How do i "reconstitute" a vial?

Discussions about sample preparation: extraction, cleanup, derivatization, etc.

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I'm having a bit of trouble prepping an impurity. I need to weigh out 2mg of Impurity X and it only comes in 1mg vial quantities. Its a gel-like semi solid gloop substance and the instructions on the vial says to "Reconstitute the vial contents in method diluent" so I added a few mls of diluent to each vial, swirled it a few times and added this, and any washings, to my final flask.

I wont see if the peak is present yet for another day or two as its on a queued run but now a co worker has told me I should have capped the vial with the diluent inside and vortexed for a minute or two before transfer to vessel to ensure dissolving of material.

Has anyone ever come across vial reconstitution before?
There are several hard to come by analytes that come in very limited quantities (1mg or less) per vial just because of the expense of the pure analyte. Often fo these you will have to just add diluent to the vial to make a standard instead of trying to accurately weigh 1mg or less which is almost impossible without a 5 place balance located inside a glovebox to prevent air currents.

If you add 1ml of diluent then you will have 1mg/ml concentration for a standard. I normally just leave the diluted standard in the vial the source is shipped in if possible. Depending on how quickly the analyte will dissolve will depend on how much mixing you will need to do after adding the diluent. If transferring to another vial I usually use a pasteur pipette and draw up the solution and push it back into the vial several times to make sure it is mixed well and dissolved, vortexing would do the same think I guess.
The past is there to guide us into the future, not to dwell in.
Thanks for the answer James. Yes, 2mg is the smallest I have had to weigh. The difficulty is I need 2mg of Impurity Y, which is a powder and easy enough to weigh out, and 2mg of Impurity X which is a gel and they both need to go into a 25ml flask as specific nominal concentrations ie (2/25) *1000 = 80mcg/mL.

Thanks for the tip on dissolving. My diluent is methanol so I put in a few mls of methanol, swirled the vial then emptied it into the 25ml flask followed by one rinsing. Probably not good enough in retrospect but Ill know tomorrow when I check the run!
If you still have the original vial you could always take some of the mix you have made and rinse the vial again, this would pick up any of the remaining analyte from the vial and should not change the total volume of the mixture.
The past is there to guide us into the future, not to dwell in.
I can only agree with James's comments but would ask how sure you are that you have been supplied with 1mg in the first place. This may only be confirmed by weighing before and after rinsing (After drying)

What is "X" ? We need to know the volatility of it
Regards

Ralph

www.itsjustabox.com
Impurity X is an impurity that is required for a resolution system suit test ie resolution between active and X needs to be greater than 1.0. Its used to be a powder but that company stopped manufacturing it and the new company only ships it in 1mg amounts plus its now a gel like substance.

Update: there WAS a peak present but the area was only about half that of the suggested method which means I didn't manage to recover it all, so I think in future I may need to wash it out more as suggested above and vortex it. But I'm happy with half the area because the resolution is miles away anyway.
If X is hygroscopic, then it could look like a gel because it is wet, which would give a reduced peak size as you have after analysis.

It is not a fun thing when we have to rely on using analytes that come in such low weights. I have the same problem wit Mycotoxins and Cyanotoxins where one I received only 50ug, you just have to trust that is what they put in the vial when you reconstitute.
The past is there to guide us into the future, not to dwell in.
Interesting point James, I didn't even consider the hygroscopic nature of the material and now you mention it, there was a mention of that on the vial instructions I must have another look at it tomorrow and if that was the case, then my areas are not going to match anyway because the method I'm following references the old Impurity which was a powder and probably returned a different area/peak response.
After rinsing and drying the vial (compare before and after), I would weigh the vial to be sure you got the exact mass.
If you only want it as a retention or resolution standard then you don't have to work quantitatively. As long as the peak is big enough to detect reliably, and not so big that its retention shifts you are good to go.

Peter
Peter Apps
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