Substances: 5-Methylpyridine-3-carboxylic-acid (DJDHHXDFKSLEQY-UHFFFAOYSA-N) 4-Hydroxy Diclofenac (KGVXVPRLBMWZLG-UHFFFAOYSA-N) 4-Methyl-Benzotriazole (CMGDVUCDZOBDNL-UHFFFAOYSA-N) Keywords: high resolution mass spectrometry monitoring