Optical Alignment
Beam Alignment with Microcell in Sample Compartment
Alignment Procedure:
1. Install single cell holder (335916) into the sample compartment.
2. Use a microcell (331752-000); make sure the cell is perfectly clean.
3. Partially (about ½ height) fill the microcell with deionized water.
4. Gently tap the cell on a padded surface to ensure that there are no bubbles in the light path.
Method (best if performed at zero order)
1. Use Service Diagnostics to continuously pulse the xenon lamp and to access zero order.
2. Place a piece of clean white paper (like the back of a calling card) up against the sample detector
window so that the clean white side faces the single cell holder.
3. Insert the microcell into the single holder.
4. Observe the intensity of light reflecting off the white paper as adjustments of Mirror C are made. Set
for maximum uniform light image intensity on the white paper.
Final Check:
1. Reassemble the unit.
2. Set the wavelength for 260nm.
3. Use a microcell (331752-000); make sure the cell is perfectly clean.
4. Fill the microcell with deionized water.
5. Gently tap the cell on a padded surface to ensure that there are no bubbles in the light path.
6. Insert the cell in the cell holder and zero the instrument.
7. Remove and re-insert the microcell in exactly the same position several times.
8. Confirm zero repeatability (should be within +/- 0.003).
An additional check is to turn the microcell 180 degrees (reverse direction), reinsert the cell and compare
the forward/reverse direction agreeability. There is no specification on this; however, it should have
similar repeatability.
Perform the above ‘Final Check’ at several wavelengths, especially at 260nm and 280nm.
Note: The ‘axial’ position of the square cuvette holder also affects the reading/repeatability. It
may be necessary to loosen the screw that secures the cuvette and turn it to ensure that
the light beam passes straight through the cell windows on BOTH sides of the cuvette
without hitting the inner side wall of the cell’s sample chamber.
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