Keywords: monitoring Substances: 5-Fluorouracil (GHASVSINZRGABV-UHFFFAOYSA-N) Acesulfame (YGCFIWIQZPHFLU-UHFFFAOYSA-N) 3-5-Diiodo-L-tyrosine (NYPYHUZRZVSYKL-ZETCQYMHSA-N) 4-Hydroxy-Benzotriazole (NPZTUJOABDZTLV-UHFFFAOYSA-N)