Processing kodak motion picture films, module 3 analytical procedures

Potentiometric Determination of Uncomplexed 1,3-PDTA In ECN-2-ML Bleach
ECN-2-ML-3255
Process ECN-2 ECP-2D VNF-1/LC RVNP
Formulas SR-32/SR-32R — — —
INTRODUCTION
The sample is buffered at a pH of approximately 4.5. A small
amount of Ferrous Ammonium Sulfate (0.001 N) is added.
The sample is then titrated with standardized 0.1 N Ferric
Ammonium Sulfate. The endpoint is determined
potentiometrically using a Platinum indicator electrode and
a double-junction reference electrode. At a pH of
approximately 4.5, the uncomplexed 1,3-Propylenediamine-N,N,N',N'-tetraacetic
Acid (1,3-PDTA) in the
sample forms a complex with the Fe(III) in the titrant, while
the Fe(II) from the Ferrous Ammonium Sulfate (0.001 N.)
remains weakly complexed. A large potential change occurs
at the equivalence point due to an abrupt change in the
relative concentrations of the Fe(II) and Fe(III) ions.
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
Three fresh hand-weighed standards containing 2, 6, and
10 g/L 1,3-PDTA were obtained. Three analysts tested each
solution in duplicate, on two separate days, resulting in 36
data points. Based on this data, the pooled standard deviation
(1s) was 0.04 g/L 1,3-PDTA with a 95 percent confidence
estimate (CE) for a single determination of ± 0.08 g/L
1,3-PDTA. A low bias was observed, but was insignificant
compared to the product specifications.
One seasoned sample was also obtained. To this seasoned
sample, a 1 g/L standard addition was made. Each of these
samples was analyzed in duplicate by three analysts, on two
separate days, for a total of 12 data points for each sample.
The mean analysis for excess 1,3-PDTA in the seasoned
sample was 4.79 g/L with a standard deviation (1s) and a
95 percent CE of 0.05 and ± 0.10 g/L, respectively. The
average recovery of the 1 g/L standard addition was
101 percent.
SPECIAL APPARATUS
pH Meter with glass electrode (CORNING #476024 or
equivalent) and calomel reference electrode (CORNING
#476002 or equivalent)
METROHM Automatic Titrator (or equivalent), with a
Platinum indicator electrode (BECKMAN #39273 or
equivalent) and a double-junction reference electrode
(ORION #90-02 or equivalent)
Note: Use pipets and volumetric glassware meeting the
“Class A” definition by the National Institute of Standards
and Technology (NIST).
REAGENTS
Glacial Acetic Acid
0.001 N Ferrous Ammonium Sulfate 6Hydrate
[Fe(NH4 ) 2 (SO4 ) 2 6H2O] 0.1 N Ferric Ammonium Sulfate 12Hydrate
[Fe(NH4 )(SO4 ) 2 l2H2O], standardized to 4 decimal
places
Processing KODAK Motion Picture Films, Module 3, Analytical Procedures H24.03 1