Operation
Agilent 55B AA Spectrometer User’s Guide 83
The nebulizer is now ready for use. If you have just installed the nebulizer, you
should carry out the Performance checks- see Page 85.
Low vacuum setting
In low vacuum mode (the high solids setting) the capillary position is adjusted
close to the end of the venturi throat. The greater clearance around the capillary tip
reduces clogging caused by solutions with a high solids content. When using this
setting, the pressure drop (vacuum) at the capillary tip is relatively low.
Consequently, you must use wide bore (0.64 mm ID) plastic sampling capillary
tube to achieve the uptake rates required for maximum sensitivity.
As the uptake rate will be sensitive to the hydrostatic head of the liquid in the
sample container, care is required to minimize variations in liquid levels in the
sample and standard containers.
To set the nebulizer to low vacuum mode:
1 Fit the wide bore (0.64 mm ID) tubing to the capillary.
2 Loosen the locking ring and turn the thimble (and ring) fully clockwise.
The nebulizer is now ready for use.
NOTE
At this setting, the uptake rate will be sensitive to the hydrostatic head of the liquid
in the sample container, thus care is required to minimize variations in liquid levels
in the sample and standard containers.
Set zero uptake rate – organic solvents
Before adjusting the nebulizer for use with organic solvents, set zero uptake rate
using distilled water as the solvent:
1 Fit the wide bore (0.64 mm ID) tubing to the capillary.
2 Turn the locking ring anti-clockwise until it is up against the thimble.
3 Turn the thimble clockwise as far as it will go.
4 Aspirating distilled water, turn the thimble counter-clockwise until bubbles
emerge from the end of the capillary tubing.
5 Turn the thimble clockwise to the point where bubbling ceases.
This is the zero-uptake point (no solution is being aspirated through the nebulizer).
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