If we purchase a standard in the form of mixture involving 5-6 compounds, Can we quantify an individual compound by using this mixture, or individual compound (Separate Standard) will also be required?
As long as the other compounds in the mix are separated from your compound of interest in the chromatography, and you know the concentration of the compound in the mix, it should not matter if you use a mix or not. We've done this for something like the Florida alkane mix, which contains several alkanes but we only needed 2-3 of them for our analysis. I'm just not sure why you'd want to purchase a standard mix to quantify one compound rather than just prepare a standard for that one compound, so perhaps I'm missing something here.
How can you determine which peak is which? Remember, ANY mistakes at this point will be carried forward! I remember peaks identified by MS were wrongly labelled (by a big pharma lab) and thus their conclusions were WRONG. I would be very careful about this standard and its implications.
In the past I have purchased a USP standard and then qualified a Sigma bottle (NIST traceable too) as a secondary standard.
Even so this standard (NIST traceable) must be 'identified and qualified' usually by UV, IR, MS, NMR...
I am trying to quantify 3 compounds from biological samples. One of these compounds of interest cannot be purchased due to licensing issues. However, this particular compound of interest has already been purchased in the form of standard mix. So, can we quantify this individual compound only by using standard mix or individual compound will be required in any case?
Using a mix raises multiple concerns. Can you trust the stability of the mix, especially if it’s a solution? How do you know for sure which peak corresponds to your analyte? Will the other compounds in the mix interfere your analysis?
This does not mean you cannot do it. But you do need to address the concerns properly and make sure the practice fits the purpose.
If you have a well-defined analytical system, with more than adequate qualitative identification (qualitative, not quantitative) then using a mixture for calibration does not cause you any problems. I don't know anything about your analytical scheme because you gave us no details, but using mixtures for calibration is quite common (see the USEPA methods 8260 and 8270, for example). You do need to absolutely know that there are no interferences and/or that the chromatography is adequately resolving your mixture. We routinely use mixtures for verifying our calibration standard (initial calibration verification, or ICV) as well as for screening type methods (pesticides in food, for example).
If you do NOT have a well-defined analytical method, or you are attempting method development, then you would certainly want individual compounds.
Hi, you could ask the technical support of the company that prepared the standard mix, if they could guide you through the process to sort out your standard curve using their mix. Greetings, Brig
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