A colorimetric and fluorescent signaling probe for assaying Pd²⁺ in practical samples

We developed an optical signaling probe to detect Pd²⁺ ions in Pd-containing catalyst and drug candidate. The Pd²⁺ signaling probe (Res-DT) was readily prepared by reacting the versatile fluorochrome resorufin with phenyl chlorodithioformate. In a phosphate-buffered saline solution (pH 7.4) containing sodium dodecyl sulfate (SDS) as a signal-boosting surfactant, Res-DT exhibited a pronounced colorimetric response with a chromogenic yellow to magenta shift, leading to a substantial increase in the fluorescence intensity. The Pd²⁺ signaling performance of Res-DT was attributed to the Pd²⁺-promoted hydrolysis of the dithioate moiety. The probe displayed high selectivity toward Pd²⁺ ions and remained unaffected by commonly encountered coexisting components. Moreover, the detection limit of Res-DT for Pd²⁺ ions was 10 nM, and the signaling was achieved within 7 min. Furthermore, to demonstrate the real-world applicability of Res-DT, a Pd²⁺ assay was performed in Pd-containing catalyst and drug candidate using an office scanner as an easily accessible measurement device. Our results highlight the prospects of Res-DT as a tool to detect Pd²⁺ ions in various practical samples, with potential applications in catalysis, medicine, and environmental science.