High pH Reverse Phase Column Life

[Kelly Johnson]

Zirconia particles are extremely stable at high pH. I have quite a bit of data I can send you directly regarding the stability of the phases if you are interested. When transferring methods for neutral analytes the ZirChrom-PBD phase most closely resembles the typical silica C18 column. For the transfer of ionic analyte methods some mobile phase adjustments may be necessary to achieve the best results on the zirconia based phase. Additionally, for ionic analytes, multimode separations are possible and adjustable through the modification of the lewis acid sites on the surface with lewis base modifiers in the mobile phase. Taking advantage of the multimode capability of zirconia can often result in superior selectivity; especially for samples containing mixed (acid, basic, & neutral) analytes.

I would be happy to send you more information specific to your application needs directly. Please feel free to contact me at the e-mail below.

Kelly
support@zirchrom.com

[Bruce Hamilton]

I'd estimate my Gemini-NX has done about 2 - 3 week total, usually in periods of 1 - 2 days, then thoroughly rinsed for storage.

I suspect -NX is more robust than the first generation, however it is telling that Phenomenex don't compare the column's high pH performance with XBridge in their brochure. I chose the column because the price was right, and because I'm currently only a casual user at high pH.

I'm sure Uwe is correct, and XBridge is far superior if you wish to use a column related to the silicon family at high pH. I don't think I'd use the -NX for dominant, routine use, I'd talk to my bank manager and buy an alternative.

It would be fun to try some of the suggested alternative column substrates, as all the reasons for high pH use extolled in the excellent free Genimi-NX brochure ( which is worth a read, and easily downloaded) are still valid.

I hope you solve the problem. I suspect your conditions are just a bit too agressive for your column, and the problem is not the sample. My experience has been that, above about pH=9.5, small increases in pH in ammonia buffers greatly reduce the lieftimeof most silicon-based columns.

Please keep having fun,

Bruce Hamilton

[ColinB]

Right, I started using high pH about 3 years ago and started with the Xterra which was quite good and then changed to the Gemini which was better and then changed to the Xbridge at the end of last year having done some testing. In the UK, column prices are the same for both the Gemini and the Xbridge. I have found that the column lifetime for the Xbridge is far superior to the Gemini. Our method and solvents haven't changed too much and we usually operate at a pH of 9.8 (10mM Ammonium Bicarbonate).
Lifetime for the Xbridge is 9-10 months and 6-8 weeks for the equivalent Gemini. I have only just started testing the NX but the peak shape looks good! The Gemini peak capacity is better that the Xbridge at low ph (similar at high) but the Gemini columns are subject to packing issues and it has been known for us to replace a Gemini column after 4 days (about 30 injections). The Xbridge appears to last about a similar lifetime at low to the Gemini (batch dependent) but I am carrying out some more rigorous testing as we speak so should know more in a month os so...depending on when they die!!

[Bruce Hamilton]

Hi Colin,

Looking forward to seeing how your trials go. Can you please elaborate a little on the Gemini "packing issues"?. That would help me watch out for them. Are you seeing retention changes, front-end voids ( distorted or split peaks?), or some other symptom?.

Thanks, and please keep having fun,

Bruce Hamilton

[PHOBIUS]

Dear Lusby,

I have recorded similar problems.
The mobile phase I am using is basic (20 mM acetate ammonium pH=10), therefore decreasing a silica based column´s lifetime rapidly.

I won´t write you much about the theory (silica dissolving, hybrid sorbents etc.) I rather share my practical experiences. I have tried different RP columns.

Synergi fusion (max pH 10) I used 9.2 Number of injections till peak broadening = 150

Gemini NX (max pH 12) I used 10.0 Number of injections 100 (!)

Xbridge (max pH 12) I use 10.0 I have done 100 injections and the column is still working perfectly. (will the fun ever stop? )

I am not sure, if it helps you. The method is working, however it will be probably "column consuming".

[ColinB]

Hi Bruce,
I will indeed keep you all updated on developements. With regard to the Gemini packing issues. This is what I know. We first used Gemin about 3 years ago and we had issues where columns would die (at low pH in 0.1% formic Acid) within a month (at best). We spoke to Phenomenex and they advised us that some of the early batches had a few "packing issues" (stability, voiding, splitting) so it was suggested that we only buy columns with a batch number of 16 and above!
We have done this but we are now on Batch 21/22 and we have started having issues again. Peaks are splitting, we are seeing voids and we have been told that there might still be "packing issues". Some columns have lasted a few days...one did 20 injctions....10 of which were testmix. We don't usually use guard columns but I even put some of those on to see how that would effect the situation...it made no difference. It has been recommended that we change to Gemini NX.....which is a nice idea but the chromatography on the NX in direct comparison with the original Gemini is quite different with the NX giving much longer retention times....hence the assessment.
I am assessing a few other columns at the same time and the initial assessment will be at low pH as the Xbridge has proven (for us) to have good lifetimes at high pH. If anone would like to know the number of injections that we do then please fell free to ask.

[Bruce Hamilton]

Hi Colin,

Thanks for the response. Yes, I would be interested in the outcome of your trials. I haven't had any problems with the -NX column so far, but will watch for voids/split peaks.

I'd normally have attributed those to sustained working at high pH, and assumed the column was OK, so it's good to consider the issue, and discuss any problems, if they arise, with their local representative.

I'm surprised that Phenomenex wouldn't find and fix such packing problems in their column QA procedures. I hope you find a robust and reliable column for your work.

Please keep having fun,

Bruce Hamilton

[Flappytango]

also this previous thread

http://www.sepsci.com/chromforum/viewto ... highlight=

I continue to be very impressed with xbridge. we run pH 10 day in day out.

[XL]

Lusby43,

For silica based C18 stationary phases (including both conventional silica and organic-inorganic hybrid materials), there are always un-derivatized sites (silanol groups) on the surface in addition to the bonded sites. In a strict sense, they are reversed phase/cation-exchange mixed-mode phases. At high pH, silica at “baredâ€

[hplcuser]

NX in direct comparison with the original Gemini is definitely different. I have also noticed the same issue with the NX giving much longer retention times.

[vikmnilu]

Hi everybody,
I consider this topic very interesting, I am analyzing some PAH metabolites and found out for certain species that pH around 9.5 (amm acetate 10mM with 1% TEA ) helps separating what I believe is 2 peaks, although my columns could not bear the pH (theoretically).
Now I am planning to buy a column that would bear that high pH and I have been thinking about the Gemini NX, but thanks to your comments I also started to consider the XBridge.... so , taking into accoun that I would like to keep the column "fit" as long as possible, would you buy the Xbridge???

I made the separations in a Zorbax C8 XDB agilent column that has been found to bear high pH conditions for about 3 months (stated at Practical HPLC method develpment, by Snyder, Kirkland and Glajch, 2nd edition, pp 203-204. Anyway, as I have plenty of samples to analyze, I also would like to know if the degradation and peak broadening tha thappens after some injections is acceptable to still run in the same conditions for some time.

Thanks in advance and I hope this topic is not completely dead, as last reply is from more than 2 years ago