SIST EN ISO 15192:2026

SLOVENSKI STANDARD
oSIST prEN ISO 15192:2024
01-februar-2024
Tla in odpadki - Določanje kroma Cr (VI) v trdnem mediju z alkalnim razklopom in
ionsko kromatografijo s spektrofotometrijsko detekcijo (ISO/DIS 15192:2023)
Soil and waste - Determination of Chromium(VI) in solid material by alkaline digestion
and ion chromatography with spectrometric detection (ISO/DIS 15192:2023)
Boden und Abfall - Bestimmung von sechswertigem Chrom in Feststoffen durch
alkalischen Aufschluss und Ionenchromatographie mit photometrischer Detektion
(ISO/DIS 15192:2023)
Déchets et sols - Dosage du chrome(VI) dans les matériaux solides par digestion
alcaline et chromatographie ionique avec détection spectrométrique (ISO/DIS
15192:2023)
Ta slovenski standard je istoveten z: prEN ISO 15192
ICS:
13.080.10 Kemijske značilnosti tal Chemical characteristics of
soils
71.040.50 Fizikalnokemijske analitske Physicochemical methods of
metode analysis
oSIST prEN ISO 15192:2024 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

oSIST prEN ISO 15192:2024
oSIST prEN ISO 15192:2024
DRAFT INTERNATIONAL STANDARD
ISO/DIS 15192
ISO/TC 190/SC 3 Secretariat: DIN
Voting begins on: Voting terminates on:
2023-12-25 2024-03-18
Soil and waste — Determination of Chromium(VI) in solid
material by alkaline digestion and ion chromatography
with spectrometric detection
Déchets et sols — Dosage du chrome(VI) dans les matériaux solides par digestion alcaline et
chromatographie ionique avec détection spectrométrique
ICS: 13.080.10
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ISO/DIS 15192:2023(E)
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oSIST prEN ISO 15192:2024
ISO/DIS 15192:2023(E)
DRAFT INTERNATIONAL STANDARD
ISO/DIS 15192
ISO/TC 190/SC 3 Secretariat: DIN
Voting begins on: Voting terminates on:

Soil and waste — Determination of Chromium(VI) in solid
material by alkaline digestion and ion chromatography
with spectrometric detection
Déchets et sols — Dosage du chrome(VI) dans les matériaux solides par digestion alcaline et
chromatographie ionique avec détection spectrométrique
ICS: 13.080.10
This document is circulated as received from the committee secretariat.
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENT AND APPROVAL. IT IS
© ISO 2023
ISO/CEN PARALLEL PROCESSING
THEREFORE SUBJECT TO CHANGE AND MAY
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NATIONAL REGULATIONS.
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ii
PROVIDE SUPPORTING DOCUMENTATION. © ISO 2023

oSIST prEN ISO 15192:2024
ISO/DIS 15192:2023(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Safety remarks . 1
5 Principle . 2
5.1 Digestion . 2
5.2 Determination . 2
5.3 Interferences and sources of error . 2
6 Apparatus . 3
7 Reagents . 3
8 Sample pretreatment .6
9 Alkaline digestion procedure . 6
9.1 General . 6
9.2 Preparation of test solutions using a hotplate or heating block . 6
10 Analytical procedure . 7
10.1 General information. 7
10.2 Instrumental set-up . 7
10.3 Calibration . 7
10.4 Test solution measurement . 7
10.5 Quality control . 8
10.5.1 General . 8
10.5.2 Blank test solution . 8
10.5.3 Verification of method . 8
10.5.4 Duplicate samples. 8
10.5.5 Soluble Cr(VI) spiked samples . 9
10.5.6 Cr(III) spiked samples . 9
10.5.7 Interpretation of quality control data . 9
11 Calculation . 9
12 Expression of results .10
13 Test report .10
Annex A (informative) Ion chromatographic system .11
Annex B (informative) Requirements for test portion preparation .13
Annex C (informative) Validation .14
Annex D (informative) Background on methods for the determination of Cr(VI) in solid
samples .19
Bibliography .23
iii
oSIST prEN ISO 15192:2024
ISO/DIS 15192:2023(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
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expressions related to conformity assessment, as well as information about ISO's adherence to
the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see
www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 190, Soil quality, Subcommittee
SC 3, Chemical and physical characterization, in collaboration with the European Committee for
Standardization (CEN) Technical Committee CEN/TC 444, Environmental Characterization, in
accordance with the Agreement on technical cooperation between ISO and CEN (Vienna Agreement).
This second edition cancels and replaces the first edition (ISO 15192:2010), which has been technically
revised.
The main changes compared to the previous edition are as follows:
— integration of the determination of the total chromium in the alkaline digestion solution;
— Addition of barium chromate as an alternative to lead chromate for the verification of the method in
clause 10.5.3 ;
— the text has been editorially revised, including updating of references.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
iv
oSIST prEN ISO 15192:2024
ISO/DIS 15192:2023(E)
Introduction
Under environmental conditions chromium in compounds exists in the trivalent, Cr(III), or the
hexavalent, Cr(VI) state. Chromium is an essential trace element for mammals, including man,
whereas it is presumed that Cr(VI) compounds are genotoxic and potentially carcinogenic in humans.
Interconversion of trivalent and hexavalent chromium species can occur during sample preparation
and analysis, but these processes are minimised, to the extent possible, by the sample preparation
methods prescribed by this document.
v
oSIST prEN ISO 15192:2024
oSIST prEN ISO 15192:2024
DRAFT INTERNATIONAL STANDARD ISO/DIS 15192:2023(E)
Soil and waste — Determination of Chromium(VI) in solid
material by alkaline digestion and ion chromatography
with spectrometric detection
1 Scope
This document specifies the determination of Cr(VI) in solid waste material and soil by alkaline
digestion and ion chromatography with spectrometric detection. This method can be used to determine
Cr(VI)-mass fractions in solids higher than 0,1 mg/kg.
NOTE In case of reducing or oxidising waste matrix no valid Cr(VI) content can be reported.
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 8466-1, Water quality — Calibration and evaluation of analytical methods — Part 1: Linear calibration
function
ISO 11464, Soil quality — Pretreatment of samples for physico-chemical analysis
ISO 11465, Soil quality — Determination of dry matter and water content on a mass basis — Gravimetric
method
ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories
EN 15002, Characterization of waste — Preparation of test portions from the laboratory sample
EN 15934, Sludge, treated biowaste, soil and waste — Calculation of dry matter fraction after determination
of dry residue or water content
3 Terms and definitions
No terms and definitions are listed in this document.
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/
4 Safety remarks
Anyone dealing with waste and soil analysis shall be aware of the typical risks of the material
irrespective of the parameters determined. Waste and soil samples may contain hazardous (e.g. toxic,
reactive, flammable, infectious) substances, which can be liable to biological and/or chemical reaction.
Consequently, these samples should be handled with special care. The gases which may be produced
by microbiological or chemical activity are potentially flammable and can pressurise sealed bottles.
Bursting bottles are likely to result in hazardous shrapnel, dust and/or aerosol. It is presupposed that
national regulations are followed with respect to all hazards associated with this method.
oSIST prEN ISO 15192:2024
ISO/DIS 15192:2023(E)
Avoid any contact with the skin, ingestion or inhalation of Cr(VI) compounds. Cr(VI) compounds are
genotoxic and potentially carcinogenic to humans.
5 Principle
5.1 Digestion
This document describes an alkaline digestion procedure for extracting Cr(VI) from soluble, adsorbed
and precipitated forms of chromium compounds in solid waste materials and soil. To quantify the
content of Cr(VI) in a solid matrix, three criteria shall be satisfied:
a) digestion solution shall solubilize all species of Cr(VI);
b) conditions of the digestion shall not induce reduction of native Cr(VI) to Cr(III);
c) method shall not cause oxidation of native Cr(III) contained in the sample to Cr(VI).
The alkaline digestion described in this document meets these criteria for a wide spectrum of soils and
wastes. Under the alkaline conditions of the digestion, negligible reduction of Cr(VI) or oxidation of
2+
native Cr(III) is expected. The addition of Mg in a phosphate buffer to the alkaline solution minimises
[1][5][8]
air oxidation of trivalent chromium .
NOTE Background on methods for the determination of Cr(VI) in solid samples is given in Annex D.
5.2 Determination
Quantification of Cr(VI) in the alkaline digestion solution should be performed using a suitable
technique with appropriate accuracy. For this purpose, e.g., ion chromatography is used to separate
Cr(VI) from interferences. Following this ion chromatographic separation, Cr(VI) is measured
spectrophotometrically either at 365 nm (direct UV detection) or after post-column derivatisation
with 1,5-diphenylcarbazide in acid solution at 540 nm. Post-column derivatisation involves reaction
of 1,5-diphenylcarbazide with Cr(VI) to produce trivalent chromium and diphenylcarbazone. These
then combine to form a trivalent chromium-diphenylcarbazone complex containing the characteristic
magenta chromagen (λ = 540 nm).
max
NOTE The choice of detection method is based upon the required sensitivity. Direct UV detection is less
sensitive than detection after post-column derivatisation with 1,5-diphenylcarbazide (see Annex C).
Hyphenated methods with suitable chromatographic separation and detection techniques, such
as inductively coupled plasma mass spectrometry (ICP-MS) or inductively coupled plasma atomic
emission spectroscopy (ICP-OES), may be used once validation of the chosen analytical method has
been performed.
A preliminary determination of the total chromium in the alkaline digestion solution by such techniques
as ICP-MS, ICP-OES, or graphite furnace atomic absorption spectrometry could reduce the number
of samples where the determination of Cr(VI) is required. If the content of alkaline-extractable total
chromium is lower than the legislative limit for Cr(VI) then the determination of Cr(VI) may be omitted.
NOTE Due to the high element concentrations, e.g. sodium, in the alkaline digestion solutions, the calibration
strategy must be adapted appropriately. In many cases, matrix matching of the calibration solutions and dilution
of the sample together with addition of internal standards or using the standard addition method is necessary.
The analytical method needs to be validated on alkaline digestion solutions prior to routine use.
5.3 Interferences and sources of error
— Use of ion chromatography is necessary for the separation of Cr(VI) from possible interferences in
[6]
the alkaline digestion solution from solid material .
oSIST prEN ISO 15192:2024
ISO/DIS 15192:2023(E)
— For waste materials or soils, where the Cr(III)/Cr(VI) ratio is expected to be high, Cr(VI) results
may be biased due to method induced oxidation. This can be particularly expected in soils high in
[3]
Mn content and amended with soluble Cr(III) salts or freshly precipitated Cr(OH) .
— Cr(VI) can be reduced to Cr(III) during digestion from the sample due to reaction with reducing
agents such as e.g. divalent iron. This problem is minimised in the described procedure using
[5]
alkaline digestion solution .
— Cr(III) can be oxidised to Cr(VI) in hot alkaline solutions. This problem is minimised in the described
[2][3][5][8]
procedure by adding magnesium to the alkaline digestion solution .
— Overloading the analytical column capacity with high concentrations of anionic species (e.g.
[9]
chloride) may cause underestimation of Cr(VI) .
6 Apparatus
6.1 Digestion equipment.
6.1.1 Hotplate with a magnetic stirrer, thermostatically controlled with a digestion vessel of
250 ml covered with a watch glass, or
6.1.2 Heating block with a magnetic stirrer, thermostatically controlled with a digestion vessel of
250 ml covered with a watch glass.
NOTE Other thermostatically controlled digestion equipment with a magnetic stirrer can be used once
validation has been performed.
6.2 Filtration equipment, suitable for using 0,45-µm membrane filters.
6.3 Membrane filters, 0,45-µm pore size, chemically inert.
6.4 Ion chromatographic system.
All components which come into contact with the sample or eluent stream shall be comprised of inert
materials, e.g. polyetherether ketone (PEEK), as shall all connecting tubing (see Annex B).
6.5 Ion chromatographic column, suitable for chromate separation with a sufficient ion exchange
capacity.
6.6 Detection system.
6.6.1 UV-VIS spectrophotometer, at 365 nm, or
6.6.2 VIS spectrophotometer, at 540 nm after post column derivatisation.
7 Reagents
7.1 General.
During the analysis, only use reagents of recognised analytical grade, and water as specified in 7.2.
7.2 Water.
-1
Water with an electrical conductivity less than 0,1 mS m (equivalent to resistivity greater than
0,01 MΩ m at 25 °C). It is recommended that the water used is obtained from a purification system
oSIST prEN ISO 15192:2024
ISO/DIS 15192:2023(E)
that delivers ultrapure water having a resistivity greater than 0,18 MΩ m (usually expressed by
manufacturers of water purification systems as 18 MΩ cm).
7.3 Sulfuric acid (H SO ), CAS 7664-93-9, concentrated, ρ(H SO ) ~1,84 g/ml, w(H SO ) ~98 %.
2 4 2 4 2 4
7.4 Sodium carbonate (Na CO ), CAS 497-19-8, anhydrous, w(Na CO ) >99,9 %.
2 3 2 3
7.5 1,5-Diphenylcarbazide (C H N O), CAS 140-22-7, w(C H N O) >98 %;.
13 14 4 13 14 4
7.6 Propanone (acetone) (C H O), CAS 67-64-1.
3 6
7.7 Methanol (CH O) , CAS 67-56-1.
7.8 Potassium dichromate (K Cr O ), CAS 7778-50-9, w(K Cr O ) >99,9 %.
2 2 7 2 2 7
Dry to constant weight at 110 °C, cool and store in a desiccator.
7.9 Sodium hydroxide (NaOH), CAS 1310-73-2, w(NaOH) >99 %.
7.10 Magnesium chloride hexahydrate (MgCl ·6H O), CAS 7791-18-6, w(MgCl ·6H O) >99 %.
2 2 2 2
7.11 Dipotassium hydrogen phosphate (K HPO ), CAS 7758-11-4, w(K HPO ) >99 %.
2 4 2 4
7.12 Potassium dihydrogen phosphate (KH PO ), CAS 7778-77-0, w(KH PO ) >99 %.
2 4 2 4
7.13 Lead chromate (PbCrO ), CAS 7758-97-6, w(PbCrO ) >99 %.
4 4
7.14 Diphenylcarbazide reagent solution.
Dissolve 0,125 g of 1,5-diphenylcarbazide (7.5) in 25 ml of propanone (7.6) or methanol (7.7) in a 250 ml
volumetric flask. Fill 125 ml of water into a separate container, slowly add 7 ml of concentrated sulfuric
acid (7.3), swirl to mix and allow to cool. Degas with e. g. helium or argon for 5 min to 10 min prior to
adding to the 1,5-diphenylcarbazide solution. After combining the solutions, fill up to the mark with
water and degas additionally for 5 min to 10 min. The solution is stable for up to 1 week if stored in a
brown glass bottle at 2 °C to 6 °C in the dark.
7.15 Eluent solution.
Use an eluent solution (see Annex A) appropriate to separate chromate over the ion chromatographic
column (6.5).
NOTE Eluents can be prepared manually or automatically by in-line dilution or electrochemically in situ.
7.16 Alkaline digestion solution.
0,5 mol/l sodium hydroxide (NaOH)/0,28 mol/l sodium carbonate (Na CO ).
2 3
Dissolve 20,0 g of sodium hydroxide (7.9) in approximately 500 ml of water (7.2). Add 30,0 g of sodium
carbonate (7.4) and swirl to mix. Quantitatively transfer the solution into a 1 l volumetric flask. Dilute
to the mark with water. The pH of the digestion solution shall be checked before use. The pH shall be
11,5 to 12. Store in a polyethylene bottle at room temperature. This reagent is stable for one month.
oSIST prEN ISO 15192:2024
ISO/DIS 15192:2023(E)
7.17 Calibration solutions of Cr(VI).
7.17.1 Cr(VI) standard stock solution, 1 000 mg/l Cr(VI).
Dissolve 0,282 9 g of potassium dichromate (7.8) in 75 ml of water (7.2) in a 100 ml volumetric flask.
Dilute to the mark with water (7.2), close and mix thoroughly. Store the solution in a polypropylene
bottle. This reagent is stable for one year.
7.17.2 Cr(VI) working standard solution, 10 mg/l Cr(VI).
Pipette 10,0 ml of the Cr(VI) standard stock solution (7.17.1) into a 1 l volumetric flask, dilute to the
mark with water (7.2), close and mix thoroughly. This reagent is stable for one month.
7.17.3 Cr(VI) calibration solutions.
Prepare a set of at least 5 calibration solutions by diluting the Cr(VI) working standard solution with a
1 + 1 diluted alkaline digestion solution (7.16). Add 25 ml of the alkaline digestion solution (7.16) into
a 50 ml volumetric flask, pipette the appropriate volume of Cr(VI) working standard solution (7.17.2)
into the volumetric flask and dilute to the mark with water (7.2), close and mix thoroughly. Prepare
fresh solutions on the day of use.
7.17.4 Cr(VI) spiking solutions.
The Cr(VI) working standard solution (7.17.2) can be used to spike samples.
7.18 Phosphate buffer solution.
0,5 mol/l dipotassium hydrogen phosphate (K HPO )/0,5 mol/l potassium dihydrogen phosphate
2 4
(KH PO ), pH 7.
2 4
Dissolve 87,09 g K HPO (7.11) and 68,04 g of KH PO (7.12) in approximately 700 ml of water and swirl
2 4 2 4
to mix. Transfer the solution into a 1 l volumetric flask. Dilute to the mark with water.
7.19 Magnesium chloride solution.
Dissolve 85,4 g MgCl ·6H O (7.10) in a 100 ml volumetric flask, dilute to the mark with water (7.2), close
2 2
and mix thoroughly.
7.20 Chromium chloride hexahydrate (CrCl .6H O), CAS 10060-12-5, w(CrCl ·6H O) >96 %.
3 2 3 2
7.21 Cr(III) spiking solution.
Use a commercial standard solution with a certified Cr(III) concentration, e.g 1 000 mg/l Cr(III)
traceable to national standards. Observe the manufacturer's expiration date or recommended shelf life.
Alternatively dissolve an appropriate known amount of chromium chloride hexahydrate (7.20) in water
(7.2) in a 100 ml volumetric flask, dilute to the mark with water (7.2), close and mix thoroughly. Store
the solution in a polypropylene bottle. This reagent is stable for one year. Before using, determine the
Cr concentration of the spiking solution.
7.22 Barium chromate (BaCrO ), CAS 10294-40-3, w(BaCrO ) >99 %.
4 4
7.23 Sand, CAS 14808-60-7, purified by acid and calcinated for analysis, or equivalent.
oSIST prEN ISO 15192:2024
ISO/DIS 15192:2023(E)
7.24 Insoluble Cr(VI) control mixture.
A control mixture is prepared by weighing 1 g of barium chromate (7.22), adding 10 g of sand (7.23) and
subsequent homogenization and grinding. From this mixture, a portion of 1 g is mixed again with 10 g
of sand, with subsequent homogenization and grinding. A 2,5 g of this final mixture contains 20,66 mg
BaCrO .
WARNING — Avoid any contact with the skin, ingestion or inhalation of Cr(VI) compounds.
Cr(VI) compounds are genotoxic and potentially carcinogenic to humans.
8 Sample pretreatment
Samples shall be collected using appropriate devices and placed in plastic or glass containers.
NOTE Requirements for test portion preparation are summarised in Annex B.
Samples shall be stored field moist at (4 ± 2) °C until analysis. Pre-treat the sample according to
EN 16179, ISO 11464 or EN 15002 if not otherwise specified.
Particle size reduction below 250 µm is necessary for solid waste and soil especially when Cr(VI)
is suspected to be included in the matrix, whereby heating and contact with stainless steel shall be
avoided.
After digestion the sample shall be analysed as soon as possible.
Cr(VI) has been shown to be quantitatively stable in field moist soil samples for 30 days from the time of
sample collection. In addition, Cr(VI) has also been shown to be stable in the alkaline digestion solution
[2]
for up to 7 days after digestion from soil .
9 Alkaline digestion procedure
9.1 General
Use either the hotplate or heating block method prescribed in 9.2 to prepare test solutions for
determination of Cr(VI) in solid waste materials and soil.
9.2 Preparation of test solutions using a hotplate or heating block
9.2.1 Adjust the temperature setting by preparing and monitoring a temperature blank (a 250 ml
vessel filled with 50 ml digestion solution). Maintain a digestion solution temperature of (92,5 ± 2,5) °C.
Do not allow the solution to boil or evaporate to dryness.
9.2.2 Transfer (2,5 ± 0,1) g of the test portion weighed to the nearest 0,1 mg into a clean 250 ml
digestion vessel.
NOTE For very high expected concentrations of Cr(VI) a smaller representative test portion can be used.
9.2.3 Add (50 ± 1) ml of the alkaline digestion solution (7.16) to each sample using a graduated
cylinder, and also add 1 ml of magnesium chloride solution (7.19) containing approximately 400 mg of
MgCl and 0,5 ml of phosphate buffer solution (7.18). Cover all digestion vessels. If using a heating block,
reflux condensers can be used.
9.2.4 Heat the samples to (92,5 ± 2,5) °C with continuous stirring, then maintain the samples at
(92,5 ± 2,5) °C for at least (60 ± 5) min with stirring continuously.
9.2.5 Cool each solution to room temperature. Transfer the contents quantitatively to the filtration
equipment (6.2), rinsing the digestion vessel three times with small portions of water (7.2). Filter
oSIST prEN ISO 15192:2024
ISO/DIS 15192:2023(E)
through a 0,45 µm membrane filter (6.3). Rinse the filtration equipment (6.2) with water (7.2) and
transfer the filtrate to a 100 ml volumetric flask and fill up to the mark with water (7.2).
NOTE Alternatively the sample can be centrifuged or allowed to settle and fill up the mark with water.
10 Analytical procedure
10.1 General information
The standard method for the determination of Cr(VI) in the alkaline digestion solution is the ion
chromatographic method with spectrophotometric detection as described in this clause.
NOTE In certain cases, direct determination of Cr(VI) in the alkaline digestion solution is possible (see
Annex A).
10.2 Instrumental set-up
10.2.1 Set up the ion chromatograph in accordance with manufacturer’s instructions.
10.2.2 For post column derivatisation, optimise the ratio of eluent solution and reagent flow rates or
adjust the sulfuric acid concentration of the diphenylcarbazide reagent solution (7.14) to obtain the best
signal to background ratio. It is important that the ratio between the eluent solution and reagent flow
rates is kept constant, that the total flow rate does not exceed the maximum flow rate for the detector
and the diphenylcarbazide reagent is present in excess. A typical value for the ratio between the eluent
solution and reagent flow rates is 3:1. After the flow rates are adjusted, allow the system to equilibrate
for 15 min.
10.2.3 For direct detection, adjust the UV-VIS detector to measure within a range of 355 nm to 375 nm,
preferably at 365 nm.
For measuring after post-column derivatisation with 1,5-diphenylcarbazide, adjust the VIS detector to
measure within a range of 530 nm to 550 nm, preferably at 540 nm.
10.3 Calibration
10.3.1 Inject a suitable volume (typically 20 µl to 250 µl), of each calibration solution (7.17.3) into the
ion chromatographic system (6.4).
10.3.2 Determine the absorbance for each of the calibration solutions using either peak height or peak
area mode.
10.3.3 Prepare a calibration graph using a linear plot of the peak height or peak area as a function
of calibration solution concentration by least squares regression analysis using suitable software,
according to ISO 8466-1.
10.4 Test solution measurement
10.4.1 Inject a suitable volume, e.g. 50 µl, of filtered sample solutions (9.2) into the ion chromatographic
system.
10.4.2 Determine the concentrations of Cr(VI) in the test solutions (9.2) by comparison with the
calibration graph (10.3.3).
oSIST prEN ISO 15192:2024
ISO/DIS 15192:2023(E)
10.4.3 If the Cr(VI) concentration of the sample exceeds the calibration range, dilute the sample with a
1 + 1 diluted alkaline digestion solution (7.16) and re-analyse. Take note of the dilution when calculating
the mass concentration of Cr(VI) in the material under investigation.
NOTE For samples expected to have very high concentrations of Cr(VI), it can be necessary to dilute the test
solutions before they are first analysed. Otherwise, swamping of the diphenylcarbazide reagent can occur and no
colour will develop.
If the chromium (VI) concentration of the sample falls lower than the calibration range, establish a
separate calibration function for the lower working range, if necessary.
10.5 Quality control
10.5.1 General
Process quality control (QC) samples with each batch of test samples, as detailed below.
10.5.2 Blank test solution
To assess glassware contamination and/or reagents, process in parallel at least one blank solution
following the same digestion procedure as applied to the test samples but omitting the test portion.
If contamination is detected control the procedure until the level of Cr(VI) is less than 0,5 times the
lowest concentration to be reported and repeat the digestions.
Analyse the blank solutions according to a frequency of 1 blank per 20 test portions or at least once in
each series of measurement.
10.5.3 Verification of method
Prepare a soluble Cr(VI) standard solution from a stock standard solution from a different source than
that used for preparing the calibration solutions. In parallel with processing the test samples, prepare a
blank solution spiked with this soluble Cr(VI) standard solution following the same digestion procedure
as applied to the test samples but omitting the test portion. Recovery of Cr(VI) must be within range of
80 % to 120 %. Process this QC sample within each batch.
Alternatively, to evaluate the dissolution of all Cr(VI) species during the digestion process, an insoluble
spike, e.g. PbCrO (7.13) or BaCrO (7.24), may be used. In parallel with processing the test samples,
4 4
prepare a blank solution spiked with, e.g., 20 mg of PbCrO or 2,5 g of the BaCrO mixture (7.24),
4 4
following the same digestion procedure as applied to the test samples but omitting the test portion.
Recovery of Cr(VI) must be within range of 75 % to 120 %.
NOTE A smaller amount of the insoluble Cr(VI) or a next dilution step of the control mixture quality control
sample can be used, as long as the homogeneity of the control sample on that mass level has been tested.
Prepare a Cr(III) standard solution from the Cr(III) spiking solution (7.21). In parallel with processing
the test samples prepare a blank solution spiked with this Cr(III) standard solution following the same
digestion procedure as applied to the test samples but omitting the test portion. Conversion of Cr(III) to
Cr(VI) shall be less than 5 %. Process this QC sample within each batch.
10.5.4 Duplicate samples
Process method duplicated samples to estimate the method accuracy according to a frequency of at
least 1 duplicate sample per 20 test portions or minimum of 1 per batch.
Duplicate samples must have a relative percent difference of <20 %, if both the original and the duplicate
are greater than four times the laboratory reporting limit. A control limit of ± the laboratory reporting
limit is used when either the original or the duplicate sample is less than four times the laboratory
reporting limit.
oSIST prEN ISO 15192:2024
ISO/DIS 15192:2023(E)
10.5.5 Soluble Cr(VI) spiked samples
Process soluble spikes, e.g. K Cr O (7.17.4), on a routine basis to estimate the method accuracy in
2 2 7
relation to possible reduction processes. Spiked samples consist of solid material to which known
amounts of Cr(VI) have been added.
Soluble pre-digestion matrix spikes should be analyzed at a frequency of at least 1 spike sample per
20 test portions or 1 per batch. The matrix spike is then carried through the digestion process. More
frequent matrix spikes should be analysed if the sample characteristics within the analytical batch
appear to have significant variability based on visual observation. An acceptance range for matrix
spike recoveries is 75 % to 125 %.
10.5.6 Cr(III) spiked samples
Process the Cr(III) spiking solution (7.21) on a routine basis to estimate the method accuracy in relation
to the possible oxidation processes, expressed as a percent Cr(VI) recovery relative to the spiked
amount of Cr(III). Spiked samples consist of solid material to which known amounts of Cr(III) have been
added.
The conversion of the Cr(III) spike can be used to assess the risk of method induced oxidation of native
Cr(III) contained in the sample to Cr(VI) and shall be less than 5 %.
10.5.7 Interpretation of quality control data
If the verification procedure performed in 10.5.3 and the recoveries from the spiked samples performed
in 10.5.5 and 10.5.6 meet laboratory criteria, the analytical result can be judged to be valid.
NOTE 1 An acceptable range for Cr(VI) spike recoveries is 75 % to 125 % in soil, sludge, sediments and similar
[7]
waste materials according to EPA-method 3060 A .
If the verification procedure performed in 10.5.3 meets the laboratory criteria, but the recovery from
a spiked sample performed in 10.5.5 do not meet the laboratory criteria, this indicates that the sample
reduced Cr(VI) (e.g., anoxic sediments), and no measurable native Cr(VI) existed in the unspiked
sample. Such a result indicates that the combined and interacting influences of oxidation reduction
2+
potential, pH and reducing agents (e.g., organic acids, Fe and sulfides) caused reduction of the Cr(VI)
spike. In this case report the value of the unspiked sample and indicate that the sample exhibits a highly
reducing condition.
NOTE 2 The assessment of the reducing/oxidising tendency of the sample matrix can be accomplished by
characterisation of each sample for additional analytical parameters, such as pH, ferrous iron (FeII), sulfides,
organic carbon content and the oxidation potential. Analysis of these additional parameters establishes the
tendency of Cr(VI) to exist or not exist in the unspiked samples and assists in interpreting QC data for matrix
spike recoveries outside conventionally accepted criteria for total metals.
11 Calculation
Calculate the mass fraction of Cr(VI) in the solid waste material or soil, using Formula (1):
ρ ⋅⋅VF
d
w = (1)
Cr()VI
mw⋅⋅10
dm
oSIST prEN ISO 15192:2024
ISO/DIS 15192:2023(E)
where
w is the mass fraction of Cr(VI) in the solid material, expressed in milligram per kilogram
Cr(VI)
(mg/kg) dry matter;
ρ is the concentration of Cr(VI) in the alkaline digested test solution, expressed in microgram
d
per litre (μg/l);
V is the final volume of the alkaline digestion solution, nominally 100 ml;
m is the weight of the test portion, expressed in grams (g), nominally 2,5 g;
w is the dry matter content of the test portion, expressed as a percentage, determined as
dm
specified by ISO 11465 for soil and EN 15934 for waste;
F is the dilution factor (F = 1 if the alkaline digestion solution of nominally 100 ml has not
been diluted prior to analysis).
12 Expression of results
Values should be rounded to 0,01 mg/kg, only three significant figures should be expressed.
EXAMPLE
w = 0,15 mg/kg
Cr(VI)
w = 15,3 mg/kg
Cr(VI)
13 Test report
Work carried out by the testing laboratory shall be covered by a report which accurately, clearly
and unambiguously presents the test results and all other relevant information as specified in
ISO/IEC 17025.
The test report shall include at least the following information:
a) a reference to this document (ISO 15192:2023);
b) identity of the sample;
c) expression of results according to Clause 12;
d) any deviation from this method;
e) any details not specified in this document or which are optional, as well as any factor which may
have affected the results, e.g., a remark that the sample exhibits a highly reducing condition in case
the recovery from a Cr(VI) spiked sample do not meet the laboratory criteria.
oSIST prEN ISO 15192:2024
ISO/DIS 15192:2023(E)
Annex A
(informative)
Ion chromatographic system
Figure A.1 — Scheme of an ion chromatographic system configured for spectrophotometric
detection
An ion chromatography system (Figure A.1), in general, consists of the following components: - Eluent
reservoir;
The preparation of a typical eluent used for the seperation column is described by the following:
Ammonium sulfate/ammonium hydroxide eluent concentrate, 2,5 mol/l ammonium sulfate
(NH ) SO /0,5 mol/l ammonium hydroxide (NH OH). Dissolve 331 g of ammonium sulfate in
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approximately 500 ml of water. Quantitatively transfer the solution into a 1 l one-mark volumetric
flask, add 75 ml of concentrated ammonium hydroxide and swirl to mix. Dilute to the mark with water,
stopper and mix thoroughly.
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