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6.6 Dealing with Plugged Cartridges
The CHDF capillaries are contained in two cartridges as follows (also see section 2.4):
1. The top, or Fractionation cartridge (white).
2. The bottom cartridge (black).
The top cartridge contains the capillary responsible for particle fractionation. The bottom
cartridge contains the “make-up”, as well as the “waste” capillaries. The CHDF cartridges can be
responsible for the following two problems:
1. No peaks are detected upon injection of samples and /or marker.
This condition is frequently caused by a faulty top cartridge.
2. High pump pressure. This is usually caused by a faulty bottom cartridge, or a plugged in-line
filter.
Normally, the top cartridge is not responsible for high pressure, even if it is totally plugged. This
is because only a very minor portion of the eluant flows into the fractionation capillary. High
pressure can also be caused by a blocked cartridge in-line filter as described in section 6.6.3.
There are 3 options for fixing the top cartridge fault which is responsible for lack of sample
detection. These are snipping off the end of the capillary, backflushing the capillary (see section
5), and replacing the fractionation capillary.
Chapter 5 discusses how to flush the cartridge with solvent, or backflush it to remove a plug. If
either of these techniques are not successful, there are two techniques discussed here that will
ultimately take care of the problem. The first, snipping off the end of the capillary, assumes the
plug is in the very end of the cartridge, and that this section will be removed when snipped off.
The second method described here, changing the fractionation cartridge, guarantees that the
plugging problem will be resolved.
A third section below shows how to clean the cartridge in-line filter in order to eliminate high
pump backpressure.
6.6.1 Snipping off the End of the Capillary
The idea is to dismount the white fractionation cartridge from the CHDF2000, with the two 5-
inch long, 1/16” stainless steel tubes still attached to the cartridge; once on the bench, remove the
inlet SS tube, leaving the capillary exposed, then snip the capillary. See Fig. 6.20. Details are
shown below.
1.
Stop the pump on the CHDF 2000, wait for the pump pressure to drop below 1,000 psi.
2.
Open the front door of the instrument. The cartridge is located in the center top position, and
is shown in Figure 6.20.
3.
Disconnect the cartridge fitting from the instrument at locations 1, 2, 3, and 4 shown in
Figure 6.20. CAUTION: DO NOT LOOSEN FITTINGS NUMBER 5 and 6 YET. The fused-
silica capillary stretches into the two stainless steel tubes, 7 and 8. Detaching tubes 7 and 8 at
this point will result in fractionation capillary breakage.
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