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Chemical Stability and Compatibility - Mixing metal standards and the correct matrix choice

 
I have some questions about multiple element standard solutions. My lab is trying to use ICP-MS to analyze metals in ambient air that is captured on a Teflon filter and prepared using a microwave digestion. I'm in the beginning of forming SOP for the experiment, and there are 16 different elements that I want to analyze and the closest multi-standard solution that you have is IV-ICPMS-71A. But it doesn't include Ti. I've seen that you are also selling single element solution of Ti (10 μg/mL). 1) I was wondering if I can mix two standards? I'm not sure, because the matrix of Ti single element solution is HNO3/HF while the matrix of multiple element solution is HNO3. 2) Or, is it possible for me to order a customized standard solution that includes all the elements that I need? The elements that is important are V, Sr, Cr, Cu, Mn, Ti, Na, Zn, Pb, Mg, K, Al, Fe, S, Ca, As. Also, I've been diluting my current standard in 5% HNO3 (I guess it was because that solution's matrix was 5% HNO3): 3) If I want to order the standard solution from you, do I need to order matrix with 5% HNO3? 4) Or, do I just need to use ICPMS-71A and dilute it with 3% HNO3? (since the matrix is 3% HNO3). Or, the percentage of HNO3 does not matter at all? (Can I use 71A with 5% HNO3?) 5) Last question is that, if I want to see Br and Cl as well, is it possible to mix it in the customized solution? Or is it impossible to mix these in a metal standard solution?
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admin Total posts: 529

These are excellent questions. As a general rule, as concentrations decrease more elements can be combined to form stable solutions. The elements you list (V, Sr, Cr, Cu, Mn, Ti, Na, Zn, Pb, Mg, K, Al, Fe, S, Ca, As) are all stable when combined at concentrations of 100 ppm or less in matrices of 2-10% HNO3 / trace HF (where trace HF is ~0.1% by volume). Therefore, combining IV-ICPMS-71A with Ti stabilized in HNO3/HF should present no issues, as long as the Ti is roughly equal in concentration to the other elements you list. We can quote a custom standard that should meet your exact needs, but the approach you mention is likely to be more cost effective. As for the final matrix, the critical consideration is that your standards and samples should have the same matrix. The IV-ICPMS-71A product can be diluted in any concentration of HNO3 between 1-10% with no concerns. As for adding Br and Cl, these elements could be added to a custom standard in an acidic matrix for ICP-MS analysis. If you choose to add these elements yourself, we do recommend using ammonia forms (i.e., NH4Br and NH4Cl) to avoid creating unintended interferences that may arise when sourcing Br and Cl from more typical salts (e.g., KBr and KCl).

Posted: 09/02/18 22:48:26

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