Analysis of trace metal Cadmium in 99% Molybdenum sample using ICP-MS

Question

The main and obvious issue with this analysis is interference due MoO being the same mass as Cd.

Even using a DRC gas doesn't help much.

using an ICP-MS/MS (Triple quad) will definitely eliminate this issue but I don't have that option.

Let me know your thoughts.

mreuer · Accepted Answer

Hello Manoj, The measurement of sub-ppb Cd in the presence of Mo is challenging given the isobaric interference of MoO on all isotopes of Cd, expect for cadmium-106 which is low abundance (1.25%). As you mentioned, the Agilent 8800 ICP-MS and oxygen addition to the Octopole Reaction System (ORS) eliminates this interference, but how do we evaluate this on single quadrupole ICP-MS? First, I would recommend creating a Cd calibration curve with your MoO matrix, and measure the Cd background equivalent concentration (BEC) and detection limit (DL) in all available gas modes - nogas, He, high energy He, and hydrogen (if available). Recommended tuning parameters are attached for the 7900 ICP-MS with the x-lens configuration. Based on empirical comparison of Cd at 110-116 amu, we can then determine the relative impact of the MoO isobaric interference. The DL and BEC results are shown in the information for each calibration curve in ICP-MS MassHunter Data Analysis, so you can get real time information on interference removal. For example, it would be interesting to compare cadmium-116 in hydrogen mode since we're mass shifting MoO (116) to MoOH (117), but possibly complicated by the InH interference. This might be a good alternative, but the BEC/DL measurements are the best guide here. This also depends on your detection limit requirements and relative cadmium concentration. So for starters I would recommend BEC and DL measurements under the different available gas modes - let the results be your guide. Best Regards, Matt Reuer

Analysis of trace metal Cadmium in > 99% Molybdenum sample using ICP-MS

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