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Daily Operation
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______________________________________________ Things to Do Before Operating the LTQ
_______________________ Finnigan LTQ Hardware Manual ______________________
3-3
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Checking the ESI Fused-Silica Sample Tube
for Elongation
Using acetonitrile in the mobile phase can cause elongation of the polyimide
coating on the fused-silica sample tube. Elongation of the polyimide coating
can degrade signal intensity and signal stability over time.
If you are running in ESI mode with a fused-silica sample tube, verify the
sample tube is not elongated past the tip of the ESI spray needle.
Cut and reposition the end of the sample tube 1 mm inside the end of the ESI
needle as follows:
1. Remove the ESI probe from the Ion Max ion source by following the
procedure described in the section Removing the ESI Probe on page 2-7
of the Finnigan Ion Max API Source Hardware Manual.
2. Loosen the sample inlet fitting.
3. Gently pull back on the sample tube to free it from the fitting.
4. Push the sample tube forward so that it extends beyond the end of the
electrospray needle.
5. Use a fused-silica cutting tool to cut off a small length of sample tube.
Ensure that you cut the end of the sample tube squarely.
6. Pull the sample tube backwards until the exit end of the sample tube is
recessed just inside the ESI needle by approximately 1 mm.
7. Tighten the sample inlet fitting securely to hold the sample tube in place.
8. Reinstall the ESI probe as described in the section Installing the ESI
Probe on page 2-9 of the Finnigan Ion Max API Source Hardware
Manual.
Go on to the next topic: Checking the System Vacuum Levels.
Note. The sample tube might move forward when you tighten the sample
inlet fitting. Ensure that the sample tube is retracted into the ESI needle
approximately 1 mm. If necessary, loosen the fitting and reposition the
sample tube.