When and how many internal standards should use for GC MS?

Question

Dear Researchers 
 I am Rizwan (Ph.D. scholar), researching the area of Fruit biochemistry and post-harvest preservation, 
 As i am new in the field of GC MS, (as i want to do the experiment about the cuticle wax chemical composition and concentration), I would like to ask some questions about GC MS as i am in it: 
 1- What criteria should keep in mind while selecting an Internal standard? 
 2-How many minimum or maximum internal standards should use? Should be only one concentration or use at different concentrations? 
 3-As i will do an experiment about the cuticle wax chemical composition and concentration of fruit surface so as i have read the articles and they mentioned n-tetracosane, so only one IS is enough or should i use C7 - C40 Saturated Alkanes Standard for the waxy compounds? 
 I shall be very thankful to you for this kindness 
 Looking forward to hearing from you 
 Regard: 
 Rizwan

Admin · Accepted Answer

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gabcaron · Answer

The general rule of thump when selecting an internal standard is taking something that has the same chemistry as your analytes. Obviously, you do not want it to be your analytes or you will essentially increase their concentration.

You want the ISTD to be at 1 concentration in everything you do, so that way you can use that known quantity to ''Correct'' samplers mistakes. The fluctuation in the injection will be reflected through your internal standard.

As far as what to choose and how many, that depends on what you want to do with it I suppose. If you found applications that apply to your case, I would start with trying to see if I can run those and then research and development to see if I can make it better, if I want it better.

When and how many internal standards should use for GC MS?

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