SIST EN ISO 14673-2:2004

Milk and milk products - Determination of nitrate and nitrite contents - Part 2: Method using segmented flow analysis (Routine method) (ISO 14673-2:2004)

ISO 14673-2|IDF 189-2:2004 specifies a routine method for the determination of the nitrate and nitrite contents of milk and milk products by segmented flow analysis. The method is applicable to milk, cheese, and liquid and dried milk products and infant foods.

Milch und Milchprodukte - Bestimmung des Nitrat- und Nitritgehaltes - Teil 2: Verfahren mit segmentierter Fließanalyse (Routineverfahren) (ISO 14673-2:2004)

Dieser Teil von ISO 14673|IDF 189 legt ein Verfahren zur Bestimmung des Nitrat- und Nitritgehaltes von Milch und Milchprodukten durch segmentierte Fließanalyse fest. Das Verfahren gilt für Milch, Käse, flüssige Milchprodukte, Trockenmilcherzeugnisse und Kleinkindernahrung.

Lait et produits laitiers - Détermination des teneurs en nitrates et en nitrites - Partie 2: Méthode d'analyse par flux continus segmentés (Méthode de routine) (ISO 14673-2:2004)

L'ISO 14673-2|FIL 189-2:2004 décrit une méthode de routine pour la détermination des teneurs en nitrates et en nitrites du lait et des produits laitiers par analyse par flux continus segmentés. La méthode est valable pour le lait, les fromages, les produits laitiers secs et liquides et les aliments pour bébés.

Mleko in mlečni proizvodi - Določevanje nitratov in nitritov - 2. del: Metoda z uporabo segmentne pretočne analize (rutinska metoda) (ISO 14673-2:2004)

General Information

• Status: Published
• Publication Date: 30-Apr-2004
• ICS: 67.100.01 - Milk and milk products in general
• Technical Committee: KŽP - Agricultural food products
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 01-May-2004
• Due Date: 01-May-2004
• Completion Date: 01-May-2004
• Ref Project: EN ISO 14673-2:2004 - Milk and milk products - Determination of nitrate and nitrite contents - Part 2: Method using segmented flow analysis (Routine method) (ISO 14673-2:2004)

Relations

• Replaces: SIST EN ISO 14673-2:2002/AC:2002 - Milk and milk products - Determination of nitrate and nitrite contents - Part 2: Method using segmented flow analysis (Routine method) (ISO 14673-2:2001)
• Effective Date: 22-Dec-2008
• Replaces: SIST EN ISO 14673-2:2002 - Milk and milk products - Determination of nitrate and nitrite contents - Part 2: Method using segmented flow analysis (Routine method) (ISO 14673-2:2001)
• Effective Date: 22-Dec-2008

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN ISO 14673-2:2004
01-maj-2004
0OHNRLQPOHþQLSURL]YRGL'RORþHYDQMHQLWUDWRYLQQLWULWRYGHO0HWRGD]
XSRUDERVHJPHQWQHSUHWRþQHDQDOL]HUXWLQVNDPHWRGD,62
Milk and milk products - Determination of nitrate and nitrite contents - Part 2: Method
using segmented flow analysis (Routine method) (ISO 14673-2:2004)
Milch und Milchprodukte - Bestimmung des Nitrat- und Nitritgehaltes - Teil 2: Verfahren
mit segmentierter Fließanalyse (Routineverfahren) (ISO 14673-2:2004)
Lait et produits laitiers - Détermination des teneurs en nitrates et en nitrites - Partie 2:
Méthode d'analyse par flux continus segmentés (Méthode de routine) (ISO 14673-
2:2004)
Ta slovenski standard je istoveten z: EN ISO 14673-2:2004
ICS:
67.100.01 0OHNRLQPOHþQLSURL]YRGLQD Milk and milk products in
VSORãQR general
SIST EN ISO 14673-2:2004 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO 14673-2:2004

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SIST EN ISO 14673-2:2004
EUROPEAN STANDARD
EN ISO 14673-2
NORME EUROPÉENNE
EUROPÄISCHE NORM
February 2004
ICS 67.100.10 Supersedes EN ISO 14673-2:2001
English version
Milk and milk products - Determination of nitrate and nitrite
contents - Part 2: Method using segmented flow analysis
(Routine method) (ISO 14673-2:2004)
Lait et produits laitiers - Détermination des teneurs en Milch und Milchprodukte - Bestimmung des Nitrat- und
nitrates et en nitrites - Partie 2: Méthode d'analyse par flux Nitritgehaltes - Teil 2: Verfahren mit segmentierter
continus segmentés (Méthode de routine) (ISO 14673- Fließanalyse (Routineverfahren) (ISO 14673-2:2004)
2:2004)
This European Standard was approved by CEN on 2 February 2004.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national
standards may be obtained on application to the Central Secretariat or to any CEN member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the official
versions.
CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France,
Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia,
Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36  B-1050 Brussels
© 2004 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 14673-2:2004: E
worldwide for CEN national Members.

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SIST EN ISO 14673-2:2004
EN ISO 14673-2:2004 (E)
CORRECTED  2004-02-25
Foreword
This document (EN ISO 14673-2:2004) has been prepared by Technical Committee ISO/TC 34
"Agricultural food products" in collaboration with Technical Committee CEN/TC 302 "Milk and
milk products - Methods of sampling and analysis", the secretariat of which is held by NEN.
This European Standard shall be given the status of a national standard, either by publication of
an identical text or by endorsement, at the latest by August 2004, and conflicting national
standards shall be withdrawn at the latest by August 2004.
This document supersedes EN ISO 14673-2:2001.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of
the following countries are bound to implement this European Standard: Austria, Belgium,
Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary,
Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland,
Portugal, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
Endorsement notice
The text of ISO 14673-2:2004 has been approved by CEN as EN ISO 14673-2:2004 without any
modifications.
NOTE Normative references to International Standards are listed in Annex ZA (normative).
2

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SIST EN ISO 14673-2:2004
EN ISO 14673-2:2004 (E)
Annex ZA
(normative)
Normative references to international publications
with their relevant European publications
This European Standard incorporates by dated or undated reference, provisions from other
publications. These normative references are cited at the appropriate places in the text and the
publications are listed hereafter. For dated references, subsequent amendments to or revisions of
any of these publications apply to this European Standard only when incorporated in it by
amendment or revision. For undated references the latest edition of the publication referred to
applies (including amendments).
NOTE Where an International Publication has been modified by common modifications, indicated
by (mod.), the relevant EN/HD applies.
Publication Year Title EN Year
ISO 1042 1998 Laboratory glassware - One- EN ISO 1042 1999
mark volumetric flasks
3

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SIST EN ISO 14673-2:2004

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SIST EN ISO 14673-2:2004



INTERNATIONAL ISO
STANDARD 14673-2
IDF
189-2
Second edition
2004-02-01


Milk and milk products — Determination
of nitrate and nitrite contents —
Part 2:
Method using segmented flow analysis
(Routine method)
Lait et produits laitiers — Détermination des teneurs en nitrates et en
nitrites —
Partie 2: Méthode d'analyse par flux continus segmentés (Méthode de
routine)




Reference numbers
ISO 14673-2:2004(E)
IDF 189-2:2004(E)
©
ISO and IDF 2004

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SIST EN ISO 14673-2:2004
ISO 14673-2:2004(E)
IDF 189-2:2004(E)
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©  ISO and IDF 2004
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 either ISO or IDF at the respective
address below.
ISO copyright office International Dairy Federation
Case postale 56 • CH-1211 Geneva 20 Diamant Building • Boulevard Auguste Reyers 80 • B-1030 Brussels
Tel. + 41 22 749 01 11 Tel. + 32 2 733 98 88
Fax + 41 22 749 09 47 Fax + 32 2 733 04 13
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Web www.iso.org Web www.fil-idf.org
Published in Switzerland

ii © ISO and IDF 2004 – All rights reserved

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SIST EN ISO 14673-2:2004
ISO 14673-2:2004(E)
IDF 189-2:2004(E)
Contents Page
Foreword. iv
1 Scope. 1
2 Normative references . 1
3 Terms and definitions. 1
4 Principle . 2
4.1 Nitrate determination . 2
4.2 Nitrite determination . 2
5 Reagents . 2
6 Apparatus. 5
7 Sampling . 5
8 Preparation of test sample. 6
8.1 Cheese. 6
8.2 Dried milk products and infant food . 6
8.3 Milk and liquid milk products. 6
9 Procedure. 6
9.1 Preparation of the reduction column . 6
9.2 Checking the reducing capacity of the column . 7
9.3 Determination of nitrate content . 7
9.4 Determination of nitrite content . 8
9.5 Calibration curve. 9
9.6 Checking the drift of standard solutions. 9
10 Calculation and expression of results . 9
10.1 Calculation. 9
10.2 Expression of results. 10
11 Precision . 10
11.1 General. 10
11.2 Nitrite content. 10
11.3 Nitrate content. 10
12 Test report. 11
Bibliography . 14

© ISO and IDF 2004 – All rights reserved iii

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SIST EN ISO 14673-2:2004
ISO 14673-2:2004(E)
IDF 189-2:2004(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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. 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.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 14673-2IDF 189-2 was prepared by Technical Committee ISO/TC 34, Food products, Subcommittee
SC 5, Milk and milk products, and the International Dairy Federation (IDF), in collaboration with AOAC
International. It is being published jointly by ISO and IDF and separately by AOAC International.
This second edition cancels and replaces the first (ISO 14673-2IDF 189-2:2001), of which it constitutes a
minor revision.
ISO 14673IDF 189 consists of the following parts, under the general title Milk and milk products —
Determination of nitrate and nitrite contents:
— Part 1: Method using cadmium reduction and spectrometry
— Part 2: Method using segmented flow analysis (Routine method)
— Part 3: Method using cadmium reduction and flow injection analysis with in-line dialysis (Routine method)

iv © ISO and IDF 2004 – All rights reserved

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SIST EN ISO 14673-2:2004
ISO 14673-2:2004(E)
IDF 189-2:2004(E)
Foreword
IDF (the International Dairy Federation) is a worldwide federation of the dairy sector with a National
Committee in every member country. Every National Committee has the right to be represented on the IDF
Standing Committees carrying out the technical work. IDF collaborates with ISO and AOAC International in
the development of standard methods of analysis and sampling for milk and milk products.
Draft International Standards adopted by the Action Teams and Standing Committees are circulated to the
National Committees for voting. Publication as an International Standard requires approval by at least 50 % of
the National Committees casting a vote.
ISO 14673-2IDF 189-2 was prepared by Technical Committee ISO/TC 34, Food products, Subcommittee
SC 5, Milk and milk products, and the International Dairy Federation (IDF), in collaboration with AOAC
International. It is being published jointly by ISO and IDF and separately by AOAC International.
All work was carried out by the Joint ISO/IDF/AOAC Action Team, Minerals and minor compounds, of the
Standing Committee on Minor components characterization of physical properties, under the aegis of its
project leader, Mr G. Bråthen (NO).
This second edition, together with ISO 14673-1IDF 189-1 and ISO 14673-3IDF 189-3, cancels and replaces
IDF 84A:1984, IDF 95A:1982, IDF 96A:1987, IDF 97A:1985 and IDF 120:1984, which have been technically
revised.

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SIST EN ISO 14673-2:2004

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SIST EN ISO 14673-2:2004
ISO 14673-2:2004(E)
INTERNATIONAL STANDARD
IDF 189-2:2004(E)

Milk and milk products — Determination of nitrate and nitrite
contents —
Part 2:
Method using segmented flow analysis (Routine method)
WARNING — The use of this International Standard may involve hazardous materials, operations and
equipment. This standard does not purport to address all the safety problems associated with its use.
It is the responsibility of the user of this standard to establish safety and health practices and
determine the applicability of regulatory limitations prior to use.
1 Scope
This part of ISO 14673IDF 189 specifies a routine method for the determination of the nitrate and nitrite
contents of milk and milk products by segmented flow analysis. The method is applicable to milk, cheese, and
liquid and dried milk products and infant foods.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 648, Laboratory glassware — One-mark pipettes
ISO 835-1, Laboratory glassware — Graduated pipettes — Part 1: General requirements
ISO 1042, Laboratory glassware — One-mark volumetric flasks
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
nitrate content
mass fraction of nitrate determined by the procedure specified in this part of ISO 14673IDF 189
–
NOTE The nitrate content is expressed as the mass in milligrams of nitrate ions (NO ) per kilogram of product.
3
3.2
nitrite content
mass fraction of nitrite determined by the procedure specified in this part of ISO 14673IDF 189
–
NOTE The nitrite content is expressed as the mass in milligrams of nitrite ions (NO ) per kilogram of product.
2
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SIST EN ISO 14673-2:2004
ISO 14673-2:2004(E)
IDF 189-2:2004(E)
4 Principle
4.1 Nitrate determination
A test portion is suspended in water. Part of the suspension is transferred to the analyser for dialysis. The
nitrate ions are reduced to nitrite. The nitrite content is determined by a spectrometric method.
Standard nitrate solutions are determined by the same procedure. The nitrate content is calculated by
comparing the reading obtained from the test portion with the readings from the standard solutions.
NOTE Any nitrite present is determined as nitrate. The amount of nitrite is generally small compared to the amount of
nitrate. Infant food based on soy-proteins can be an exception to the rule. A correction for the nitrite present can be
applied after determination of the nitrite content.
4.2 Nitrite determination
A test portion is suspended in a solution of ammonium and sodium chloride. Part of the suspension is
transferred to the analyser for dialysis. The nitrite content is determined by a spectrometric method.
Standard nitrite solutions are determined by the same procedure. The nitrite content is calculated by
comparing the reading obtained from the test portion with that from the standard solution.
5 Reagents
Use only reagents of recognized analytical grade unless otherwise specified.
5.1 Water, distilled or deionized, or water of equivalent purity, free from nitrate and nitrite ions.
To avoid the possible inclusion of small gas bubbles in the copperized cadmium column (6.9), freshly boil the
distilled or deionized water and cool to room temperature. Use the thus-prepared water for the preparation of
the column (9.1), to check the reducing capacity of the column (9.2), and for regeneration of the column.
5.2 Cadmium granules, of diameter 0,3 mm to 0,8 mm.
Prepare cadmium granules, if not available commercially, as follows.
Place a suitable number of zinc rods in a beaker. Cover the rods with cadmium sulfate solution (5.3). Scrape
the cadmium sponge from the rods from time to time over a period of 24 h. Remove the zinc rods and decant
the liquid until only sufficient remains to cover the cadmium sponge. Wash the sponge two or three times with
water. Transfer the cadmium sponge to a laboratory blender together with 400 ml of the dilute hydrochloric
acid (5.6) and blend for a few seconds to obtain granules of the required size. Return the contents of the
blender to the beaker and leave to stand for several hours, while stirring occasionally to remove bubbles.
Decant most of the liquid and immediately copperize the granules as described in 9.1.2.
WARNING — Because of its toxicity, the used cadmium should be delivered as chemical waste to the
relevant authorities.
5.3 Cadmium sulfate solution, c(CdSO ⋅8H O) = 40 g/l.
4 2
Dissolve 40 g of cadmium sulfate in water in a 1 000 ml volumetric flask (6.4). Dilute to the mark with water
and mix.
5.4 Copper(II) sulfate solution, c(CuSO ⋅5H O) = 20 g/l.
4 2
Dissolve 2 g of copper(II) sulfate in water in a 100 ml volumetric flask (6.4). Dilute to the mark with water and mix.
5.5 Hydrochloric acid (HCl), (ρ = 1,19 g/ml).
20
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SIST EN ISO 14673-2:2004
ISO 14673-2:2004(E)
IDF 189-2:2004(E)
5.6 Dilute hydrochloric acid, c(HCl) ≈ 1 mol/l.
Carefully add 80 ml of hydrochloric acid (5.5) to about 700 ml water in a 1 000 ml volumetric flask (6.4) while
regularly swirling the contents. Cool the contents to room temperature. Dilute to the mark with water and mix
carefully.
5.7 Disodium ethylenediaminetetraacetate dihydrate (EDTA) solution (Na C H N O ⋅2H O).
2 10 14 2 8 2
Dissolve 33,5 g of EDTA in about 900 ml water in a 1 000 ml volumetric flask (6.4). Dilute to the mark with
water and mix.
5.8 Poly(oxyethylene lauryl ether) solution, 30 % mass fraction.
5.9 Ammonium and sodium chloride solution I.
Dissolve 40 g of ammonium chloride (NH Cl) and 200 g of sodium chloride (NaCl) in about 950 ml water in a
4
1 000 ml volumetric flask (6.4). Use concentrated ammonia to adjust the pH to 8,5. Dilute to the mark with
water. Add 2 ml of poly(oxyethylene lauryl ether) solution (5.8) and mix.
5.10 Ammonium and sodium chloride solution II.
Dissolve 10 g of ammonium chloride (NH Cl) and 50 g of sodium chloride (NaCl) in 950 ml water in a 1 000 ml
4
volumetric flask (6.4). Add 20 ml EDTA solution (5.7) and mix. Use concentrated ammonia to adjust the pH to
8,5. Dilute to the mark with water. Add 2 ml of poly(oxyethylene lauryl ether) solution (5.8) and mix.
5.11 Ammonium and sodium chloride solution III.
Dissolve 10 g of ammonium chloride (NH Cl) and 50 g of sodium chloride (NaCl) in 950 ml water in a 1 000 ml
4
volumetric flask (6.4). Use concentrated ammonia to adjust the pH to 8,5. Dilute the contents to the 1 000 ml
mark with water. Add 2 ml of poly(oxyethylene lauryl ether) solution (5.8) and mix.
5.12 Phosphoric acid solution (H PO ), 85 %, (ρ = 1,71 g/ml).
3 4 20
5.13 Colour reagent.
Add 100 ml of phosphoric acid solution (5.12) to 800 ml water in a 1 000 ml volumetric flask (6.4). Add in the
following order: 10 g sulfanilamide (NH C H SO NH) and 0,5 g N-1-naphthylethylene diamine
2 6 4 2 2
dihydrochloride (C H NHCH CH NH ⋅2HCl) and mix. Dilute to the mark with water. Add 0,5 ml of
10 7 2 2 2
poly(oxyethylene lauryl ether) solution (5.8) and mix again.
If stored in a refrigerator, the colour reagent solution may be kept for up to 1 month.
–
5.14 Sodium nitrate stock solution (NaNO ), c(NO ) = 0,400 g/l.
3 3
Dry an amount of sodium nitrate in the oven (6.18) set at 110 °C to 120 °C for 2 h. Dissolve 0,548 4 g of the
dry sodium nitrate in water in a 1 000 ml volumetric flask (6.4). Dilute to the mark with water and mix.
–
5.15 Sodium nitrate working solution, c(NO ) = 40 µg/ml.
3
Pipette (6.5) 10 ml of the sodium nitrate stock solution (5.14) into a 100 ml volumetric flask (6.4). Dilute to the
mark with water and mix.
5.16 Sodium nitrate calibration solutions.
Prepare a series of sodium nitrate calibration solutions with an increasing concentration of nitrate by pipetting
into six 200 ml volumetric flasks respectively, 1 ml, 2 ml, 3 ml, 6 ml, 9 ml and 12 ml of the sodium nitrate
–
working solution (5.15). Dilute each solution to the mark with water and mix. The nitrate (NO ) contents of the
3
obtained sodium nitrate calibration solutions are 0,2 µg/ml, 0,4 µg/ml, 0,6 µg/ml, 1,2 µg/ml, 1,8 µg/ml and
2,4 µg/ml respectively.
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SIST EN ISO 14673-2:2004
ISO 14673-2:2004(E)
IDF 189-2:2004(E)
5.17 Sodium nitrite stock solutions (NaNO ).
2
Dry an amount of sodium nitrite in the oven (6.18) set at 110 °C to 120 °C for 2 h.
–
5.17.1 Sodium nitrite stock solutions I, c(NO ) = 0,297 mg/ml.
2
Dissolve 0,445 g of the dry sodium nitrite (5.17) in water in a 1 000 ml volumetric flask (6.4). Dilute to the mark
with water and mix. Stock solution I may be stored for up to 1 day.
–
5.17.2 Sodium nitrite stock solutions II, c(NO ) = 1,001 mg/ml.
2
Dissolve 1,502 g of sodium nitrite (5.17) in water in a 1 000 ml volumetric flask (6.4). Dilute to the mark with
water and mix. If stored in a refrigerator, stock solution II may be kept for up to 1 month.
5.18 Sodium nitrite working solutions.
–
5.18.1 Sodium nitrite working solution I, c(NO ) = 0,89 µg/ml.
2
Transfer with a pipette (6.5) 3 ml of the sodium nitrite stock solution I (5.17.1) to a 1 000 ml volumetric flask
(6.4). Dilute to the mark with water and mix.
–
5.18.2 Sodium nitrite working solution II, c(NO ) = 0,100 1 µg/ml.
2
Pipette (6.5) 10 ml of the sodium nitrite stock solution II (5.17.2) into a 1 000 ml volumetric flask (6.4). Dilute to
the mark with water and mix. Pipette 10 ml of this solution into another 1 000 ml volumetric flask (6.4). Dilute
to the mark with ammonium and sodium chloride solution III (5.11) and mix.
5.19 Sodium nitrite calibration solutions.
Prepare a series of sodium nitrite calibration solutions with an increasing concentration of nitrite by pipetting
into five 200 ml volumetric flasks (6.4) respectively, 10 ml, 20 ml, 40 ml, 100 ml and 200 ml of sodium nitrite
working solution II (5.18.2). Except for the 200 ml solution, dilute each solution to the 200 ml mark with
ammonium and sodium chloride solution III (5.11) and mix. The sodium nitrite calibration solutions have a
–
nitrite (NO ) content of 0,005 µg/ml, 0,010 µg/ml, 0,020 µg/ml, 0,050 µg/ml and 0,100 µg/ml, respectively.
2
5.20 Alkaline detergent.
Use one of the solutions mentioned below.
5.20.1 Extran solution, 5 % volume fraction.
Pipette (6.5) 50 ml of extran solution into a 1 000 ml volumetric flask (6.4). Dilute to the mark with water and
mix.
5.20.2 Sodium hydroxide solution, c(NaOH) = 0,1 mol/l.
Dissolve 4 g of sodium hydroxide (NaOH) in water in a 1 000 ml volumetric flask (6.4). Dilute to the mark with
water and mix.
5.21 Regenerating fluid.
Add 50 ml of EDTA solution (5.7) and 2,0 ml of dilute hydrochloric acid (5.6) to 1 litre of water (5.1) and mix.
5.22 Reference test sample.
Use as a reference test sample, samples from a milk powder with a known nitrate content.
5.23 pH indicator paper.
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SIST EN ISO 14673-2:2004
ISO 14673-2:2004(E)
IDF 189-2:2004(E)
6 Apparatus
Clean all glassware thoroughly and rinse with distilled water to ensure that it is free from nitrate and nitrite ions.
Usual laboratory equipment and, in particular, the following.
6.1 Analytical balance, capable of weighing to the nearest 1 mg, with a readability of 0,1 mg.
6.2 Sample container, provided with an airtight lid.
6.3 Conical flasks, of capacity 250 ml and 500 ml.
6.4 Volumetric flasks, of nominal capacity 100 ml, 500 ml and 1 000 ml, complying with the requirements
of ISO 1042, class B.
6.5 Pipettes, capable of delivering 1 ml, 2 ml, 3 ml, 6 ml, 9 ml, 10 ml, 12 ml, 20 ml, 40 ml, 50 ml and 100 ml,
complying with the requirements of ISO 648, class A, or ISO 835-1. Where appropriate, burettes may be used
instead of pipettes.
6.6 Graduated cylinders, of capacities 100 ml and 150 ml.
6.7 Glass beakers, of capacities 100 ml and 150 ml.
6.8 Glass funnels, with a stem of internal diameter about 2 mm.
6.9 Suitable tube, U-shaped, of length about 30 cm and internal diameter 2 mm.
6.10 Analyser, capable of determining the nitrate and nitrite contents according to the described procedure.
6.11 Suspension apparatus, appropriate to suspend the test samples.
6.12 Grinding device, appropriate for grinding the laboratory sample, if necessary.
To avoid loss of moisture the device should not produce undue heat. A hammer mill shall not be used.
6.13 Laboratory mixer or homogenizer, with glass containers of capacity 250 ml or 400 ml, suitable for
suspending test portions of cheese and whey cheese.
6.14 Glass wool.
6.15 Spatula.
6.16 Magnetic stirrer.
6.17 Water baths, capable of being maintained at 35 °C to 40 °C and of boiling water.
6.18 Oven, capable of being maintained at 110 °C to 120 °C.
7 Sampling
Sam
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