Interference of H₂S During CO Detection by Probes Which Respond Through Tsuji–Trost Reaction—Does the Lack of Response Confirm Lack of Interference?

There is a great interest in getting deeper insights into the signaling roles and pathophysiological connections of gasotransmitters such as CO, NO, and H₂S. Among the probes for CO detection, those which respond through fluorescence outputs after activation through Tsuji-Trost reaction are popular. Interestingly, a number of reports in this area have shown that these probes are nonresponsive toward H₂S under the conditions employed. Since these analytes were tested individually, the question of whether H₂S interferes with the generation of Pd(0) species or influences the CO-releasing ability of CORM-3 needed scrutiny. To understand this, we have carried out a series of studies using two different probes, namely Cou-CO and FL-CO, which give fluorescence responses at 450 nm and 520 nm, respectively, on activation. The results clearly showed large variations in emission intensity in presence of H₂S which can be linked to its interaction with either Pd²⁺ source or CORM-3. These trends were also reflected in the outcome from fluorescence imaging and flow cytometry studies involving A549 cells. Implications of this in analytical studies involving gasotransmitters are discussed in this report.