Water quality - Determination of polychlorinated naphthalenes (PCN) - Method using gas chromatography (GC) and mass spectrometry (MS)

Qualité de l'eau - Détermination des naphtalènes polychlorés (PCN) - Méthode par chromatographie en phase gazeuse (CG) et spectrométrie de masse (SM)

Kakovost vode - Določevanje polikloriranih naftalenov (PCN) - Metoda plinske kromatografije (GC) in masne spektrometrije (MS)

General Information

Status
Not Published
Public Enquiry End Date
30-Apr-2014
Technical Committee
Current Stage
98 - Abandoned project (Adopted Project)
Start Date
25-Apr-2018
Due Date
30-Apr-2018
Completion Date
25-Apr-2018

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SLOVENSKI STANDARD
oSIST ISO/DIS 16780:2014
01-april-2014
.DNRYRVWYRGH'RORþHYDQMHSROLNORULUDQLKQDIWDOHQRY 3&1 0HWRGDSOLQVNH
NURPDWRJUDILMH *& LQPDVQHVSHNWURPHWULMH 06

Water quality - Determination of polychlorinated naphthalenes (PCN) - Method using gas

chromatography (GC) and mass spectrometry (MS)
Qualité de l'eau - Détermination des naphtalènes polychlorés (PCN) - Méthode par
chromatographie en phase gazeuse (CG) et spectrométrie de masse (SM)
Ta slovenski standard je istoveten z: ISO/DIS 16780
ICS:
13.060.50 3UHLVNDYDYRGHQDNHPLþQH Examination of water for
VQRYL chemical substances
71.040.50 Fizikalnokemijske analitske Physicochemical methods of
metode analysis
oSIST ISO/DIS 16780:2014 en,fr

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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oSIST ISO/DIS 16780:2014
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oSIST ISO/DIS 16780:2014
DRAFT INTERNATIONAL STANDARD ISO/DIS 16780
ISO/TC 147/SC 2 Secretariat: DIN
Voting begins on Voting terminates on
2013-04-08 2013-07-08

INTERNATIONAL ORGANIZATION FOR STANDARDIZATION • МЕЖДУНАРОДНАЯ ОРГАНИЗАЦИЯ ПО СТАНДАРТИЗАЦИИ • ORGANISATION INTERNATIONALE DE NORMALISATION

Water Quality — Determination of polychlorinated naphthalenes
(PCN) — Method using gas chromatography (GC) and mass
spectrometry (MS)

Qualité de l'eau -- Détermination des naphtalènes polychlorés (PCN) -- Méthode par chromatographie en

phase gazeuse (CG) et spectrométrie de masse (SM)
ICS 13.060.50

To expedite distribution, this document is circulated as received from the committee

secretariat. ISO Central Secretariat work of editing and text composition will be undertaken at

publication stage.

Pour accélérer la distribution, le présent document est distribué tel qu'il est parvenu du

secrétariat du comité. Le travail de rédaction et de composition de texte sera effectué au

Secrétariat central de l'ISO au stade de publication.

THIS DOCUMENT IS A DRAFT CIRCULATED FOR COMMENT AND APPROVAL. IT IS THEREFORE SUBJECT TO CHANGE AND MAY NOT BE

REFERRED TO AS AN INTERNATIONAL STANDARD UNTIL PUBLISHED AS SUCH.

IN ADDITION TO THEIR EVALUATION AS BEING ACCEPTABLE FOR INDUSTRIAL, TECHNOLOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT

INTERNATIONAL STANDARDS MAY ON OCCASION HAVE TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL TO BECOME STANDARDS TO

WHICH REFERENCE MAY BE MADE IN NATIONAL REGULATIONS.

RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT, WITH THEIR COMMENTS, NOTIFICATION OF ANY RELEVANT PATENT RIGHTS OF WHICH

THEY ARE AWARE AND TO PROVIDE SUPPORTING DOCUMENTATION.
© International Organization for Standardization, 2013
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oSIST ISO/DIS 16780:2014
ISO/DIS 16780
COPYRIGHT PROTECTED DOCUMENT
© ISO 2013

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form or by any

means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permission.

Permission can be requested from either ISO at the address below or ISO’s member body in the country of the requester.

ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland
ii © ISO 2013 – All rights reserved
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oSIST ISO/DIS 16780:2014
ISO/DIS 16780
Contents Page

Foreword ............................................................................................................................................................ iv

1 Scope ...................................................................................................................................................... 1

2 Normative references ............................................................................................................................ 1

3 Terms, definitions and abbreviations .................................................................................................. 2

4 Principle.................................................................................................................................................. 5

5 Contamination and interferences ........................................................................................................ 6

6 Reagents and standards ....................................................................................................................... 6

7 Apparatus and materials..................................................................................................................... 10

8 Sample collection, preservation, storage and holding times ......................................................... 13

9 Quality assurance (QA)/quality control (QC) .................................................................................... 13

10 Calibration ............................................................................................................................................ 15

11 Sample preparation ............................................................................................................................. 18

12 Extraction ............................................................................................................................................. 20

13 Extract clean-up ................................................................................................................................... 24

14 HRGC/HRMS analysis ......................................................................................................................... 27

15 Qualitative determination ................................................................................................................... 28

16 Quantitative determination ................................................................................................................. 29

17 Tables ................................................................................................................................................... 32

18 Test report ............................................................................................................................................ 37

Annex A (informative) Use of alternate mass spectrometry detectors (LRMS, MSMS) ............................. 38

Annex B (informative) Quality control (QC) and initial precision and recovery (IPR)................................ 42

Annex C (informative) Calculation of toxic equivalents (TEQs) ................................................................... 43

Annex D (informative) Pollution prevention ................................................................................................... 44

Annex E (informative) Waste management .................................................................................................... 45

Bibliography ...................................................................................................................................................... 46

© ISO 2013 – All rights reserved iii
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oSIST ISO/DIS 16780:2014
ISO/DIS 16780
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.

International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.

The main task of technical committees is to prepare International Standards. Draft International Standards

adopted by the technical committees are circulated to the member bodies for voting. Publication as an

International Standard requires approval by at least 75 % of the member bodies casting a vote.

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.

ISO 16780 was prepared by Technical Committee ISO/TC 147, Water quality, Subcommittee SC 2, Physical,

chemical and biochemical methods.
iv © ISO 2013 – All rights reserved
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oSIST ISO/DIS 16780:2014
DRAFT INTERNATIONAL STANDARD ISO/DIS 16780
Water quality — Determination of polychlorinated naphthalenes
(PCN) — Method using gas chromatography (GC) and mass
spectrometry (MS)

WARNING — Persons using this document should be familiar with normal laboratory practice. This

standard does not purport to address all of the safety problems, if any, associated with its use. It is

the responsibility of the user to establish appropriate safety and health practices and to ensure

compliance with any national regulatory conditions.

Attention is drawn to any relevant national safety regulations. A number of PCN congeners have

dioxin-like properties and are toxic chemicals. All work with PCNs requires the utmost care; the

national safety measures which correspond to those for toxic substances shall be strictly followed.

IMPORTANT — It is absolutely essential that tests conducted in accordance with this document be

carried out by suitably trained staff.
1 Scope

This International Standard specifies a method for the determination of mono- to octa-polychlorinated

naphthalenes (PCNs) in waters and waste waters (containing less than 2 g/l solid particulate material (SPM))

using high resolution gas chromatography/high resolution mass spectrometry (HRGC/HRMS). The congeners

analysed by this method are listed in Table 1. The working range of the method is 20 pg/l to 8 ng/l. The

method is optimized for PCNs, but may be modified to include other co-planar compounds such as

polychlorinated dioxins and furans (PCDDs/PCDFs) and dioxin-like tetra- to hepta-chlorinated biphenyls

(dlPCBs). This method may be used to determine PCNs in other matrices (e.g. biota, sediments, air), however

additional clean-up steps and techniques may be required for samples with high organic loadings. Low

resolution mass spectrometry (LRMS) and mass spectrometry/mass spectrometry (MS/MS) may be used and

conditions are summarized in Annex A. Both LRMS and MS/MS may be less selective than HRMS and there

is a possibility of bias due to interfering compounds if these techniques are used.

The detection limits and quantification levels in this method are dependent on the level of interferences as well

as instrumental limitations. The minimum levels (ML) in Table 2 are the levels at which the PCNs can typically

be determined with no interferences present.

This method is “performance based". The analyst is permitted to modify the method e.g. to overcome

interferences, provided that all performance criteria in this method are met. The requirements for establishing

method validation / equivalency are given in Clause 9.
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

ISO 5667-1, Water quality — Sampling — Part 1: Guidance on the design of sampling programmes and

sampling techniques
© ISO 2013 – All rights reserved 1
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oSIST ISO/DIS 16780:2014
ISO/DIS 16780

ISO 5667-3, Water quality — Sampling — Part 3: Preservation and handling of water samples

ISO/TS 13530, Water quality — Guidance on analytical quality control for chemical and physicochemical

water analysis

ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories

3 Terms, definitions and abbreviations

For the purposes of this document, the following terms, definitions and abbreviations apply.

3.1 Terms and definitions
3.1.1
analyte

polychlorinated naphthalene (PCN) congener tested for by this method (see Table 1)

3.1.2
calibration standard

solution prepared from a secondary standard and/or stock solutions and used to calibrate the response of the

instrument with respect to analyte concentration
[2]
[SOURCE: ISO 17858:2007, , definition 3.1.2]
3.1.3
calibration verification standard
(VER)
midpoint calibration standard that is used to verify calibration
[2]
[SOURCE: ISO 17858:2007, , definition 3.1.3]
3.1.4
congener
a member of the same kind, class or group
EXAMPLE Any one of the 75 individual PCNs.
3.1.5
critical pair

a pair of isomers that must be separated to a predefined degree (e.g. 50 % valley) to ensure chromatographic

separation meets minimum quality criteria
NOTE 1 to entry Adapted from ISO 17858:2007.
3.1.6
dioxin-like isomer

PCN for which a relative potency to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) has been calculated (see

Table 6)
3.1.7
homologue group
the complete group of isomers
EXAMPLE Tetrachloronaphthalenes.
[2]
[ISO 17858:2007, , definition 3.1.8]
2 © ISO 2013 – All rights reserved
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oSIST ISO/DIS 16780:2014
ISO/DIS 16780
3.1.8
isotope dilution

method using labelled (usually C) internal standards to correct for losses during sample preparation and

analysis
NOTE 1 to entry Adapted from ISO 17858:2007.
3.1.9
method blank

aliquot of reagent water free of analytes treated exactly as a sample through the complete analytical

procedure including extraction, clean-up, identification and quantification including all relevant reagents and

materials
NOTE 1 to entry Adapted from ISO 17858:2007.
3.1.10
recovery standard

C -labelled PCN or alternate compound with similar properties, added before injection into the GC, to

monitor variability of instrument response
3.1.11
solid particulate material (SPM, also suspended solids)
non dissolved particle matter present in the sample
3.1.12
toxic equivalent factor
TEF
relative toxicity to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)
[2]
[SOURCE: ISO 17858:2007, , definition 3.1.17]
3.1.13
toxic equivalent quantity
TEQ
sum of toxic equivalents of each individual congener
3.1.14
surrogate standard

C -labelled PCN added to the sample prior to analysis and used to correct for losses of the PCN analytes

during sample extraction or clean-up

Note 1 to entry: Surrogate standards have the same chemical formula and structure as the analyte of interest.

3.1.15
internal standard

C -labelled PCN or analogue added to the sample prior to analysis and used to correct for losses of the

PCN analytes during sample extraction or clean-up

Note 1 to entry: Internal standards do not have the same structure as the analyte of interest but may or may not have

the same chemical formula.
© ISO 2013 – All rights reserved 3
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oSIST ISO/DIS 16780:2014
ISO/DIS 16780
3.2 Abbreviations
AR analytical reagent
CRM certified reference material
GC/MS gas chromatography/mass spectrometry
GPC gel permeation chromatography
HPLC high-performance liquid chromatography
HRGC high-resolution gas chromatography
HRMS high-resolution mass spectrometry
IPR initial precision and recovery
LRMS low-resolution mass spectrometry
MDL method detection limit
ML minimum level (see Table 2)
PAR precision and recovery
PCB polychlorinated biphenyl
PCDD/PCDF polychlorinated dibenzo-p-dioxin/dibenzofuran
PCN polychlorinated naphthalene
PFK perfluorokerosene
PLE pressurized liquid extractor
SIM selected ion monitoring
SMS spiked matrix samples
SPE solid-phase extraction
SPM solid particulate material
TEF toxic equivalent factor
TEQ toxic equivalent quantity
VER calibration verification standard
4 © ISO 2013 – All rights reserved
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oSIST ISO/DIS 16780:2014
ISO/DIS 16780
4 Principle
4.1 Extraction

4.1.1 Stable isotopically labelled analogues of PCNs (diluted in a suitable solvent such as acetone) are

spiked into a ~1 l aqueous sample. Sample size can be adjusted in order to meet required detection limits and

data quality objectives. Where available a minimum of one labelled standard per homologue group should be

used and the sample extracted using the procedures as described in 4.1.2 or 4.1.3.

4.1.2 Samples containing no visible particles are extracted using liquid/liquid extraction or by solid phase

extraction (SPE) cartridge or disk. The extract is concentrated for clean-up.

4.1.3 Samples containing visible particles are vacuum filtered through a glass fibre filter. The filter is

extracted in a Soxhlet extractor or a pressurized liquid extractor (PLE). The filtrate is extracted in a separatory

funnel. The extract is concentrated and combined with the Soxhlet extract prior to clean-up. Alternatively, the

sample is vacuum filtered through a solid phase extraction (SPE) diskor cartridge. The disk is eluted with

suitable solvent mixtures or extracted in a Soxhlet or a PLE, and the extract is concentrated for clean-up.

NOTE Other solvents and extraction techniques may be substituted, provided that all the performance criteria can be

met.
4.2 Clean-up

After extraction, sample extracts are cleaned to remove interfering components. Sample clean-up procedures

may include washes with acid and/or base, gel permeation, silica, florisil and activated carbon

chromatography. Due to the large number of potential interfering compounds, efforts should be taken to

ensure unique identification and accurate quantification of as many PCN congeners as possible.

4.3 Identification/quantification

An individual PCN is identified by comparing the GC retention time and ion abundance ratio of two exact

masses monitored (see Table 7) with the corresponding retention time of a labelled internal standard (isotope

dilution) and the theoretical or acquired ion-abundance ratio of the two exact masses. The isomers and

congeners for which there are no labelled analogues (internal standard method) are identified when retention

times or relative retention times and ion-abundance ratios agree within predefined limits.

NOTE Resolution of greater than or equal to 10 000 is recommended. High resolution gas chromatography/high

resolution mass spectrometry at a resolution of greater than or equal to 10 000 is at present required to achieve adequate

sensitivity and selectivity, and to allow the use of some C labelled standards. If the sample extract is being analysed for

multi-component analyte groups (PCDD/Fs, PCBs, PCNs), a resolution of 10 000 is necessary. Resolutions of less than

10 000 may be used for specific analytes groups (PCBs, PCNs) where the matrix and potential interferences such as

chlordane and related compounds are well characterized.
4.4 Quality

The quality of the analysis is assured through reproducible calibration and testing of the extraction, clean-up,

and GC/MS systems. Interferences, biases and limitations should be determined and identified for each target

analyte through intercalibration (round-robin) studies, certified reference materials (CRM) and spiked matrix

samples (SMS). A series of quality control (QC) samples (CRM, SMS) should be analysed with each set of

samples and monitored through control charting or other quality review procedures.

© ISO 2013 – All rights reserved 5
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oSIST ISO/DIS 16780:2014
ISO/DIS 16780
5 Contamination and interferences
5.1 Reagents

Solvents, reagents, labware, and other sample processing hardware can yield artefacts and/or elevated

baselines causing misinterpretation of chromatograms. Reagents should be checked for potential interfering

compounds and labware must be cleaned and checked to ensure that analytes of interest are not present in

labware. Specific selection of reagents and purification may be required. When a clean reference matrix that

simulates the sample matrix under test is not available, use reagent water (6.6) or a matrix that most closely

resembles the sample.
5.2 Clean labware, to meet the method blank requirements of this method (9.5.).
An example of a cleaning procedure is given below.

Disassemble labware with removable parts, particularly separatory funnels with fluoropolymer stopcocks, prior

to detergent washing. Rinse labware with solvent and wash with a detergent solution as soon after use as is

practical. Sonication of labware containing a detergent solution for approximately 30 s may aid in cleaning.

After detergent washing, rinse labware immediately with hot tap water. The tap water rinse shall be followed

by solvent rinse/soak (use suitable solvent (6.3.1) to remove contaminants. For known contaminated labware,

use toluene as a final rinse/soak.

Number each piece of re-usable labware or minimally identify each set of specific type of labware (e.g.

Soxhlet extractors, round bottom flasks) to associate that specific labware with the processing of a particular

sample or set of samples. This will assist the laboratory in tracking possible sources of contamination for

individual samples, identifying labware associated with highly contaminated samples that may require extra

cleaning, and determining when labware must be discarded.

NOTE 1 Proper cleaning of labware is extremely important, because labware can contaminate the samples but can

also remove the analytes of interest by surface adsorption if the surface is activated during the cleaning procedure.

Glassware may be checked for contamination by analysing solvent rinses.

Demonstrate that all materials used in the analysis are free from interferences by running reference matrix

method blanks initially and with each sample batch (to a maximum of 20 samples); (see 9.4, 14.5).

The reference matrix shall simulate, as closely as possible, the sample matrix under test. Ideally, the

reference matrix shall not contain analytes in detectable amounts, but shall contain matrix compounds and

potential interferents in the concentrations expected to be found in the samples to be analysed.

NOTE 2 Interferences co-extracted from samples can vary considerably from source to source, depending on the

diversity of the site being sampled. Interfering compounds, including PCBs of higher degrees of Cl substitution,

dibenzofurans of lower degrees of Cl substitution, chlordane and related compounds and labelled dibenzo-p-dioxins can

be present at concentrations orders of magnitude higher than the PCNs being analysed. Because the levels of PCNs are

measured by this method are typically lower than these compounds, the elimination of interferences is essential. The

example clean-ups given in Clause 13 can be used to reduce or eliminate these interferences and thereby permit reliable

determination of the PCNs at the levels shown in Table 2.
6 Reagents and standards

If not stated otherwise, use reagent grade chemicals and water according to grade 3 in ISO 3696.

6.1 pH adjustment and back-extraction
6.1.1 Potassium hydroxide solution
Dissolve 20 g of potassium hydroxide (KOH) in 100 ml of water.
6 © ISO 2013 – All rights reserved
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oSIST ISO/DIS 16780:2014
ISO/DIS 16780
6.1.2 Sulfuric acid, ρ(H SO ) = 1,84 mg/l.
2 4
6.1.3 Hydrochloric acid, c(HCl) = 6 mol/l.
6.1.4 Sodium chloride solution
Dissolve 5 g of sodium chloride (NaCl) in 100 ml of water.
6.1.5 Sodium thiosulfate, Na S O .
2 2 3
6.2 Reagents for drying and evaporation

6.2.1 Sodium sulfate, Na SO , granular, anhydrous, baked at 300 °C for 24 h minimum, cooled in a

2 4

desiccator, and stored in a pre-cleaned glass bottle with screw cap that prevents moisture from entering.

If, after heating, the sodium sulfate develops a noticeable greyish cast (due to the presence of carbon in the

crystal matrix), discard that batch of reagent as it is not suitable for use. Rinse with about 20 ml of

dichloromethane (6.3.1) per gram of Na SO or extract with dichloromethane (6.3.1) if background

2 4
contamination is detected.
6.2.2 Prepurified nitrogen, N , volume fraction 99,999 %.

6.3 Solvents for extraction and clean-up, in glass, pesticide quality, free of interferences.

6.3.1 2-propanone, C H O.
3 6
6.3.2 Toluene, C H .
7 8
6.3.3 Cyclohexane, C H .
6 12
6.3.4 Hexane, C H .
6 14
OH.
6.3.5 Methanol, CH
6.3.6 Dichloromethane, CH Cl .
2 2
6.3.7 Diethyl ether, C H O.
4 10
6.3.8 Ethanol, C H O.
2 6
6.3.9 Nonane, C H , distilled.
9 20
6.4 Gel permeation chromatography (GPC) calibration

6.4.1 GPC calibration solution, containing 300 mg/ml of corn oil, 15 mg/ml of bis(2-ethylhexyl) phthalate

(C H O ), 1,4 mg/ml of pentachlorophenol, (C Cl OH), 0,1 mg/ml of perylene, (C H ), and 0,5 mg/ml of

24 38 4 6 5 20 12
sulfur, (S).
6.5 Adsorbents for sample clean-up
6.5.1 Silica, 70 µm to 230 µm.
Prepare each type of silica at least every 2 weeks.

6.5.1.1 Activated silica, baked at 180 °C for a minimum of 1 h, cooled in a desiccator, and stored in a

pre-cleaned glass bottle with screw cap that prevents moisture from entering.
© ISO 2013 – All rights reserved 7
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oSIST ISO/DIS 16780:2014
ISO/DIS 16780
6.5.1.2 Acid silica

To prepare 30 % mass fraction acid silica, thoroughly mix 44,0 g of sulfuric acid (6.1.2) with 100 g of activated

silica in a clean container. Break up aggregates with a stirring rod until a uniform mixture is obtained. Store in

a bottle with a fluoropolymer-lined screw cap. Prepare 22 % acid silica and 44 % acid silica in a similar

manner using 29 g and 80 g of sulfuric acid, respectively.
6.5.1.3 Basic silica

Thoroughly mix 30 g of 1 mol/l sodium hydroxide solution with 100 g of activated silica in a clean container.

Break up aggregates with a stirring rod until a uniform mixture is obtained. Store in a bottle with a

fluoropolymer-lined screw cap.
6.5.1.4 Potassium silicate, 36 % mass fraction.

Dissolve 56 g of high purity potassium hydroxide (6.1.1) in 300 ml of methanol (6.3.1) in a 750 ml flat-bottom

flask. Add 100 g of silica (6.5.1) and a stirring bar, and stir on a hotplate at 60 °C to 70 °C for 1 h to 2 h.

Decant the liquid and rinse the potassium silicate twice with 100 ml portions of methanol, followed by a single

rinse with 100 ml of dichloromethane (6.3.1). Spread the potassium silicate on solvent-rinsed aluminium foil

and dry for 2 h to 4 h in a hood. Activate overnight at 200 °C to 250 °C. Store in a bottle with a

fluoropolymer-lined screw cap.
6.5.2 Activated carbon

Thoroughly mix 9,0 g of carbon packing material and 41,0 g of Celite 545 to produce a mass fraction of 18 %

of the mixture. Activate the mixture at 130 °C for a minimum of 6 h. Store in a desiccator.

6.5.3 Florisil, 70 µm to 250 µm.

Activate in an oven above 130 °C for a minimum of 24 h. Use as soon as possible after removal from oven.

Activity of florisil may be dependant on relative humidity.
Prepare freshly for each use.

6.5.4 Silver nitrate/silica, (10 % mass fraction) for elimination of organosulfur and organohalogen

compounds, made of silver nitrate (AgNO ) analytical reagent (AR) grade or equivalent and silica (6.5.1.1).

Dissolve 10 g of silver nitrate in 40 ml water, add in portions 90 g silica and shake until the mixture is

homogeneous. Let stand for 30 min. Transfer the mixture to a drying oven pre-heated to 70 °C and heat from

70 °C to 125 °C over a 2 h period. Activate at 125 °C for at least 10 h. Store the mixture in a brown glass

bottle.
Prepare freshly for each use.
6.6 Blank reference matrices

Matrices in which PCNs and interfering compounds are not detected by this method, e.g. reagent water,

bottled water purchased locally, HPLC grade water or water prepared by passage through activated carbon.

6.7 Standard solutions

Purchase standard solutions as final working / calibration solutions or mixtures with certification indicating their

purity, concentration, and authenticity. Alternatively, prepare standard solutions from materials of known purity

and composition.

NOTE 1 If the chemical purity is 98 % or greater, the mass may be used without correction to compute the

concentration of analytes in the standard.
8 © ISO 2013 – All rights reserved
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oSIST ISO/DIS 16780:2014
ISO/DIS 16780

When not being used, store standards in the dark in sealed ampoules or screw capped vials with

fluoropolymer lined caps. Check the concentrations regularly so that solvent loss by evaporation can be

detected. If solvent loss has occurred, replace the solution.

NOTE 2 Standard preparation (6.7 to 6.15) and Tables 3 and 4 give examples of a standard scheme that are

acceptable. Other concentrations and spiking schemes may be used provided the performance criteria of the method can

be met.

Check stock standard solutions for signs of degradation prior to the preparation of calibration or performance

test standards.
NOTE 3 Use certified reference standards and so
...

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