ISO 17318:2015
(Main)Fertilizers and soil conditioners — Determination of arsenic, cadmium, chromium, lead and mercury contents
Fertilizers and soil conditioners — Determination of arsenic, cadmium, chromium, lead and mercury contents
ISO 17318:2015 specifies the test methods for determination of metals soluble in nitric acid: arsenic, cadmium, chromium, lead, and mercury contents in fertilizers. ISO 17318:2015 is applicable to the analysis of arsenic, cadmium, chromium, lead, and mercury contents in fertilizers. Special attention should be given when analysing some micro-nutrients fertilizers.
Matières fertilisantes — Détermination de l'arsenic, du cadmium, du plomb, du chrome et du mercure dans les engrais
General Information
Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 17318
First edition
2015-06-01
Fertilizers and soil conditioners —
Determination of arsenic, cadmium,
chromium, lead and mercury contents
Matières fertilisantes — Détermination de l’arsenic, du cadmium, du
plomb, du chrome et du mercure dans les engrais
Reference number
©
ISO 2015
© ISO 2015, Published in Switzerland
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ii © ISO 2015 – All rights reserved
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Principle . 1
4 Reagents . 1
5 Apparatus and materials. 2
6 Procedure. 2
6.1 Sample preparation . 2
6.2 Preparation of the test solution . 2
6.3 Preparation of the blank test solution . 2
6.4 Preparation of the working standard solution . 2
6.5 Determination of arsenic, cadmium, chromium, lead and mercury contents by
inductively coupled plasma .
optical emission spectroscopy (ICP-OES) . 3
6.6 Calculation and expression of the results . 4
7 Precision . 4
7.1 Ring test . 4
7.2 Repeatability . 4
7.3 Reproducibility . 4
8 Test report . 4
Annex A (informative) Interlaboratory testing . 6
Bibliography .30
Foreword
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to Trade (TBT), see the following URL: Foreword — Supplementary information.
The committee responsible for this document is ISO/TC 134, Fertilizers and soil conditioners.
iv © ISO 2015 – All rights reserved
INTERNATIONAL STANDARD ISO 17318:2015(E)
Fertilizers and soil conditioners — Determination of
arsenic, cadmium, chromium, lead and mercury contents
1 Scope
This International Standard specifies the test methods for determination of metals soluble in nitric acid:
arsenic, cadmium, chromium, lead, and mercury contents in fertilizers.
This International Standard is applicable to the analysis of arsenic, cadmium, chromium, lead, and
mercury contents in fertilizers. Special attention should be given when analysing some micro-nutrients
fertilizers.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
ISO 3696, Water for analytical laboratory use — Specification and test methods
3 Principle
Arsenic, cadmium, chromium, lead, and mercury in the test portion are extracted by means of nitric
acid digestion in a microwave digestion system. The digested solution will be measured by inductively
coupled plasma – optical emission spectroscopy (ICP-OES). Indium will be used as internal standard
substance when chromium or lead is determined.
NOTE An internal standard is recommended for metals to correct for solution matrix differences between
the calibration standards and the fertilizer digests, any other internal standard materials with equal effect could
be utilized, provided none of these are contained in the fertilizer samples.
4 Reagents
WARNING — Nitric acid is corrosive and oxidizer. The related operations shall be performed
in fume hood. This standard does not point out all possible safety problems, and the user shall
bear the responsibility to take proper safety and health measures, and ensure the operations
compliant with the conditions stipulated by the related laws and regulations of the state.
Use only reagents of recognized analytical grade, and water conforming to grade 3 of ISO 3696:1987.
4.1 Nitric acid, d = 1,40 g/ml, recommend to use trace element grade nitric acid.
4.2 Nitric acid solution, add 1 volume of nitric acid to 9 volume of water.
4.3 Standard stock solution of arsenic, cadmium, chromium, lead, mercury, 1 000 mg/l certificated
substance.
4.4 Indium standard stock solution, 1 000 mg/l.
Weigh In(NO ) × H O [containing 0,262 0 g In(NO ) ] to a 100 ml beaker, dissolved by nitric acid solution
3 3 2 3 3
(4.2), then transfer to a 100 ml volumetric flask, fill to the mark with nitric acid solution (4.2), and mix.
4.5 Indium standard solution, 5 mg/l.
Dilute 1 000 mg/l Indium standard stock solution with nitric acid solution (4.2) to 5 mg/l.
4.6 High-purity argon, content ≥ 99,999 %.
5 Apparatus and materials
Ordinary laboratory apparatus and the following:
5.1 Microwave digestion system.
5.2 Inductively coupled plasma — optical emission spectroscopy (ICP-OES), with a mixing device
to add an internal standard.
5.3 Sieve, with the aperture size of 0,50 mm.
6 Procedure
6.1 Sample preparation
Take a representative fertilizer subsample of 100 g. Grind it until it passes through a sieve of aperture
size 0,5 mm, mix thoroughly for reasons of homogeneity, place in a clean, and dry bottle with lid.
6.2 Preparation of the test solution
The replicate experiments shall be done for the determination.
Weigh 1 g sample (accurate to 0,1 mg, for fertilizer containing liming material or organic matrixes,
reduce the weight properly) and transfer into a digestion vessel, keep the sample from adhering to sides
of vessel. Place the digestion vessel into a fume hood, and add 10 ml of nitric acid (4.1). Predigest at room
temperature until vigorous foaming subsides. Then seal the vessel and put into the microwave digestion
system.
The ramped temperature program should be set under the instruction of the instrument manual.
Ramping temperature from ambient to 160 °C slowly in 10 min, and then hold at 160 °C for another
10 min. Cool vessels to room temperature, vent, and transfer digests to a 100 ml volumetric flask, fill
to the mark with water, and mix. Then the solution should be filtered through a dry, folded filter paper.
Discard the first few millilitres portions of filter solution.
6.3 Preparation of the blank test solution
The experiment steps are the same as the preparation of the test solution, with the exception of adding
the sample.
6.4 Preparation of the working standard solution
Pipet appropriate amount of element standard stock solution (4.3), dilute with nitric acid solution (4.2)
into volumetric flasks according to Table 1, prepare blended multi-element standard solution series.
Table 1 — Typical concentrations of blended multi-element standard solutions (mg/l)
Element As Cd Cr Pb Hg
standard
No. 0 0 0 0 0 0
2 © ISO 2015 – All rights reserved
Table 1 (continued)
Element As Cd Cr Pb Hg
standard
No. 1 0,02 0,02 0,02 0,02 0,02
No. 2 0,1 0,1 0,1 0,1 0,1
No. 3 0,5 0,5 0,5 0,5 0,5
No. 4 2,0 2,0 2,0 2,0 2,0
No. 5 5,0 5,0 5,0 5,0 5,0
NOTE Useful concentrations for standardization can be quite different for different instrument types.
6.5 Determination of arsenic, cadmium, chromium, lead and mercury contents by
inductively coupled plasma–optical emission spectroscopy (ICP-OES)
Before the determination, refer to the instrument operation manual. Select the best operation conditions
in accordance with the elements properties. The recommended operating conditions of ICP are listed in
Table 2. Other conditions which can achieve the same results can also be used.
Table 2 — Recommended operating conditions of ICP
Wavelength As 189,042 nm, Cd 228,802 nm, Pb 220,353 nm, Cr 283,563 nm, Hg
184,950 nm, In 230,606 nm.
Maximum integration time Low wavelength scale: 10 s, High wavelength scale: 10 s
Flush velocity of 50 r/min
sample pump
Analysis velocity of sample pump 50 r/min
Sample pump stable time 5 s
Light source Radiofrequency, power of 1 150 W
Flow rate of auxiliary gas 0,5 l/min
Flow rate of gas within the nebu- 0,5 l/min
lizer
NOTE Special attention should be given on the wavelength resolution of ICP instrument, the use of a second
or third wavelength for confirmation purposes may be recommended, if appropriate.
Determine the working standard solutions (6.4), the blank test solution (6.3), and the test solutions
(6.2) in order. When the concentration of Cr or Pb are determined, use the 5mg/l indium standard
solution (4.5) as the internal standard substance, mix the internal standard substance solution and test
solution (1:5 V/V) by a mixing device. If the concentration of the element in the test solution exceeds
the concentration range of the standard curve, dilute the test solution to a certain ratio with nitric acid
solution (4.2) for re-determination.
6.6 Calculation and expression of the results
The determination results of elements (mg/kg) are calculated as follows:
cc− ××100 D
()
X = (1)
m
where
C is the concentration in mg/l
...
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