uplc glogging

[aldij]

dear members,
for our new lc-msms-system we are considering uplc io normal hplc. because we are injecting "dirty" samples( precipitates of whole-blood samples) one posble isue is the fast gloging of the uplc-column.
my point of view is that there are two ways to glog the column:

-injecting particles. this will also be a problem with normal hplc-columns with 3 µm particles. we think we must filter our samples thru a .45 µm filter. will this after filtration be a much bigger problem with 1,7 µm particles then with 3 µm particles?

- injecting matter that will precipitate on the column. i think this will allso be a problem with 3µm particles and we think we must back-flush the column on a weekly basis to avoid problems wih this ( this backflushing will also avoid problems coming fom the injection of particles).

so i think the problems will not be much bigger then with hplc.

am i seeing some wrong here? anybody has any ideas about this matter?

aldij

[Kostas Petritis]

I think you have it right.

I think that you have problems of this kind when you go from analytical to nano-LC than from HPLC to UPLC (with some assumptions been made).

[Chris Pohl]

aldij,

I was just at the ASMS meeting last week and while I can't contradict your assumptions based on my own personal experience, the data reported there seems to contradict one of your assumptions. In two separate oral presentations, the speakers reported rather substantial increases in pressure with fairly modest sample numbers (if you're interested in specifically which papers, I think I can get that up) when performing UPLC. Of course, perhaps they were both doing something wrong.

From my experience, you have to keep in mind that filters are not exact in terms of particle size cut off so I wouldn't expect that you can get away with using a 0.45 µ filter was 1.7 µ stationary phase particle size. In fact, I believe both speakers specifically mentioned they used 0.22 µ filters and had pressure buildup problems anyway so you definitely won't be able to get away with using 0.45 µ filter media.

[Kostas Petritis]

Chris,

I would be interested to know which oral presentations mentioned this. The beauty of this year ASMS is that they recorded the talks and you can have access to them until June 24.

There is another possibility of the backpressure build up, however I would prefer not to discuss on the forum.

[Uwe Neue]

All the usual things that cause high pressure with normal LC also cause high pressure with UPLC. These things are the type of stuff that aldij was talking about. Some of these problems can be made to go away with an in-line filter. All of these problems can be made to go away with a guard column.

[Chris Pohl]

Kostas,

The two papers I mentioned that I saw at the 53rd ASMS meeting in San Antonio, Texas last week were: MOAam 11:15am (Coupling Ultra Performance Liquid Chromatography (UPLC) to Mass Septrometers for Faster Pharmaceutical Analysis) and TOBam 10:35 (Determination and Screening of Multiclass Pharmaceuticals in Surface Water Samples by LC-Tandem MS and LC-Q-TOF-MS). The latter paper is a bit ambiguous on the filtration point since one of the slides indicates that 0.45 µ filters were used whereas the concluding slide indicates that 0.22 µ filters were used. They mention observing a 67% increase in pressure (column pressure increased from 7500 psi to 12,500 psi) associated with the injection of 400 filtered samples, 20% of which were wastewater samples. The presenter made the point that you need to be careful when injecting wastewater samples.

[aldij]

uwe,
if i ame remembering right, you are working for Waters ( unlike some people i don't mean this as a offence ).
about the inline filter, can a in-line filter be placed in an UPLC? then changing the filter every 100 injections would avoid the problems.
about the guard column, as i understood the problem with glogging maily happens at the last frit that has to be fine enaugh to hold the particles in the column ( correct me if i ame wrong). does the quard-column has a fine enaugh frit to give the problems with glogging in the frit of the guard-column istead of the frit of the analitical column? otherwise the guard-column will do nothing for you.

aldij

[aldij]

kostas,

please tell me about the "other posibility"

aldij

[Uwe Neue]

aldij,

An in-line filter can be placed into the UPLC. No problem.

I do not know, after how many injections you need to replace the filter. This is of course dependent on the load that one is putting on the filter.

My colleagues have looked carefully into the location of column plugging. This is something that is easy to do. You get a plugged column, you verify that it is plugged, you exchange the inlet filter, and 90% of the time, the pressure decreases. Thus most of the time, the increase of column backpressure is due to the plugging of the inlet filter. To me the simple solution to this problem is to put the same filter upstream and replace it when needed.

Clogging of the bottom frit without clogging of the inlet frit is close to impossible and it does not agree with our experience.