Clinical Spectroscopic Diagnostics

CO-releasing molecules (CORMs) are developed for investigations of the interaction between the signaling molecule carbon monoxide (CO) and cells or tissue. Prior to their application these molecules require to be fully characterized with respect to their CO release mechanism. One widely used CORM for biological application is sodium boranocarbonate (CORM-A1), which has a pH depending CO liberation. The complete reaction mechanism of CORM-A1 is not fully understood yet. Therefore, in this contribution time-resolved IR gas phase spectroscopy was used to monitor the headspace above decaying CORM-A1 solutions at four different pH values (5.8 to 7.4). Borane carbonyl was found as an intermediate in the gas phase, which was formed during the CORM degeneration and further decayed to CO. Concentration profiles of a pseudo consecutive first-order reaction were successfully fitted to specific band areas of the measured gas phase spectra and the rate constants were obtained. The production of borane carbonyl is strongly pH dependent (half-lives between 5 min and 106 min), while the decay of borane carbonyl in the gas phase is nearly constant with a half-life of about 33 min. The ratio of liberated CO molecules per CORM-A1 was determined as 0.91 ± 0.09 and boric acid was identified as further end product.