UGANDA STANDARD
 
        US ISO 5517
First Edition
2009-mm-dd
 
Reference numbe r 
    US ISO 5517:1978
 © UNBS 2009
  
Fruit and vegetable products — Determination of iron content 
— 1,10 Phenanthroline photometric method 
 US ISO 5517: 1978 
 
© UNBS  2009 – All rights reserved ii Compliance with this standard does not, of itself confer immunity from legal obligations 
A Uganda Standard does not purport to include all necessary provisions of a contract. Users are 
responsible for its correct application  
© UNBS 2009 
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilised in any 
form or by any means, electronic or mechanical, in cluding photocopying and microfilm, without prior written 
permission from UNBS. 
Requests for permission to reproduce this document should be addressed to 
The Executive Director 
Uganda National Bureau of Standards 
P.O. Box 6329 
Kampala  
Uganda 
Tel: 256 41 505 995 
Fax: 256 41 286 123 
E-mail: unbs@infocom.co.ug
Web: www.unbs.go.ug  
        US ISO 5517:1978  
© UNBS  2009 - All rights rese rved                iii National foreword 
Uganda National Bureau of Standards (UNBS) is a parastatal under the Ministry  of Tourism, Trade and 
Industry established under Cap 327, of the Laws of U ganda. UNBS is mandated to co-ordinate the elaboration 
of standards and is  
(a) a member of International Organisation for Standardisation (ISO) and  
(b) a contact point for the WHO/FAO Codex A limentarius Commission on Food Standards, and  
(c) the National Enquiry Point on TBT/SPS Agr eements of the World Trade Organisation (WTO). 
The work of preparing Uganda Standards is carried out through Technical Committees. A Technical 
Committee is established to deliberate on standards in a gi ven field or area and consists of representatives of 
consumers, traders, academician s, manufacturers, governme nt and other stakeholders. 
Draft Uganda Standards adopted by the Technical Committ ee are widely circulated to stakeholders and the 
general public for comments. The committee reviews the comments before recommending the draft standards 
for approval and declaration as Uganda Standards by the National Standards Council. 
This Uganda Standard, US ISO 5517, Fruit and vegetable products — Determination of iron content — 1,10
Phenanthroline photometric method,  is identical with and has been reproduced from an International
Standard, ISO 5517:1978, Fruit and vegetable products — Determination of iron content — 1,10 Phenanthroline
photometric method, and adopted as a Uganda Standard.  
This standard was developed under the subcommittee on fruits and vegetables by the Food and agriculture 
Standards Technical Committee (UNBS/TC 2). 
Wherever the words, "International Standard" a ppear, they should be replaced by "Uganda Standard." 
 FOREWORD 
ISO (the International Organization for Standardization) is a worldwide federation 
of national Standards institutes (ISO member bodies). The work of developing 
International Standards is carried out through ISO technical committees. Every 
member body interested in a subject for which a technical committee has been set 
up 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. 
Draft International Standards adopted by the technical committees are circulated 
to the member bodies for approval before their acceptance as International 
Standards by the ISO Council. 
International Standard ISO 5517 was developed by Technical Committee 
ISO/TC 34, Agricultural food products, and was circulated to the member bodies 
in March 1977. 
lt has been approved by the member bodies of the following countries : 
Austral ia Ghana 
Austria Hungary 
Bulgaria India 
Canada Iran 
Czechoslovakia Israel 
Egypt, Arab Rep. of Korea, Rep. of 
France Mexico 
Germany New Zealand Poland 
Portugal 
Romania 
South Africa, Rep. of 
Spain 
Thailand 
No member body expressed disapproval of the document. 
0 International Organkation for Standard izat ion, 1978 l 
Printed in Switzerland --. 
INTERNATIONAL STANDARD ISO 55174978 (E) 
Fruits, vegetables and derived products - Determination of 
iron content - 1 ,IO-Phenanthroline photometric method 
1 SCOPE AND FIELD OF APPLICATION 
This International Standard specifies a 1 ,IO-phenanthroline 
photometric method for the determination of the iron 
content of fruits, vegetables and derived products. 
2 REFERENCES 
ISO 5515, Fruits, vegetables and derived products - 
Decomposition of organic matter - Wet method. 1 ) 
ISO 5516, Fruits, vegetables and derived products - 
Decomposition of organic matter - Ashing method? ) 
3 PRINCIPLE 
Decomposition of the organic matter, followed by 
reduction of trivalent iron by hydroxylammonium chloride. 
Formation, in a buffered medium, of the stable iron( II)/ 
1 ,IO-phenanthroline complex. Photometric measurement of 
the red-coloured complex at a wavelength of 508 nm. 
4 REAGENTS 
All reagents used shall be of recognized analytical quality. 
The water used shall be distilled water or watet- of at least 
equivalent purity. 
4.1 Sulphuric acid, pzO 1,84 g/ml. 
4.2 Nitrit acid, pzO 132 g/mI. 
4.3 Hydrochlorit acid, pzo 1 ,18 ghl. 
4.4 Hydroxylammonium chloride (NH,OH.HCI), 200 g/l 
solution. 
4.5 Buffer solutions. 
4.5.1 Sodium acetate trihydrate (NaCH&02.3H20), 
450 g/l solution. 4.5.2 Sodium acetate trihydrate (NaCH3COZ.3H20), 
272 g/l (2 M) Solution. 
4.6 1 ,IO-Phenanthroline, 10 g/l Solution. 
Dissolve 1 g of 1 ,IO-phenanthroline in 80 ml of water at 
80 “C and a minimum volume of the hydrochloric acid 
(4.3) diluted with an equal volume of water, in a 100 ml 
one-mark volumetric flask. 
After cooling, dilute to the mark and mix. 
This Solution, stored in a cool place and protected from 
light, is stable for several weeks. 
NOTE - Instead of 1 ,i O-phenanthroline, the corresponding 
quantity of phenanthroline hydrochloride, which is soluble in cold 
water, may be used. 
4.7 Iron, 0,020 g/l Standard Solution, prepared according 
to one of the two following procedures : 
a) Weigh, to the nearest 0,001 g, 7,024 g of ammonium 
iron( II) sulphate hexahydrate [(NH& Fe(SO,),.GH,O]. 
Dissolve in water and add 2 drops of the hydrochloric 
acid (4.3). Transfer quantitatively to a 500 ml one-mark 
volumetric flask, dilute to the mark with water and mix. 
Using a pipette, transfer 10 ml of this Solution to a 
1 000 ml one-mark volumetric flask. Dilute to the mark 
with water and mix. 
b) Weigh, to the nearest 0,001 g, 0,200 g of iron wire 
of analytical purity. Dissolve in 200 ml of the 
hydrochloric acid (4.3) and add 50 ml of water. Transfer 
quantitatively to a 1 000 ml one-mark volumetric flask, 
dilute to the mark and mix. Using a pipette, transfer 
50 ml of this Solution to a 500 ml one-mark volumetric 
flask. Dilute to the mark with water and mix. 
4.8 Magnesium acetate [Mg(CH,C02)J, 150 g/l solution. 
1) At present at the Stage of draft. 
1 ISO 5517-1978 (E) 
5 APPARATUS 
Ordinary laboratory apparatus and Transfer to the beaker the volume of buffer Solution (4.5.1) 
required to obtain a reading on the pH meter (5.8) between 
3,5 and 4,5. Let X ml be the volume of buffer Solution 
added. 
5.1 Kjeldahl flask, of capacity 250 or 300 ml. 
6.4 Determination 
5.2 Pipettes, of capacity 5, 10 and 20 ml, complying with 
class A of ISO 648. 
5.3 Burettes, of capacity 50 ml, graduated in 0,l ml, 
complying with class A of ISO/R 385. 
5.4 One-mark volumetric flasks, of capacity 50 and 
100 ml, complying with class A of ISO 1042. 
5.5 Beaker, of capacity 50 ml. 
5.6 Spectr tophotometer or photoelectric absorptiometer 
suitable for measurements at a wavelength o f 508 nm. 
5.7 Analytical balance. According to the expected iron content, take a volume 
V, ml (see 6.3) of the test Solution obtained in 6.2 and 
transfer to a 50 ml one-mark volumetric flask (5.4). If 
necessary, make up the volume to 20 ml with water. 
Add 5 ml of the hydroxylammonium chloride Solution 
(4.4) and X ml (see 6.3) of the buffer Solution (4.5.1) in 
Order to obtain a pH between 3,5 and 4,5*. 
Add 2 ml of the 1 ,IO-phenanthr oline Solution (4.61, dilute 
to the mar k with water and mix. Allow to stand for 5 min 
Measure the absorbance using the spectrophotometer or 
the photoelectric absorptiometer (5.6) at a wavelength of 
508 nm. If the coloration is too strong, begin again, taking 
a smaller volume VI or, if this is not possible, a smaller 
test Portion. 
5.8 pH meter. 
6.5 Number of determinations 
Carry out two determinations on the same test Sample (6.1). 
6 PROCEDURE 
6.6 Blank test 
6.1 Preparation of test Sample and test Portion 
See ISO 5515 or ISO 5516, according to the method of 
decomposition Chosen (6.2). Take as the test Portion 
about IO g of the test Sample, weighed to the nearest 
0,001 g, or take IO ml of the test Sample using a pipette 
(5.2). 
6.2 Decomposition 
Proceed according to ISO 5515 or ISO 5516, diluting the 
test Solution to 100 ml. (Note that if the decomposition 
is carried out according to ISO 5516, the dissolution of the 
ash is carried out after moistening it with 5 ml of sulphuric 
acid instead of 1 ml.) 
6.3 Preliminary test 
Carry out a preliminary test to determine the volume of 
buffer Solution (4.5.1) to be added. According to the 
expected iron content, take, using a pipette (5.2), a volume 
VI ml (5, IO or 20 ml) of the test Solution obtained in 6.2. 
Transfer to the 50 ml beaker (5.5), if necessary make up 
the volume to 20 ml with water, and then add 5 ml of the 
hydroxylammonium chloride Solution (4.4). Carry out a blank test, following the same procedure and 
using the same quantities of all the reagents as used for 
the determination but omitting the test Portion. 
6.7 Preparation of the calibration curve 
Into a series of seven 100 ml one-mark volumetric flasks 
(5.4), introduce respectively 0 - 5 - IO - 20 - 30 - 40 and 
50 ml of the Standard iron Solution (4.7) and 2 ml of the 
hydrochloric acid (4.3). Dilute to the mark and mix. Then, 
into a series of seven 50 ml one-mark volumetric flasks (5.4), 
introduce 20 ml of each of the preceding solutions, corre- 
sponding respectively to 0 - 20-40-80-120-160and 
2OOpg of iron. Add 5 ml of the hydroxylammonium chloride 
Solution (4.4). Shake. Add 3,5 ml of the buffer Solution 
(4.5.2). Shake. Add 2 ml of the 1 ,IO-phenanthroline 
Solution (4.6). Dilute to the mark and mix. Allow to stand 
for 5 min. Shake. 
Measure the absorbance using the spectrophotometer or 
the photoelectric absorptiometer (5.6) at a wavelength of 
508 nm. Subtract from the values found the absorbance 
corresponding to the blank test (6.6). Plot the calibration 
curve showing the number of micrograms of iron as a 
function of the absorbance. 
* Although coloration deveiops at a pH between 2 and 9, its intensity is constant only between pH 3,5 and 4,5. 
2 ISO 55174978 (E) 
7 EXPRESSION OF RESULTS 
7.1 Method of calculation and formulae 
7.1 .l Test Portion taken by pipetting 
The iron content, expressed in milligrams per litre of 
product, is given by the formula 
“1 100 1000 177, x 100 
loooxv,xv,= 5 x Vo 
ml is the mass, in micrograms, of iron read on the 
calibration curve (6.7); 
V, is the volume, in millilitres, of the test Portion 
(6.1); 
VI is the volume, in millilitres, 
taken for the determination (6.4). m0 is the mass, in grams, of the test Portion (6.1); 
ml is the mass, in micrograms, of iron read on the 
calibration curve (6.7); 
Vl is th e volume, 
take n for th e determ 
7.2 Repeatability in mill il itres, 
(6.4). of the final Portion 
The differente between the results of the two determi- 
nations carried out simultaneously or in rapid succession 
by the same analyst, on the same test Sample, shall not 
exceed $r 3 % of the mean value. 
of the final Portion 
8 TEST REPORT 
7.1.2 Test Portion taken by weighing 
The iron content, expressed in milligrams per kilogram of 
product, is given by the formula 
m1 100 1000 m, x 100 
10ooXV,Xm,= h Xmo The test report shall indicate the method used and the 
results obtained. lt shall also mention all operating 
conditions not specified in this International Standard, or 
regarded as optional, as well as any circumstances which 
may have influenced the results. 
The test report shal I give all deta 
comp lete i dentif ication of the Sample. ils required for the 
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