Processing kodak motion picture films, module 3 analytical procedures

Determination of Sodium Sulfite in KODAK Color Developer
ECN-2-1305B
ECP-2-1305C
ECR-1305L
Process ECN-2 ECP-2D VNF-1/LC RVNP
Formulas SD-49 SD-50/51 DR-100/101
DR-150/151
DR-105
DR-150
INTRODUCTION
This method is used to determine sodium sulfite in a Process
ECN-2, ECP-2D, or VNF/RVNP Color Developer sample.
The sulfite content is determined by reacting the sample with
excess iodine (liberated from the reaction of potassium
iodine under acidic conditions). The unreacted iodine is
titrated with standard sodium thiosulfate either
potentiometrically or to a visual starch end point. The sulfite
content is equivalent to the reacted iodine, which is the
difference between the total iodine formed and the unreacted
iodine titrated.
The potentiometric titration is recommended over the
visual end point titration. With the visual method, it is
difficult to pick the end point in highly seasoned (colored)
samples. Also, there is a tendency to over-titration, visually,
which leads to low sulfite results. The potentiometric
method overcomes both these problems because the end
point is detected potentiometrically and displayed
graphically by the titrator.
Use of this methods requires handling of potentially
hazardous chemicals. Material Safety Data Sheets should be
consulted for each chemical before use. These can be
obtained from each chemical supplier.
PROCEDURE A – POTENTOMETRIC
TITRATION
Precision and Bias
Process ECN-2—Three fresh and two seasoned samples of
Process ECN-2 Color Developer were analyzed by four
analysts on two separate days using multiple titrators. The
samples were run in duplicate on each day. The fresh
samples were prepared at 1, 3, and 5 g/L Na2SO3 . The
seasoned sample consisted of Process ECN-2 Color
Developer from a processor, analyzed as received
(at 1.658 g/L Na2SO3 ) and with a standard addition of
0.35 g/L Na2SO3 .
Process ECP-2D—Three fresh and two seasoned samples of
Process ECP-2D Color Developer were analyzed by three
analysts on two separate days using multiple titrators. The
samples were run in duplicate on each day. The fresh
samples were prepared at 1, 3, and 5 g/L Na 2SO 3. The
seasoned sample consisted of Process ECP-2D Color
Developer from a processor, analyzed as received
(at 3.35 g/L Na 2SO 3) and with a standard addition of
0.65 g/L Na 2SO 3.
Process VNF/RVNP—No reliability information was
generated for the reversal process VNF-1 and RVNP.
Customer Standard Deviation, s c
Thew customer standard deviation (1s c ) is an estimate of the
variability a customer could expect when submitting a
sample to any Photoprocessing Quality Services laboratory,
where any analyst could test the sample using any instrument
on any day.
ECN-2 Sample N
Customer Standard
Deviation, 1Sc Fresh 1 g/L Na2SO3 16 0.029 g/L
Fresh 3 g/L Na2SO3 16 0.042 g/L
Fresh 5 g/L Na2SO3 16 0.090 g/L
Seasoned Sample
(mean = 1.66 g/L Na2SO3 )
16 0.042 g/L
Seasoned Sample with Addition
(mean = 1.99 g/L Na2SO3 )
16 0.032 g/L
ECP-2D Sample N
Customer Standard
Deviation, 1Sc Fresh 1 g/L Na2SO3 12 0.045 g/L
Fresh 3 g/L Na2SO3 12 0.046 g/L
Fresh 5 g/L Na2SO3 12 0.055 g/L
Seasoned Sample
(mean = 3.35 g/L Na2SO3 )
12 0.122 g/L
Seasoned Sample with Addition
(mean = 3.99 g/L Na2SO3) 12 0.130 g/L
Processing KODAK Motion Picture Films, Module 3, Analytical Procedures H24.03 1