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Operation
Nebulizer Setup
This section assumes you have correctly assembled the nebulizer,
and installed the nebulizer/spray chamber assembly in the sample
compartment.
The nebulizer is fully adjustable, allowing you to change the position
of the internal capillary to vary the uptake rate from 0-8 mL/min,
compensating for the fueling effect of organic solvents.
The setting of the thimble determines the position of the capillary in
the venturi of the nebulizer. This allows you to select the nebulizer
setting best suited to the characteristics of your samples.
High Vacuum Setting
For samples with relatively low levels of dissolved solids, optimum
performance is achieved with the nebulizer in high vacuum mode,
where the capillary is set to give the maximum pressure drop
(vacuum) at the capillary tip. This setting uses narrow-bore plastic
capillary tubing (0.38 mm ID). A nebulizer set up in this way will
show minimum variation in uptake rate with variation in liquid level
in the sample tubes. It may, however, be more susceptible to clogging
by salts deposited from the sample.
To set the nebulizer in high vacuum mode:
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Take one length of the narrow-bore (0.38 mm ID) plastic capillary
tubing supplied with your nebulizer and fit the flared end of this
tubing to the nebulizer capillary.
Set up the instrument to measure absorbance using an easily
atomized element (such as copper) in an air-acetylene flame.
Since the uptake rate will be low, the initial sensitivity will be
less than normal.
Set the instrument in continuous read mode.
Zero the instrument by pressing the Alt and Read keys together.
Loosen the locking ring and turn the ring and thimble fully
clockwise.
While nebulizing a suitable standard solution, observe the
absorbance. Slowly and carefully turn the thimble counter-
clockwise until the absorbance reaches a maximum.
Agilent 55B AA Spectrometer User's Guide
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