SIST EN 15749:2010
(Main)Fertilizers - Determination of sulfates content using three different methods
Fertilizers - Determination of sulfates content using three different methods
This document specifies three different methods (Methods A, B and C) for the determination of sulfur present in fertilizers extracts in the form of sulfates. Method A specifies the gravimetric procedure. Method B specifies the method using inductively coupled plasma optical spectrometry (ICP-OES). Method C specifies the method using ion chromatography (IC).
Düngemittel - Bestimmung von Sulfat mit drei verschiedenen Verfahren
Diese Europäische Norm legt drei verschiedene Verfahren (Verfahren A, B und C) für die Bestimmung des in Düngemittelextrakten vorliegenden Schwefels in Form von Sulfaten fest. Als Verfahren A ist das gravimetrische Verfahren festgelegt. Als Verfahren B ist die Bestimmung mittels optischer Emissionsspektro¬metrie mit induktiv gekoppeltem Plasma (ICP OES) festgelegt. Als Verfahren C ist die Vorgehensweise mittels Ionenchromatographie (IC) festgelegt.
Engrais - Dosage des sulfates selon trois méthodes différentes
Le présent document spécifie trois méthodes différentes (méthodes A, B et C) de dosage du soufre présent dans les extraits d’engrais sous forme de sulfate. La méthode A utilise la gravimétrie. La méthode B emploie la spectrométrie d’émission optique à plasma inductif (ICP-OES). La méthode C a recours à la chromatographie par échange d’ions (IC).
Gnojila - Določevanje sulfatov s tremi različnimi metodami
Ta evropski standard opredeljuje tri različne metode (Metodo A, B in C) za določanje žvepla, prisotnega v ekstraktih gnojil v obliki sulfatov. Metoda A določa gravimetrično metodo. Metoda B določa metodo z uporabo optične spektrometrije z induktivno sklopljeno plazmo (ICP-OES). Metoda C določa metodo z uporabo ionske kromatografije (IC).
General Information
Relations
Standards Content (Sample)
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Düngemittel - Bestimmung von Sulfat mit drei verschiedenen VerfahrenEngrais - Dosage des sulfates selon trois méthodes différentesFertilizers - Determination of sulfates content using three different methods65.080GnojilaFertilizersICS:Ta slovenski standard je istoveten z:EN 15749:2009SIST EN 15749:2010en,fr,de01-februar-2010SIST EN 15749:2010SLOVENSKI
STANDARDSIST-TS CEN/TS 15749:20081DGRPHãþD
SIST EN 15749:2010
EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM
EN 15749
October 2009 ICS 65.080 Supersedes CEN/TS 15749:2008English Version
Fertilizers - Determination of sulfates content using three different methods
Engrais - Dosage des sulfates selon trois méthodes différentes
Düngemittel - Bestimmung von Sulfat mit drei verschiedenen Verfahren This European Standard was approved by CEN on 20 September 2009.
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 CEN 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 CEN Management Centre has the same status as the official versions.
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:
Avenue Marnix 17,
B-1000 Brussels © 2009 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 15749:2009: ESIST EN 15749:2010
EN 15749:2009 (E) 2 Contents Page Foreword .3Introduction .41Scope .52Normative references .53Terms and definitions .54Principle .55Sampling and sample preparation .66Method A – Gravimetric method .67Method B – ICP-OES method .78Method C – IC method . 119Precision of methods A, B and C . 1710Test report . 18Annex A (informative)
Statistical results of the inter-laboratory tests . 19Bibliography . 22 SIST EN 15749:2010
EN 15749:2009 (E) 3 Foreword This document (EN 15749:2009) 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 2010, and conflicting national standards shall be withdrawn at the latest by April 2010. 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. This document supersedes CEN/TS 15749:2008. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: 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.
SIST EN 15749:2010
EN 15749:2009 (E) 4 Introduction This document specifies three different methods for the determination of sulfur. Based on the statistical results of the inter-laboratory tests, obtained with the same samples, the three methods produce equivalent results, and hence can be used all three methods on decision of the user and availability of equipment. SIST EN 15749:2010
EN 15749:2009 (E) 5 1 Scope This European Standard specifies three different methods (Methods A, B and C) for the determination of sulfur present in fertilizers extracts in the form of sulfates. Method A specifies the gravimetric method. Method B specifies the method using inductively coupled plasma optical spectrometry (ICP-OES). Method C specifies the method using ion chromatography (IC).
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 CEN/TS 15925, Fertilizers — Extraction of total sulfur present in various forms CEN/TS 15926, Fertilizers — Extraction of water soluble sulfur where the sulfur is in various forms CEN/TS 15960, Fertilizers — Extraction of total calcium, total magnesium, total sodium and total sulfur in the forms of sulfates CEN/TS 15961, Fertilizers — Extraction of water soluble calcium, magnesium, sodium and sulfur (in the forms of sulfates) 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: Gravimetric method Sulfur is extracted from the sample according to the methods described in CEN/TS 15925, CEN/TS 15926, CEN/TS 15960 or CEN/TS 15961 and determined based on the gravimetric determination as barium sulfate. 4.2 Method B: ICP-OES Sulfur is extracted from the sample according to the methods described in CEN/TS 15925, CEN/TS 15926, CEN/TS 15960 or CEN/TS 15961 and its concentration in the extract is measured by inductively coupled plasma-optical emission spectrometry (ICP-OES). SIST EN 15749:2010
EN 15749:2009 (E) 6 4.3 Method C: IC Sulfur is extracted from the fertilizer according to the methods described in CEN/TS 15925, CEN/TS 15926, CEN/TS 15960 or CEN/TS 15961 in the form of sulfate. The sulfate concentration of the extract is measured by ion chromatography (IC) equipped with a suppressor device and a conductivity detector. 5 Sampling and sample preparation Sampling is not part of the methods specified in this European Standard. A recommended sampling method is given in EN 1482-1. Sample preparation shall be carried out in accordance with EN 1482-2. 6 Method A – Gravimetric method 6.1 Reagents Use only reagents of recognized analytical grade and distilled or demineralized water (grade 3 according to EN ISO 3696). 6.1.1 Diluted hydrochloric acid Mix one volume of ρ(HCl) = 1,18 g/ml with one volume of water. 6.1.2 Barium chloride solution, ρ(BaCl2.2 H2O) = 122 g/l. 6.1.3 Silver nitrate solution, ρ = 5 g/l. 6.2 Apparatus 6.2.1 Porcelain crucibles 6.2.2 Hot water bath 6.2.3 Drying oven, set at 105 °C ± 1 °C. 6.2.4 Electric oven, set at 800 °C ± 50 °C. 6.3 Procedure 6.3.1 Sampling of the solution Pipette an aliquot part of one of the extraction solutions containing between 20 mg and 100 mg of sulfur or 50 mg and 250 mg of SO3. Place this aliquot in a beaker of suitable capacity. Add 20 ml of diluted hydrochloric acid (6.1.1). Make up to about 300 ml with water. 6.3.2 Preparation of the precipitate Bring the solution to the boil. Add, drop by drop, about 20 ml of the barium chloride solution (6.1.2) while stirring the solution vigorously. Boil for a few minutes. SIST EN 15749:2010
EN 15749:2009 (E) 7 Place the beaker, covered with a watch glass, in a boiling hot water bath (6.2.2) for 1 h. Then leave standing hot (± 60 °C) until the supernatant liquor is clear. Decant the clear solution through a slow filtration ash-free filter. Wash the precipitate several times with hot water. Continue to wash the precipitate on the filter until the filtrate is chloride free. This can be checked by using a silver nitrate solution (6.1.3). 6.3.3 Incineration and weighing of the precipitate Place the filter paper and precipitate in a porcelain crucible (6.2.1) previously weighed to the nearest 0,1 mg. Dry in the oven (6.2.3) and ash at approximately 800 °C for half an hour (6.2.4). Allow to cool in a desiccator and weigh to 0,1 mg. 6.4 Calculation and expression of the result 1 mg of barium sulfate corresponds to 0,137 mg of sulfur or to 0,343 mg of SO3. Calculate the sulfates content, wS, as mass fraction in percent of the fertilizer according to Equation (1): 2211S0,0137mvvmw×××= (1)
Calculate the SO3 content, wSO3, as mass fraction in percent of the fertilizer according to Equation (2): 2,5SSO3×=ww (2) where m1 is the mass of the barium sulfate precipitate, in mg; m2 is the mass of the test portion, in g; v1 is the volume of the extraction solution, in ml; v2 is the aliquot volume, in ml. 7 Method B – ICP-OES method 7.1 Reagents Use only reagents of recognized analytical grade, and water conforming to grade 2 of EN ISO 3696. Stock solutions shall be replaced after a maximum of one year, but the standard solution shall be freshly prepared monthly as a minimum.
7.1.1 Hydrochloric acid, ρ approximately 1,18 g/ml; 7.1.2 Diluted hydrochloric acid, mix 40 ml of hydrochloric acid (7.1.1) in 1 l of water; 7.1.3 Sulfur stock solution, corresponding to 1 000 mg/l sulfur. Dry in a pre-treatment step some grams of sodium sulfate (Na2SO4) at 105 °C for 1 h. Let cool in a desiccator. Weigh to the nearest 0,1 mg, approximately 4,437 5 g of sodium sulfate (Na2SO4). Dissolve the weighted SIST EN 15749:2010
EN 15749:2009 (E) 8 mass in a small quantity of water in volumetric flasks of nominal capacity of 1 000 ml, fill to the mark with water. The solution is stable for several months if stored at 4 °C to 6 °C. NOTE Sulfur stock solution of 1 000 mg/l is also readily available commercially, and may be used instead. 7.2 Apparatus Common laboratory equipment and glassware, in particular equipment according to 7.2.1 to 7.2.2. 7.2.1 Analytical balance, capable of weighing to an accuracy of 0,1 mg. 7.2.2 Inductively coupled plasma – Optical emission spectrometer Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES) with radial viewing of the plasma and simultaneous measurement of emission signals. For measuring sulfur at wavelengths below 190 nm the optical system shall be evacuated or be filled or continuously flushed with an inert gas as recommended by the instrument manufacturer to obtain high and stable signal intensities. The instrument shall be equipped with radial plasma as a minimum requirement; axial plasma is equally acceptable, as long as it can be shown that the results are statistically equal to the results obtained with radial plasma. Background correction shall also be performed. Settings of the working conditions (e.g. viewing height, gas flows, RF or plasma power, sample uptake rate, integration time, number of replicates) shall be optimized according the manufacturer’s instructions.
7.3 Preparation of the extract The sulfur is extracted from the sample according to one of the methods described in CEN/TS 15925, CEN/TS 15926, CEN/TS 15960 or CEN/TS 15961.
7.4 Procedure 7.4.1 General Calibration shall be performed by means of the standard addition technique. This method allows the analysis of fertilizers with unknown matrix composition or with a matrix that cannot be synthetically imitated easily. 7.4.2 Preparation of the test solution Dilute the extraction solution with the diluted hydrochloric acid (7.1.1) to obtain a concentration between 10 mg/l and 150 mg/l of sulfur. 7.4.3 Preparation of the blank test solution Carry out a blank test at the same time as the extraction, with only the reagents. 7.4.4 Preparation of the calibration solutions The additions to the test solution, prior to the dilution step, should be about 20 %, 50 % and 100 % of the expected sulfur content. After the additions, dilute each of the samples with the diluted hydrochloric acid (7.1.1). SIST EN 15749:2010
EN 15749:2009 (E) 9 A (external) calibration curve method can also be used instead of the standard addition method where the analytical results are demonstrated to be statistically equal. Appropriate matrix matching of the calibration solutions shall be performed if an (external) calibration method is used. 7.5 Determination 7.5.1 General Set up the instrument according to the manufacturer’s instructions using appropriate conditions, and with the suitable background correction system in operation. For each instrument used, selectivity, limits of detection and quantification, precision, linear working area, and interference shall be established separately. 7.5.2 Determination by ICP-OES Aspirate the blank test solution (7.4.3), the test solution (7.4.2) and the various additions (7.4.4) in ascending order separately into the plasma, and measure the emission of sulfur. Perform at least two replicates and average the values if the values fall within an accepted range. After each measurement, aspirate water or diluted hydrochloric acid (7.1.2). The following special procedures can be used to obtain high precision and accuracy necessary to analyse high sulfur contents in fertilizers: a) optimised instrument settings; b) simultaneous measurement of the signals of analyte and an appropriate internal standard element; c) adjustment of the matrix of calibration solutions to the sample matrix; d) consistent identical treatment of samples and calibration solutions during preparation and measurement, or use gravimetric dilution instead of volumetric dilution; e) correction of instrumental drift and background (if required). Table 1 — General analytical conditions for sulfur determination by ICP-OES Wavelength, nm 181,978 alternatives: 180,676
182,568
Background correction Yes Working range mg/l 1 to 150 Possible internal standard: Molybdenum 202,030 nm 281,615 nm 7.6 Calculation and expression of the results NOTE Net signal is defined as the number of counts per time unit at the selected wavelength, corrected for background contributions. SIST EN 15749:2010
EN 15749:2009 (E) 10 7.6.1 Calculation In case of several additions, regression techniques on the linear model of variable y as a function of variable x, have to be used to determine the sulfur concentration of the test solution. Generally, this model can be written as: iixbay⋅+= (3) In this particular case of three standard additions:
iiSy= (i = 0, 1, 2, 3) (4) isiVx⋅=ρ (i = 0, 1, 2, 3) (5) where sρis the concentration, in mg/l, of the standard solution; iVare the various volumes, in l, of the standard solution added; iSare the net signals after the various additions. Calculate the values of a and b as follows: ()∑∑∑∑∑−⋅−⋅=22iiiiiixxnyxyxnb (6) nxbyaii∑∑⋅−= (7) where nis the number of solutions measured (n = 4 in case of three additions). Calculate the sulfur concentration fρ, in mg/l, of the filtrate of the test portion using the following equation: ffVba=ρ (8) where fVis the volume, in l, of
...
SLOVENSKI STANDARD
kSIST FprEN 15749:2009
01-julij-2009
*QRMLOD'RORþHYDQMHVXOIDWRYVWUHPLUD]OLþQLPLPHWRGDPL
Fertilizers - Determination of sulfates content using three different methods
Düngemittel - Bestimmung von Sulfat mit drei verschiedenen Verfahren
Engrais - Dosage des sulfates selon trois méthodes différentes
Ta slovenski standard je istoveten z: FprEN 15749
ICS:
65.080 Gnojila Fertilizers
kSIST FprEN 15749:2009 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
---------------------- Page: 1 ----------------------
kSIST FprEN 15749:2009
---------------------- Page: 2 ----------------------
kSIST FprEN 15749:2009
EUROPEAN STANDARD
FINAL DRAFT
FprEN 15749
NORME EUROPÉENNE
EUROPÄISCHE NORM
March 2009
ICS 65.080 Will supersede CEN/TS 15749:2008
English Version
Fertilizers - Determination of sulfates content using three
different methods
Engrais - Dosage des sulfates selon trois méthodes Düngemittel - Bestimmung von Sulfat mit drei
différentes verschiedenen Verfahren
This draft European Standard is submitted to CEN members for unique acceptance procedure. It has been drawn up by the Technical
Committee CEN/TC 260.
If this draft becomes a European Standard, 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.
This draft European Standard was established by CEN 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 CEN Management Centre has the
same status as the official versions.
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.
Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without notice and
shall not be referred to as a European Standard.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2009 CEN All rights of exploitation in any form and by any means reserved Ref. No. FprEN 15749:2009: E
worldwide for CEN national Members.
---------------------- Page: 3 ----------------------
kSIST FprEN 15749:2009
FprEN 15749:2009 (E)
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 – Gravimetric method .5
7 Method B – ICP-OES method .6
8 Method C – IC method . 10
9 Precision of methods A, B and C . 16
10 Test report . 18
Annex A (informative) Statistical results of the inter-laboratory tests . 19
Bibliography . 22
2
---------------------- Page: 4 ----------------------
kSIST FprEN 15749:2009
FprEN 15749:2009 (E)
Foreword
This document (FprEN 15749:2009) has been prepared by Technical Committee CEN/TC 260 “Fertilizers and
liming materials”, the secretariat of which is held by DIN.
This document is currently submitted to the Unique Acceptance Procedure.
This document will supersede CEN/TS 15749:2008.
This document has been prepared under a mandate given to CEN by the European Commission and the
European Free Trade Association.
3
---------------------- Page: 5 ----------------------
kSIST FprEN 15749:2009
FprEN 15749:2009 (E)
1 Scope
This document specifies three different methods (Methods A, B and C) for the determination of sulfur present
in fertilizers extracts in the form of sulfates. Method A specifies the gravimetric procedure. Method B specifies
the method using inductively coupled plasma optical spectrometry (ICP-OES). Method C specifies the method
using ion chromatography (IC).
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 3696:1995, 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: Gravimetric method
Sulfur is extracted from the sample according to the methods described in [1], [2], [3] or [4] and determined
based on the gravimetric determination as barium sulfate.
4.2 Method B: ICP-OES
Sulfur is extracted from the sample according to the methods described in [1], [2], [3] or [4] and its
concentration in the extract is measured by inductively coupled plasma-optical emission spectrometry (ICP-
OES).
4.3 Method C: IC
Sulfur is extracted from the fertilizer according to the methods described in [1], [2], [3] or [4] in the form of
sulfate. The sulfate concentration of the extract is measured by ion chromatography (IC) equipped with a
suppressor device and a conductivity detector.
4
---------------------- Page: 6 ----------------------
kSIST FprEN 15749:2009
FprEN 15749:2009 (E)
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 [5].
Sample preparation shall be carried out in accordance with EN 1482-2.
6 Method A – Gravimetric method
6.1 Reagents
6.1.1 General
Use only reagents of recognized analytical grade and distilled or demineralized water (grade 3 according to
EN ISO 3696:1995).
6.1.2 Diluted hydrochloric acid
Mix one volume of ρ(HCl) = 1,18 g/ml with one volume of water.
.
6.1.3 Barium chloride solution, ρ(BaCl 2 H O) = 122 g/l.
2 2
6.1.4 Silver nitrate solution, ρ = 5 g/l.
6.2 Apparatus
6.2.1 Porcelain crucibles
6.2.2 Hot water bath
6.2.3 Drying oven, set at 105 °C ± 1 °C.
6.2.4 Electric oven, set at 800 °C ± 50 °C.
6.3 Procedure
6.3.1 Sampling of the solution
Pipette an aliquot part of one of the extraction solutions containing between 20 mg and 100 mg of sulfur or
50 mg and 250 mg of SO .
3
Place this aliquot in a beaker of suitable capacity. Add 20 ml of diluted hydrochloric acid (6.1.2). Make up to
about 300 ml with water.
6.3.2 Preparation of the precipitate
Bring the solution to the boil. Add, drop by drop, about 20 ml of the barium chloride solution (6.1.3) while
stirring the solution vigorously. Boil for a few minutes.
Place the beaker, covered with a watch glass, in a boiling hot water bath (6.2.2) for 1 h. Then leave standing
hot (± 60 °C) until the supernatant liquor is clear. Decant the clear solution through a slow filtration ash-free
filter. Wash the precipitate several times with hot water. Continue to wash the precipitate on the filter until the
filtrate is chloride free. This can be checked by using a silver nitrate solution (6.1.4).
5
---------------------- Page: 7 ----------------------
kSIST FprEN 15749:2009
FprEN 15749:2009 (E)
6.3.3 Incineration and weighing of the precipitate
Place the filter paper and precipitate in a porcelain crucible (6.2.1) previously weighed to the nearest 0,1 mg.
Dry in the oven (6.2.3) and ash at approximately 800 °C for half an hour (6.2.4). Allow to cool in a desiccator
and weigh to 0,1 mg.
6.4 Calculation and expression of the result
1 mg of barium sulfate corresponds to 0,137 mg of sulfur or to 0,343 mg of SO .
3
Calculate the sulfates content, w , as mass fraction in percent of the fertilizer according to Equation (1):
S
v
1
w = m × 0,0137× (1)
S 1
v ×m
2 2
Calculate the SO content, w , as mass fraction in percent of the fertilizer according to Equation (2):
3 SO3
w = w × 2,5 (2)
SO S
3
where
m is the mass of the barium sulfate precipitate, in milligrams;
1
m is the mass of the test portion, in grams;
2
v is the volume of the extraction solution, in millilitres;
1
v is the aliquot volume, in millilitres.
2
7 Method B – ICP-OES method
7.1 Reagents
7.1.1 General
Use only reagents of recognized analytical grade, and water conforming to grade 2 of EN ISO 3696:1995.
Stock solutions shall be replaced after a maximum of one year, but the standard solution shall be freshly
prepared monthly as a minimum.
7.1.2 Hydrochloric acid, ρ approximately 1,18 g/ml;
7.1.3 Diluted hydrochloric acid, mix 40 ml of hydrochloric acid (7.1.2) in 1 l of water;
7.1.4 Sulfur stock solution, corresponding to 1 000 mg/l sulfur.
Dry in a pre-treatment step some grams of sodium sulfate (Na SO ) at 105 °C for 1 h. Let cool in a desiccator.
2 4
Weigh to the nearest 0,1 mg, approximately 4,4375 g of sodium sulfate (Na SO ). Dissolve the weighted mass
2 4
in a small quantity of water in volumetric flasks of nominal capacity of 1 000 ml, fill to the mark with water.
The solution is stable for several months if stored at 4 °C to 6 °C.
6
---------------------- Page: 8 ----------------------
kSIST FprEN 15749:2009
FprEN 15749:2009 (E)
NOTE Sulfur stock solution of 1 000 mg/l is also readily available commercially, and may be used instead.
7.2 Apparatus
7.2.1 General
Common laboratory equipment and glassware, in particular equipment according to 7.2.2 to 7.2.3.
7.2.2 Analytical balance, capable of weighing to an accuracy of 0,1 mg.
7.2.3 Inductively coupled plasma – Optical emission spectrometer
Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES) with radial viewing of the plasma and
simultaneous measurement of emission signals.
For measuring sulfur at wavelengths below 190 nm the optical system shall be evacuated or be filled or
continuously flushed with an inert gas as recommended by the instrument manufacturer to obtain high and
stable signal intensities.
The instrument shall be equipped with radial plasma as a minimum requirement; axial plasma is equally
acceptable, as long as it can be shown that the results are statistically equal to the results obtained with radial
plasma. Background correction shall also be performed. Settings of the working conditions (e.g. viewing
height, gas flows, RF or plasma power, sample uptake rate, integration time, number of replicates) shall be
optimized according the manufacturer’s instructions.
7.3 Preparation of the extract
The sulfur is extracted from the sample according to one of the methods described in [1], [2], [3] or [4].
7.4 Procedure
7.4.1 General
Calibration shall be performed by means of the standard addition technique. This method allows the analysis
of fertilizers with unknown matrix composition or with a matrix that cannot be synthetically imitated easily.
7.4.2 Preparation of the test solution
Dilute the extraction solution with the diluted hydrochloric acid (7.1.2) to obtain a concentration between
10 mg/l and 150 mg/l of sulfur.
7.4.3 Preparation of the blank test solution
Carry out a blank test at the same time as the extraction, with only the reagents.
7.4.4 Preparation of the calibration solutions
The additions to the test solution, prior to the dilution step, should be about 20 %, 50 % and 100 % of the
expected sulfur content. After the additions, dilute each of the samples with the diluted hydrochloric acid
(7.1.2).
A (external) calibration curve method can also be used instead of the standard addition method where the
analytical results are demonstrated to be statistically equal. Appropriate matrix matching of the calibration
solutions shall be performed if an (external) calibration method is used.
7
---------------------- Page: 9 ----------------------
kSIST FprEN 15749:2009
FprEN 15749:2009 (E)
7.5 Determination
7.5.1 General
Set up the instrument according to the manufacturer’s instructions using appropriate conditions, and with the
suitable background correction system in operation.
For each instrument used, selectivity, limits of detection and quantification, precision, linear working area, and
interference shall be established separately.
7.5.2 Determination by ICP-OES
Aspirate the blank test solution (7.4.3), the test solution (7.4.2) and the various additions (7.4.4) in ascending
order separately into the plasma, and measure the emission of sulfur. Perform at least two replicates and
average the values if the values fall within an accepted range. After each measurement, aspirate water or
diluted hydrochloric acid (7.1.3).
The following special procedures can be used to obtain high precision and accuracy necessary to analyse
high sulfur contents in fertilizers:
a) optimised instrument settings;
b) simultaneous measurement of the signals of analyte and an appropriate internal standard element;
c) adjustment of the matrix of calibration solutions to the sample matrix;
d) consistent identical treatment of samples and calibration solutions during preparation and measurement,
or use gravimetric dilution instead of volumetric dilution;
e) correction of instrumental drift and background (if required).
Table 1 — General analytical conditions for sulfur determination by ICP-OES
181,978
alternatives:
Wavelength, nm
180,676
182,568
Background correction Yes
Working range mg/l 1 to 150
202,030 nm
Possible internal standard: Mo
281,615 nm
7.6 Calculation and expression of the results
NOTE Net signal is defined as the number of counts per time unit at the selected wavelength, corrected for
background contributions.
8
---------------------- Page: 10 ----------------------
kSIST FprEN 15749:2009
FprEN 15749:2009 (E)
7.6.1 Calculation
In case of several additions, regression techniques on the linear model of variable y as a function of variable x,
have to be used to determine the sulfur concentration of the test solution. Generally, this model can be written
as:
y = a+b⋅x (3)
i i
In this particular case of three standard additions:
y = S (i = 0, 1, 2, 3) (4)
i i
x =c ⋅V (i = 0, 1, 2, 3) (5)
i s i
where
c is the concentration, in milligrams per litre, of the standard solution;
s
V are the various volumes, in litres, of the standard solution added;
i
S are the net signals after the various additions.
i
Calculate the values of a and b as follows:
n⋅ x y − x y
∑ i i∑∑i i
b = (6)
2
2
n⋅ x −()x
∑∑i i
y −b⋅ x
∑∑i i
a = (7)
n
where
n is the number of solutions measured (n = 4 in case of three additions).
Calculate the sulfur concentration c , in milligrams per litre, of the filtrate of the test portion using the
f
following equation:
a
b
c = (8)
f
V
f
where
V is the volume, in litres, of the filtrate of the test portion used to prepare the test solution.
f
7.6.2 Expression of the sulfur content in the sample
The sulfur content in the sample or mass fraction of sulfur, w , expressed in milligrams of sulfur per kilogram
S
of fertilizer, is determined using the following equation:
9
---------------------- Page: 11 ----------------------
kSIST FprEN 15749:2009
FprEN 15749:2009 (E)
(c −c )
f bl
w = ⋅V (9)
S t
m
where
c is the concentration, in milligrams per litre, of the filtrate of the test portion, as determined using
f
Equation (8);
c is the concentration, in milligrams per litre, of the blank solution;
bl
m is the mass of sample, in kilograms, taken for the extraction, and corrected for water content;
V is the total volume, in litres, of extract (filtrate of the test portion).
t
Sulfur contents of secondary nutrient fertilizers are to be expressed in the oxide form (SO ) or the elemental
3
form (S). As the results of the determination are expressed as sulfur (S), the following conversion factor shall
be used:
S = 0,400 SO
3.
8 Method C – IC method
8.1 Reagents
8.1.1 General
Use only reagents of recognized analytical grade, and water conforming to grade 2 of EN ISO 3696:1995.
Stock solutions shall be replaced after a maximum of one year, but the standard solution shall be renewed
monthly as a minimum.
8.1.2 Hydrochloric acid, ρ approximately 1,18 g/ml;
8.1.3 Sulfate stock solution, corresponding to 1 000 mg/l SO .
4
Dry to constant weight in an oven at (150 ± 2) °C a sufficient quantity of anhydrous sodium sulfate (Na SO ).
2 4
Allow to cool in
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.