Detection of trace palladium by direct analysis in real time mass spectrometry (DART-MS)

Abstract A detection method for palladium by direct analysis in real time (DART-MS) was developed. The method was used for the detection and semi-quantification of palladium in compound samples for which palladium was used during synthesis from compound collections in early drug discovery. The samples containing palladium were mixed with the chelating agent 4-methyl-piperazine-1-carbodithioate and a palladium chelating complex was subsequently formed and detected by DART-MS. The distinct isotopic pattern of palladium was observed and used for its qualitative identification. Semi-quantification was performed based on the peak areas of the extracted ion currents for the four most abundant isotope peaks at m / z 456, 457, 459 and 461. The limit of detection for this method was observed to be 1.2 μM (120 ppb). With DART ionization, rapid analysis of 18 s per sample was achieved with low carryover. Different solvents and chelating agents were also tested for this analysis, and satisfactory signal intensity was obtained using both volatile and nonvolatile solvents.