Chromatography Forum

Hi,
I'm experiencing a very "expensive" problem with SB-CN 1.8µm column, after vey few sequences, sometimes two or three or even one, the column has huge back pressure and I can't run it anymore. The method I'm using is quite simple: methanol/buffer (KH2PO4 and sodium1-octansulfonate pH 3) gradient, 1 ml/min. The matrix is a tablet. the solvent of the method methanol/HCl 0.01N.
Is there anything I'm missing? Does this column require a special care or my mobile phase is particularly nasty for it?
Thanks in advance

Maybe something is crashing out. If there are guard cartridges available for your format this is
exactly the situation to use them.

Maybe something is crashing out. If there are guard cartridges available for your format this is
exactly the situation to use them.

I sure tried to use guard column, but it didn't worked as I hoped. The pressure is quite stable along a single sequence, but sgnificantly increases next time I use it (I wash it with H2O/ACN and store it in ACN)....

As a rule, buffer salts are not soluable in 100% ACN, so you're most likely not fully washing the salt off the column with your H2O:ACN wash then crashing it out with the ACN.

If I were you, I'd wash it with a MeOH:H2O solution in the same proportion as your mobile phase. ie. make up your mobile phase with no salt/acid/base in it. There is no real need to store your columns in ACN unless you're leaving them for months on end between uses.

I tried just a few minute mixing KH2PO4 Buffer with ACN and seem be a small partical appear or not clear solution is occured after mixed them, maybe this cuase of column clog after you clean and store a column with ACN.

Jetjamnong

Hi Barmassy, with 1.8µm columns, it is recommended to filter mobile phase and samples through 0.2µm filters. Are you doing this?
We have had a similar problem following installation of our first UPLC system here (steep learning curve!). What we do now is:
1) Filter all aqueous buffer components of mobile phases through 0.2µm filters
2) Filter samples through 0.2µm filters
3) Have installed an inline 0.2µm filter (just in case) between the autosampler and the column
4) After the run flush the column with ~10 column volumes 50:50 organic:water to remove any buffer (and store our columns in this unless the manufacture specifies otherwise)
5) Flush all lines with 100% acetonitrile and leave them in that.

So far, touch wood, the pressure issues have gone away .....

Mike

If you're forming salts at any stage if you can decrease the organis content of your mobile phase slightly this may help to dissolve them better (i.e. more water), our lab deals with very saline brines and all sorts every day including blocking columns constantly no matter how hard we filter! Using 100% organic at any stage may, as has been mentioned previously, crash out in your column. Increasing the column oven temperature may help solubility and make them last a wee bit longer?

If you know you are at risk of blocking a column lower the pressure threshold on your HPLC, it will then alert you that the column is beginning to block and shut off (allowing you to recondition etc) before it becomes completely stuck. We have to do this routinely to maximise the life of our columns and run them through with mobile phase gradually increasing the water content to wash the salts off until the pressure comes back down and off we go again. Some of our methods we can use a water "flush" inbetween injections but our detectors (CAD and ELSD) take too long to equilibrate so this becomes impossible.

lynz x

Thanks all. I'll try to follow your advidce and post it back results...

saw this
http://digital.findanalytichem.com/nxtb ... umn111611/