What does a Particle Trap do?
30 Apr 2009
PLOT columns are coated with adsorbents which is usually deposited as a layer of particles.
A particle trap is a 2-2.5 m piece of fused silica tubing coated with 0.2-0.5 um of Rtx-1 phase. If a particle is released from the surface, it will be ‘caught” by the particle trap, so it does not enter the detector. The coating on the particle trap will act as a "glue". Because the retention of adsorbents used in PLOT columns is much higher then the liquid phase deposition in the particle trap, the retention of the column is virtually similar.
When using valve switching, often particle traps are positioned between the valve and the PLOT column to protect the valve from damage. Connection is done with a PressTight. Particles may also accumulate in the PressTight, forming a restriction.
Conventional PLOT columns showed a lot of particle generation, they're often even supplied with a particle trap.
New generation PLOT columns are stabilized/bonded in the best possible way minimizing the risk of particle-release. For majority applications, particle traps are not required anymore. I still would recommend to use a particle trap in cases of extreme situations like: valve switching when high pressure drops are expected or when a PLOT column is connected into the MS. In this last case, it is recommended to use a smaller bore capillary to deal with the big pressure drop that exist at the end of the column. ( vacuum of the MS). A 5m length of 0.15/0.18 or 0.25mm ID fused silica will provide good interface, so that the vacuum will not rip-off the particles from the PLOT column. You can take a 5 m section of Rtx-1 or 5 coated column for that(0.25um film). This 5m section will also act as a particle trap in case some particles are released. Coupling is done with PresTights. Using the right procedure, there should be no problem with leaks, even with MS.
Also note that transportation of PLOT columns can always cause some particles to release. Before connecting it is recommended to condition any PLOT column at a higher flow (+30%), without connecting to detector, and program the column to a temperature that is 10-20C above the application temperature. ( do not exceed Tmax). This way any loose particle caused by transportation, will have a chance to elute and we can safely set up the column with the detector and/or valving.