Processing kodak motion picture films, module 3 analytical procedures

Spectrophotometric Determination of Citrazinic Acid in Reversal Color Developers
ECR-1611D
Process ECN-2 ECP-2D VNF-1/LC RVNP
Formulas — — DR-150/151 DR-150
INTRODUCTION
Citrazinic acid is determined by measuring the absorbance of
its sodium salt solution on a spectrophotometer at 345 nm.
Since the decomposition products of the developer also
absorb at this wavelength and vary with solution use and air
exposure, the citrazinic acid must first be separated from the
rest of the mix. Citrazinic acid has very low solubility in an
acidic solution, but can be dissolved by forming the sodium
salt. Therefore, it can be separated from the mix by acid
precipitation and filtration. The precipitate is then dissolved
and measured in an alkaline solution.
This method requires handling potentially hazardous
chemicals. Consult the Material Safety Data Sheet for each
chemical before use. MSDS's are available from your
chemical supplier.
RELIABILITY
The calibration curve was prepared by analyzing several
standard laboratory mixes containing varying known
amounts of specially purified citrazinic acid and constant
amounts of the other constituents. The absorbance values,
determined by following the analytical procedure, were
plotted against the corresponding concentrations of
citrazinic acid. The best straight line was determined from
the data.
The individual results obtained by this method have
95 percent confidence limits of ± 0.08 g/L. These limits are
based upon 35 individual analyses of standard laboratory
mixes.
SPECIAL APPARATUS
Fritted Pyrex Disc Buchner Funnel, 40 mm dia. fine
porosity
Spectrophotometer with a hydrogen lamp
1-cm Silica Cell
Note: Use pipets and volumetric glassware meeting the
“Class A” definition by the National Institute of Standards
and Technology (NIST).
REAGENTS
Use ACS Reagent Grade reagents unless specified
otherwise.
Celite filter-aid
7.0 N Sulfuric Acid, H 2 SO 4
0.10 N Sulfuric Acid, H 2 SO 4
0.10 N Sodium Hydroxide, NaOH
PROCEDURE
Precipitation
1. Using a No. 4 Coors porcelain spoon, add four scoops
of Celite to a 150-mL beaker.
2. Pipet (wipe the pipet before leveling) 20.0 mL of
sample into the beaker.
3. Add 2 mL of 7.0 N sulfuric acid from a tip-up pipet.
Swirl the beaker to mix the Celite, sample, and acid
thoroughly.
4. Allow ten minutes for complete precipitation.
Filtration
1. Prepare an aspirator-filter assembly Use a 250- or
500-mL filtering flask and a fine-porosity, 40-mm
fritted-glass Buchner funnel.
2. After ten minutes have elapsed, filter the reacted
sample.
3. Rinse the beaker, then the funnel, with two 10 mL
portions of 0.10 N sulfuric acid from a tip-up pipet.
Retain the beaker.
4. Disconnect the aspirator-filter assembly. Discard the
filtrate and rinse the inside of the flask three times with
distilled water.
Salt Formation
1. Mount the funnel in the filtering flask. Add, from a
tip-up pipet, 20 mL of 0.10 N sodium hydroxide to the
beaker, and then transfer the solution to the funnel.
Retain the beaker.
2. Mix the contents of the funnel by gently swirling the
funnel for one minute.
3. Apply suction and filter the dissolved precipitate.
4. Rinse the beaker, then the funnel with four 15 mL
portions of distilled water from a tip-up pipet.
5. Quantitatively transfer the filtrate to a l00-mL
volumetric flask. Dilute to volume with distilled water.
Stopper and invert 6 to 12 times.
6. Pipet 10.00 mL of the dilution into a 250-mL
volumetric flask. Dilute to volume with distilled water.
Stopper and invert 6 to 12 times.
Processing KODAK Motion Picture Films, Module 3, Analytical Procedures H24.03 1