Preventing Blocking Of The Nebuliser - Thermo Scientific iCAP 6000 Series Maintenance Manual

iCAP Customer Training Manual
8.4 Preventing blocking of
the nebuliser
The most common problem with the
nebuliser is the blockage of the tip by
the deposition of particulate matter. In
this section we provide a series of
suggestions to minimise blockage.
In most instances blockage in the
nebuliser is caused by either
particulate matter (from the sample)
or chemical deposits. It normally
occurs in the nozzle where the flow
passages are extremely small and
constriction is greatest in the annular
gas channel between the tip of the
capillary and the taper of the nozzle
o Tip:
Filter the carrier gas. Low-impedance in-line gas filters should be installed
to prevent particles from being carried into the nebuliser and lodging in the gas
annulus. This is especially important when Teflon® tape has been used in the
gas line plumbing. Shreds of this tape have been found wedged in the gas
annulus and have resulted in drastic reductions in performance. For the same
reason, we suggest that you avoid using Teflon or other friable sealants at the
gas connection to the nebuliser
o Tip:
Filter the sample. The sample capillary is more tolerant of particulate
matter than the gas annulus. For high sample uptake nebulisers, the capillary
will frequently transport visibly turbid suspensions. We suggest that you filter or
centrifuge the sample if the solids are not of analytical importance. Particulates
and colloids of a polar nature such as silica, peptides, polyvalent metal
hydroxides and others tend to build up on the (polar) glass and impede the fluid
flow. In some instances you can prevent deposition by adjusting the pH of the
suspension away from its isoelectric point.
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