Different ISTD Lot Sample Concentration Conundrum

Discussions about GC and other "gas phase" separation techniques.

2 posts Page 1 of 1
Howdy everyone! First time posting here, long time lurker as a non-registered member.

So I'm a GC-MS method (a method that honestly could be on a FID) and I was given my samples to analyze on this method. I prepared my ISTD (lot 1) for this method and I had more "last minute samples" come in and I didn't account for the additional samples when preparing my initial ISTD batch. So these samples are the "worlds supply" and have been diluted with my ISTD (lot 1) diluent. I prepared another batch of ISTD (lot 2) for my 5 pt calibration curve at the same concentration as lot 1.

So here's my possible issue, lot 1 conc is 3.02 mg/mL and lot 2 is 2.99 mg/mL. I haven't started the sequence yet because I realized there might be an issue if I were to calculate the samples true concentration as the RF might be different.

Would it be wise to use relative RF or Area % to calculate my "worlds supply" of samples w/w%?

The problem is the method is pretty old (contains chart speed parameters, lol) and the person who developed it and validated the method isn't available and there's no commentary in the method about relative RF. I just want to ensure I give out as accurate results as possible on this. Any assistance is greatly appreciated!
For 1% difference in internal standard concentration?
2 posts Page 1 of 1

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