Bsi bs en 13466 2 2001 (2011)

BRITISH STANDARD

BS EN
13466-2:2001

Fertilizers —
Determination of water
content (Karl Fischer
methods) —
Part 2: 2-propanol as extracting medium

The European Standard EN 13466-2:2001 has the status of a
British Standard

Confirmed
June 2011
ICS 65.080

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BS EN 13466-2:2001

National foreword
This British Standard is the official English language version of
EN 13466-2:2001.
The UK participation in its preparation was entrusted to Technical Committee
CII/37, Fertilizers and related chemicals, which has the responsibility to:
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EN 13466-2

EUROPEAN STANDARD
NORME EUROPÉENNE
EUROPÄISCHE NORM

October 2001

ICS 65.080

English version

Fertilizers - Determination of water content (Karl Fischer
methods) - Part 2: 2-propanol as extracting medium
Engrais - Détermination de la teneur en eau (Méthodes Karl
Fischer) - Partie 2: 2-propanol comme milieu d'extraction

Düngemittel - Bestimmung des Wassergehaltes (KarlFischer-Verfahren) - Teil 2: 2-Propanol als Extraktionsmittel

This European Standard was approved by CEN on 18 August 2001.
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 Management Centre 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 Management Centre has the same status as the official
versions.
CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece,
Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.

EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG

Management Centre: rue de Stassart, 36

© 2001 CEN

All rights of exploitation in any form and by any means reserved
worldwide for CEN national Members.

B-1050 Brussels

Ref. No. EN 13466-2:2001 E


EN 13466-2:2001 (E)

Contents
page
Foreword......................................................................................................................................................................3
Introduction .................................................................................................................................................................4
1

Scope ..............................................................................................................................................................5

2

Normative references ....................................................................................................................................5

3

Principle ..........................................................................................................................................................5

4

Reagents .........................................................................................................................................................5

5

Apparatus .......................................................................................................................................................5

6

Installation and test of the Karl Fischer titrator..........................................................................................6

7

Sampling .........................................................................................................................................................6

8

Procedure .......................................................................................................................................................6

9

Calculation and expression of results.........................................................................................................8

10

Precision .........................................................................................................................................................8

11

Test report ......................................................................................................................................................8

Bibliography ..............................................................................................................................................................10

2


EN 13466-2:2001 (E)

Foreword

This European Standard has been prepared by Technical Committee CEN/TC 260 "Fertilizers and liming
materials", the secretariat of which is held by DIN.
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 April 2002, and conflicting national standards shall be withdrawn at the latest by
April 2002.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to implement this European Standard: Austria, Belgium, Czech Republic, Denmark, Finland,
France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden,
Switzerland and the United Kingdom.

3


EN 13466-2:2001 (E)

Introduction
The water content of fertilizers has a significant effect on their quality and, especially, their storage and handling
properties.
Water can be present in a number of forms such as free water, bound water and water of crystallization. It is often
important to be able to distinguish between these forms of water. The gravimetric methods for determination of
water standardized in EN 12048 and EN 12049 have only limited applicability.
The Karl Fischer method is applicable to a wide range of fertilizers. However, there are several variations to the
basic technique, different formulations of the Karl Fischer reagents are commercially available and a number of

different solvents can be used. In this standard, methanol and 2-propanol are used as extracting media to
distinguish between the different forms of water present in fertilizers.
EN 13466 "Fertilizers – Determination of water content (Karl Fischer methods)" consists of two parts:



Part 1 : Methanol as extracting medium




Part 2 : 2-propanol as extracting medium

As examples of the difference between methanol and 2-propanol as extracting media methanol gives a result which
is a combination of free water and extracted water of crystallization from the following components of fertilizers:
calcium nitrate tetrahydrate (Ca(NO3)2·4H2O); calcium hydrogen phosphate dihydrate (CaHPO4·2H2O) ; calcium
sulfate dihydrate (gypsum, CaSO4·2H2O) calcium sulfate hemihydrate (CaSO4·0,5H2O) ; magnesium sulfate
heptahydrate (MgSO4·7H2O); potassium chloride magnesium sulfate water (1/1/2,75, Kainite, KCl·
MgSO4·2,75H2O) ; potassium magnesium sulfate hexahydrate (Schoenite, K2SO4·MgSO4·6H2O) ; potassium
magnesium sulfate tetrahydrate (Leonite, K2SO4·MgSO4·4H2O) ; potassium sulfate calcium sulfate monohydrate
(Syngenite, K2SO4·CaSO4·H2O); potassium chloride magnesium chloride hexahydrate (Carnallite, KCl·
MgCl2·6H2O); magnesium nitrate hexahydrate (Mg(NO3)2·6H2O).
Extraction with 2-propanol gives a result which is a combination of free water and extracted water of crystallization
from the following components of fertilizers: calcium nitrate tetrahydrate (Ca(NO3)2·4H2O) ; magnesium sulfate
heptahydrate (MgSO4·7H2O); potassium chloride magnesium chloride hexahydrate (Carnallite, KCl·MgCl2·6H2O);
magnesium nitrate hexahydrate (Mg(NO3)2·6H2O).

4


EN 13466-2:2001 (E)

1

Scope

This European standard specifies a Karl Fischer titrimetric method for the determination of the water content of
fertilizers based on the use of 2-propanol as extracting medium.
The method is applicable to all solid mineral fertilizers. The result (KFP water) includes "free" water and extracted
water of crystallization from the following components of fertilizers: calcium nitrate tetrahydrate (Ca(NO3)2·4H2O);
magnesium sulfate heptahydrate (MgSO4·7H2O); potassium chloride magnesium chloride hexahydrate (Carnallite,
KCl·MgCl2·6H2O); magnesium nitrate hexahydrate (Mg(NO3)2·6H2O).

2

Normative references

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).
EN 1482, Sampling of solid fertilizers and liming materials.

3

Principle

Extraction of water from the fertilizer into 2-propanol, separation of the clear solution and titration of the extracted
water with a Karl Fischer reagent, previously standardized by titration with a known mass of water.

4

4.1

Reagents
General

All reagents shall be of recognized analytical grade.
4.2

2-propanol, containing less than a mass concentration of 250 mg/l water.

4.3

Karl Fischer reagent, equivalence from 1 mg to 5 mg water/ml reagent (see Table 1).

4.4

Sodium tartrate dihydrate Na2C4H4O6 · 2H2O (15,66% mass fraction of water).

Sodium tartrate dihydrate Na2C4H4O6 · 2H2O can be stored over 60% H2SO4 in a desiccator. Check the water
content by drying at about 150°C.

5

Apparatus

Ordinary laboratory apparatus and glassware and in particular the following:
5.1

Balance, capable of weighing to the nearest 0,0001 g.

5.2

Centrifuge capable of operating at a rate of 3 500 min .

5.3

Centrifuge tubes, diameter 4,5 cm, height 10 cm fitted with rubber stoppers.

-1

5


EN 13466-2:2001 (E)
-1

5.4

Dispersing apparatus : turbine type, minimum rotational frequency 9 500 min , suitable for introduction into
centrifuge tubes (5.3), for instance Ultra Turrax1

5.5

Karl Fischer titrator

NOTE

6

There are several titrators on the market for the Karl Fischer method.

Installation and test of the Karl Fischer titrator

Follow the instruction manual for the particular titrator used.

7

Sampling

Carry out sampling in accordance with EN 1482.

8

Procedure

8.1 Calibration of the Karl Fischer reagent
Titrate a known amount of water or sodium tartrate dihydrate (4.4) accurately weighed to the nearest 0,0001 g
following the instruction manual for the titrator.
NOTE

Calibration frequency should be adapted to the frequency of analysis.

8.2 Drift
Control the diffusion of water from the air into the titration vessel during the determination following the instruction
manual for the titrator. Take account of any recorded drift (md) when expressing results.

8.3 Test portion
Weigh to the nearest 0,0001 g a test portion of the test sample in accordance with clause 7 and Table 1 directly
into the previously dried and tared centrifuge tube (5.3).
Table 1 — Mass of test portion

Expected water content
[mass fraction in %]

Mass of test portion
titre of KF-Reagent

titre of KF-Reagent

5 mg/ml

2 mg/ml

<5

5g

5g

5 to 20

1g

1g

>20 to 50

1g

---

Ultra Turrax S25 equipped with dispersing turbine S25KR - 18G is an example of equipment commercially
available. This information is given for the convenience of users of this European Standard and does not constitute
an endorsement by CEN of these products.

1

6


EN 13466-2:2001 (E)
8.4 Extraction
Add 25 ml of 2-propanol (4.2) with a calibrated pipette to the test portion in the centrifuge tube. Insert the dispersing
apparatus (5.4) ensuring that the distance from any part of the dispersing tool to the inner surface of the centrifuge
tube is greater than the grain size of the fertilizer.
Place the dispersing tool near to the surface of the fertilizer layer. Disperse for 60 s at room temperature at
-1
9 500 min at least.
Make sure that the temperature during the dispersion-extraction does not exceed 40 °C or, in the case of fertilizer
containing magnesium sulfate, 25 °C.
Repeat the dispersion for a further 60 s if the fertilizer has not been completely dispersed in the first operation.
Repeat the extraction if the dispersion is still not complete.
NOTE

The dispersion can be controlled acoustically; the turbine pitch changes once the dispersion is complete.

8.5 Separation
Remove the dispersion apparatus from the centrifuge tube and stopper the latter with the rubber stopper.
Centrifuge the tube for 5 min. Repeat for 5 min if the supernatant liquid is not clear.

8.6 Titration

Introduce 5,0 ml of the clear solution (8.3) into the reaction vessel of the titrator (5.5). Start stirring. Titrate with the
Karl Fischer reagent (4.3) until the equivalence point is reached, following the instruction manual for the titrator.
Record the mass ms, in milligrams of water, indicated by the titrator.

8.7 Blank test
Carry out a blank test following the procedure specified in 8.2 but omitting the test portion. Record the mass mb.

8.8 Replication
Repeat the procedure described in 8.1 to 8.6 using a second test portion from the same test sample. After use the
dispersing tool should be cleaned and dried.

8.9 Alternative procedure for a series of samples
8.9.1 If a serial analysis is contemplated for several samples an alternative procedure may be used provided
enough 2-propanol can be held in the titrator reaction vessel to accomodate all the samples and the ensuing
quantity of Karl Fischer reagent. The procedure is as given in 8.9.2 to 8.9.8.
8.9.2

Check for drift as described in 8.2.

8.9.3

Introduce 5 ml of 2-propanol (4.2).

8.9.4

Add the Karl Fischer reagent until the equivalence point is reached. Reset the titrator readings to zero.

8.9.5

Introduce exactly 5 ml of extractant resulting from the separation (see 8.5).

8.9.6

Titrate to the equivalence point whilst stirring. Record the reading. Reset the readings to zero. Stop stirring.

8.9.7 Introduce a further 5 ml of extractant resulting from the separation (see 8.5). Repeat the procedure
described in 8.9.6.
8.9.8

Carry out a blank test as described in 8.7.

7


EN 13466-2:2001 (E)

9

Calculation and expression of results

The water content of the sample, wKFP, expressed as mass fraction in percent, in accordance with the Karl Fischer
method with 2-propanol as extracting medium is given by the following equation:

wKFP 

5 (ms  mb  md )  100
mt

where

ms

is the mass of water in the sample recorded in 8.6, in milligrams;

mb

is the mass of water obtained by blank test (8.7), in milligrams;

md

is the mass of water measured as per 8.2, in milligrams;

mt

is the mass of the test portion, in milligrams.

Report the mean of two determinations.

10 Precision
10.1 Interlaboratory test
An interlaboratory test was carried out in April 1997 with 15 participating laboratories and five different fertilizer
formulae. These formulae were: ammonium nitrate (AN) from two different sources, calcium ammonium nitrate
(CAN), NPK of the formula 12+12+17+2 and Thomas Kali (PK). For additional information see [1].

10.2 Repeatability
The absolute difference between two single test results obtained with the same method on identical test material in
the same laboratory by the same operator using the same equipment within the shortest feasible time interval will
exceed the repeatability limit r in not more than 5 % of the cases.

r = 0,033 + 0,049 wKFP

The equation being a + b
wKFP.

10.3 Reproducibility
The absolute difference between two single test results obtained with the same method on identical test material in
different laboratories with different operators using different equipment will exceed the reproducibility limit R in not
more than 5 % of the cases.

R = 0,177 + 0,293 wKFP
The equation being a + b
wKFP.

11 Test report
The test report shall include the following information:
a)

a reference to this European Standard;

b)

a complete identification of the sample;

c)

a reference to the test method used;

8


EN 13466-2:2001 (E)
d)

the methods of sampling and sample preparation;

e)

the result written as mass fraction wKFP water = x %;

f)

any unusual features noted during the determination or sample preparation.

9


EN 13466-2:2001 (E)

Bibliography

EN 12048, Solid fertilizers and liming materials – Determination of moisture content – Gravimetric method by drying
at (105
2) °C (ISO 8190:1992 modified).
EN 12049, Solid fertilizers and liming materials – Determination of moisture content – Gravimetric method by drying
under reduced pressure (ISO 8189:1992 modified).
[1] Document CEN/TC 260 N 385, Supplement on EN 13466-1 and EN 13466-2 regarding interlaboratory tests to
obtain precision data for the Karl Fischer methods.

10


blank

BS EN
13466-2:2001

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