PerkinElmer aanalyst 200, User Manual

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AAnalyst 200 User’s Guide
9-41
Adjusting the Nebulizer for Maximum Absorbance
Adjust the nebulizer to achieve maximum absorbance as follows:
1. Ignite the flame. Refer to the procedure for igniting the flame in Chapter 6 , Operation of the
Instrument .
2. Set up the spectrometer for the determination of copper, magnesium, or another element
which has an absorbing wavelength above 250 nm and whose sensitivity is not dependent on
the fuel/oxidant ratio.
Do not select an element requiring a nitrous oxide-acetylene
flame. If necessary, adjust the burner height using the procedure described in Chapter 6 ,
Operation of the Instrument .
3. Aspirate a blank and let the flame stabilize as described Chapter 6 , Operation of the
Instrument .
4. If you see bubbles at the end of the capillary tube (in the sample solution), loosen the
nebulizer locking nut and slowly turn the adjustment nut clockwise until the bubbling stops.
5. Aspirate a standard and adjust the burner position as described in Chapter 6, Operation of
the Instrument . Optimize the burner position by using the rotational and horizontal
adjustment knobs identified in Chapter 6 , Operation of the Instrument .
6. While still aspirating the standard, turn the nebulizer locking nut clockwise until it is free of
the nebulizer adjustment nut.
7. Slowly turn the nebulizer adjustment nut counter clockwise until bubbles begin to appear at
the end of the capillary tube in the sample solution.
8. Slowly turn the nebulizer adjustment nut clockwise until the absorbance goes to a
maximum and then begins to decrease .
9. Lock the nebulizer adjustment nut in its current (optimum) position by turning the nebulizer
locking nut counter-clockwise while carefully holding the nebulizer adjustment nut.
10. Check the characteristic concentration as instructed in the User’s Guide.
Using Organic Solvents
It is often beneficial to lower the nebulizer uptake rate when aspirating organic solvents. The
normal nebulizer uptake rate is typically 6-8 mL/min.
By reducing the uptake rate to 2-4 mL/min, it is usually possible to operate with a leaner (blue)
flame than is possible with higher nebulizer uptake rates. This leaner flame typically provides
improved precision, particularly when aspirating xylene.
To adjust the nebulizer uptake rate, unlock the nebulizer locking nut and rotate the nebulizer
adjustment nut until you locate a position which provides reduced sample uptake. Then lock the
nebulizer locking nut.
NOTE: The uptake rate is easily measured by using a graduated cylinder.