Chromatography Forum

In my previous post I was seeking help to figure out where some ghost peaks came from in some of our gradient methods. It was identified that these peaks were actually from acetonitrile. The brand of acetonitrile we are using is from EM Science. Right now the problem is that, we found out that some of the lots are great, some of the lots are not suitable for gradient.

Can anyone recommend a brand of acetonitrile which give consistent great quality and is suitable for gradient? Thanks.

J.T baker gives me very nice constant results(for UV and MS detection). I have tried a local brand which is cheaper, but with lower quality, I'm using it for my more preparative work…

We use mainly Fisher and Baker, but we have also used E&M without a problem.

Are you sure that the peaks are not coming from your water? Often, with a gradient method (all gradient methods are guilty of this to some degree), non-polar compounds in the water that stick to the column during the initial gradient conditions are 'flushed out' as the gradient progresses. This explains why after a long equilibration with the initial conditions, the first gradient run usually has the worst baseline.

I have noticed this problem esp with methods that go from a very low to very high org content.

Thanks for sharing your opinion, Albany.

I think it is evidenced that the peaks are from acetonitrile, at least some peaks are from it. Our chemists were running a gradient method and seeing some ghost peaks. The ghost peaks disappeared after she/he switched to a different lot of ACN (everything else was exactly same). And this has been proved a few times.

Initially I thought it might be from TEA but it wasn't the case. I also followed a suggestion from someone in this forum to filter water with Empore C18 cartridge but still didn't work out for us.

To correct myself, we are using acn from EMD chemicals. On the label it says good for GC, HPLC and gradient analysis. But...I wish we could find one with consistent quality.

Oh well - that was my best guess.

Do you filter your mobile phases? I try not to filter those used for gradients (unless I have to) since I end up getting some leachables from my filters sporatically.

I have had good experience with ACN from Fisher and EMD Chemicals. I used EMD Omnisolv (HPLC Grade, AX0145) without problems in gradient separations.
Most "ghost peaks" I have encountered over the years came from solvent filters, mobile phase inlet frits (polymer based ones), the DI water and ion-pairing reagents (TEA for example).

Best regards,

I have tried JT Baker, Merck, and Mallinckrodt Baker. They are ok for gradient run HPLC.
We never found that the organic solvent is the source of problem in gradient run as water did.

I've used Merck gradient grade with no problems - so far. Not the cheapest, but has matched my needs.

However, I'd strongly recommend going back to the manufacturer of the product giving you grief. Providing them with good and bad batch numbers and the analytical conditions, and asking the manufacturer to investigate why you had the problem.

If they really care about their products, they will at least investigate and report back. If it's an unhelpful response, then you can avoid their other products as well. If they work to solve your problem, you can balance that good experience against the cost of future use of their products.

Bruce Hamilton

In this laboratory he best tests results (UV, Fluorescence) were obtained with Riedel-deHaen Acetonitrile G (now part of Sigma Aldrich Fluka?).