What are the methods you use for 68Ga-PSMA-617 QC?
When using two methods (TLC & HPLC) do they always give you the same result? What is the correlation value between two methods?
Have you ever analyzed 68Ga-PSMA-617 (or any 68Ga-peptide) with RCP < 80%?
Here is an observation we made comparing different chromatography methods with 68Ga-PSMA-617:
RCP obtained with HPLC (1) is higher than RCP obtained with TLC (citrate buffer or ammonium acetate in water:methanol) for 10-20 % and even more. The lower RCP is the higher the gap between TLC and HPLC results is.
In fact, previously we observed similar HPLC behavior of “unbounded 68Ga” in 68Ga-DOTA-TATE conjugates.
Does anyone have any ideas on what’s wrong here?
If Ge-68 is present It will grow Ga-68 and Ge-68 may also contribute some activity
The value of 68Ge breakthrough is incomparable with 68Ga activity.
But thank you for trying to help anyway.
Hey!
Here are couple of examples with DOTA-TATE. I think you know this TLC system :) 68Ga-DOTA-TATE is in the middle, and TLC percentages are counted as if there's no colloid.
Dear Alesya..
I suggest if you would use sodium citrate (pH 5) as mobile phase by using papaer chromatography then may the RCP values will give same as HPLC.We found i our lab most of the cases 68Ga labelled pepetide shows more free 68Ga by using ITLC-SG.
Dear Mr Kumar!
Thank you for the answer!
We had possibility to carry out TLC experiments with a lot of mobile phases, including sodium citrate (0.1 M, pH 4.6), and different strips. Indeed, in some cases we observed free 68Ga value obtained by this method being lower by 5% (comparing to othe methods, including 0.05 M citric acid). This is another interesting observation in 68Ga chromatographic behaivior.
Anyway, it's not obtaining the same results by TLC and HPLC that we are trying to achieve. We want to find out the reason of what we see. That is why we are asking other researchers to confirm or deny the phenomenon.
So, please, will you be so kind to tell us more about ITLC-SG showing more free 68Ga? More than what? How much more? And What exactly did you observe?
Dear Alesya..
68Ga labeled peptide shows free 68Ga more than 5-8% by ITLC-SG by comparing to paper chromatography the only intrested thing is that in ITLC-SG peak of 68Ga labeled compound is sharped while paper chromatography is little broad peak observed.
And the reason behind the HPLC really i have to ask the expert..
Thanks..
We have also observed this difference between paper and ITLC. It's not the same, that the deifference between all TLC data and what we get with HPLC (with PCP < 80%), but maybe all of it has something in common.
Thank you for shairing! It's nice to know that we are not completely out of our minds :)
Dear Professor Hofman!
Thank you for your answer!
Unfortunately I can't see nothing but medical data with the link you provided. This can be caused by some counry view settings or maybe I'm doing something in the wrong way. Please, let me know if there's a way to see results of chemical research, I believe they are very interesting!
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