Colorimetric analysis of palladium using thiocarbamate hydrolysis and its application for detecting residual palladium in drugs

Abstract

In this research, we report a practical colorimetric method for the convenient analysis of residual palladium ions in drugs and drug intermediates. In a phosphate-buffered (pH 7.0) 50% aqueous DMSO solution, chlororhodol-based probe PP-1 demonstrated a prominent colorimetric (APP-1+Pd(II)/APP-1 at 531 nm is over 780) and turn-on type fluorescence signaling behavior (IPP-1+Pd(II)/IPP-1 at 561 nm is over 2000) toward palladium. The signaling was realized through the palladium-assisted hydrolysis of the thiocarbamate protecting moiety of the probe. Palladium-selective signaling was feasible in the presence of possibly interfering chemical species, and it was concluded within 7 min. The selective signaling was observed for palladium species with different oxidation states (Pd2+, Pd4+, and Pd0). The detection limit of the probe for palladium analysis was sufficiently sensitive to analyze the residual palladium in drugs and related products (LODPP-1 = 1.0 × 10–8 M, LODPP-2 = 4.3 × 10–8 M). In particular, palladium analysis could be performed in the presence of ibuprofen and 2-cyano-4′-methylbiphenyl, as the drug and drug intermediate, respectively. © 2022 Elsevier B.V.