ISO 18917:1999
(Main)Photography — Determination of residual thiosulfate and other related chemicals in processed photographic materials — Methods using iodine-amylose, methylene blue and silver sulfide
Photography — Determination of residual thiosulfate and other related chemicals in processed photographic materials — Methods using iodine-amylose, methylene blue and silver sulfide
1.1 This International Standard specifies test methods for the determination of residual thiosulfate and other related chemicals in processed photographic materials. 1.2 This International Standard applies to silver halide/gelatin products that have been processed with a final thiosulfate fixing bath and a water wash. This International Standard does not apply to stabilised black-and-white products, thermally processed films, or instant-type products. The procedures given in this International Standard measure residual thiosulfate, and the silver densitometric method measures residual related polythionate materials as well. Measurements carried out by the procedures in this International Standard may, within the limitations stated in annexes A and B, correlate with the image stabilities of processed photographs. 1.3 Film or plates with photographic-sensitive layers on both sides, or with a photographic sensitive layer on one side and a gelatin backing layer on the reverse side, may contain approximately twice as much thiosulfate after processing as samples having a coating on one side only. This situation will be true for materials for which residual thiosulfate is determined by the iodine-amylose or methylene blue procedures. NOTE For the method of reporting such results, see figure 1, example 2. 1.4 The iodine-amylose can be used with fibre-based paper, resin-coated paper, films and plates. It is the method to be used with films and papers containing incorporated developing agents. 1.5 The methylene blue method can be used with fibre-based paper, resin-coated paper, films and plates but not with films and paper containing incorporated developing agents. 1.6 The silver sulfide densitometric method measures thiosulfates, polythionates and all other residual chemicals in a processed product that react with silver ion to form a silver "stain" under the conditions of the test. 1.7 A tabulated summary of methods, scope, etc. is given in annex B.
Photographie — Détermination du thiosulfate résiduel et d'autres produits chimiques dans les produits photographiques traités — Méthodes à l'iode-amylose, au bleu de méthylène et au sulfure d'argent
General Information
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Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 18917
First edition
1999-06-01
Photography — Determination of residual
thiosulfate and other related chemicals in
processed photographic materials —
Methods using iodine-amylose, methylene
blue and silver sulfide
Photographie — Détermination du thiosulfate résiduel et d'autres produits
chimiques dans les produits photographiques traités — Méthodes à l'iode-
amylose, au bleu de méthylène et au sulfure d'argent
A
Reference number
ISO 18917:1999(E)
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ISO 18917:1999(E)
Contents
1 Scope .1
2 Normative references .1
3 General requirements.2
4 Iodine-amylose method.3
5 Methylene blue method.7
6 Silver densitometric method .11
Annex A (informative) Appraisal of keeping characteristics .16
Annex B (informative) Guidance in the selection of test method.17
Annex C (informative) Preparation for 0,2 mol/l sodium hydroxide solution.18
Annex D (informative) Preparation of 1,000 mol/l sodium thiosulfate solution .19
Bibliography.21
© ISO 1999
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic
or mechanical, including photocopying and microfilm, without permission in writing from the publisher.
International Organization for Standardization
Case postale 56 • CH-1211 Genève 20 • Switzerland
Internet iso@iso.ch
Printed in Switzerland
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© ISO
ISO 18917:1999(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO
member bodies). The work of preparing International Standards is normally carried out through ISO technical
committees. Each member body interested in a subject for which a technical committee has been established has
the right to be represented on that committee. International organizations, governmental and non-governmental, in
liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical
Commission (IEC) on all matters of electrotechnical standardization.
Draft International Standards adopted by the technical committees are circulated to the member bodies for voting.
Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote.
International Standard ISO 18917 was prepared by Technical Committee ISO/TC 42, Photography.
This first edition cancels and replaces the second edition of ISO 417 (ISO 417:1993) which has been technically
revised. As in the second edition, it includes the iodine-amylose and methylene blue procedures, but the reactant
levels have been modified to provide more reproducible results.
Annexes A, B, C and D of this International Standard are for information only.
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© ISO
ISO 18917:1999(E)
Introduction
This International Standard is one of a series of specifications on photographic processing. Individuals without a
working knowledge of analytical chemistry may occasionally use this International Standard. Hazard warnings have
therefore been given using a system of symbols with letter codes designating the nature of the hazard. More
detailed information regarding hazards, handling and use of these chemicals may also be available from the
manufacturer.
Determination of residual thiosulfate and its decomposition products is of use in appraising the adequacy of washing
and therefore the permanence of the silver image on photographic films, plates and papers. Inadequate washing
can cause a loss in image density and the formation of stain in low-density areas. These deleterious effects are
accelerated by improper storage conditions.
Determination of residual thiosulfate and related compounds, by itself, is not sufficient to insure the permanence of
photographic records. Long term or archival storage requires proper attention to enclosure materials, storage
environment, and the like. These considerations are specified in ISO 3897, ISO 5466, ISO 6051 and ISO 10602.
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INTERNATIONAL STANDARD © ISO ISO 18917:1999(E)
Photography — Determination of residual thiosulfate and other
related chemicals in processed photographic materials — Methods
using iodine-amylose, methylene blue and silver sulfide
1 Scope
1.1 This International Standard specifies test methods for the determination of residual thiosulfate and other
related chemicals in processed photographic materials.
1.2 This International Standard applies to silver halide/gelatin products that have been processed with a final
thiosulfate fixing bath and a water wash. This International Standard does not apply to stabilised black-and-white
products, thermally processed films, or instant-type products. The procedures given in this International Standard
measure residual thiosulfate, and the silver densitometric method measures residual related polythionate materials
as well. Measurements carried out by the procedures in this International Standard may, within the limitations stated
in annexes A and B, correlate with the image stabilities of processed photographs.
1.3 Film or plates with photographic-sensitive layers on both sides, or with a photographic sensitive layer on one
side and a gelatin backing layer on the reverse side, may contain approximately twice as much thiosulfate after
processing as samples having a coating on one side only. This situation will be true for materials for which residual
thiosulfate is determined by the iodine-amylose or methylene blue procedures.
NOTE For the method of reporting such results, see figure 1, example 2.
1.4 The iodine-amylose can be used with fibre-based paper, resin-coated paper, films and plates. It is the method
to be used with films and papers containing incorporated developing agents.
1.5 The methylene blue method can be used with fibre-based paper, resin-coated paper, films and plates but not
with films and paper containing incorporated developing agents.
1.6 The silver sulfide densitometric method measures thiosulfates, polythionates and all other residual chemicals
in a processed product that react with silver ion to form a silver "stain" under the conditions of the test.
1.7 A tabulated summary of methods, scope, etc. is given in annex B.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of
this International Standard. For dated references, subsequent amendments to, or revisions of, any of these
publications do not apply. However, parties to agreements based on this International Standard are encouraged to
investigate the possibility of applying the most recent editions of the normative documents indicated below. For
undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC
maintain registers of currently valid International Standards.
ISO 5-3:1995, Photography — Density measurements — Part 3: Spectral conditions.
ISO 10349-1:1992, Photography — Photographic-grade chemicals — Test methods — Part 1: General.
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ISO 18917:1999(E)
3 General requirements
3.1 Safety and hazard concerns
3.1.1 Handling
Reagents shall be handled in conformity with health and safety precautions as shown on containers or as given in
other sources of such information. Proper labelling of prepared reagents includes chemical name, date of
preparation, expiration date, restandardization date, name of preparer, and adequate health and safety precautions.
The discharge of reagents shall conform to applicable environmental regulations.
3.1.2 Hazard warnings
Some of the chemicals specified in the test procedures are caustic, toxic or otherwise hazardous. Safe laboratory
practice for the handling of chemicals requires the use of safety glasses or goggles, rubber gloves and other
protective apparel such as face masks or aprons where appropriate. Specific danger notices are given in the text for
particularly dangerous materials, but normal precautions are required during the performance of any chemical
procedure at all times.
The first time that a hazardous is noted in the test procedure, the hazard shall be indicated by the word “DANGER”
followed by a symbol consisting of angle brackets "Æ æ" containing a letter which designates the specific hazard. A
double bracket " " shall be used for particularly perilous situations.
In subsequent statements involving handling of these hazardous materials, only the hazard symbol consisting of the
brackets and letter(s) shall be displayed. Furthermore, for a given material, the hazard symbols shall be used only
once in a single paragraph.
Detailed warnings for handling chemicals and their diluted solutions are beyond the scope of this International
Standard.
Employers shall provide training and health and safety information in conformance with legal
requirements.
The hazard symbol system used in this International Standard is intended to provide information to the users and is
not meant for compliance with legal requirements for labelling, as these vary from country to country.
It is strongly recommended that anyone using these chemicals obtain from the manufacturer pertinent
information about the hazards, handling, use and disposal of these chemicals.
3.1.3 Hazard information code system
ÆBæHarmful if inhaled. Avoid breathing dust, vapour, mist or gas. Use only with adequate ventilation.
ÆCæHarmful if contact occurs. Avoid contact with eyes, skin or clothing. Wash thoroughly after handling.
ÆSæHarmful if swallowed. Wash thoroughly after handling. If swallowed, obtain medical attention immediately.
S May be fatal if swallowed. If swallowed, obtain medical attention immediately.
ÆFæWill burn. Keep away from heat, sparks, and open flame. Use with adequate ventilation.
ÆOæOxidizer. Contact with other material may cause fire. Do not store near combustible materials.
The flammable warning symbol, ÆFæ, shall not be used for quantities of common solvents under 1 litre.
2
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ISO 18917:1999(E)
3.2 Reagents
Reagents used in the test procedures shall be certified reagent-grade chemicals and shall meet appropriate
standards or be chemicals of purity acceptable for the analysis.
NOTE Further details are given in ISO 6353-1, ISO 6353-2 and ISO 6353-3 (see bibliography).
Whenever water is specified without other qualifiers in the test procedures, only distilled water or water of at least
equal purity shall be used.
3.3 Glassware
1)
All glassware subject to heating shall be of heat-resistant borosilicate glass.
Pipettes and other volumetric glassware shall meet the volume requirements of Class A or Class B glassware as
specified in ISO 10349-1.
4 Iodine-amylose method
4.1 Use
The iodine-amylose method is applicable to the determination of residual thiosulfate ions in film and resin-coated
2
photographic paper containing incorporated developing agents. The procedure covers the range from 0,002 mg/cm
2
to 0,40 mg/cm . The method is also applicable to measuring residual thiosulfate ion in fibre-based paper, film and
plates. This method measures only thiosulfate ions and gives results comparable to those obtained by the
methylene blue method.
The method gives results that correlate well with accelerated keeping tests of several processed microfilms and is
applicable to colour as well as black-and-white products.
4.2 Principle
The eluent (4.4.4) is added to the sample to extract residual thiosulfate, tetrathionate and pentathionate ions.
Formalin is added to form a complex with any sulfite ion present. Iodine is added to an amylose (fractionated linear
potato starch) indicator to form a blue-coloured solution. The thiosulfate in the eluent, when added to the iodine-
amylose solution, will react with the iodine and proportionately reduce the intensity of the blue colour. The loss in
colour corresponds to the thiosulfate concentration.
4.3 Chemical reactions
a) Starch (C H O ) + I (in KI solution) fi Blue-coloured solution
6 10 5 n 2
2-
b) Blue-coloured solution + fi Decrease in blue colour intensity
SO
23
4.4 Reagents
4.4.1 Potassium iodate, c(KIO ) = 0,000 017 mol/l (0,003 57 g/l)
3
Prepare a 0,0167 mol/l solution of potassium iodate by weighing 0,357 g of potassium iodate (DANGER:ÆOæ) and
placing it in a 100 ml one-mark volumetric flask, making up to the mark with water and mixing well. Pipette 1,0 ml of
the 0,016 7 mol/l potassium iodate solution into a 1 litre one-mark volumetric flask, making up to the mark with
water.
1)
PyrexÒ is an example of suitable glassware available commercially. This information is given for the convenience of users of
this International Standard and does not constitute an endorsement by ISO of this brand.
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© ISO
ISO 18917:1999(E)
4.4.2 Formate buffer, pH 2,0
Add, from a graduated cylinder, 110 ml of formic acid (HCO H)) (88-90 %) (DANGER: ÆCæ ÆBæ ÆSæ ÆFæ) to a 1 litre
2
one-mark volumetric flask containing 500 ml to 600 ml of water, and make up to the mark with water. Using a pH
meter, adjust the solution to pH 2,0 ± 0,1 at 21 °C with 10 mol/l sodium hydroxide solution (4.4.8) (DANGER: C )
from a dropping pipette.
4.4.3 Formate buffer, pH 2,8
Pipette 10,0 ml of pH 2,0 formate buffer (4.4.2) into a 1 litre one-mark volumetric flask and make up to the mark with
water.
4.4.4 Eluent
Dissolve 1,0 g ± 0,1 g of potassium iodide (KI) and 1,0 g ± 0,1 g of potassium monohydrogen phosphate trihydrate
(K HPO ·3H O) and dilute to 1 litre with water. Using a pH meter, adjust to pH 8,5 at 21 °C by adding 0,5 mol/l
2 4 2
sulfuric acid (4.4.9) drop by drop from a dropping pipette.
4.4.5 Cadmium iodide-amylose reagent (CdI -amylose)
2
NOTE Batches should be limited to 1 litre volumes.
2)
Add and dissolve 11,0 g ± 1 g of cadmium iodide (CdI ) (DANGER: Carcinogen ) in 400 ml of water, and boil
2
gently for 15 min. Add a further 400 ml of water and heat to boiling. Continue boiling and slowly add, while stirring,
3)
5,0 g of amylose . Boil and stir for 5 min. Continue boiling and slowly add, with stirring, 5,0 g of acid-washed
4)
analytical filter aid . Boil and stir for 5 min.
While the solution is still hot, filter it under a high vacuum, using a Buchner funnel (4.5.1.5) with the fine porosity
filter paper (4.5.1.6) into a 1 litre vacuum flask. Transfer the filtrate to a 1 litre volumetric flask. Rinse the vacuum
flask with water and add the rinsings to the volumetric flask. Dilute to 1 litre with water.
4.4.6 Sodium thiosulfate, c(Na S O ) = 0,100 0 mol/l (15,8 g/l)
2 2 3
Commercially available analysed reagent solutions are recommended. Annex D provides a procedure for the
preparation of standard sodium thiosulfate solution using sodium thiosulfate penthahydrate (Na S O ·5H O).
2 2 3 2
4.4.7 Formalin (DANGER:ÆBæ ÆCæ ÆSæ)
4.4.8 Sodium hydroxide, c(NaOH) = 10 mol/l (DANGER: C )
This solution may be prepared from sodium hydroxide (DANGER: C ).
4.4.9 Sulfuric acid, c(H SO ) = 0,5 mol/l
2 4
This solution may be prepared from sulfuric acid (1,84 g/ml approx.) (DANGER: C ).
2)
Zinc iodide (ZnI ) has reportedly been used in at least two laboratories to avoid the use of cadmium iodide (CdI ). An
2 2
equimolar amount of zinc iodide (9,59 g) is to be used.
3)
Examples of suitable commercially available amylose are Aldrich Chemical Company No. 85573-1, ICN Biomedical Inc. No.
100669 and Sigma No. A0512 (Type 3 from potato). This information is given for the convenience of users of this International
Standard and does not constitute an endorsement by ISO of these products.
4)
A diatomaceous earth such as Aldrich Chemical Company No. 16,743-6 or BDH 33134-2K are examples of suitable
materials. This information is given for the convenience of users of this International Standard and does not constitute an
endorsement by ISO of these products.
4
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4.5 Apparatus and glassware
4.5.1 Apparatus
4.5.1.1 Transmission spectrometer, suitable for recording optical absorbance over the wavelength range of
interest, and a 5 cm cell.
4.5.1.2 pH meter
4.5.1.3 Interval timer
4.5.1.4 Dropping pipettes (also known as medicine droppers) (as required).
4.5.1.5 Buchner funnel
4.5.1.6 Filter paper, 11,0 cm diameter: ashless; fine porosity (2,5 mm particle retention); slow flow [240 s for
5)
100 ml prefiltered water)]; smooth surface; dense.
4.5.2 Glassware
All glassware shall be free from reducing or oxidizing materials. One way to assure this is to rinse the glassware
with an iodide-iodine solution made from the following reagents. (see. 3.3).
Mix 10 ml of potassium iodate solution (4.4.1), 5 ml of pH 2,0 formate buffer (4.4.2), 5 ml CdI -amylose reagent
2
(4.4.5), and about 100 ml of water for a rinsing solution. Rinse glassware first with this solution and then with water.
4.6 Absorbance of blank solution
Run a reagent blank before and after the analyses of the samples. If the group of samples is large (greater than
six), also run blanks in the middle of the group.
NOTE In developmental and experimental work, absorbances of the blank have been between 0,70 and 0,80.
The blank absorbance is obtained by adding all the following reagents to a 50 ml one-mark volumetric flask:
10 ml of eluent (4.4.4)
1 ml of formalin (4.4.7) (ÆBæ ÆCæ ÆSæ)
3 ml of pH 2,8 formate buffer solution (4.4.3)
5,0 ml of potassium iodate solution (4.4.1)
5 ml of cadmium iodide-amylose reagent (4.4.5)
5 ml of pH 2,0 formate buffer solution (4.4.2)
Swirl to mix, and make up to the mark with water. Stopper the flask and mix thoroughly. After 3 min, measure the
absorbance of this solution as described in 4.8.3 and 4.8.4.
4.7 Preparation of test sample
Analyze samples within 2 weeks of photographic processing.
5)
Whatman Ò No. 42 filter paper is an example of a suitable product available commercially. This information is given for the
convenience of users of this International Standard and does not constitute an endorsement by ISO of this product.
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ISO 18917:1999(E)
2
Cut a 10 cm strip of paper or film, obtained from a non-image area or an area of minimum density. Fold the
4.7.1
strip into a "W" with the emulsion side inwards. Place the folded sample in a dry 30 ml beaker.
4.7.2 Add 10 ml of eluent (4.4.4) to the beaker. Swirl the beaker until the sample is completely immersed. Swirl
again after 1 min and 5 min. Total elution time shall be 10 min for resin-coated (RC) paper, lightweight paper, and
single-weight paper. For medium-weight or double-weight paper, the contact time with the eluent shall be increased
to 20 min.
4.7.3 Add 1 ml of formalin (4.4.7) (ÆBæ ÆCæ ÆSæ) to the beaker. Swirl, making sure that the solution reaches any
droplets on the beaker wall. Allow a reaction time of 1 min.
4.7.4 Add 3 ml of pH 2,8 formate buffer (4.4.3). Swirl to reach any droplets on the 30 ml beaker wall and allow
2 min for completion of the reaction. During these 2 min, carry out the following steps in a 50 ml volumetric flask:
Pipette 5,0 ml of potassium iodate solution (4.4.1); add 5 ml of cadmium iodide-amylose reagent (4.4.5) and swirl
the flask; add 5 ml of pH 2,0 formate buffer (4.4.2) and swirl the flask.
4.8 Colorimetric Measurement
4.8.1 Set a timer for 3 min.
4.8.2 Transfer the liquid from the 30 ml beaker (see 4.7.4) to the 50 ml volumetric flask containing the iodine-
amylose solution (4.7.4). Rinse the sample and beaker with 10 ml of water and transfer the rinsings to the 50 ml
volumetric flask containing the reagent mixture (see 4.7.4). Make up to the mark with water and mix well.
4.8.3 After 3 min from the time of transfer, measure the absorbance of the solution at 610 nm in a 5 cm glass cell
versus air using the spectrometer (4.5.1.1).
2-
4.8.4 Convert the absorbance obtained into the level, r , of thiosulfate ions (S O ), in grams per square metre,
23
s
from an appropriate calibration curve (see 4.9).
DA = A - A
s b
where
DA is the absorbance difference;
A is the absorbance of the blank solution;
b
A is the absorbance of the test solution.
s
If A falls below 0,090, re-extract the sample using a smaller sample. Correct the result then obtained from the
s
calibration curve as follows:
10r
c
r=
s
S
where
2-
r is the level of SO ions read from the calibration curve, in grams per square metre;
23
c
S is the sample area, in square centimetres.
2 2
Low levels of thiosulfate (0,001 g/m to 0,009 g/m ) are generally achieved only in well-washed, fine-grain, black-
6)
and-white films.
6)
2 -2 2
1 mg/cm = 10 g/m
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4.9 Calibration, including blank
Prepare a stock sodium thiosulfate solution (0,001 0 mol/l) by pipetting 1,00 ml of 0,100 0 mol/l sodium
4.9.1
thiosulfate (4.4.6) into a 100 ml one-mark volumetric flask. Make up to the mark with water.
2
4.9.2 Assuming a 10 cm sample, pipette the volumes of stock solution given in table 1 into appropriately labelled
30 ml beakers.
Table 1 — Preparation of samples for calibration
Volume of stock solution
r
Equivalent
s
2
2
g/m
ml mg/cm
50 0,005 6 0,56
100 0,011 1,1
300 0,034 3,4
None Blank Blank
4.9.3 Analyse the samples starting at 4.7.2 by adding the eluent (4.4.4) and continuing the procedure steps up to
and including 4.8.3. The sample sizes given in 4.7.1 are replaced by the pipetted quantities given in 4.9.2. If the
sample has a gelatin coating on each side of the base, it may contain twice the level of thiosulfate ions as a sample
coated on one side only.
2
4.9.4 Plot DA against r , in grams per square metre (for a 10 cm sample).
s
5 Methylene blue method
5.1 Use
The methylene blue method determines only thiosulfate ions. The procedure as specified covers the range from
2 2 2 2
0,005 g/m to 0,34 g/m (0,5 mg/cm to 34 mg/cm ) of thiosulfate for fibre-based paper, resin-coated paper, film or
plates.
5.2 Principle
Residual thiosulfate that is extracted (eluted) from the sample is reduced by potassium borohydride to sulfide. The
sulfide reacts with oxidized N,N-dimethyl-p-phenylenediamine (DP) to form methylene blue (MB). The absorbance
of the blue colour is measured with a photometer or spectrometer. The thiosulfate level is determined from a
calibration curve. A curve is to be prepared in each laboratory to eliminate errors due to variations in the reagents,
equipment or technique, but it should approximate to the curve in figure 1.
NOTE The curve shown in figure 1 is only an example and is not to be used as a working calibration curve. A working
calibration curve is to be established only by following the procedures described in this International Standard.
5.3 Chemical reactions
The following reactions occur:
2-----
32fiH O++S O BH HS+ HSO+ H BO+2H
22323232
-
HS++12FeCl 2DPfiMB
3
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5.4 Reagents
5.4.1 Eluent
Dissolve 1,0 g ± 0,1 g of potassium iodide (KI) and 1,0 g ± 0,1 g of potassium dihydrogen phosphate (KH PO ) in
2 4
water in a 1 litre one-mark volumetric flask. Make up to the mark with water and mix well. This reagent is stable for
at least one month.
5.4.2 Borohydride reagent
7)
Dissolve 3,0 g of fresh potassium borohydride (KBH ) (DANGER: ÆCæ ÆBæ ÆFæ) in 100 ml of sodium hydroxide
4
solution (5.4.6). This reagent is stable for 1 week in a cool place. Package solutions to be used beyond 1 week in
small individual bottles which, once opened, shall be discarded at the end of the day.
DANGER: Potassium borohydride is hazardous in the following ways:
a) Personnel: Potassium borohydride is flammable and corrosive. It liberates hydrogen gas when in contact with
water or acid, and poisonous gases in the presence of acid. In concentrated form, it causes severe skin burns.
Handle with extreme care and store in a bottle with a loose stopper.
b) Sensitized materials: Potassium borohydride is a powerful fogging agent. Avoid contamination of unprocessed
film, paper, and processing solutions. Thoroughly wash hands and equipment after the use of solid borohydride
or borohydride reagent.
5.4.3 Acetone (DANGER: ÆFæ ÆBæ)
5.4.4 Ferric chloride reagent
To approximately 50 ml of water in a beaker, carefully add, while stirring, 37,5 ml of hydrochloric acid (HCl)
(r ’ 1,18 g/ml) (DANGER: ÆCæ). Dissolve 8,45 g ± 0,01 g of ferric chloride hexahydrate (FeCl ·6H O) in the diluted
3 2
acid, cool to room temperature, and transfer to a 100 ml one-mark volumetric flask. Make up to the mark with water
and mix well. This reagent is stable for at least 3 months.
5.4.5 NND Reagent
To approximately 50 ml of water in a beaker, carefully add, while stirring, 12,5 ml of hydrochloric acid (HCl)
8)
(r ’ 1,18 g/ml) (DANGER: ÆCæ). Dissolve 3,00 g ± 0,01 g of N,N-dimethy-p-phenylenediamine sulfate in the
diluted acid, cool to room temperature, and transfer to a 100 ml one-mark volumetric flask. Make up to the mark
with water and mix well. This reagent is stable for at least 1 week.
5.4.6 Sodium hydroxide solution, c(NaOH) = 0,20 mol/l (8,0 g/l)
Commercially available analysed reagent solution is recommended. A procedure for the preparation of this is given
in annex C
5.5 Apparatus and glassware
See 4.5.2 for details of the cleaning of glassware.
5.5.1 Sample vials (scintillation vials), polyethylene, of 20 ml capacity with screw caps; nine are required.
7)
Also known as potassium tetrahydroborate.
8)
Bis (N,N-dimethy-p-phenylenediamine sulfate), M.W. 370,47. An equivalent commercially available salt, with one equivalent
of amine per mole (M.W. 234,28) can also be used and if so use 3,78 g of amine per 100 ml of solution
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9
)
adjustable, of 1 ml capacity ; four are required.
5.5.2 Repeating dispensers
5.5.3 Visible photometer or spectrophotometer, with 1 cm cells
5.6 Procedure
5.6.1 Analysis of test sample
Analyse samples within 2 weeks of photographic processing
2 2
5.6.1.1 Cut a 1 cm sample of film, paper or plate from an area of minimum density; a 1,0 cm punch may be used
for film or paper samples. Place the sample in a clean, dry sample vial (5.5.1). Add 10,0 ml of eluent (5.4.1) and
allow the mixture to stand for 10 min with occasional swirling (once every 1 min to 3 min). Pipette 5,0 ml of the
extract into another sample vial.
NOTE If destruction of the plate is undesirable, immerse the entire plate in a tray slightly larger than the plate (0,5 cm on
each side) and elute as above but use a larger volume of eluent (5.4.1), keeping the proportion of eluent volume to plate area
constant. After elution, pipette 5,0 ml of the resulting test solution into a sample vial (5.5.1). Continue with the procedure given
in 5.6.1.2. Wash the plate with water after testing, to remove the residual eluent.
5.6.1.2 Transfer the following four reagents to separate reservoirs for the repeating dispensers; set each dispenser
for the requisite volume.
Borohydride reagent (5.4.2) 0,25 ml
Acetone (5.4.3) 0,50 ml
Ferric chloride reagent (5.4.4) 0,25 ml
NND reagent (5.4.5) 0,25 ml
Flush each dispenser by dispensing and discarding at least 10 aliquots of reagent before the first determination of
the day.
Complete all of the following reagent additions without delay between additions.
a) Add 0,25 ml of the borohydride reagent (5.4.2). Swirl to mix.
b) Add 0,50 ml of acetone (5.4.3). Swirl to mix.
c) Add 0,25 ml of the ferric chloride reagent (5.4.4) and 0,25 ml of the NND reagent (5.4.5).
Immediately cap the vial securely. Shake the vial vigorously for 1 min. Then carefully vent the pressure formed by
evolved hydrogen, making sure that the vial is pointed away from the face. Proceed immediately with the next step.
5.6.1.3 Measure the absorbance of the test solution at 665 nm in a 1 cm cell versus air (no cuvette in the light
beam) using the photometer (5.5.3).
5.6.1.4 Analyse a reagent blank by substituting 5,0 ml of eluent instead of the extract in 5.6.1.1. Calculate the net
absorbance of the test solution by subtracting the bl
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