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

• A convenient detection method for trace palladium by DART-MS was developed and the distinct palladium isotopic pattern was used for palladium detection.
• Fast detection of 18 s per sample was achieved which makes the method possible for high throughput analysis.
• Limit of detection at 120 ppb was achieved with a chelating agent 4-methyl-piperazine-1-carbodithioate.
• Good intensity was obtained with both volatile (methanol or acetonitrile) and nonvolatile solvents (DMSO or DMF).
• Semi-quantitation of palladium content was achieved for samples from compound collections in early drug discovery.

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.

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