Column life

MikeT

<p><span>Greetings</span></p><p></p><p><span>I'm wondering what would be the average life expectancy of BEH C-18 columns. I have been using a 2.1 x 50 mm BEH C18 and a 2.1 x 50 mm BEH Shield RP18 for over a year now. Both have about a 1000 injections. I'm thinking a year is a long time but at $700 for a column why replace them if I don't need to. There is a little tailing but not much. And if I use a 30:70 ammonium acetate:ACN mobile phase would I see any benefit going to the 3.0 mm ID column?</span></p><p></p><p><span>TIA</span></p><p><span>Mike</span></p>

dougm

As with an HPLC column, the lifetime of a UPLC column depends upon how well or poorly it is treated. With well prepared samples and mobile phases we have seen examples of UPLC column lifetimes exceeding 70000 injections. So, there is no single quantitative answer as to how long a UPLC column lasts since every application is slightly different. Several thousand injections is normal, assuming reasonable care is exercised.

Assuming that you scale everything properly (by a factor of ~2.0) I do not see how going to a larger ID UPLC column will improve column lifetimes. I agree with your comment that if the UPLC column is performing well there is no need to replace it. Do you have a normal frequency of replacement based upon number of injections for your HPLC methods/columns?

--Doug

sazimi

Changing the column w/o column efficiency check never be recommended, use any polar analytes (like paracetamol, aspirin or any or waters recommended) determine the theoretical plates (N) routinely (may be after 1000-1200 injections). But before this understand factors effecting column life & these are quality of solvents, sample prep.,pH & column temperature. pH range of BEH columns are 1-12, but bw pH 7.5 - 11 dont go above 40'C (especially with BEH Shield, at pH 7-11 work at 30'C).

Dont worry in your case 30:70 ammonium acetate:ACN, pH range should bw 3-6, you can work max. 60'C w/ BEH C18 & max. 50'C w/ Shield,

Column is not only the cause of peak tailing, try little TEA & then observe, if still PT then you must check your sample prep., injection modes, pump pressures, in-line filters etc. & also column cleaning is the must try (10%MeOH=12min, 70%MeOH=8min, w/ 40'C, 0.4mL/m) - if polar compounds then equilibrate with mobile phase & inject your samples.

We are still getting v. good peaks above 3400 injections (BEH C18) & 2100 injs (Shield) so why you going to 3.0mm ID it will increase the consumption of your ACN.

Salman Azimi

Analytical Specialist

MikeT

Thank-you for your reply. I am not very experienced with LC. I did use a HP1090 years ago for Cyclosporin and that column (don't remember what kind) did not last very long. Most of our work is GC/MS and GC columns don't last very long either. We've only had our UPLC for two years so I haven't determined any normal frequency of replacement.

I was thinking of trying the new 3.0 ID UPLC column since I figured there would be less pressure required but it didn't occur to me I'd be using more mobile phase so I guess I'll not bother.

Thx

Mike

MikeT

Thank you for your reply. I'm not sure I can use TEA, I use alkaline pH mobile phase (pH 10). I run at 30°. Will forget idea of 3.0 mm column.

Mike