Chromatography Forum

Hi Uwe,

Thank you for your comment.

Pardon me for my ignorance/ poor understanding as I am new to LCMSMS.

Exactly what do you mean by adjusting the sampling rate?

We're doing MRM, monitoring 4 ions. By increasing the sampling rate, do you mean adjusting scanning rate?

Sorry, the more I look into the manual of my LCMSMS system, the more I am confused as to what is referred to.

-
Wan

I understand now: you have 100 ms dwell time, you monitor 4 ions, this takes about 0.5 seconds per cycle. You accumulate 4 cycles into a displayed data point, i.e. your visible sampling rate is about 2 seconds, and that is what the "good" chromatogram shows.
I had missed the point that you monitor 4 ions.

Bumping the thread because my lab is looking to do melamine and cyanuric acid in infant formula by LC-MS/MS as well. We've been mainly buying Agilent supplies (to go with our 6460 LC-MS/MS) but I don't see an Agilent zwitterionic column similar to the ZIC-HILIC. Any thoughts?

A nice bonus would be if the column we obtain turns out to give good retention of acrylamide, since that is another tricky analyte that's difficult to retain on RPLC.

Macherey-Nagel Nucleodur HILIC has applications for both melamine and cyanuric acid, and an application for acrylamide.

http://www.mn-net.com/DesktopModules/Ta ... fauld.aspx

http://www.mn-net.com/DesktopModules/Ta ... fauld.aspx

Interesting. And the Nucleodur columns appear to be around half the price of ZIC-HILIC in Canada.

I notice however that M-N has part numbers for 2 mm ID columns on their web site, but none of the North American distributors have any smaller than 4.0 mm. So if I wanted one to match the dimensions in the FDA paper we might have to make a special request.

here mixed-mode application for both:
http://www.sielc.com/Compound-Melamine- ... amine.html

contact me if you have questions.

I contacted one of the reps we often deal with about this question, and he basically started off with all the reasons not to go with HILIC (mainly long equilibration times). He mentions columns like Pursuit RFP and Bonus RP that can handle high aqueous.

Any thoughts in that vein? I was thinking one argument for having at least one HILIC column is for greater compatibility with these tricky analytes in methods that produce acetonitrile extracts - such as QuEChERS, or anything with a protein precipitation step. In which case ACN in the injection solvent severely distorts peak shape when your separation requires highly aqueous phase, but is beneficial when your separation requires high organic.

Also how about the Thermo Syncronis HILIC column? Looks like we can get it much cheaper than ZIC-HILIC and it's also zwitterionic, but it looks like the actual phase is proprietary - so no way to know how comparable it is with the others. And pretty new so not in a lot of publications.