Chromatography Forum

Hi,
I am looking for input and experiences of different ACN grades. I use UHPLC-MS grade but different brands give different specs for this quality. The brand I have been using increased the price five fold since last order. I can find a different brand with UHPLC-MS stated quality for lest than 10% of the new increased price of the previous brand.

I am comparing Merck and VWR brand so two of the big suppliers and most spec are not that different but some are different for example:

Residue value as 2 ppm and the other 1 ppm
Water content 0.01% and the other 0.02%

The more expensive brand does give higher spec but cost 10 times more and both are stated as UHPLC MS quality. I find it difficult to know how important these differences are.

1) I understand that it depends on you assay and if you get background ions but in terms of contaminating the UHPLC-MS systems, would 1 ppm residue vs 2 ppm make much differences?

2) For your applications do you often see advantage of going to the highest grade and difference between UHPLC-MS grades of solvents between brands?

3) What parameter in specifications are most important to evaluate when comparing/changing solvent?

The prices fluctuate to a large degree and we cant keep large stocks of solvent in the lab for the fire hazard so some flexibility in supplier can save a lot of money.

For some tests I have been able to use normal HPLC grade solvents even in LCMS without any problems. The one test I had to absolutely have LCMS grade solvent was for doing PFAS/PFOA testing, it is nearly impossible to find one that doesn't have some contamination from those analytes as such super low levels.

The best I found at the time was the Honeywell Burdick and Jackson LCMS grade.

I doubt 1ppm difference in residue will make any difference in performance unless that residue happens to be an interference to your target analyte. Also those are normally the limits the producer sets as a failure point so the actual value of residue or water could be even lower than what is listed as a spec.

My methods are with chromatograpy and mrm so hopefully small changes in the contaminats wont be a problem for the mrms, which will likely be seen in blanks. The samples we run are valuable so one is always a bit paranoid of potential problems and changes. The price fluctuations are really excessive for lc solvents.

I really appreciate to have this forum to be able to ask questions and get feedback. Thanks!

The key is "fit for purpose". The tiny percentage of water isn't a concern if your other mobile phase is aqueous, but the wrong contaminant at a few ppb could be a disaster for a trace-level assay. More costly is not always better.

With any change in mobile phase vendor, lot, or grade, we always immediately run a "double blank" (aka "solvent") sample scanning all of the MRMs for interferences.

And, also importantly, a QC standard or calibrator to see if the raw area counts are off from the most recent data from that standard using the old mobile phase.

Some seemingly invisible (either due to poor ionization or high molecular weight) impurities can cause matrix suppression (or rarely enhancement) when they elute. This can cause serious headaches identifying the problem.

My advice is to track raw peak areas of MRMs and try a sample bottle of a mobile phase before committing to purchase a large number of bottles from a single lot.

You may also use a solvent filter like this one: https://www.shimadzu.eu/sites/shimadzu. ... E0001B.pdf

The key is "fit for purpose". The tiny percentage of water isn't a concern if your other mobile phase is aqueous, but the wrong contaminant at a few ppb could be a disaster for a trace-level assay. More costly is not always better.

With any change in mobile phase vendor, lot, or grade, we always immediately run a "double blank" (aka "solvent") sample scanning all of the MRMs for interferences.

And, also importantly, a QC standard or calibrator to see if the raw area counts are off from the most recent data from that standard using the old mobile phase.

Some seemingly invisible (either due to poor ionization or high molecular weight) impurities can cause matrix suppression (or rarely enhancement) when they elute. This can cause serious headaches identifying the problem.

My advice is to track raw peak areas of MRMs and try a sample bottle of a mobile phase before committing to purchase a large number of bottles from a single lot.

Thanks that is good advice I do have the higher quality left so I can compare. I was considering two aspects one is to have low background for my method the other is to minimize the the contamination of lcms system over time. When price difference become 10x one needs to investigate when the higer cost is justified. We run some water on mobilephase so a little water wont be a problem.