Processing kodak motion picture films, module 3 analytical procedures

Quartz Cell Check
Perform the quartz cell check whenever a
spectrophotometric method is used that does not require the
measurement of a blank.
1. Inspect the cell for cracks, chips, and discoloration. If
any are found, use another cell.
2. Rinse the cell with reagent water several times.
3. Fill the cell with reagent water.
a. Wipe all outside surfaces of the cell completely
dry with optical lens tissue, making sure all
traces of lint are removed.
b. Do not touch either of the optical faces with bare
fingers.
c. Look through the cell toward a light. Make sure
nothing is in the water or on the optical surfaces
of the cell (this includes tiny air bubbles, streaks,
water spots, lint, fingerprints and anything else
that might create an imperfection in the optical
path).
4. Set the wavelength of the spectrophotometer to
240 nm for the ultraviolet range, or 650 nm for the
visible range.
a. Make sure that the cell holder is positioned
correctly in the sample compartment.
5. Adjust the spectrophotometer to read an absorbance of
0 at the set wavelength.
6. Insert the cell in the cell holder.
a. The correct cell position is determined in the
initial cell check. There is usually a difference in
absorbance if the cell is placed in the holder in a
reversed position.
Rotating the cell 180° in its holder should not
give an absorbance difference greater than
0.005.1
b. The cell must fit firmly and squarely into the
holder (no weak or misaligned springs or
corrosion).
c. The optical surfaces of the cell must be perfectly
aligned (at right angles) with the light beam of
the spectrophotometer.
7. Measure and record the absorbance reading.
8. The absorbance for each wavelength should be
≤ 0.093.
9. If the control limits exceed 0.093, do the following to
clean the cell:
a. Soak the cell in water or a mild sulfonic
detergent.
b. If residue persists, soak the cell in a mixture of:
one volume of concentrate hydrochloric acid,
three volumes of reagent water, and four
volumes of methanol.
Caution
Prepare and use this mixture only in an adequate fume hood.
c. Alkaline solutions, detergents containing optical
bleaches, abrasive powders, fluorides, and
materials that might etch optical windows
should be avoided.
10. Rinse the cell thoroughly with reagent water.
11. If the reading is still high, check the purity of the
reagent water or use another quartz cell.
Note:
Do not store a cell in reagent water; let air dry.
Do not use swabs or other mechanical devices to
remove surface contamination; use acid/alcohol
cleaning solution.
Sample Measurement
1. Perform the quartz cell check procedure, if the method
does not require a blank. If it does involve the
measurement of a blank, make sure that the cell is
clean.
2. Follow steps 1 - 7 of the Quartz Cell Check, but
substitute the sample for reagent water and use the
wavelength indicated in the specific method (step 4 of
the Quartz Cell Check).
3. Rinse the cell with reagent water.
4. Measure the absorbance of the blank, if the method
requires one.
5. Using the appropriate calculation or table, determine
the concentration of the component being measured.
REFERENCES
1. Standard Practice for Describing and Measuring
Performance of Ultraviolet, Visible, and Near-
Infrared Spectrophotometers; American Society for
Testing and materials: ASTM designation E 275-93,
Philadelphia, PA, February 1994.
2. Standard Terminology Relating to molecular
Spectroscopy; American Society for Testing and
materials: ASTM designation E 131-94, Philadelphia,
PA, August 1994.
2 Processing KODAK Motion Picture Films, Module 3, Analytical Procedures H24.03