I make ESI emitters for LC-MS nano-column packing with P2000 Sutter puller. The problem is that I cannot find a parameter set which will provide me with a large orifice for the emitter (in the manual they promise an orifice from 2 to 15 um). So far I get emitters with the cone ID around 3-5 um for 75 um ID capillaries and ~1 um for 20 um ID capillaries more or less independently of the parameters I use. I want to get 10 um for both of them. Parameters I tried so far ranged in temperatures from 240 to 330oC (no principal difference), pull force 10-20 (similarly, no principal difference) and time delay 128 everywhere. It is possible to go very far from recommended parameters, but it will take time.
Why not cut off some capillary from the 3~5 um end to get the size you needed?
Could you please explain what you mean by "cut off"? It is theoretically possible to grind it a little bit with a polishing disk, however the emitter must have sharp angles at the pulled end to give stable ESI spray and after polishing it will have have some flat surfaces.
Hi Sergey, try to use fused silica capillaries with a larger inner diameter. Then the pulled emitter ends will have also a larger inner diameter. But be aware that you need to set up your flow conditions for your LC run also.
Best,
Murat
Dear Murat, the task is to make emitters which add as little post-column dead volume as possible. The column ID is 75 um and the flow rate is 300 nl/min. Addition of large ID capillaries as emitters will end up with peak broadening. That is why it is necessary to make emitters from as small as possible ID capillaries (well, in reasonable limits). But it is also good to keep the opening of the emitter as large as possible (ultimately, as large as ID of the capillary - like in TaperTips). Otherwise small opening leads to higher clogging probability and higher backpressure. NewObjective somehow make such capillaries. The question is how....
But what is the bead size of yor HPLC stationary phase? Is it larger than 10 um?
1.9 or 3 um (in most cases) RP C18. The column can be from 15 to 50 cm length.
But how will an Emitter end of 10 um hold your smaller beads when you pack the column, are you using kasil frits?
@Murat: This paper describes the self-assembled frits:
https://www.ncbi.nlm.nih.gov/pubmed/?term=12498253
@Shao-En Ong: I did not asked for how to make frits. My question was how an emitter with in inner diameter of 10um will hold beads with a size of 3um. It would be very difficult to form the necessary "bridge" at the columns end.
Best,
Murat
@Murat. The idea is that the particles self-assemble themselves into a frit. Form the abstract of that article: " A five to one ratio of outlet size to particle diameter appears to be the upper maximum. In these situations the particles assembled into an arch over the outlet like the stones in a stone bridge. When 3 microm particles were packed into a tapered column with an 8 microm outlet, two particles bridged the outlet with 0.3 pl dead volume and perfect success rate. "
Sergey, did you ever figure out the parameters on the P2000 Sutter puller ?
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