GHASVSINZRGABV-UHFFFAOYSA-N) 1-3-Dimethyl-2-imidazolidinon (CYSGHNMQYZDMIA-UHFFFAOYSA-N) Keywords: high resolution mass spectrometry