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- Mass Spec Tips1 - Freon for use in Mass Spectrometer Leak Checking 2 - Mass Spectrometer Probe Cooling 3 - Sample Vials for Direct Probes 4 - Selection of Vacuum Pump Oils for Lowest Mass Spec Background 5 - Determination Linkages in Biomolecules of Disulfide 6 - Transfer of H.P. ChemStation MS and GC Chromatograms from PC to MAC Computer 7 - Repairing Clogged Thermospray Probes 8 - Tuning a Finnigan 5100 to Meet BFB or DFTPP Criteria 9 - H.P. 5971 Transfer Line Tip for Direct Introduction of Capillary Column 10 - Troubleshooting Finnigan 5100 GC/MS Systems 11 - Leak Checking Mass Spectrometers 12 - Elimination of Memory Peaks and GC Background Noise 13 - SuperIncos Mapped Software Print Buffer Lockup 14 - Reduction of Peak Tailing 15 - Electron Multiplier Sensitivity 16 - INCOS Procedure for Calibrating on the Finnigan 4500 17 - Extending Electron Multiplier Life 18 - What techniques or methods do you use to determine if the electron multiplier 19- What techniques or methods do you use to detect vacuum leaks in your mass spectrometer 20 - Extending Lenear Range of the Mass Spec Article - Improving Sensitivity in the HP 5971 Mass Spectrometer - Part 1 and Part 2
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- 7 - Repairing Clogged Thermospray Probes (This Page)
Mass Spec Tips is a collection of tips relating to the operation
and service of mass spectrometers. Some of these Tips have been
reported in our newsletter, "The Mass Spec Source."
If you have a question relating to the operation or service of
mass spectrometers or would like to add your comments to the below
tip and would like to have it included in this forum, please contact us.
Input to this database of MS Tips is needed from our readers
to complete this section.
Christopher Baker
Scientific Instrument Services
Probe inserts for the thermospray interfaces used by Vestec, Hewlett-Packard and others become clogged by salts, polymers and particles. Use of an in-line filter before the probe removes the particles, but will not completely eliminate the problem. The probe, with its small inner diameter, typically 100 microns, is still susceptible to clogging.
We have designed a probe insert in which clogged capillaries are easily replaced by the user. There is a guide tube inside the 1/4Ó thermospray insert which has an inner diameter which allows a new 100 micron stainless steel (s.s.) capillary to be inserted. The thermocouples are spotwelded to the outside of this guide tube. See the schematic on page 16 of this newsletter. Replacement of the clogged 100 micron s.s. capillary is fast and simple because of this design. When a capillary becomes clogged, it is cut at the back of the insert using a tubing cutter. Use of a tubing cutter is necessary so as to obtain a smooth surface, important because the capillary has to slide through the guide tube which is closely matched to the outside diameter of the capillary. The swagelok fitting is loosened at the tip of the probe and the clogged capillary slid out the end of the probe. A new 100 micron s.s. capillary is then inserted through the guide tube, and a new stainless steel ferrule placed at the tip of the probe and tightened. The probe is then ready for use.
Operation parameters of the probes are similar to the original manufacturers probes, especially when using filament or discharge modes. These probes have been shown to produce a very stable baseline with similar or better sensitivity. Take-off temperatures may be different than those observed with the original manufacturers probes, perhaps important for those doing ion evaporation experiments where no filament or discharge electrode is being used as a source of electrons. However these new probes have been used successfully on both the Hewlett-Packard 5988 and 5989 mass spectrometers as well as the Vestec 201 LC/MS system.