EN 14662-2:2005

Ambient air quality - Standard method for measurement of benzene concentrations - Part 2 : Pumped sampling followed by solvent desorption and gas chromatography

This part of EN 14662 is in accordance with the generic methodology for the determination of benzene in ambient air [1] for the purpose of comparison of measurement results with limit values with a one-year reference period.
This part of EN 14662 gives general guidance for the sampling and analysis of benzene in air by pumped sampling, solvent desorption and capillary gas chromatography.  
This part of EN 14662 is valid for the measurement of benzene in a concentration range of approximately 0,5 µg/m3  to 50 mg/m3 in an air sample of 1 m3 volume, typically collected over a period of 24 hours.
The upper limit of the useful range is set by the sorptive capacity of the sorbent and by the linear dynamic range of the gas chromatograph column and detector or by the sample splitting capability of the analytical instrumentation used. The lower limit of the useful range depends on the noise level of the detector and on blank levels of benzene and/or interfering artefacts on the sorbent and in the desorption solvent.
The method described here is based on sampling on sample tubes typically containing 100 mg of activated charcoal and desorption using carbon disulphide.
Alternative sorbents to activated charcoal may be used provided that the equivalence in performance characteristics of the procedure is demonstrated.
Alternative desorption solvents to carbon disulphide may be used provided that the equivalence in performance characteristics of the procedure is demonstrated.

Luftbeschaffenheit - Standardverfahren zur Messung von Benzolkonzentrationen - Teil 2: Probenahme mit einer Pumpe mit anschließender Lösemitteldesorption und Gaschromatographie

Dieser Teil von prEN 14662 ist in Übereinstimmung mit der allgemeinen Methode, die als Grundlage des
Referenzverfahrens der Europäischen Union zur Bestimmung von Benzol in Außenluft [1] gewählt wurde, um
Messwerte mit Grenzwerten auf Basis von Jahresmittelwerten zu vergleichen.
Dieser Teil von prEN 14662 gibt allgemeine Anleitungen für die Probenahme und Analyse von Benzol in
Außenluft durch aktive Probenahme, Lösemitteldesorption und Kapillar-Gaschromatographie.
Dieser Teil von prEN 14662 ist anwendbar auf die Bestimmung von Benzol in einem
Massenkonzentrationsbereich von etwa 0,5 µg/m³ bis 50 µg/m³ in Luftproben, die typischerweise über eine
Zeitspanne von 24 h genommen wurden..
Die obere Grenze des anwendbaren Bereiches wird durch die Sorptionskapazität des Sorbens und dem
linearen dynamischen Bereich des Gaschromatographen und des Detektors bzw. vom Trennvermögen der
verwendeten Analysengeräte angegeben. Die untere Grenze des anwendbaren Bereiches hängt vom
Rauschpegel des Detektors und von den Benzolblindwerten und/oder störenden Artefakten auf dem Sorbens
und in der Desorptionslösung ab.
Das hier beschriebene Verfahren beruht auf der Probenahme auf Sorptionsrohren, die typischerweise 100 mg
Aktivkohle enthalten, und auf der Desorption mit Kohlenstoffdisulfid.
Andere Sorbenzien als Aktivkohle dürfen verwendet werden, wenn äquivalente Verfahrenskenngrößen
nachgewiesen werden können.
Andere Desorptionslösemittel als Kohlenstoffdisulfid dürfen verwendet werden, wenn äquivalente
Verfahrenskenngrößen nachgewiesen werden können.

Qualité de l'air ambiant - Méthode normalisée pour le mesurage de la concentration en benzène - Partie 2 : Prélèvement par pompage suivi d'une désorption au solvant et d'une analyse par chromatographie en phase gazeuse

La présente partie de l’EN 14662 est conforme à la méthodologie générique pour la détermination du benzène dans l’air ambiant [1] en vue de la comparaison des résultats de mesurage avec des valeurs limites pour une période de référence d’un an.
La présente partie de l’EN 14662 fournit des lignes directrices pour le prélèvement et l’analyse du benzène dans l’air par prélèvement par pompage, désorption au solvant et chromatographie en phase gazeuse sur colonne capillaire.
La présente partie de l’EN 14662 est applicable au mesurage du benzène présent dans un volume d’air prélevé de 1 m3, généralement prélevé pendant une période de 24 heures, pour une concentration comprise environ entre 0,5 mg/m3 et 50 mg/m3.
La limite supérieure de la gamme utile est établie en fonction de la capacité d’adsorption de l’adsorbant de la gamme linéaire dynamique de la colonne et du détecteur du chromatographe en phase gazeuse et de la capacité de séparation des échantillons des instruments d’analyse utilisés. La limite inférieure de la gamme utile dépend du niveau de bruit du détecteur et des niveaux de blanc en benzène et/ou de la présence d’artéfacts d’interférence sur du sorbant et dans le solvant de désorption.
La méthode décrite dans le présent document est fondée sur un prélèvement effectué à l’aide de préleveurs à tubes contenant généralement 100 mg de charbon actif suivi d’une désorption au disulfure de carbone.
Il est possible de remplacer le charbon actif par d’autres adsorbants sous réserve que l’équivalence des caractéristiques de performance soit démontrée.
Il est possible de remplacer le disulfure de carbone par d’autres solvants de désorption sous réserve que l’équivalence des caractéristiques de performance soit démontrée.

Kakovost zunanjega zraka - Standardna metoda za določevanje koncentracije benzena - 2. del: Vzorčenje s črpanjem in določevanje s plinsko kromatografijo po desorpciji v topilu

General Information

• Status: Published
• Publication Date: 30-Aug-2005
• Withdrawal Date: 29-Nov-2005
• ICS: 13.040.20 - Ambient atmospheres
• Technical Committee: CEN/TC 264 - Air quality
• Drafting Committee: CEN/TC 264/WG 13 - Reference method for determination of benzene in ambient air
• Current Stage: 9093 - Decision to confirm - Review Enquiry
• Completion Date: 03-Dec-2019
• Directive: 2000/69/EC - Directive 2000/69/EC of the European Parliament and of the Council of 16 November 2000 relating to limit values for benzene and carbon monoxide in ambient air. Benzene, CO-2nd Daughter Directive
• Directive: 96/62/EC - Ambient air quality assessment and management
• Mandate: M/257 - Standardization mandate to CEN and CENELEC for standard measuring methods of benzene in ambiant air
• Ref Project: SIST EN 14662-2:2005 - Ambient air quality - Standard method for measurement of benzene concentrations - Part 2 : Pumped sampling followed by solvent desorption and gas chromatography

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN 14662-2:2005
01-september-2005
.DNRYRVW]XQDQMHJD]UDND6WDQGDUGQDPHWRGD]DGRORþHYDQMHNRQFHQWUDFLMH

EHQ]HQDGHO9]RUþHQMHVþUSDQMHPLQGRORþHYDQMHVSOLQVNRNURPDWRJUDILMRSR

GHVRUSFLMLYWRSLOX

Ambient air quality - Standard method for measurement of benzene concentrations - Part

2 : Pumped sampling followed by solvent desorption and gas chromatography

Luftbeschaffenheit - Standardverfahren zur Messung von Benzolkonzentrationen - Teil 2:

Probenahme mit einer Pumpe mit anschließender Lösemitteldesorption und
Gaschromatographie

Qualité de l'air ambiant - Méthode normalisée pour le mesurage de la concentration en

benzene - Partie 2 : Prélevement par pompage suivi d'une désorption au solvant et d'une

analyse par chromatographie en phase gazeuse
Ta slovenski standard je istoveten z: EN 14662-2:2005
ICS:
13.040.20 Kakovost okoljskega zraka Ambient atmospheres
SIST EN 14662-2:2005 en,fr,de

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

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SIST EN 14662-2:2005
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SIST EN 14662-2:2005
EUROPEAN STANDARD
EN 14662-2
NORME EUROPÉENNE
EUROPÄISCHE NORM
May 2005
ICS 13.040.20
English version
Ambient air quality - Standard method for measurement of
benzene concentrations - Part 2 : Pumped sampling followed by
solvent desorption and gas chromatography

Qualité de l'air ambiant - Méthode pour le mesurage des Luftbeschaffenheit - Standardverfahren zur Messung von

concentrations en benzène - Partie 2 : Echantillonnage par Benzolkonzentrationen - Teil 2: Probenahme mit einer

pompage suivi d'une désorption au solvant et d'une Pumpe mit anschließender Lösemitteldesorption und

chromatographie en phase gazeuse Gaschromatographie
This European Standard was approved by CEN on 21 March 2005.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European

Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national

standards may be obtained on application to the Central Secretariat or to any CEN member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by translation

under the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the official

versions.

CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France,

Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia,

Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36 B-1050 Brussels

© 2005 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 14662-2:2005: E

worldwide for CEN national Members.
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SIST EN 14662-2:2005
EN 14662-2:2005 (E)
Contents

Foreword ..................................................................................................................................................................3

1 Scope ...........................................................................................................................................................4

2 Normative References ................................................................................................................................4

3 Terms and definitions.................................................................................................................................4

4 Method description.....................................................................................................................................6

4.1 Principle.......................................................................................................................................................6

4.2 Reagents and Materials ..............................................................................................................................6

4.3 Apparatus ....................................................................................................................................................9

4.4 Setting of sampling flow rate ...................................................................................................................10

4.5 Sampling....................................................................................................................................................10

4.6 Procedure ..................................................................................................................................................11

4.7 Calculation of mass concentration of benzene ......................................................................................12

4.8 Report ........................................................................................................................................................13

5 Determination of measurement uncertainty ...........................................................................................13

5.1 Introduction...............................................................................................................................................13

5.2 Parameters contributing to measurement uncertainty ..........................................................................14

6 Recommendations for use .......................................................................................................................15

Annex A (informative) Determination of breakthrough volume .......................................................................16

Annex B (informative) Assessment of performance indicators and uncertainty contributions....................18

Annex C (informative) Performance characteristics..........................................................................................28

Bibliography...........................................................................................................................................................30

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SIST EN 14662-2:2005
EN 14662-2:2005 (E)
Foreword

This European Standard (EN 14662-2:2005) has been prepared by Technical Committee CEN/TC 264 “Air quality”,

the secretariat of which is held by DIN.

This European Standard shall be given the status of a national standard, either by publication of an identical text or

by endorsement, at the latest by November 2005, and conflicting national standards shall be withdrawn at the latest

by November 2005.

This document has been prepared under a mandate given to CEN by the European Commission and the European

Free Trade Association, and supports essential requirements of EU Directive 2000/69/EC and EU Directive 96/62

EC.

According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following

countries are bound to implement this European Standard: Austria, Belgium, Cyprus, Czech Republic, Denmark,

Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta,

Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.

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SIST EN 14662-2:2005
EN 14662-2:2005 (E)
1 Scope

This part of EN 14662 is in accordance with the generic methodology for the determination of benzene in ambient

air [1] for the purpose of comparison of measurement results with limit values with a one-year reference period.

This part of EN 14662 gives general guidance for the sampling and analysis of benzene in air by pumped sampling,

solvent desorption and capillary gas chromatography.

This part of EN 14662 is valid for the measurement of benzene in a concentration range of approximately 0,5 µg/m

3 3

to 50 µg/m in an air sample of 1 m volume, typically collected over a period of 24 hours.

The upper limit of the useful range is set by the sorptive capacity of the sorbent and by the linear dynamic range of

the gas chromatograph column and detector or by the sample splitting capability of the analytical instrumentation

used. The lower limit of the useful range depends on the noise level of the detector and on blank levels of benzene

and/or interfering artefacts on the sorbent and in the desorption solvent.

The method described here is based on sampling on sample tubes typically containing 100 mg of activated

charcoal and desorption using carbon disulphide.

Alternative sorbents to activated charcoal may be used provided that the equivalence in performance

characteristics of the procedure is demonstrated.

Alternative desorption solvents to carbon disulphide may be used provided that the equivalence in performance

characteristics of the procedure is demonstrated.
2 Normative References

The following referenced documents are indispensable for the application 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.
ENV 13005, Guide to the expression of uncertainty in measurement

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

17025:1999)

ISO 6144, Gas analysis – Preparation of calibration gas mixtures – Static volumetric method

ISO 6145, Gas analysis – Preparation of calibration gas mixtures using dynamic volumetric methods

3 Terms and definitions

For the purposes of this European standard the following terms and definitions apply.

NOTE. Attention is drawn to the fact that the terms Ambient Air and Limit Value are defined in Directive 96/62/EC [2].

3.1
Certified reference material

A reference material [3.5], accompanied by a certificate, one or more of whose property values are certified by a

procedure which establishes its traceability to an accurate realisation of the unit in which the property values are

expressed, and for which each certified value is accompanied by an uncertainty at a stated level of confidence.

[ISO Guide 30:1992]
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EN 14662-2:2005 (E)
3.2
Combined standard uncertainty

Standard uncertainty of the result of a measurement when that result is obtained from the values of a number of

other quantities, equal to the positive square root of a sum of terms, the terms being the variances or covariances

of these other quantities weighted according to how the measurement result varies with changes in these quantities.

[ENV 13005:1999]
3.3
Desorption efficiency
Ratio of the mass of analyte desorbed from a sampling device to that applied.
[EN 1076:1997]
3.4
Expanded uncertainty

Quantity defining an interval about the result of a measurement that may be expected to encompass a large

fraction of the distribution of values that could reasonably be attributed to the measurand.

[ENV 13005:1999]

NOTE 1 The fraction may be viewed as the coverage probability or level of confidence of the interval.

NOTE 2 To associate a specific level of confidence with the interval defined by the expanded uncertainty requires explicit of

implicit assumptions regarding the probability distribution characterised by the measurement result and its combined standard

uncertainty. The level of confidence that can be attributed to the interval can be known only to the extent to which such

assumptions may be justified.
NOTE 3 Expanded uncertainty is termed overall uncertainty in ENV 13005:1999.
3.5
Reference material

A material or substance, one or more of whose property values are sufficiently homogeneous and well established

to be used for the callibration of an apparatus, the assessment of a measurement method, or for assigning values

to materials.
[ISO Guide 30:1992]
3.6
Repeatability conditions

Conditions where independent test results are obtained with the same method on identical test items in the same

laboratory by the same operator using the same equipment within short intervals of time.

[ISO 3534-1:1993]
3.7
Sampling efficiency
Ratio of the mass of analyte collected by a sampling device to that applied.
3.8
Standard uncertainty
Uncertainty of the result of a measurement expressed as a standard deviation.
[ENV 13005:1999]
3.9
Uncertainty (of measurement)

Parameter, associated with the results of a measurement, that characterises the dispersion of values that could

reasonably be attributed to the measurand
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NOTE 1 The parameter may be, for example, a standard deviation (or given multiple of it), or the half width of an interval

having a stated level of confidence.

NOTE 2 Uncertainty of measurement comprises, in general, many components. Some of these components may be

evaluated from the statistical distribution of the results of a series of measurements and can be characterised by experimental

standard deviations. The other components, which can also be characterised by standard deviations, are evaluated from

assumed probability distributions based on experience or other information.

NOTE 3 It is understood that the result of a measurement is the best estimate of the value of a measurand, and that all

components of uncertainty, including those arising from systematic effects, such as components associated with corrections and

reference standards, contribute to this dispersion.
[ENV 13005:1999].
4 Method description
4.1 Principle

A measured volume of sample air is drawn through an activated charcoal sorbent tube. Provided suitable sampling

conditions are chosen, benzene is retained by the sorbent and thus is removed from the flowing air stream. The

collected vapour is desorbed using carbon disulphide and is analyzed on a gas chromatograph equipped with a

capillary column and a flame ionisation detector or other suitable detector. The analysis is calibrated by means of

charcoal tube calibration standards or calibration solutions of known amounts of benzene in carbon disulphide.

4.2 Reagents and Materials

During the analysis, use only reagents of known purity appropriate to the application.

Use only volumetric glassware and syringes that are calibrated to ensure traceability of volume to primary

standards.
4.2.1 Benzene

Benzene is required as a reagent for calibration purposes and for the determination of desorption efficiency.The

benzene used shall be of a minimum established purity of 99,5%.
4.2.2 Carbon disulphide

The carbon disulphide used for the desorption of benzene from the charcoal shall be free from compounds

interfering with the analysis of the benzene sampled.

Grades of carbon disulphide used shall contain benzene in concentrations less than 0,1 µg/ml.

4.2.3 Internal standard

An internal standard may be used to correct for small variations in the volume of carbon disulphide injected. It shall

not interfere with benzene and it shall not be removed from the elution solvent by the charcoal. The internal

standard shall contain less than 0,1 % benzene. The internal standard is added to the carbon disulphide before the

preparation of calibration solutions (4.2.8) or the desorption of samples (4.6) or calibration standards (4.2.5).

Internal standards used in practice include 2-fluorotoluene (flame-ionization detection; photo-ionization detection)

and benzene-d6 and toluene-d8 (mass-spectrometric detection).
4.2.4 Activated charcoal

A particle size of 0,35 mm to 0,85 mm is recommended. Before use, the charcoal shall be heated in an inert

atmosphere, e.g. high-purity nitrogen, at approximately 600 °C for 1 hour. To prevent recontamination of the

charcoal, it shall be kept in a clean atmosphere during cooling to room temperature, storage, and loading into the

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EN 14662-2:2005 (E)

tubes. Tubes prepacked by manufacturers with pre-conditioned charcoal are also available and require no further

conditioning.

NOTE The sorptive capacity and desorption efficiency of different batches of activated charcoal may vary. Commercial

tubes, if used, should be purchased from the same batch and in sufficient number to provide consistent performance for a

definite period of time.
4.2.5 Calibration standards

Calibration standards can be prepared by loading the required amounts of benzene from standard atmospheres

(4.2.6) on charcoal tubes of the same batch as those used for sampling as this procedure most closely resembles

the practical sampling situation.

The concentrations of the desorbed solutions of the sample tubes may then be compared directly with the solutions

resulting from desorption of these tube standards, i.e., without the need for applying corrections for desorption

efficiency (4.6.5).

If it is not practical to prepare calibration standards in this way, then calibration solutions in carbon disulphide can

be prepared (see 4.2.8) in order to compare the concentrations of desorbed solutions (4.6.2) with those calibration

standards in the gas chromatographic analysis.

In this case, appropriate corrections for desorption efficiency shall be applied (see 4.6.5).

NOTE The use of an internal standard as a surrogate to correct for desorption efficiency is not allowed. Desorption

efficiency should be determined directly with benzene.
4.2.6 Standard atmospheres

Prepare standard atmospheres of known concentrations of benzene by a recognized procedure. Methods

described in ISO 6144 and ISO 6145 are suitable. If the procedure is not applied under conditions that will allow the

establishment of full traceability of the generated concentrations to primary standards of mass and/or volume or if

the chemical inertness of the generation system cannot be guaranteed, the concentrations need to be confirmed

using an independent procedure.
4.2.7 Standard charcoal tubes loaded by spiking from standard atmospheres

Prepare loaded charcoal tubes by passing an accurately known volume of the standard atmosphere through the

sorbent tube, e.g., by means of a mass-flow controller or a pump. After loading, the tubes are disconnected and

sealed.
EXAMPLE
3 3

Prepare standard atmospheres with benzene concentrations in the range of 0,5 mg/m to 50 mg/m . Prepare

charcoal tube standards at a minimum of 5 levels corresponding to a range of 0,5 µg to 50 µg by sampling 100 ml

to 1 l of these standard atmospheres.

NOTE The loading ranges given are not mandatory and approximate to the application range given in the scope for a 1 m

sample. For specific applications where other volumes are used and/or the concentration range of benzene is limited other

loading ranges may be more appropriate.
Prepare fresh standards at appropriate intervals depending upon their stability.

Standards containing approximately 5 µg of benzene are known to be stable for at least 1 year when stored in a

clean environment at room temperature [3].
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4.2.8 Preparation of calibration solutions in carbon disulphide
4.2.8.1 General

Prepare a series (5 at minimum) of calibration solutions of benzene in carbon disulphide in the range corresponding

3 3

to ambient concentrations of 0,5 µg/m to 50 µg/m of benzene. Guidance for the preparation of such solutions can

be found in [4]. In general, procedures based on gravimetry and volumetry may be used to prepare calibration

solutions under the conditions described below.
4.2.8.2 Gravimetric procedure

By preparing serial dilutions of benzene (4.2.1) in carbon disulphide (4.2.2) by weighing, the traceability of the

composition of the final calibration standards is ensured. A suitable mass of internal standard (4.2.3) may be added

to the carbon disulphide to correct for small evaporation losses of carbon disulphide or variations in the injected

volume of carbon disulphide on analysis. The concentrations of benzene in the standard solutions are then

expressed as mass fractions. By weighing the mass of carbon disulphide used for desorption of samples, blanks or

standards for the determination of desorption efficiency (4.6.2) the analysis will yield the mass of benzene in the

sample, blank or standard.
EXAMPLE

Accurately weigh approximately 100 mg of benzene into a 10 ml volumetric flask or vial using a balance with a

resolution ≤ 0,1 mg. Make up to 10 ml with carbon disulphide (4.2.2), stopper or cap, weigh and shake to mix.

From this stock solution calibration standards may be prepared in the range of 100 µg/ml to 1000 µg/ml of benzene by pipetting

0,1 ml to 1 ml into 10 ml volumetric flasks or vials, capping, weighing, and subsequent addition of a known mass of carbon

disulphide corresponding to approximately 10 ml.

From these solutions calibration standards in the range of 1 µg/ml to 50 µg/ml of benzene are prepared as above.

The standard solution of 50 µg/ml is used to prepare the calibration standard containing 0,5 µg/ml of benzene.

NOTE In order to ensure an uncertainty of the final mass fractions of benzene appropriate to the application the uncertainty

of the weighing equipment used (k=2) should be less than ± 0,1 mg.
4.2.8.3 Volumetric procedure

Alternatively, calibration solutions may be prepared by serial dilution of a stock solution of benzene in carbon

disulphide using volumetric glassware and syringes that are traceably calibrated. The calibration may be performed

by repeated weighing of the corresponding volume of water, using the appropriate specific density to calculate the

volume of the glassware. A suitable mass of internal standard (4.2.3) may be added to the carbon disulphide to

correct for small evaporation losses of carbon disulphide or variations in the injected volume of carbon disulphide

on analysis. When preparing solutions in carbon disulphide by volumetry the temperature in the working room shall

be controlled to within ±2 K in order to limit the effect of variations of the specific density of carbon disulphide.

The dilution steps described in the above example (4.2.8.2) may be used to prepare calibration standard solutions

in the appropriate benzene concentration range, using calibrated flasks, vials, syringes and pipettes.

4.2.9 Stability of calibration solutions

Stock solutions are stable for at least one month when stored in dark glass flasks or vials with suitable caps at

room temperature.

Typically, calibration solutions with concentrations between 0,5 µg/ml and 50 µg/ml should be prepared fresh

weekly, or more frequently if evidence is noted of deterioration.
4.2.10 Standards for desorption efficiency

Prepare loaded sorbent tubes from standard atmospheres (4.2.6) according to the procedure described in 4.2.7.

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If the generation of standard atmospheres is not practicable, the standards may be prepared by a liquid spiking

procedure, provided that the accuracy of the spiking technique is established by using procedures giving spiking

levels traceable to primary standards of mass and/or volume, or is confirmed by an independent procedure.

Load the sorbent tubes by injecting aliquots of standard solutions (4.2.8) of accurately known mass or volume onto

clean sorbent tubes as follows: a sorbent tube is fitted to a T-piece of which one end is fitted with a septum, or

injection facility of a gas chromatograph, through which inert purge gas is passed at 100 ml/min. Inject a known

mass or volume through the septum and purge for 5 minutes. Disconnect the tube and seal.

4.3 Apparatus
The following specific items of laboratory equipment are required.
4.3.1 Sorbent tubes

A typical sampling tube consists of a glass tube with both ends flame-sealed, 70 mm long with an outside diameter

of 6 mm and an inside diameter of 4 mm, containing two sections of sorbent. In the case of charcoal, the sorbing

section contains 100 mg of charcoal and the back-up section, 50 mg. The sections are separated and their

contents are held in place with an inert material, e.g. glass wool plugs (preferably silanized).

Glass tubes shall be held in protective holders to prevent breakage.

The desorption efficiency (D) for each batch of tubes shall be checked by one of the methods described in 4.6.5. If

D is lower than 0,9 (90%), the tubes shall not be used.

NOTE 1 Instead of commercial two-section tubes, single section tubes may be used. This arrangement has the advantage

that it is not necessary to store tubes at sub-ambient temperatures after sampling to prevent migration of the sorbed compounds

from one section to the other.

NOTE 2 Tubes meeting these requirements are commercially available; however, they may also be made by the user. Self-

packed samplers should not be used unless they can be shown to have reproducible and constant sorption properties.

4.3.2 End caps

Caps made of a suitable material to fit over the sorbent tubes (4.3.1) to prevent leakage.

NOTE Commercially available tubes are supplied with polyethylene end caps.
4.3.3 Syringes

A precision 10 µl liquid syringe readable to 0,1 µl. The volume of the solvent delivered shall be calibrated by

gravimetry.
4.3.4 Volumetric flask

Precision volumetric flasks of an accurately known volume, to be used for the preparation of calibration solutions

(4.2.8). These should be obtained from suppliers issuing certificates of calibration traceable to internationally

accepted standards or be traceably calibrated in the laboratory by weighing of water.

4.3.5 Sampling device

Sampling device capable of maintaining a preset flow rate of 500 ml/min to 1000 ml/min within ±5% during the

required sampling period (typically 24 hours). As such, the following devices may be used:

• pump with an adjustable flow rate
• vacuum pump with a critical orifice
• vacuum pump with a mass-flow controller
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EN 14662-2:2005 (E)
• vacuum pump with a constant pressure drop over a restriction.

NOTE The sampling device should be in accordance with local safety regulations, if any.

4.3.6 Tubing

Tubing of appropriate length and internal diameter to ensure a leak-proof fit to both pump and sample tube or tube

holder, if used.
4.3.7 Flow calibration device

A flow meter that is traceably calibrated to a primary flow standard over the desired flow range (4.3.5). The

uncertainty in the calibration of the flow meter shall be ≤2%.

NOTE The use of an uncalibrated integral flow meter for the calibration of pump flow rates may result in large systematic

errors.
4.3.8 Precipitation shield

A protective cover to prevent the entrance of particles or water droplets into the sampling tube during the sampling.

NOTE EN 13528-3 describes various shields for diffusive samplers that may also be suitable for pumped samplers.

4.3.9 Support

A device capable of positioning the sampling device and sorbent tube at the appropriate height and distance from

obstacles to warrant undisturbed sampling.
4.3.10 Gas chromatograph

A gas chromatograph fitted with a flame ionization, photoionization detector, mass spectrometric or other suitable

detector, capable of detecting an injection of 0,5 ng benzene with a signal-to-noise ratio of at least 5 to 1.

A gas chromatograph column capable of separating benzene from other components.
4.3.11 Autosampler

The use of an autosampler is recommended because of the better repeatability of the injected volume of carbon

disulphide.

NOTE. Autosamplers with liquid-chilled sample trays, suitable for the analysis of volatile solvents, are commercially available.

4.4 Setting of sampling flow rate

Switch on the sampling device; allow sufficient time for the flow rate to stabilize. Adjust the flow rate of the sampling

device with a representative sorbent tube assembly in line, using an appropriate calibration device (4.3.7) to a

value between 500 ml/min and 1000 ml/min. One end of the calibration device should be at atmospheric pressure

to ensure proper operation.

Determine the flow rate by taking the average of a minimum of 3 consecutive measurements. The uncertainty in the

measured flow shall be ≤ 2,5%.
4.5 Sampling

Break open both ends of the sample tube, ensuring that each opening is at least one half the inside diameter of the

tube. Insert the tube into its protective holder, if any. Fit the precipitation shield, and mount the sampler in a vertical

position at the appropriate site using the support (4.3.9).
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SIST EN 14662-2:2005
EN 14662-2:2005 (E)

Attach the sampling device to the sorbent tube or tube assembly with suitable tubing. Turn on the sampling device

for a period sufficient to sample the recommended volume of air.

NOTE 1 The recommended air sample volume for benzene is 1 m for a period of 24 hours.

NOTE 2 Sampling efficiency will be 100 % (quantitative), provided the sampling capacity of the sorbent is not exceeded. If

this capacity is exceeded, breakthrough of benzene from the tube assembly will occur. The breakthrough volume may be

measured by sampling from a standard atmosphere, whilst monitoring th
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