UGANDA STANDARD 
      US ISO 6633
First Edition
2009-mm-dd
 
Reference numbe r 
     US ISO 6633:1984
 © UNBS 2009
  
Fruits, vegetables and derived products — Determination of 
lead content — Flameless atomic absorption spectrometric 
method 
 US ISO 6633: 1984 
 
© 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 
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permission from UNBS. 
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The Executive Director 
Uganda National Bureau of Standards 
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Uganda 
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Fax: 256 41 286 123 
E-mail: unbs@infocom.co.ug
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      US ISO 6633:1984  
© 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 6633, Fruits, vegetables and derived products — Determination of lead
content — Flameless atom ic absorption spectrometric method, is identical with and has been 
reproduced from an Internati onal Standard, ISO 6633:1984, Fruits, vegetables and derived products — 
Determination of lead content — Flameless atomic absorption spectrometric 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." 
 International Standard 
INTERNATIONAL ORGANIZATION FOR STANDARDIZATION~MEIK~YHAPOCZHAR OPrAHM3AUMR f-t0 CTAHI1APTbl3ALWl~ORGANlSATlON INTERNATIONALE DE NORMALISATION 
Fruits, vegetables and derived products - Determination 
of lead content - Flameless atomic absorption 
spectrometric method 
Fruits, legumes et produits d&iv& - D&termination de la teneur en plomb - IWthode par spectrom&rie d’absorption atomique 
sans flamme 
First edition - 1984-09-15 
UDC 634.V635.6 : 543.422 : 546.815 Ref. No. IS0 6633-1984 (E) 
Descriptors : agricultural products, fruit and vegetable products, fruits, vegetables, chemical analysis, determination of content, lead, atomic 
absorption method. 
Price based on 3 pages Foreword 
IS0 (the International Organization for Standardization) is a worldwide federation of 
national standards bodies (IS0 member bodies). The work of preparing International 
Standards is normally carried out through IS0 technical committees. Every 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, govern- 
mental 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 IS0 Council. They are approved in accordance with IS0 procedures requiring at 
least 75 % approval by the member bodies voting. 
International Standard IS0 6633 was prepared by Technical Committee lSO/TC 34, 
Agricultural food products. 
0 International Organization for Standardization, 1984 
Printed in Switzerland INTERNATIONAL STANDARD IS0 6633-1984 (E) 
Fruits, vegetables and derived products - Determination 
of lead content - Flameless atomic absorption 
spectrometric method 
1 Scope and field of application 
This International Standard specifies a flameless atomic ab- 
sorption spectrometric method for the determination of the 
lead content of fruits, vegetables and derived products. 
2 Principle 
Decomposition of organic matter in a nitric acid medium at high 
temperature and under pressure. Determination of the lead(H) 
cation by flameless atomic absorption spectrometry after the 
addition of orthophosphoric acid. 
3 Reagents 
All reagents shall be of recognized analytical grade and, in par- 
ticular, shall be free from lead [with the exception of the stan- 
dard lead solution (3.311. The water used shall be water double 
distilled in a borosilicate glass apparatus or water of equivalent 
purity. 
3.1 Nitric acid (@20 = I,38 g/ml). 
3.2 Nitric acid, solution. 
Dilute 1 part by volume of nitric acid (3.1) with 9 parts by 
volume of water. 
3.3 Orthophosphoric acid, 85 % solution 
(e20 = I,71 g/ml), or other equivalent matrix modifier used in 
the same quantities. 
3.4 Lead, standard solution corresponding to 1 g of Pb per 
litre. 
Dissolve 1,598 5 g of lead nitrate in 1 % ( V/ V) nitric acid sol- 
ution and dilute to 1 000 ml. 
Store in a borosilicate glass bottle with a glass stopper. 
1 ml of this standard solution corresponds to 1 mg of Pb. 4 Apparatus 
NOTE - The capsule (4.2) and all glassware should be washed before 
use with hot concentrated nitric acid and should be rinsed with double 
distilled water. 
Usual laboratory equipment, and 
4.1 Mechanical grinder, the inner walls and blades of 
which shall be coated with PTFE.1) 
4.2 Uniseal type decomposition capsule, consisting of a 
cylindrical crucible, the rim of which is coated with PTFE, of 
capacity 23 ml, in a stainless steel jacket with a screw top. A 
circular PTFE seal, which presses against the top of the cru- 
cible, ensures the airtightness of the capsule (see the figure). 
4.3 Thermostatically controlled oven, capable of being 
maintained at 80 OC. 
4.4 One-mark volumetric flasks, of capacities 50 and 
1 000 ml. 
4.5 Funnel. 
4.6 Haemolysis tubes. 
4.7 Pipettes, of capacities 2; 5; 10; and 20 ml. 
4.8 Eppendorf micropipettes, of capacities 10 and 100 ~1, 
with Standartys Eppendorf tips. 
NOTE - Some micropipettes are 10 % or more inaccurate. Unless 
they have been calibrated for this procedure, it is preferable that the 
same pipette be used for the test solution, the calibration solutions and 
the blank test solution. 
4.9 Atomic absorption spectrometer, with a standard 
graphite furnace (without pyrolytic coating) and a corrector for 
non-specific absorptions (deuterium lamp) and a multipoten- 
tiometric recorder?) 
- Source : lead hollow cathode lamp 
- Measurement wavelength : 283,3 nm 
- Purging gas : argon, or, if this is not available, nitrogen 
1) Polytetrafluoroethylene. 
2) The use of a L’vov platform with the furnace is recommended. IS0 66334984 (El 
4.10 Analytical balance. Transfer 500 ~1 
tubes (4.6) and 
(3.3). of each of these solutions to four haemolysis 
add to each 10 pi of the ortho phosphoric acid 
5 Procedure 
5.4.1.2 Test solution 
5.1 Preparation of the test sample Transfer to a haemolysis tube (4.6) 500 1-11 of the solution ob- 
tained in 5.3 and add 10 1-11 of the orthophosphoric acid (3.3). Mix the laboratory sample well. If necessary, first remove 
stones and hard seed-cavity walls and pass through the 
mechanical grinder (4.1) _ Allow frozen or deep frozen products 
to thaw in a closed vessel and add the liquid formed during this 
process to the product before mixing. 5.4.2 Programming the furnace 
Programming the furnace 
to be performed : allows the foll owing three operations 
5.2 Test portion 
- drying of the solution 
5.2.1 Liquid products thermal decomposition 
Take, by means of a pipette (4.71, 5 ml of the test sample (5.1) 
and transfer it to the crucible (see 4.2). - atomization 
The conditions are as follows : 
NOTE - If the liquid contains alcohol, it is preferable to remove it 
beforehand by boiling and, after cooling, to make up the volume to the 
initial volume by adding water. - drying at 110 OC for 30 s 
- gradual increase of temperature to 700 OC (in 45 S) 
5.2.2 Pasty, solid or dried products 
- thermal decomposition at 700 OC for 30 s 
Weigh, to the nearest 0,Ol g, into the crucible (see 
portion of about 1 g, expressed as fresh product. 4.2), a test 
- atomization at 2 300 OC for 10 s. During this stage, the 
apparatus records the variation of absorbance. The purging 
gas circulation is interrupted (“gas stop”) in order to pro- 
long the stay of the atoms in the furnace 5.3 Decomposition 
Add to the test portion 10 ml of the nitric acid (3.11, place the 
PTFE seal on the rim of the crucible and place the crucible in its 
stainless jacket. Fit the top. Transfer to the oven (4.3), main- 
tained at 80 OC, and leave for 24 h. - raising the temperature 
the end of the operation to 2 700 OC to purge the oven 
at 
5.4.3 Spectrometric measurements Remove the capsule from the oven, allow to cool in a 
refrigerator, open the jacket and wash the condensed drops on 
the seal into the crucible by washing down with a few millilitres 
of water. Transfer the solution, pouring through the funnel 
(4.51, to a 50 I m one-mark volumetric flask (4.4) and rinse the 
crucible several times with water. Dilute to the mark. Mix by 
shaking. 5.4.3.1 Preparation of the calibration graph 
Inject into the furnace programmed in accordance with 5.4.2, 
by means of a micropipette (4.8), successively three times IO ~1 
of each of the calibration solutions (5.4.1.1). Determine the ab- 
sorbance of each from the heights of the peaks recorded. 
Calculate the mean absorbance from the values obtained. NOTE - If a more sensitive lead determination is required, 
the sol ution in a 25 ml volumetric flask. make UP 
The absorbances thus determined correspond to 0,000 2; 
0,000 5; 0,001; and 0,002 pg of lead. Plot the calibration graph. 5.4 Determination 
5.4.3.2 Measurement on the test solution 5.4.1 Preparation of solutions to be injected 
Inject into the furnace programmed in accordance with 5.4.2, 
by means of a micropipette (4.8), successively three times 10 1-11 
of the test solution (5.4.1.2). Measure the respective ab- 
sorbances and determine the mean absorbance. 5.4.1.1 Calibration solutions 
Transfer, by means of a pipette (4.71, 10 ml of the standard lead 
solution (3.4) to a 1 000 ml one-mark volumetric flask and dilute 
to the mark with water. 
5.5 Blank test 
Take 2; 5; 10; and 20 ml aliquot portions of this solution and 
transfer to four 1 000 ml one-mark volumetric flasks. Dilute 
each to the mark with nitric acid (3.2). (These solutions corre- 
spond, respectively, to 0,02; 0,05; 0,lO; and 0,20 mg of lead 
per litre.) Carry out a blank test, using the same procedure for decompo- 
sition (5.31, but replacing the test portion by 5 ml of water. 
Prepare the blank test solution in accordance with 5.4.1.2. 
2 IS0 6633-1984 (El 
Inject into the furnace programmed in accordance with 5.4.2, 
by means of a micropipette (4.81, successively three times IO 1-11 
of the blank test solution. The absorbances shall be zero or less 
than 0,005. 
NOTE - The blank test is not necessary if the absence of lead in the 
reagents used has been established. 
6 Expression of results 
6.1 Method of calculation and formulae 
6.1.1 Liquid products 
The lead content, expressed in milligrams per litre, of the 
sample is equal to 
1 000 m, 
where ml is the mass, in micrograms, of lead in 10 1-11 of the 
solution obtained in 5.3, corrected if necessary for the blank 
test, and read from the calibration graph. 
6.1.2 Pasty, solid or dried products 
The lead content, expressed in milligrams per kilogram, of the 
sample is equal to 
ml 
5 000 - 
m0 where 
m0 is the mass, in grams, of the test portion; 
ml is the mass, in micrograms, of lead in IO PI of the sol- 
ution obtained in 5.3, corrected if necessary for the blank 
test, and read from the calibration graph. 
If it is wished to express the lead content on the dry basis, take 
the water content of the sample into account in the calculation. 
6.2 Repeatability 
The difference between the results of two determinations car- 
ried out simultaneously or in rapid succession by the same 
analyst on the same sample should not exceed 10 % (relative). 
7 Test report 
The test report shall show the method used and the results ob- 
tained, indicating clearly the method of expression used. It shall 
also mention any operating details not specified in this Inter- 
national Standard, or regarded as optional, together with 
details of any incidents likely to have influenced the results. 
The test report shall include all the information necessary for 
the complete identification of the sample. 
Dimensions in millimetres 
Jacket screw top 
Stainless steel jacket 
Figure - Decomposition capsule 
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