Processing kodak motion picture films, module 3 analytical procedures

Spectrophotometric Determination of Iron (Total) and Iron (II) in “ML” Bleach
ECN-2-ML-3260
Process ECN-2 ECP-2D VNF-1/LC RVNP
Formulas SR-32/SR-32R — — —
INTRODUCTION
This method contains analytical procedures for measuring
Iron(II) and total Iron in KODAK Process ECN-2, Type ML
Bleach. Calculations, derived from the analytical data, are
included for determining Iron(III).
Total Iron is determined by oxidizing any Iron(II) Iron(III)
with Persulfate. A Thiocyanate complex of the Iron(III) is
formed in a dilute acid solution. A direct measurement of the
Iron-Thiocyanate is made using a calibrated
spectrophotometer at 474 nm. Each spectrophotometer is
calibrated for the Iron-Thiocyanate complex using standard
samples. The standard samples are prepared and analyzed
using this procedure. An average absorptivity measurement
is calculated from the standard data. This average
absorptivity is used to calculate a sample concentration.
The Iron(II) is determined by adding a sample to
deaerated 1,10-Phenanthroline/Sodium Acetate reagent.
Any Iron(II) present in the sample will form a colored
complex with the reagent that can be measured on a
spectrophotometer at 510 nm. Bleach samples should be
protected from aeration between the time of sampling and
analysis. The Iron(II) content of the bleach increases
gradually upon standing. Bleach solutions should be
analyzed for Iron(II) within 4 hours of sampling. The
1,10-Phenanthroline/Sodium Acetate reagent is deaerated
with Nitrogen prior to use to prevent any additional
oxidation.
Iron(III) is Calculated by subtracting the g/L Iron(II) from
the g/L total Iron.
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
Total Iron
Three fresh samples of concentration 6.0, 14.0 and 20.0 g/L
total Iron were prepared in KODAK Process ECN-2-ML
bleach solution. Each solution was run in duplicate by four
analysts on one day. Based on this data (n = 24), the
95 percent confidence estimate is ± 0.4 g/L total Iron
(1s± = ± 0.2 g/L) for fresh solutions.
A seasoned KODAK Process ECN-2-ML bleach and that
sample containing a 2 g/L total Iron standard addition were
analyzed in duplicate by four analysts. Based on this data
(n = 16), the 95 percent confidence estimate is ± 0.4 g/L
total Iron (is ± 0.2 g/L) for seasoned samples. The recovery
of the 2 g/L total Iron addition indicated no bias due to the
analytical technique.
Iron(II)
Ten mixes of aqueous solutions of Ferrous Ammonium
Sulfate were analyzed by three analysts in two laboratories
and over two ranges.
Range 1: 0.5-2.5 g/L of Ferrous Iron
The 95 percent confidence estimate for a single
determination based on a 2-variable linear regression of
13 data points is ± 0.1 g/L Ferrous Iron.
Range 2: 2.5-12.5 g/L Ferrous Iron
The 95 percent confidence estimate for a single
determination based on 2-variable linear regression of
13 data points is ± 0.45 g/L Ferrous Iron.
SPECIAL APPARATUS
50-µL Eppendorf micropipet or equivalent micropipet
100-µL Eppendorf micropipet or equivalent micropipet
Rapid-delivery glass transfer pipes or automatic pipet
Spectrophotometer equipped with a tungsten lamp
Note: Follow the manufacturer's instructions for care and
use of micropipets.
Use pipets and volumetric glassware meeting the “Class
A” definition by the National Institute of Standards and
Technology (NIST).
REAGENTS
2.5 N Sulfuric Acid, H 2 SO 4
40 g/L Potassium Persulfate, K 2 S 2 O 8
200 g/L Ammonium Thiocyanate, NH 4 SCN
1,10-Phenanthroline/Sodium Acetate reagent
Ferric Nitrate, Fe(NO 3 ) 3 9H 2 O ACS reagent grade
0.1 N Sodium Thiosulfate, standardized Na 2 S 2 O 3
Potassium Iodide, KI ACS reagent grade
Starch indicator
0.1 N Nitric Acid, HNO 3
Hydrochloric Acid, HCl concentrated
Processing KODAK Motion Picture Films, Module 3, Analytical Procedures H24.03 1