ISO 20702:2017

Fertilizers and soil conditioners — Determination of microamounts of inorganic anions in fertilizers by ion chromatography

ISO 20702:2017 specifies the ion chromatography method for the determination of microamounts of water soluble inorganic anions, such as fluoride (F−), chloride (Cl−), bromide (Br−), iodide (I−), nitrite (NO2−) and thiocyanate (SCN−), in fertilizers.

Engrais et amendements — Détermination des microquantités d'anions inorganiques dans les fertilisants par chromatographie d'échange d'ions

General Information

• Status: Published
• Publication Date: 07-Dec-2017
• ICS: 65.080 - Fertilizers
• Technical Committee: ISO/TC 134 - Fertilizers, soil conditioners and beneficial substances
• Drafting Committee: ISO/TC 134 - Fertilizers, soil conditioners and beneficial substances
• Current Stage: 9060 - Close of review

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 20702
First edition
2017-12
Fertilizers and soil conditioners —
Determination of microamounts of
inorganic anions in fertilizers by ion
chromatography
Engrais et amendements — Détermination des microquantités
d'anions inorganiques dans les fertilisants par chromatographie
d'échange d'ions
Reference number
©
ISO 2017
© ISO 2017, Published in Switzerland
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ii © ISO 2017 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Reagents . 1
6 Apparatus and materials. 3
7 Test procedure . 4
7.1 General . 4
7.2 Preparation of test sample . 4
7.3 Activation of the filter columns. 4
7.4 Preparation of the test solution . 4
7.5 Ion chromatography condition A (Gradient chromatography condition) . 5
7.6 Ion chromatography condition B (Isocratic chromatography condition). 6
7.7 Determination of standard working solutions and sample test solutions . 6
8 Calculation and expression of results . 7
8.1 General . 7
8.2 Precision . 7
8.2.1 Ring test . 7
8.2.2 Repeatability, r . 7
8.2.3 Reproducibility, R . 7
9 Test report . 7
Annex A (informative) Ring test report — Report of international laboratories ring test .9
Annex B (informative) Typical ion chromatogram for gradient chromatography conditions .46
Annex C (informative) Typical ion chromatogram for isocratic chromatography conditions .47
Annex D (informative) Additional statistical index of the test results .48
Bibliography .50
Foreword
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This document was prepared by Technical Committee ISO/TC 134, Fertilizers and soil conditioners.
iv © ISO 2017 – All rights reserved

Introduction
Microamounts of inorganic anions such as fluoride, chloride, bromide, iodide, nitrite and thiocyanate
are usually contained in fertilizers. Excessive amounts of such inorganic anions can not only impede
the growth of crops, but can also cause harmful effects on the arable land and the environment.
Current standards around the world mostly focus on a few specific anions. This method, which uses
ion chromatography, provides a high-throughput screening and rapid determination pathway targeting
microamounts of six anions as an alternative to traditional chemical analysis.
INTERNATIONAL STANDARD ISO 20702:2017(E)
Fertilizers and soil conditioners — Determination of
microamounts of inorganic anions in fertilizers by ion
chromatography
1 Scope
This document specifies the ion chromatography method for the determination of microamounts of
− − − −
water soluble inorganic anions, such as fluoride (F ), chloride (Cl ), bromide (Br ), iodide (I ), nitrite
− −
(NO ) and thiocyanate (SCN ), in fertilizers.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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 8157, Fertilizers and soil conditioners — Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 8157 apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http://www.electropedia.org/
— ISO Online browsing platform: available at https://www.iso.org/obp
4 Principle
Water soluble inorganic anions are extracted by sonication, centrifugation and purification using a
C18 column and a Ba-ion column (where applicable). During pre-treatment, the anions are filtered by
a 0,22 μm aqueous filter. They are determined by ion chromatography. Anions are separated based
on their affinity for the exchange sites on the analytical column. The suppressor device reduces
the background conductivity of the eluent to a low level by replacing the cations with the hydrogen
ions, thereby converting the anions in the fertilizer sample to their corresponding acids with higher
conductivity. The separated anions (in their acid forms) are measured by an electrical-conductivity
detector. Anions are identified based on their retention times compared to known standards.
Quantitation is accomplished by measuring the peak height or area compared to a calibration curve
generated from known standards.
5 Reagents
WARNING — Acetone and methanol are flammable and toxic. Refer to the applicable safety data
sheet (SDS). The related operations shall be performed in the fume hood. This document does
not point out all possible safety problems; therefore, the user shall bear the responsibility to
take proper safety and health measures.
Analytical grade reagent (A.R.) chemicals shall be used in all tests, unless otherwise indicated.
The purity of water used throughout shall be understood to mean reagent water with electrical
resistivity ≥18,2 MΩ·cm. In the list below, G.R. refers to guarantee reagent.
5.1 Ultrapure water, HPLC grade water with electrical resistivity ≥18,2 MΩ·cm.
5.2 Potassium hydroxide (G.R.).
5.3 Sodium carbonate (G.R.).
5.4 Sodium bicarbonate (G.R.).
5.5 Acetone, HPLC grade.
5.6 Methanol, HPLC grade.
NOTE Methanol is be used for the activation of SPE-C18 column (6.8).
5.7 Potassium hydroxide eluent. Dissolve 5,611 g potassium hydroxide (0,1 mol, 5.2) in water (5.1).
Dilute this solution to 1 l with water (5.1) and mix thoroughly. The potassium hydroxide solution can also
be prepared by automated eluent generation system (OH- type). The potassium hydroxide eluent is used
for gradient chromatography conditions.
5.8 Carbonate eluent. Dissolve 0,530 g sodium carbonate (5,0 mmol) (5.3) and 0,168 g sodium
bicarbonate (2,0 mmol) (5.4) in water (5.1), and add 40 ml of acetone (5.5) to the aqueous solution.
Dilute to 1 l with water (5.1) and mix thoroughly by ultrasonic treatment for 10 min. The carbonate
eluent is used for isocratic chromatography conditions.
5.9 Stock solutions
5.9.1 Fluoride stock solution (1 000 mg/l).
Dissolve 2,210 0 g NaF (sodium fluoride, A.R., pre-treated at 105 °C for 2 h) into water (5.1). Transfer the
aqueous solution into a 1 000 ml volumetric flask, dilute it to 1 l with water (5.1) and mix thoroughly.
Keep the fluoride stock solution in a polyethylene bottle for storage.
5.9.2 Chloride stock solution (1 000 mg/l).
Dissolve 1,648 0 g NaCl (sodium chloride, A.R., pre-treated at 105 °C for 2 h) in water (5.1). Transfer the
aqueous solution into a 1 000 ml volumetric flask, dilute it to 1 l with water (5.1) and mix thoroughly.
5.9.3 Bromide stock solution (1 000 mg/l).
Dissolve 1,490 0 g KBr (potassium bromide, A.R., pre-treated at 105 °C for 2 h) in water (5.1). Transfer
the aqueous solution into a 1 000 ml volumetric flask, dilute it to 1 l with water (5.1) and mix thoroughly.
Keep the bromide stock solution in an amber glass bottle for storage.
5.9.4 Iodide stock solution (1 000 mg/l).
Dissolve 1,308 0 g KI (potassium iodide, A.R., pre-treated at 105°C for 2 h) in water (5.1). Transfer the
aqueous solution into a 1 000 ml volumetric flask, dilute it to 1 l with water (5.1) and mix thoroughly.
Keep the iodide stock solution in an amber glass bottle for storage.
5.9.5 Nitrite stock solution (1 000 mg/l).
Dissolve 1,489 0 g NaNO (sodium nitrite, A.R., pre-dried in a desiccator for approximately 24 h) in
water (5.1). Transfer the aqueous solution into a 1 000 ml volumetric flask, dilute it to 1 l with water
(5.1) and mix thoroughly.
2 © ISO 2017 – All rights reserved

Nitrite is easily oxidized, especially in the presence of moisture, thus only fresh reagents are to be used.
Place approximately 2 g of NaNO
...