ISO 19822:2018
(Main)Fertilizers and soil conditioners — Determination of humic and hydrophobic fulvic acids concentrations in fertilizer materials
Fertilizers and soil conditioners — Determination of humic and hydrophobic fulvic acids concentrations in fertilizer materials
This document specifies the procedure for the analysis of humic acids and hydrophobic fulvic acids which is applicable to dry and liquid materials used as ingredients in commercial fertilizers, soil amendments, and geological deposits.
Engrais et amendements minéraux basique - Détermination des acides humique et fulvique
General Information
Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 19822
First edition
2018-08
Fertilizers and soil conditioners —
Determination of humic and
hydrophobic fulvic acids
concentrations in fertilizer materials
Engrais et amendements minéraux basique - Détermination des
acides humique et fulvique
Reference number
©
ISO 2018
© ISO 2018
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ii © ISO 2018 – All rights reserved
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative References . 1
3 Terms and definitions . 1
4 Principles . 2
5 Warnings . 2
6 Reagents . 2
7 Apparatus . 3
8 Preparing crucibles, drying, and weighing samples . 4
8.1 Preparing crucibles . 4
8.2 Drying and weighing solid analytical samples . 4
8.3 Drying and weighing liquid samples . 5
9 Extraction procedure . 5
10 Determination of ash content . 6
11 Separation of Hydrophobic Fulvic Acids (HFA) . 6
12 Hydrogen ion exchange . 7
13 Calculations. 8
13.1 Determination of ash-free HA weight . 8
13.2 Determination of ash-free HFA weight . 8
13.3 Determination of % analyte in solid analytical samples . 8
13.4 Determination of % analyte in liquid samples . 8
14 Resin regeneration and column preparation . 8
Annex A (informative) Procedure to confirm the presence lignosulfonates .10
Annex B (informative) ISO/CD 19822 interlaboratory study .13
Bibliography .16
Foreword
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This document was prepared by Technical Committee ISO/TC 134, Fertilizers and soil conditioners.
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iv © ISO 2018 – All rights reserved
Introduction
Humic substances are present in all ecosystems: oceans, rivers, lakes, and top soils. Quantifying the
amount of humic material present in these systems is essential for academic research and commercial
applications, specifically agricultural soil and plant management.
The increased use of humic substances in agriculture has generated intense interest among producers,
consumers, and regulators for a reliable method for quantification of the active ingredients in raw
humic ores and commercial fertilizer products; specifically humic and fulvic acids. As both commercial
trade and regulation of humic products are based on percentage (%) of the humic and fulvic acids in
commercial humic products, use of % units instead of SI units is warranted, therefore incorporated
into this standard.
This document establishes a method for the determination of humic acids (HA) and acidic hydrophobic
fulvic acids (HFA). The method is based on an existing preparative procedure use by the International
[1]
Humic Substances Society (IHSS) for extracting high purity HA and HFA from soil samples , which is a
[2]
modified form of the “classical” technique described in detail by Stevenson . The “classical” methods
and the IHSS method were developed as preparative methods for the fractionation of soil organic
matter; they were not intended to be used as quantitative analytical methods. The classical method of
extracting humic acids and fulvic acids from soil humus utilize a “strong base” to extract the alkaline
soluble materials, and then the alkaline extract solution is acidified to flocculate the humic acids, which
appear to precipitate out of solution. The remaining substances in solution after alkaline and acid
treatment were called fulvic acids.
This method modifies the “classical” technique in a number of ways:
— it determines the quantity of humic substances on an “ash free” basis (mineral salts excluded);
— the alkali extraction is done under anoxic conditions to reduce oxidation of the analytical sample
during extraction;
— it defines the materials that are soluble in both alkali and acid as the Fulvic Fraction;
— it can differentiate products containing certain non-humic materials that some manufactures claim
to contain humic substances;
[3] [4]
— it further defines HFA as materials of low sulfur content that bind to a hydrophobic resin at pH 1
[5][6]
, instead the classical, and perhaps more common definition, for fulvic acids as materials that are
defined as soluble in both acid and alkali solution. This stricter definition is necessary to distinguish
HFA from mineral salts, polysaccharides, amino sugars, amino acids, proteins, acids, and carbohydrates
[1][4]
that are extracted along with humic substances when using the “classical” method .
See Annex B for information on ISO/CD 19822 interlaboratory study.
INTERNATIONAL STANDARD ISO 19822:2018(E)
Fertilizers and soil conditioners — Determination of humic
and hydrophobic fulvic acids concentrations in fertilizer
materials
1 Scope
This document specifies the procedure for the analysis of humic acids and hydrophobic fulvic acids
which is applicable to dry and liquid materials used as ingredients in commercial fertilizers, soil
amendments, and geological deposits.
2 Normative References
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https: //www .iso .org/obp
— IEC Electropedia: available at https: //www .electropedia .org/
3.1
hydrophobic fulvic acids
HFA
materials composed of less than 0,75 % elemental sulfur (S) that are soluble in aqueous alkaline and
acid solution and are adsorbed at pH 1 onto a polymeric adsorbent resin of moderate polarity. The resin
is of a type designed for adsorption of amphiphilic compounds having molecular weights typical of
fulvic acids
3.2
fulvic fraction
alkali extracted portions of humic substances that are soluble in both alkali and acid aqueous solutions
3.3
humic acids
HA
alkali extracted humic substances that are insoluble in strongly acidic solution and will precipitate
from the alkali extract in acid solutions of pH 1
3.4
humic substance
major organic constituent of natural organic matter consisting of complex heterogeneous mixtures
of carbon-based substances formed by biochemical reactions during the decay and transformation of
plant and microbial remains
3.5
lignosulfonates
amorphous light to dark brown powder or liquid derived from the sulfite pulping of softwoods. The
lignin framework is a sulfonated random polymer of three aromatic alcohols: coniferyl alcohol,
p-coumaryl alcohol, and sinapyl alcohol, of which coniferyl alcohol is the principle unit
4 Principles
4.1 This method determines ash-free quantities of HA and HFA gravimetrically after separation from
their matrix.
4.2 The method of extracting HA and HFA utilizes a strong base to extract the alkaline-soluble materials,
and then, after removal of non-soluble components, the alkaline solution is acidified to flocculate the HA.
4.3 The liquid supernatant remaining after the removal of the HA is called the Fulvic Fraction. The
Fulvic Fraction, which can contain Hydrophobic Fulvic Acids (HFA), is treated to determine the quantity
of HFA in the Fulvic Fraction by selective adsorption onto a methacrylic-ester resin designed to separate
the HFA from non-humic compounds. The material retained by the hydrophobic resin is referred to in the
[3]
literature as the hydrophobic acid fraction of soluble organic matter .
5 Warnings
5.1 Requirements
5.1.1 Good laboratory practices
Related standards (e.g. ISO/IEC 17025) should be followed at all times in regards to personal protective
equipment (safety glasses, handling strong acids, hydrochloric acid) and alkali (sodium hydroxide).
5.1.2 Moisture control
Humic and fulvic acids are hygroscopic materials; it is critical to prev
...
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