CEN/TS 15750:2008
(Main)Fertilizers - Determination of total nitrogen in fertilizers containing nitrogen only as nitric, ammoniacal and urea nitrogen by two different methods
Fertilizers - Determination of total nitrogen in fertilizers containing nitrogen only as nitric, ammoniacal and urea nitrogen by two different methods
This document specifies two different methods (Methods A and B) for the determination of the total nitrogen content in fertilizers. Method A specifies the titrimetric method after distillation according to ISO 5315:1984 [2]. Method B specifies a method by reduction of nitrate with iron and tin(II)-chloride.
Düngemittel - Bestimmung von Gesamtstickstoff in Düngemitteln mit Stickstoff in Form von Ammonium, Nitrat und Harnstoff unter Anwendung von zwei verschiedenen Verfahren
Dieses Dokument legt zwei verschiedene Verfahren (Verfahren A und B) zur Bestimmung des Gesamt-Stickstoff¬gehalts in Düngemitteln fest. Als Verfahren A ist das titrimetrische Verfahren nach Destillation entsprechend ISO 5315:1984 [2] festgelegt. Als Verfahren B ist ein Verfahren der Reduktion von Nitrat mit Eisen und Zinn(II)-chlorid festgelegt.
Engrais - Détermination de l’azote total dans les engrais ne contenant l'azote que sous forme nitrique, ammoniacale et uréique en présence les unes des autres selon deux méthodes différentes
Le présent document spécifie deux méthodes différentes (les méthodes A et B) de dosage de l’azote total dans les engrais. La méthode A spécifie la méthode titrimétrique après distillation selon l’ISO 5315:1984 [2], la méthode B spécifiant une méthode de réduction des nitrates par le fer et le chlorure stanneux.
Gnojila - Določevanje različnih oblik dušika v gnojilih, ki vsebuje dušik v nitratni, amonijevi in sečninski obliki z dvema različnima metodama
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
01-oktober-2008
*QRMLOD'RORþHYDQMHUD]OLþQLKREOLNGXãLNDYJQRMLOLKNLYVHEXMHGXãLNYQLWUDWQL
DPRQLMHYLLQVHþQLQVNLREOLNL]GYHPDUD]OLþQLPDPHWRGDPD
Fertilizers - Determination of different forms of nitrogen in fertilizers containing nitrogen
only as nitric, ammoniacal and urea nitrogen by two different methods
Düngemittel - Bestimmung verschiedener nebeneinander anwesender Stickstoff-Formen
in Düngemitteln mit Stickstoff in Form von Ammonium, Nitrat und Harnstoff unter
Anwendung von zwei verschiedenen Verfahren
Engrais - Détermination des teneurs des différentes formes d'azote en présence les
unes des autres dans les engrais ne contenant l'azote que sous forme nitrique,
ammoniacale et uréique en utilisant deux méthodes différentes
Ta slovenski standard je istoveten z: CEN/TS 15750:2008
ICS:
65.080 Gnojila Fertilizers
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
TECHNICAL SPECIFICATION
CEN/TS 15750
SPÉCIFICATION TECHNIQUE
TECHNISCHE SPEZIFIKATION
August 2008
ICS 65.080
English Version
Fertilizers - Determination of different forms of nitrogen in
fertilizers containing nitrogen only as nitric, ammoniacal and
urea nitrogen by two different methods
Engrais - Détermination des teneurs des différentes formes Düngemittel - Bestimmung von Gesamtstickstoff in
d'azote en présence les unes des autres dans les engrais Düngemitteln mit Stickstoff in Form von Ammonium, Nitrat
ne contenant l'azote que sous forme nitrique, ammoniacale und Harnstoff unter Anwendung von zwei verschiedenen
et uréique en utilisant deux méthodes différentes Verfahren
This Technical Specification (CEN/TS) was approved by CEN on 11 May 2008 for provisional application.
The period of validity of this CEN/TS is limited initially to three years. After two years the members of CEN will be requested to submit their
comments, particularly on the question whether the CEN/TS can be converted into a European Standard.
CEN members are required to announce the existence of this CEN/TS in the same way as for an EN and to make the CEN/TS available
promptly at national level in an appropriate form. It is permissible to keep conflicting national standards in force (in parallel to the CEN/TS)
until the final decision about the possible conversion of the CEN/TS into an EN is reached.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,
Romania, 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
© 2008 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TS 15750:2008: E
worldwide for CEN national Members.
Contents Page
Foreword.3
1 Scope .4
2 Normative references .4
3 Terms and definitions .4
4 Principle.4
5 Sampling and sample preparation.5
6 Method A.5
7 Method B.11
8 Precision of methods A and B.13
9 Test report .14
Annex A (informative) Statistical results of the inter-laboratory tests .15
Bibliography .16
Foreword
This document (CEN/TS 15750:2008) has been prepared by Technical Committee CEN/TC 260 “Fertilizers
and liming materials”, the secretariat of which is held by DIN.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.
This document has been prepared under a mandate given to CEN by the European Commission and the
European Free Trade Association.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to announce this Technical Specification: Austria, Belgium, Bulgaria, Cyprus, Czech
Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain,
Sweden, Switzerland and the United Kingdom.
1 Scope
This document specifies two different methods (Methods A and B) for the determination of the total nitrogen
content in fertilizers. Method A specifies the titrimetric method after distillation according to ISO 5315:1984 [2].
Method B specifies a method by reduction of nitrate with iron and tin(II)-chloride.
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.
EN 1482-2, Fertilizers and liming materials - Sampling and sample preparation - Part 2: Sample preparation
EN 12944-1:1999, Fertilizers and liming materials and soil improvers - Vocabulary - Part 1: General terms
EN 12944-2:1999, Fertilizers and liming materials and soil improvers - Vocabulary - Part 2: Terms relating to
fertilizers
EN ISO 385:2005, Laboratory glassware – Burettes (ISO 385:2005)
EN ISO 3696, Water for analytical laboratory use - Specification and test methods (ISO 3696:1987)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in EN 12944-1:1999 and EN 12944-2:1999
apply.
4 Principle
4.1 Method A – Titrimetric method after distillation according to ISO 5315:1984
Reduction of nitrate to ammonia by chromium powder in acid medium. Conversion of organic and urea
nitrogen into ammonium sulfate by digestion with concentrated sulfuric acid in the presence of a catalyst.
Distillation of the ammonia from an alkaline solution, absorption in an excess of standard volumetric sulfuric
acid solution and back-titration with standard volumetric sodium hydroxide solution in the presence of methyl
red or screened methyl red as indicator.
4.2 Method B – Reduction of nitrate with iron and tin(II)-chloride
Reduction of nitrate to ammonia by iron powder and tin chloride in acid medium. Conversion of organic and
urea nitrogen into ammonium sulfate by digestion with concentrated sulfuric acid in the presence of a catalyst.
Distillation of the ammonia from an alkaline solution, absorption in an excess of standard volumetric sulfuric
acid solution and back-titration with standard volumetric sodium hydroxide solution in the presence of an
indicator solution.
5 Sampling and sample preparation
Sampling is not part of the methods specified in this Technical Specification. A recommended sampling
method is given in EN 1482-1 [1].
Sample preparation shall be carried out in accordance with EN 1482-2.
6 Method A
6.1 Reagents
6.1.1 General
Use only reagents of recognized analytical grade having, in particular, low nitrogen contents and distilled or
demineralized water (grade 3 according to EN ISO 3696).
6.1.2 Chromium metal, powder, of particle size less than or equal to 250 µm;
6.1.3 Aluminium oxide, fused, pumice is suitable;
6.1.4 Anti-foaming agent, for example paraffin wax of melting point not lower than 100 °C, or a silicone;
6.1.5 Ammonium nitrate, dried at 100 °C to constant mass;
6.1.6 Digestion catalyst mixture, finely ground, comprising
potassium sulfate (K SO ): 1 000 g
2 4
copper(II) sulfate pentahydrate (CuSO .5H O): 50 g
4 2
6.1.7 Sulfuric acid, concentrated, ρ approximately 1,84 g/ml;
6.1.8 Hydrochloric acid, concentrated, ρ approximately 1,18 g/ml;
6.1.9 Sodium hydroxide, approximately 400 g/l solution;
6.1.10 Sodium hydroxide, standard volumetric solution, c(NaOH)=0,10 mol/l;
6.1.11 Sulfuric acid, standard volumetric solution, c(H SO )=0,25 mol/l;
2 4
SO )=0,10 mol/l;
6.1.12 Sulfuric acid, standard volumetric solution, c(H
2 4
6.1.13 Sulfuric acid, standard volumetric solution, c(H SO )=0,05 mol/l;
2 4
6.1.14 Indicator solution,
Use either the screened methyl red solution (6.1.14.1) or the methyl red solution (6.1.14.2).
6.1.14.1 Screened methyl red, ethanolic indicator solution;
Mix 50 ml of a 2 g/l ethanolic solution of methyl red with 50 ml of a 1 g/l ethanolic solution of methylene blue.
6.1.14.2 Methyl red, ethanolic indicator solution;
Dissolve 0,1 g of methyl red in 50 ml of 95 % (volume fraction) ethanol;
6.1.15 pH indicator paper, wide range.
6.2 Apparatus
6.2.1 General
Common laboratory equipment and glassware, in particular equipment according to 6.2.2 to 6.2.6.
6.2.2 Digestion apparatus, comprising an 800 ml Kjeldahl flask and a pear-shaped hollow glass stopper;
6.2.3 Distillation apparatus
The components of the distillation apparatus may be connected by means of rubber bungs and tubing or by
the use of spherical ground glass joints.
Spherical ground glass joints should be held spring clamps to ensure that they are leak tight. Rubber bungs
and tubing shall be replaced when they begin to perish or show signs of wear.
Suitable apparatus is illustrated in Figure 1. An automatic distillation apparatus may also be used, provided
that the results are statistically equivalent.
Dimensions in millimetres
Key
1 Kjeldahl flask (6.2.2) or round-bottomed, long-necked flask of 1 000 ml capacity
2 distillation tube with a single-bulb splash head, connected to the condenser by means of a spherical joint (No 18) (the
spherical joint for the connection to the condenser may be replaced by an appropriate rubber connection)
3 funnel with a polytetrafluoroethylene (PTFE) tap (6) (the tap may likewise be replaced by a rubber connection with a
clip)
4 seven-bulb condenser with spherical joint (No 18) at the entrance and joined at the issue to a glass extension tube by
means of a small rubber connection (when the connection to the distillation tube is effected by means of a rubber tube, the
spherical joint may be replaced by a suitable rubber bung)
5 500 ml flask in which the distillate is collected
6 PTFE-tap
a
hole
Figure 1 – Typical distillation apparatus (using a round bottom flask)
6.2.4 Anti-bumping granules, or anti-bumping device, consisting of a 100 mm×5 mm glass rod
connected to a 25 mm length of polyethylene tubing;
6.2.5 Two burettes, of capacity 50 ml, according to EN ISO 385:2005, I class A;
6.2.6 Glass beads, of diameter 2 mm to 3 mm.
6.3 Procedure
6.3.1 Test portion
Weight, to the nearest 0,001 g, between 0,5 g and 2,0 g of the test sample, containing not more than 60 mg of
nitrate nitrogen and 235 mg of total nitrogen.
6.3.2 Determination
6.3.2.1 Reduction
NOTE 1 This step is not required if nitrate nitrogen is known to be absent.
Transfer the test portion (6.3.1) to the flask (6.2.2) and add sufficient water to make up the total volume to
35 ml. Allow the flask to stand for 10 min with occasional gentle swirling to ensure dissolution of all nitrate
salts.
Add 1,2 g of the chromium powder (6.1.2) and 7 ml of the hydrochloric acid solution (6.1.8). Allow the flask to
stand for at least 5 min, but not more than 10 min, at ambient temperature.
Place the flask on a heating device in a fume cupboard with the heat input regulated to pass a 7 min to7,5 min
boil test and heat the flask for 4,5 min. Remove from the heat and allow to cool.
NOTE 2 The heat input is that required to bring 250 ml of water at 25 °C to a "rolling" boil in 7 min to 7,5 min.
6.3.2.2 Hydrolysis
NOTE This step can be used instead of the digestion (6.3.2.3) if it is known that the only forms of organic nitrogen
present are urea and cyanamide forms.
Stand the flask in a fume cupboard and add 1,5 g of the fused aluminium oxide (6.1.3). Carefully add 25 ml of
the sulfuric acid (6.1.7) to the flask. Insert the pear-shaped hollow glass stopper into the neck of the flask and
place on a heating device and initially heat until gently boiling. Then adjust the heat input to pass a 7 min to
7,5 min boil test (see 6.3.2.1, NOTE 2).
Continue to heat the flask and contents until dense white fumes of sulfuric acid have been involving for at
least 15 min. Allow the flask to cool to room temperature and carefully add 250 ml of water. Allow the flask to
cool.
6.3.2.3 Digestion
NOTE This step is necessary only if organic forms of nitrogen other than urea or cyanamide forms are pr
...
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