Sample Preparation - Sample Recovery- Open-cup evaporation
Hi all,
We recently purchased a ThermoFisher iCap RQ ICP-MS. We are analyzing 14 metals in our Dimethyl Sulfoxide (DMSO) product. We utilize open-cup evaporation on a hot plate followed by reconstituting in 2%HNO3 & 0.5% HCl. Currently, I am adding 30mL of DMSO sample into a teflon beaker, then spiking from a stock solution an aliquot equivalent to 1ppb of the 14 metal solution. I allow the sample to evaporate to dryness (between a pin-tip and a light char mark). I then use my diluent to squirt into the cup ~5-10mL. This portion is transferred to a sample vial and diluted back up to 30mL.
I am struggling with recovery. The data is inconsistent to say the least. My 2ppb samples are sometimes lower than my 1ppb samples. Sometimes they are 2-3 times higher than they should be.
Performance reports look great, and standard curve looks great.
Any tips for improving recovery of metals following evaporation? Any help would be highly appreciated. Thanks in advance.
Andrew
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Brian Alexander, PhD
Total posts: 18
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Many metals behave conservatively during open vessel hot plate processes, whether an agressive acid digestion or a simple evaporation. However, some metals can be lost depending upon their chemical form and/or the reagents used. If you could provide a list of the 14 elements that could help us troubleshoot your issues. Are all metals affected equally with poor recovery? Have you performed a recovery test using solely the spike, i.e., without the DMSO, and if so, are the results similar to or different from the recoveries observed when DMSO is evaporated? And lastly, what blank values do you observe when you perform the evaporation without any spike or sample? |