Processing kodak motion picture films, module 3 analytical procedures

Potentiometric Determination of Kodak PBA-1 in Eastman Color Print -2 Bleach Accelerator
ECP-0027-01
INTRODUCTION
Strong base is added to the sample to hydrolyze the KODAK
persulfate bleach accelerator PBA-1 to a titratable
mercaptan. The PBA-1 content is measured by means of a
potentiometric titration with silver nitrate titrant using a
silver/silver sulfide indicator electrode and a double junction
reference electrode. This analysis is performed with an
automatic titrator.
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.
PRECISION AND BIAS
Repeatability Standard Deviation, 1sr and 95
Percent Confidence Estimate (not including Bias)
Repeatability standard deviation is an estimate of the
variability one trained analyst should be able to obtain under
favorable conditions (analyzing a sample, with one
instrument, within one day).
The 95 percent confidence estimate (calculated using the
repeatability standard deviation) around a single test result
will include the mean value 95 percent of the time.
To obtain the repeatability data, a single skilled analyst
performed five (5) replicates on each of the following
solutions during methods development.
1. A “fresh” Accelerator tank solution prepared with all
components at their respective “working tank” aim
concentrations.
2. A “seasoned” Accelerator tank solution analyzed as
received, at 3.87 g/L PBA-1.
3. The same “seasoned” solution as in number 2, above,
reanalyzed after making an analytically weighed,
standard addition of 1.1794 g/L PBA-1.
Sample
“Fresh”
(prepared at
3.31 g/L)
“Seasoned”
As
Received
“Seasoned”
plus
Standard
Addition
PBA-1
Mean
(g/L PBA-1) N
Repeatability
Standard
Deviation, 1s r
(g/L PBA-1)
95 Percent
Confidence
Estimate
(g/L PBA-1)
3.38 5 0.023 ± 0.06
3.87 5 0.011 ± 0.03
5.11 5 0.008 ± 0.02
Bias
Bias is a statistically significant deviation of the mean from
the known mix level at a 95 percent confidence level. It is
determined for fresh samples only. Bias was not determined
for this sample because the component concentration level
was not determined independently of the test method.
Instead, a recovery was calculated for the component in a
fresh sample.
A bias of 0.07 g/L PBA-1 was found to be statistically
significant at the 95 percent confidence level, however it was
judged not to be practically significant
Recovery
Recovery is used for seasoned samples, since the component
concentration level was not determined independently of the
test method. It is defined as the calculated mean for the
seasoned sample with a standard addition of the component
minus the mean for the seasoned sample, divided by the
actual amount of the standard addition. It is expressed as a
percentage.
Statistically the recovery of 105.14 percent was
significantly different from 100 percent at the 95 percent
confidence level, but was judged not to be practically
significant.
Processing KODAK Motion Picture Films, Module 3, Analytical Procedures H24.03 1