EN 14662-5:2005

SLOVENSKI STANDARD
01-september-2005
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Ambient air quality - Standard method for measurement of benzene concentrations - Part
5: Diffusive sampling followed by solvent desorption and gas chromatography
Außenluftbeschaffenheit - Standardverfahren zur Bestimmung von
Benzolkonzentrationen - Teil 5: Diffusionsprobenahme mit anschließender
Lösemitteldesorption und Gaschromatographie
Qualité de l'air ambiant - Méthode normalisée pour le mesurage de la concentration en
benzene - Partie 5 : Prélevement par diffusion suivi d'une désorption au solvant et d'une
analyse par chromatographie en phase gazeuse
Ta slovenski standard je istoveten z: EN 14662-5:2005
ICS:
13.040.20 Kakovost okoljskega zraka Ambient atmospheres
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN 14662-5
NORME EUROPÉENNE
EUROPÄISCHE NORM
May 2005
ICS 13.040.20
English version
Ambient air quality - Standard method for measurement of
benzene concentrations - Part 5: Diffusive sampling followed by
solvent desorption and gas chromatography
Qualité de l'air ambiant - Méthode pour le mesurage des Luftbeschaffenheit - Standardverfahren zur Bestimmung
concentrations en benzène - Partie 5 : Echantillonnage par von Benzolkonzentrationen - Teil 5: Diffusionsprobenahme
diffusion suivi d'une désorption au solvant et d'une 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 14662-5:2005: E
worldwide for CEN national Members.

Contents Page
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 .7
4.3 Apparatus .9
4.4 Sampling.10
4.5 Procedure .11
4.6 Calculations of mass concentration of benzene .12
4.7 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
a
Annex A (informative) Suppliers of charcoal-based organic vapour diffusive samplers .16
Annex B (informative) Specific information of sampler type A.17
Annex C (informative) Specific information of sampler type B.19
Annex D (informative) Assessment of performance indicators and uncertainty contributions.21
Annex E (informative) Performance characteristics .29
Bibliography.31

Foreword
This European Standard (EN 14662-5:2005) 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.
1 Scope
This part of EN 14662 is in accordance with the generic methodology selected as the basis of the European
Union 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 diffusive
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
3 3
µg/m to 50 µg/m in an air sample typically collected over a period of several days or several weeks. A
number of devices are recommended for the sampling of benzene, each device having a different range of
applicability, particularly with regard to the optimum period of exposure.
The upper limit of the useful range is set by the sorptive capacity of the activated charcoal and, subject to
dilution of the analysed solution, 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
sampling devices or in the 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 13005:1999, Guide to the expression of uncertainty in measurement
EN 13528-2:2002, Ambient air quality - Diffusive samplers for the determination of concentrations of gases
and vapours - Requirements and test methods. Part 2: Specific requirements and test methods
EN 13528-3:2003, Ambient air quality - Diffusive samplers for the determination of concentrations of gases
and vapours – Part 3: Guide for selection, use and maintenance
EN ISO/IEC 17025:2000, General requirements for the competence of testing and calibration laboratories
(ISO/IEC 17025:1999)
ISO 5725-2:1994, Accuracy (trueness and precision) of measurement methods and results - Part 2: Basic
method for the determination of repeatability and reproducibility of a standard measurement method
ISO 5725-3:1995, Accuracy (trueness and precision) of measurement methods and results - Part 3:
Intermediate measures of the precision of a standard measurement method
3 Terms and definitions
For the purposes of this European Standard, the following terms and definitions apply.
3.1
certified reference material
A reference material [3.7], 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]
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 838:1995]
3.4
Diffusive sampler
a device which is capable of taking samples of gases or vapours from the atmosphere at a rate controlled by a
physical process such as gaseous diffusion through a static air layer or a porous material and/or permeation
through a membrane, but which does not involve the active movement of air through the device
NOTE 1  Active normally refers to the pumped movement of air.
NOTE 2  This definition differs from that in EN 838:1995 by the addition of the words “or a porous material”.
3.5
Diffusive uptake rate
rate at which the diffusive sampler collects a particular gas or vapour from the atmosphere, expressed in
picograms per parts per billion per minute (pg/ppb/min) or cubic centimetres per minute (cm /min)
NOTE 1  pg/ppb/min are equivalent to ng/ppm/min.
NOTE 2 This definition differs from that in EN 838:1995 by the substitution of “picograms per parts per billion” for
“nanograms per parts per million”. The expression is numerically the same, but ambient concentrations are usually in the
ppb range.
3.6
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

-9 -6
ppb is volume fraction, (φ)=10 ; ppm is volume fraction, (φ)=10 .
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.
3.7
reference material
material or substance, one or more of whose property values are sufficiently homogeneous and well
established to be used for the calibration of an apparatus, the assessment of a measurement method, or for
assigning values to materials.
[ISO Guide 30:1992]
3.8
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]
3.9
standard uncertainty
uncertainty of the result of a measurement expressed as a standard deviation
[ENV 13005:1999]
3.10
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
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].
Attention is drawn to the fact that the terms Ambient Air and Limit Value are defined in Directive 96/62/EC [1].
4 Method description
4.1 Principle
The diffusive sampler is exposed to air for a measured time period. The rate of sampling is determined by
prior calibration in a standard atmosphere (4.2.6) The benzene vapour migrates into the sampler by diffusion
and is collected on the sorbent, normally activated carbon. The collected vapour is desorbed by a solvent,
normally carbon disulphide, and the solution is analysed with a gas chromatograph equipped with a flame
ionisation detector, mass spectrometer or other selective detector. The analysis is calibrated by means of
vapour spiking onto a diffusive sampler or from calibration solutions of known amounts of benzene in carbon
disulphide.
Information on possible saturation of the sorbent, the effect of transients and the effect of face velocity is given
in EN 13528-3. This also explains the dependence of diffusion uptake rates on the concentration level of
pollutants and the time of diffusive sampling, for non-ideal sorbents, which results in different values being
given in Annexes B and C. The theory of performance of diffusive samplers is also given in EN 13528-3.
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 to prepare standard solutions (4.2.7) and for the
determination of the desorption efficiency (4.2.9). 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 co-
eluting with benzene.
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 (4.2.7.1) or the desorption of samples (4.5.2) 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).
The internal standard may also be added to each sample, after the solvent, in order to correct for variations in
the carbon disulphide volume, due to desorption heat.
4.2.4 Activated charcoal
A particle size of 0,35 mm to 0,85 mm is recommended. Before packing the samplers, the charcoal shall be
heated in an inert atmosphere, e.g. high-purity nitrogen, at approximately 600 °C for 1 h. To prevent
recontamination of the charcoal, it shall be kept in a clean atmosphere during cooling to room temperature,
storage, and loading into the samplers. Samplers prepacked by manufacturers with pre-conditioned charcoal
are also available and require no further conditioning.
4.2.5 Calibration standards
Calibration standards are preferably prepared by exposing the diffusive devices (of the same batch as those
used for sampling) in a standard atmosphere of benzene (4.2.6) for an appropriate time, as this procedure
most closely resembles the practical sampling situation.
The concentrations of the desorbed solutions of the devices used for sampling may then be compared directly
with the solutions resulting from desorption of these calibration standards, i.e., without the need for applying
corrections for desorption efficiency (4.5.5), but allowing for any difference between the exposure times of the
calibration standards and samples.
If it is not practicable to prepare calibration standards in this way, then calibration solutions in carbon
disulphide can be prepared (4.2.7) in order to compare the concentrations of desorbed solutions (4.5.2) with
those calibration standards in the gas chromatographic analysis.
4.2.6 Standard atmospheres
Prepare standard atmospheres of known concentrations of benzene by a recognised 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 Preparation of calibration solutions in carbon disulphide
4.2.7.1 General
Prepare a series (5 at minimum) of calibration solutions of benzene in carbon disulphide in the range
3 3
corresponding 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 [12]. In general, procedures based on gravimetry and volumetry may be used
to prepare calibration solutions under the conditions described below.
4.2.7.2 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 (4.2.9) 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.
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) shall be less than ± 0,1 mg.
4.2.7.3 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 (4.2.7.2) may be used to prepare calibration standard
solutions in the appropriate benzene concentration range, using calibrated flasks, vials, syringes and pipettes.
4.2.8 Stability of calibration solutions
Storage times for calibration solutions vary according to application. In the above examples, calibration
solutions described in 4.2.7.2 or 4.2.7.3 are stable for at least one year when stored in dark glass bottles with
suitable caps at below 4 °C.
Typically, solutions described in 4.2.7.2 or 4.2.7.3 should be prepared fresh monthly, or more frequently if
evidence is noted of deterioration.
4.2.9 Standards for desorption efficiency
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.
This is the procedure usually recommended by manufacturers: follow the manufacturer’s guidance for specific
instructions. These will vary significantly with the sampler type, and some examples are given in Annexes A,
B and C. In principle, load the devices by injecting aliquots of standard solutions (4.2.7.2 or 4.2.7.3) of
accurately known mass or volume at three or more levels onto clean samplers, seal the samplers and leave to
equilibrate.
4.3 Apparatus
The following specific items of laboratory apparatus are required.
4.3.1 Diffusive samplers
A number of solvent-desorption diffusive samplers are available commercially. Information on available
devices is given in Annex A. Data on the characteristics of two typical sampler types are given in Annexes B
and C.
If required, the desorption efficiency (D) for each batch of samplers shall be checked by one of the methods
described (4.5.5). If D is lower than 0,9 (90 %), the diffusive samplers shall not be used.
4.3.2 Syringes
A precision 10 µl liquid syringe readable to 0,1 µl. The volume of the solvent delivered shall be calibrated by
gravimetry.
4.3.3 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.
4.3.4 Support
A device capable of positioning the sampling device at the appropriate height and distance from obstacles to
warrant undisturbed sampling.
4.3.5 Gas chromatograph
A gas chromatograph fitted with a flame ionization (FID), photo-ionization (PID), 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.
4.3.6 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 Sampling
Select a diffusive sampler appropriate for the compound or mixture to be sampled. Guidance on the
availability of suitable samplers is given in Annex A. Annexes B and C give information on the diffusive uptake
rates for two typical devices.
Mount the sampler at the appropriate site, using the support (4.3.4), and fit the precipitation shield (4.3.3).
Follow the manufacturer’s guidance for specific sampling instructions for the actual period of sampling. These
will vary significantly with the sampler type, and some examples are given in Annexes B and C. In principle,
any protective cover is removed before the diffusive sampler is exposed to the target atmosphere, and the
sampler is re-sealed again at the end.
For sampling ambient air recommendations for site selection and for the protection of samples from adverse
environmental conditions are given in EN 13528-3. Attention has to be paid to three main considerations: air
velocity, protection from precipitation, and security.
Expose the sampling tubes only under conditions where the face velocity requirement can be expected to be
satisfied.
The recommended exposure time for the devices covered by this part of EN 14662 depends on the sampler
design. Different designs of diffusive sampler have different diffusive sampling rates and the exposure time
will have to be selected to bring the collected mass of benzene into the calibration range of the calibration
solutions (4.2.7.2 or 4.2.7.3). For example, a type A sampler exposed to an atmosphere of 5 µg/m benzene
for 4 weeks and desorbed in 2,0 ml carbon disulphide will result in a solution (assuming 100% desorption
efficiency) of approximately 0,9 µg/ml, whilst a type B sampler exposed for 4 days and desorbed in 2 ml
carbon disulphide will result in a solution of approximately 1,3 µg/ml. Sampling over longer or shorter periods
is possible, provided that the resulting solution is within the concentration range of the calibration standards
(0,5 µg/ml to 50 µg/ml) and any dependency of the diffusive sampling rate on the concentration and/or
sampling time has been established.
Samplers should be uniquely labelled. Solvent-containing paints and markers or adhesive labels should not be
used to label the samplers.
Knowledge of the average temperature and barometric pressure of the sampled air is required in order to
express concentrations reduced to standard conditions (4.6). This information may be obtained from
measurements on the site using a traceably calibrated thermometer and barometer. Alternatively information
from a nearby weather station may be used.
Field blanks should be prepared by using tubes identical to those used for sampling and subjecting them to
the same handling procedure as the samples except for the actual period of sampling. Label these as blanks.
4.5 Procedure
4.5.1 Safety precautions
This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appropriate health and safety practices and determine
the applicability of regulatory limitations prior to use.
4.5.2 Desorption and analysis
Perform the desorption of the samplers (4.3.1), standards for the determination of desorption efficiency, if any
(4.2.9), field samples and field blanks (4.4) in a clean atmosphere in a fume hood.
Follow the manufacturer’s guidance for specific desorption instructions. These will vary significantly with the
sampler type, and two examples are given in Annexes B and C. In principle, the collected benzene is
extracted from the activated charcoal with carbon disulphide. In some cases, the desorption is done without
dissembling the device; in others, the sorbent is removed and desorbed in a separate vessel.
If there is a back-up section of sorbent, this should be desorbed separately.
NOTE  In some circumstances, a higher desorption efficiency (D) may be obtained with ultrasonic extraction as
opposed to mechanical shaking.
Set up the gas chromatograph for the analysis of benzene. A variety of chromatographic columns may be
used for the analysis. Typical examples are 50 m x 0,22 mm fused silica columns with thick-film dimethyl
polysiloxane, phenyl methyl polysiloxane or cyanopropyl phenyl methyl polysiloxane chemically bonded
stationary phases. A typical film thickness is in the range 0,5 µm to 2,0 µm. Typical operating conditions for
o o o
these columns are temperature programming from 50 C to 200 C at 5 C/min with a carrier gas flow of 0,7

ml/min to 2 ml/min helium.
Identification of benzene shall not be based on correspondence of retention time on a single column.
4.5.3 Calibration
Analyse the desorbate of each diffusive sampler standard or each calibration solution (4.2.7.2 or 4.2.7.3) by
injecting a fixed volume (1 µl to 5 µl) into the gas chromatograph. A standardized injection technique should
be used so that repeatable peak areas are obtained. Typically, for a series of replicate injections, the relative
standard deviation should be better than ± 2 %. Autosamplers normally achieve better than ± 1 %.
Prepare a calibration function from the responses of these calibration standards and the corresponding
masses of benzene in the standards. Various functions, such as linear, exponential or polynomial, may be
more or less suitable, depending on the linearity of the detector response. Application of weighted regression
may be necessary to obtain an appropriate goodness of fit of the function over the entire concentration range.
The goodness of fit of the calibration function shall be determined by examining the residuals calculated for
each calibration standard concentration level as the difference between the mass of benzene calculated by
application of the calibration function and the actual mass of benzene in the standard. The requirements given
in Clause 5.2 shall be fulfilled.
The calibration shall be repeated at regular intervals. These intervals may vary in practice and will depend on
the response drift of the detector used. The calibration interval is to be established based on practical
determinations of the detector response drift. The response drift between determinations shall be < ± 5 %.
4.5.4 Determination of sample concentration
Analyse the samples and sample blanks as described for the calibration standards in 4.5.3.
Determine the responses of the samples and field blanks and calculate from the calibration function the mass
of benzene in the desorbed samples and field blanks.
4.5.5 Determination of desorption efficiency
If the desorption efficiency is not included in the uptake rate it shall be determined using EN 13528-2.
Manufacturers' instructions for desorption shall be followed.
The desorption efficiency (D) of benzene can vary with the type and batch of the charcoal used. Thus it is
necessary for each batch of charcoal to determine D over the sample concentration range. Samples are
prepared as described in 4.2.9 and analysed as described in 4.5.2. D is then the amount recovered divided
by the amount applied.
If the desorption efficiency data can be shown to be a homogeneous set, then D is given by the pooled mean.
Otherwise the data should be examined to determine whether it can be modelled using an appropriate
mathematical relationship, with D increasing with the ratio of analyte mass to sorbent mass. In such cases, D
can be estimated using this relationship.
Alternatively to the procedure of using spiked samples (4.2.9) the phase-equilibrium method, in which
accurately known volumes of calibration standard solutions (4.2.7.2 or 4.2.7.3) are added to the sorbent
material removed from unused blank samplers, may be applied, provided equivalence to the above procedure
is demonstrated on a regular basis. When the resulting solutions are used directly for calibration the
desorption efficiency is incorporated in the calibration function and can be ignored in further calculations.
4.5.6 Calibration of uptake rate
Diffusive uptake rates for two typical samplers are given in Annexes B and C. Unless otherwise specified,
rates are appropriate for standard conditions (20 °C and 101 kPa). Some rates already include an allowance
for desorption efficiency.
If an uptake rate for a particular device is not available, it shall be determined experimentally using the
procedure given in EN 13528-2.
4.6 Calculations of mass concentration of benzene
Calculate the concentration of the benzene in the sampled air, in µg/m , by means of the following equation:
m −m
sam bl 6
C = ⋅10         (1)
m
D ⋅U ⋅t
where:
C is the concentration of benzene in the air sampled, in µg/m ;
m
D is the desorption efficiency as found in 4.5.5, for a mass m if devices exposed to standard
sam
atmospheres or the phase equilibrium method have been used as calibration standards, then D = 1
m is the mass of benzene present in the actual sample as found in 4.5.4, in µg;
sam
m is the mass of benzene present in the blank tube, in µg;
bl
U is the diffusive uptake rate in cm /min under operational conditions (Tables B.1, B.2, C.1);
t is the exposure time in min.
For application of the measurement result within the frame of EU Directive 2000/69/EC [1], conversion of the
concentration value to conditions of standard temperature and pressure (STP, 20 °C, 101,3 kPa) is required.
Correct the concentration to the required conditions of standard temperature and pressure (293 K, 101,3 kPa)
as follows:
101.3 T + 273
C = C ⋅ ⋅         (2)
c m
P
where:
-3
C is the concentration of the benzene in air sampled, reduced to specified conditions, in µg m .
c
P is the average pressure of the air sampled, in kPa;
T is the average temperature of the air sampled, in °C
4.7 Report
The test report shall contain at least the following information:
a) complete identification of the sample;
b) reference to this part of EN 14662;
c) sampling location, sampling time period and the diffusive uptake rate used;
d) average barometric pressure and temperature;
e) test result;
f) any unusual features noted during the determination;
g) any operation not included in this part of EN 14662 or in the European Standard to which reference is
made or regarded as optional.
5 Determination of measurement uncertainty
5.1 Introduction
The measurement of the concentration of benzene in ambient air has to fulfil the requirement of a maximum
uncertainty in the measured values prescribed by Directive 2000/69/EC. In order to fulfil this requirement, the
measurement uncertainty has to be assessed by methods described in ENV 13005, ISO 5725 or equivalent
documents. In practice, input data for uncertainty assessment may be obtained from different experimental
sources, e.g. validation studies (comprising laboratory tests, field tests and/or inter-laboratory comparisons) or
QA/QC procedures (including replicate measurements of blank and control samples and certified reference
materials, and calibration procedures).
In this Standard the uncertainty assessment is based on results from laboratory tests that are used to
determine performance characteristics of the method used. The uncertainty assessment is based on Equation
(1) that - in general terms - describes the measurement problem under consideration.
This information is supplemented by results from experiments that were performed in support of the validation
of the Standard Method.
This approach is not meant to exclude evaluations based on data from ongoing QA/QC procedures, field
studies or inter-laboratory comparisons as long as these evaluations are consistent with ENV 13005 and/or
ISO 5725.
5.2 Parameters contributing to measurement uncertainty
5.2.1 Parameters to be assessed and minimum requirements
Based on Eq. (1) the parameters given in Table 1 have been identified to contribute to the uncertainty of
benzene concentrations measured by diffusive sampling and subsequent sample analysis by thermal
desorption and gas chromatography.
For each of these parameters minimum requirements are given; these serve as the basis for the
establishment of ongoing QA/QC programmes : when uncertainties based on these minimum requirements
are calculated, combined and expanded according to the rules given in Annex D, the uncertainties of the
measured concentrations will fulfil the uncertainty requirement of Directive 2000/69/EC.
Table 1 - Uncertainty parameters and minimum requirements
Uncertainty contribution Symbol Section Criterion
Effective uptake rate U D.2 Relative uncertainty ≤ ± 5 %
eff
Sampling time t D.3 Relative uncertainty ≤ ± 0,1%
Conversion to standard D.4 Relative uncertainty ≤ ± 4%
temperature and pressure
Desorption efficiency D D.5 ≥ 98 % at the limit value with a relative
uncertainty of ≤ ± 3%
Mass of benzene sampled m D.6
sam
• Analyte stability A D.6.2 No significant difference between results of
analysis of samples before and after storage
Mass of benzene measured D.6.3
m D.6.3.1 Relative uncertainty ≤ ± 2%
• Mass of benzene in
CS
calibration standards
• Lack-of-fit of calibration F D.6.3.2 Relative residuals over the calibration range
≤ ± 3%; at the limit value ≤ ± 2%
function
d D.6.3.3 ≤ ± 5%
• Response drift between
calibrations
w D.5 ≤ ± 3%
• Analytical repeatability
anal
• Selectivity S D.6.3.4 Resolution factor > 1
Mass of benzene in sample blank m D.7 ≤ 2% of the mass sampled at the limit value
bl
with an uncertainty of ≤ ± 1% of that mass
Between-laboratory uncertainty 5.2.2
5.2.2 Between-laboratory uncertainty
The procedures described in Clause 4 are not restrictive but allow variations in approaches between
laboratories. In a limited series of inter-laboratory comparisons that have been performed within the frame of
the evaluation of the above standard method it has been found that – even for laboratories that on an
individual basis are proficient in the performance of the analysis – significant between-laboratory uncertainties
are found (see Annex E). However, this uncertainty cannot be attributed to a single source, but is the
combination of contributions from several sources.
In principle, this between-laboratory uncertainty needs to be taken into account in order to ensure that
comparable measurement data will be obtained by laboratories using this Standard. This can be achieved by
allowing for individual laboratories only a fraction of the uncertainty requirement of Directive 2000/69/EC (see
Clause D.11).
6 Recommendations for use
An appropriate level of quality control according to EN ISO/IEC 17025 shall be applied. In addition to the
internal quality control measures described in this Standard (purity checks, blank tests and desorption
efficiency tests) the laboratory shall employ external quality control measures (use of reference materials,
participation in inter-laboratory comparisons).
A certified reference material CRM 562 containing 15 µg of benzene per unit is available from IRMM (Institute
of Reference Materials and Measurements of the European Commission Joint Research Centre). Other
reference materials containing benzene at various levels between 0,5 µg and 50 µg per sample certified on
the basis of traceability of preparation are commercially available [13]. These certified reference materials may
be applied on a regular basis for verification of the calibration function and for checking desorption efficiencies.
In order to fulfil the requirements of the EU Air Quality Framework Directive 96/62/EC [2] the laboratories
using this Standard will have to demonstrate to be working in accordance with the requirements of EN ISO
17025. One of the ways of demonstrating compliance with these requirements is through formal accreditation
of the test described by an accreditation body falling under the Multi-Lateral Agreement (MLA) of the
European Cooperation for Accreditation (EA).
Annex A
(informative)
Suppliers of charcoal-based organic vapour diffusive samplers
a
Table A.1 – Suppliers of charcoal based organic vapour diffusive samplers
Analyst sampler Marbaglass S.n.C.
Via Degli Ausoni, 7
I-00185 Rome, Italy
+39 06 4455756
Arelco GABIE sampler Arelco A.R.C.
2 avenue Ernest Renan, 94120 Fontenay-sous-Bois,
France
+33 1 43 94 06 09
Assay Technology 541 sampler Assay Technology,
1252 Quarry Lane, Pleasanton, CA 94566, USA
+1 800 833 1258
Dräger ORSA-5 Drägerwerk Aktiengesellschaft,
Moislinger Allee 53-55
D-23542 Lübeck, Germany
+49 451 882 3873
Perkin-Elmer diffusive tube sampler Perkin-Elmer Ltd
(with charcoal sorbent) Post Office Lane, Beaconsfield, Bucks HP9 1QA, UK
+44 1494 676161
Radiello Fondazione Salvatore Maugeri - IRCCS
Environmental Research Centre, via Svizzera, 16
I-35127 Padova, Italy
+39 0498 064511
SKC Passive sampler 575 SKC Inc
Valley View Road, Box 334,
Eighty Four, PA 15330-9614, USA
+1 800 752 8472
3M Organic Vapour Monitor 3500/3520 3M Occupational Health and Environmental Safety Division
3M Center, Building 0235-02-W-70,
St. Paul, MN 55144-1000, USA
+1 800 243 4630
a
The devices in this table are examples of suitable products available commercially. T
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