Chroma:
Unfortunately, I don't think you've provided enough information for me to answer your specific questions, but here are some general comments.
The term "capillary" simply means narrow tubing. In HPLC capillary tubing usually refers to one of several things:
- fused silica
1/32 inch outside diameter (OD) (or less) hard polymer tubing (usually PEEK)
1/32 inch OD metal tubing (usually stainless steel)
PEEK-clad fused silica
Each of these tubing materials requires its own types of fittings and cutting procedures.
Fused silica can be cut by hand in the lab using various types of inexpensive diamond scribes. (New Objective sells a very simple one
http://www.newobjective.com/products/ess_tools.html.) For micro and nanoflow systems, it's a good idea to inspect the cuts with a low-power microscope or good hand lens to insure the cut is clean.
Capillary PEEK is more difficult to cut, but IDEX Health and Science (
http://www.idex-hs.com/default.aspx) sells such a cutter.
Although 1/16 inch OD and bigger steel tubing can be cut by hand, the results are poor. It's hard to get a straight, square cut. I've never tried to cut 1/32 inch. Most people use pre-cut steel with polished ends.
PEEK-clad silica can not be cut at all and is only used in pre-cut lengths.
As far as fittings go, I highly recommend finding a copy of the book "All About Fittings" by John W. Batts IV. This book used to be distributed for free by Upchurch but seems to have disappeared since Upchurch was acquired by IDEX. The IDEX fittings catalog also makes excellent reading.
Most fittings consist of a ferrule and compression nut ("two piece") or a combined ferrule/compression nut ("one piece"). There are also some fittings that use two ferrules. Some capillary tubing fittings also require a "sleeve". For these fittings, the ferrule compresses on the sleeve and the sleeve compresses onto the capillary. Some compression nuts just need to be "finger tight" while others require some sort of wrench.
The best way to assemble a fitting (usually) the following:
- Slide the nut and ferrule way up the piece of tubing.
Press the end of the tubing into the port so that the bottom of the tubing makes contact with the bottom of the port.
While keeping the tubing pressed into the port, slide the ferrule and nut down the tubing and tighten. This step is important because it insures that there will not be a gap between the end of your tubing and the bottom of the port.
I hope that helps!
