“…The prospect of developing CO into a therapeutic agent for colitis, sickle cell disease, and acute kidney injury, among others, , is supported by the corresponding animal model studies. Extensive efforts have been made in recent years in evaluating inhaled CO gas in clinical trials, , developing non-gaseous CO delivery approaches, including liquid and foam formulations, metal-based CO-releasing molecules (CORMs), ,, and organic light-activated CORMs, − organic prodrugs, ,− and their formulations . A unique challenge to studying the dose–response relationship of CO is the lack of facile methods for the sensitive and selective determination of its concentration in the blood and various tissues. − Along this line, there is still much to be desired from existing methods.…”