An inductively coupled plasma mass spectrometer (ICP-MS, Nexion 350X, Perkin Elmer) was used in two ways during this study. First, it was used to determine the elemental composition of the drop-casting ink. Later, it was used to record the operando dissolution of selected compositions identified during the MOBO-guided experiments. For the latter, the ICP-MS was connected through Tygon tubings (Proliquid) with the outlet of the SFC. The ICP-MS was always calibrated before measurements by a four-point calibration (0, 1, 10, 50 μg L -1 ) using Merck Certipur ICP standards. Co, Mn, 121 Sb, 120 Sn, and Ti were used as analyte. Ti, which would be the more abundant isotope for Ti, was deliberately not chosen as it had higher background counts, increasing the detection limit. The calibration matrix was 0.1 M HNO3 to mimic the supporting electrolyte for subsequent operando measurements. Internal standards were prepared in 1-2% HNO 3 at 5 µg L -1 , where Ge was the internal standard for Co and Mn, 138 Ba for Sb, Rh for Sn, and Sc for Ti. Internal standards were used to ensure a stable and reliable system performance. A Y-connector was used to simultaneously ingest the analyte and internal standard during measurements.