Chromatography Forum

Recently we have observed that few times the sample when injected from a particual vial is giving different area than the same solution when refilled in a different vial. The 1st vial repeatedly gives the same area even on changing the cap & septa, injection by removing both caps & septa, injection by removing only septa.

Vials were rinsed with sample solution 2-3 times prior to filling & vials, sepa & caps set is of highly repute brand.

Please comment.

We have currently a similar problem for an HPLC method (Alliance).

We observed that the control standards were always negative, and that they became more negative over time. This phenomenon disappeared when we started to use the pre-slit vial caps (UPLC vials). Now all control samples are centered around 100%.

I have no idea why this is so, but it was the solution in this case.

I went through a similar issue with two very similar compounds that we assay at very low levels. I even went so far as to do a vial study. I tried four different manufacturers, using both clear and amber vials. For each vial, I did a set of six vials, one injection per vial and checked %RSD. Some vials gave an %RSD as low as under 1%, while the worst offender was over 13%. For any single vial, six injections I got a %RSD under 0.4%. Each vial type/manufacturer had a different level of response for the same solution. Clearly I had a vial to vial variation issue.

What I found in my case was that I had oxidation issues. I ended up adding sodium metabisulfite to my diluent and the issue went away for all vials. The solutions were stable in volumetric glassware on the tabletop for at least three days. To this day, I'm not sure what about the vials caused the issue, I suspect some processing aid, but it sure annoyed me to no end for a while.

Paul

We have currently a similar problem for an HPLC method (Alliance).

We observed that the control standards were always negative, and that they became more negative over time. This phenomenon disappeared when we started to use the pre-slit vial caps (UPLC vials). Now all control samples are centered around 100%.

I have no idea why this is so, but it was the solution in this case.

You have this observed only with Waters Alliance System?

We have currently a similar problem for an HPLC method (Alliance).

We observed that the control standards were always negative, and that they became more negative over time. This phenomenon disappeared when we started to use the pre-slit vial caps (UPLC vials). Now all control samples are centered around 100%.

I have no idea why this is so, but it was the solution in this case.

You have this observed only with Waters Alliance System?

Have not tested it on any other equipment!

We are using pre-slitted septa only.

for polar compounds this is sometimes a problem..active silanols on glass reacts with polar compounds..to avoid this silanized vials should be used..

We have currently a similar problem for an HPLC method (Alliance).

We observed that the control standards were always negative, and that they became more negative over time. This phenomenon disappeared when we started to use the pre-slit vial caps (UPLC vials). Now all control samples are centered around 100%.

I have no idea why this is so, but it was the solution in this case.

You have this observed only with Waters Alliance System?

Have not tested it on any other equipment!

My colleagues operating Alliance system observed this problems too. After the followed the waters recommendation to use pre-slit vials the problems were dissapeared.

I'm just wondering, because I was also operating Alliance system some years ago and I have never heared about this problem.