ISO 19822:2018/Amd 1:2026

International
Standard
ISO 19822
First edition
Fertilizers and soil conditioners —
2018-08
Determination of humic and
hydrophobic fulvic acids
AMENDMENT 1
concentrations in fertilizer
2026-08
materials
AMENDMENT 1: DAX-8 resin
alternative
Engrais et amendements minéraux basique — Détermination des
acides humique et fulvique
AMENDEMENT 1: Alternative à la résine DAX-8
Reference number
ISO 19822:2018/Amd.1:2026(en) © ISO 2026

ISO 19822:2018/Amd.1:2026(en)
© ISO 2026
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Published in Switzerland
ii
ISO 19822:2018/Amd.1:2026(en)
Foreword
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iii
ISO 19822:2018/Amd.1:2026(en)
Fertilizers and soil conditioners — Determination of humic
and hydrophobic fulvic acids concentrations in fertilizer
materials
AMENDMENT 1: DAX-8 resin alternative
4.3
Replace paragraph 4.3 with the following:
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 macroporous polymeric adsorbent resin. The substances retained by
[3]
the resin are referred to in the literature as the hydrophobic acid fraction of soluble organic matter .

6.7
Replace paragraph 6.7 with the following:
−1 −1
Methacrylic-ester resin, 20–60 mesh, 0,75 ml·g to 1,15 ml·g pore volume, mean pore size of 225 Å to
2 −1 2 −1
600 Å, 140 m ·g to 550 m ·g surface area, for adsorption of materials up to 60 000 MM, e.g. Supelite DAX-
8 Resin, or Amberlite XAD-7HP, or any other available resin meeting equivalent properties.

7.18
Replace paragraph 7.18 with the following:
Glass chromatography column, 4 cm × 25 cm for the adsorbent resin.

11.1
Replace the first sentence in 11.1 with the following:
Hydrophobic fulvic acids (HFA) are separated from other acid-soluble substances in the fulvic fraction
by selective adsorption to a macroporous adsorbent resin (i.e. DAX-8 or Amberlite XAD-7HP), to which
hydrophilic acid-soluble components do not bind and can thus be removed from the solution.

11.1
Add the following sentence at the end of 11.1:
Annex C provides supporting data comparing alternative resins used for HFA separation.

Annex C
Add the following Annex after Annex B, before the Bibliography:

ISO 19822:2018/Amd.1:2026(en)
Annex C
(informative)
Resin comparison laboratory study
C.1 General
Currently, the ISO 19822 method for determining humic and hydrophobic fulvic acids concentrations
involves separating the hydrophobic fulvic acids (HFA) fraction from the fulvic fraction as per Clause 11.
The separation of HFA involves selective adsorption to an acidified hydrophobic resin that does not bind
hydrophilic acid-soluble components. The standard resin widely employed across research and industry for
HFA separation is the Supelite DAX-8 resin, which has been discontinued by the manufacturer. The purpose
of this resin comparison is to identify a suitable alternative, as DAX-8 is no longer commercially available for
purchase.
C.2 Properties of the two resins tested
The DAX-8 and XAD-7HP resins possess physical properties suitable for adsorbing hydrophobic fulvic acids.
The DAX-8 resin is slightly more polar than the XAD-7HP. The molecular mass capacity differs between the
resins, with DAX-8 cited as having a capacity of up to 150 000 and XAD-7HP up to 60 000. DAX-8 has a surface
2 ‒1 2 ‒1
area of 140 m g , while XAD-7HP has a larger surface area of 520 m g . The particle diameter for DAX-8 is
250 µm to 420 µm and 250 µm to 841 µm for XAD-7HP. The mean pore size for DAX-8 is 225 Å, whereas it is
‒1 ‒1
approximately 350 Å for XAD-7HP, and pore volumes are 0,79 ml g and 0,50 ml g , respectively.
It should be noted that XAD-7 was improved to create XAD-7HP, which has a broader pH application range,
making it suitable for this application.
C.3 Multiple laboratory study
The purpose of the laboratory study was to evaluate the comparative performance of XAD-7HP resin as an
alternative to DAX-8 resin for separating hydrophobic fulvic acids from the fulvic fraction as per Clause 11.
[9][10]
The study design was based on previous experiments performed to discover alternative resins. Three
laboratories generated three replicated analyses for HFA on three different materials.
C.4 Materials
Materials traceable to their vetted sources, with varying concentrations and chemical compositions of humic
substances, were chosen for quantitative analysis using the two different resins. The selected materials
were:
— QCM 1.1, a quality control material prepared using best manufacturing practices, which is the same
material used as the quality control material in the development of this document;
— PPS, Pahokee Peat soil reference material obtained from the International Humic Substances Society
(IHSS) has a higher degree of heterogeneity than QCM 1.1, as it is derived from partially humified peat;
— GL, Gascoyne leonardite reference material, also sourced from IHSS, has a higher degree of heterogeneity
than the QCM 1.1.
ISO 19822:2018/Amd.1:2026(en)
C.5 Methods
The materials were analysed for hydrophobic fulvic acid (HFA) content using the method described in this
document. The precision of the data was evaluated in accordance with ISO 5725-2. Since the data were
non-parametric, correlation analysis was conducted using Spearman’s rank correlation coefficient (r ) to
s
compare the data generated by each resin. Raw data and statistical analysis for QCM 1.1 is displayed for
DAX-8 (Table C.1), XAD-7HP (Table C.2), and QCM 1.1 resin correlation (Table C.3). Raw data and statistical
analysis for material GL is displayed for DAX-8 (Table C.4), XAD-7HP (Table C.5), and GL resin correlation
(Table C.6). Raw data and statistical analysis for material PPS is displayed for DAX-8 (Table C.7), XAD-7HP
(Table C.8), and PPS resin correlation (Table C.9).
C.6 Results of quantitative analysis
C.6.1 Results for Material QCM 1.1

ISO 19822:2018/Amd.1:2026(en)
Table C.1 — Hydrophobic fulvic acids content in QCM 1.1 using DAX-8 resin
Precision data: repeatability (r) and reproducibility (R) calculations
Method: HPTA Lab Study Remarks: raw data - outliers included
Tested level: QCM 1.1 - HPTA Study - DAX 8
Data Laboratory (i), from 1 to p
Repetition (n) Lab 1 Lab 2 Lab 3 Lab 4 Lab 5 Lab 6 Lab 7 Lab 8
General information 1 1,60 4,95 2,09
Number of lab
(p) 3 2 2,08 4,87 2,16
mean m 2,89 3 1,94 4,15 2,14
Standard
deviation 0,253 2 4
SD 0,064 1 5
SD % 8,770 1 6
mean min 1,873 7
mean max 4,657 8
Statistics for
Preliminary sums
each lab
number of labs
(p) 1 1 1
number of reps
T 3 9 (n) 3 3 3
mean (m) 1,87 4,66 2,13
T 4 27 n 9 9 9
T 1 25,98 n × m 5,62 13,97 6,39
T 2 89,192 n × m 10,53 65,05 13,61
minimum 1,60 4,15 2,09
maximum 2,08 4,95 2,16
standard devia-
tion (SD) 0,25 0,44 0,04
SD 0,06 0,19 0,00
SD % (SD × 100 /
m) 13,18 9,46 1,69
T 5 (SCE) 0,512 733 (n ‒ 1) × SD 0,12 0,39 0,00
Statistics
s 0,09 Level nb, Lab. mean r R r % R %
r
QCM 1.1 - HPTA Study -
s 2,34 DAX 8 3 2,89 0,819 4,359 28,36 150,99
L
s 2,42
R
r 0,82 Confidence Interval (95 %)
R 4,36 min max range
r % 28,36 2,721 3,052 0,331
R % 150,99
ISO 19822:2018/Amd.1:2026(en)
Table C.2 — Hydrophobic fulvic acids content in QCM 1.1 using XAD-7HP resin
Precision data: repeatability (r) and reproducibility (R) calculations
Method: HPTA Lab Study  Remarks: raw data - outliers included
Tested level: QCM 1.1 - HPTA Study - XAD-7HP
Data Laboratory (i), from 1 to p
Lab
Repetition (n) Lab 1 Lab 2 Lab 3 Lab 4 Lab 5 Lab 6 Lab 7 8
General information 1 2,00 5,59 2,63
Number of lab
(p) 3 2 1,88 5,17 2,13
mean m 3,14 3 1,77 4,93 2,14
Standard
deviation 0,227 2 4
SD 0,051 6 5
SD % 7,241 7 6
mean min 1,883 7
mean max 5,230 8
Statistics for
Preliminary sums
each lab
number of labs
(p) 1 1 1
number of reps
T 3 9 (n) 3 3 3
mean (m) 1,88 5,23 2,3
T 4 27 n 9 9 9
T 1 28,24 n × m 5,65 15,69 6,9
T 2 108,570 n × m 10,64 82,06 15,87
minimum 1,77 4,93 2,13
maximum 2,00 5,59 2,63
standard devia-
tion (SD) 0,12 0,33 0,29
SD 0,01 0,11 0,08
SD % (SD × 100
/ m) 6,11 6,39 12,43
T 5 (SCE) 0,413 067 (n ‒ 1) × SD 0,03 0,22 0,16
Statistics
s 0,07 Level nb. Lab. mean r R r % R %
r
QCM 1.1 - HPTA Study –
s 3,30 XAD-7HP 3 3,138 0,735 5,142 23,41 163,87
L
s 3,37
R
r 0,73 Confidence Interval (95 %)
R 5,14 min max range
r % 23,41 2,989 3,286 0,297
R % 163,87
The correlation results for QCM 1.1 are presented in Table C.3.

ISO 19822:2018/Amd.1:2026(en)
Table C.3 — Correlation comparing resins DAX-8 and XAD-7HP for QCM 1.1
Spearman’s r  0,883
s
Fisher 95 % CI  0,513 to 0,976
t approximation  4,99
p-value  0,001 6
C.6.2 Results for material GL
The hydrophobic fulvic acid content results for material GL using the DAX-8 resin are presented in Table C.4.

ISO 19822:2018/Amd.1:2026(en)
Table C.4 — Hydrophobic fulvic acids content in material GL using DAX-8 resin
Precision data: repeatability (r) and reproducibility (R) calculations
Method: HPTA Lab Study Remarks: raw data - outliers included
Tested level: GL - HPTA Study - DAX-8
Data Laboratory (i), from 1 to p
Repetition (n) Lab 1 Lab 2 Lab 3 Lab 4 Lab 5 Lab 6 Lab 7 Lab 8
General information 1 5,23 3,50 3,42
Number of lab
(p) 3 2 5,06 3,77 3,82
mean m 4,03 3 4,94 3,18 3,05
Standard
deviation 0,322 4 4 4,32
SD 0,103 9 5
SD % 8,002 8 6
mean min 3,427 7
mean max 4,888 8
Stati
...