Insulating liquids - Contamination by polychlorinated biphenyls (PCBs) - Method of determination by capillary column gas chromatography

Specifies a method for the determination of polychlorinated biphenyl (PCB) concentration in non-halogenated insulating liquids by high-resolution capillary column gas chromatography using an electron capture detector (ECD). Gives total PCB content; especially useful when a detailed analysis of PCB congeners is necessary.

Isolierflüssigkeiten - Verunreinigung durch polychlorierte Biphenyle (PCBs) - Verfahren zur Bestimmung mittels Kapillar-Gaschromatographie

Isolants liquides - Contamination par les polychlorobiphényles (PCB) - Méthode de détermination par chromatographie en phase gazeuse sur colonne capillaire

Spécifie une méthode de détermination de la concentration des polychorobiphényles (PCB) dans les liquides isolant non halogénés, par chromatographie en phase gazeuse sur colonne capillaire à haute résolution utlisant un détecteur à capture d'électrons (ECD). Donne la teneur totale en PCB et est particulièrement utile quand une analyse détaillée des conénères des PCB est nécessaire.

Insulating liquids - Contamination by polychlorinated biphenyls (PCBs) - Method of determination by capillary column chromatography (IEC 61619:1997)

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SIST EN 61619:1998
Insulating liquids - Contamination by polychlorinated biphenyls (PCBs) - Method
of determination by capillary column chromatography (IEC 61619:1997)
Insulating liquids - Contamination by polychlorinated biphenyls (PCBs) - Method of
determination by capillary column gas chromatography
Isolierflüssigkeiten - Verunreinigung durch polychlorierte Biphenyle (PCBs) - Verfahren
zur Bestimmung mittels Kapillar-Gaschromatographie
Isolants liquides - Contamination par les polychlorobiphényles (PCB) - Méthode de
détermination par chromatographie en phase gazeuse sur colonne capillaire
Ta slovenski standard je istoveten z: EN 61619:1997
29.040.10 Izolacijska olja Insulating oils
SIST EN 61619:1998 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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Première édition
First edition
Isolants liquides –
Contamination par les polychlorobiphényles (PCB) –
Méthode de détermination par chromatographie
en phase gazeuse sur colonne capillaire
Insulating liquids –
Contamination by polychlorinated biphenyls (PCBs) –
Method of determination by capillary column gas
 IEC 1997 Droits de reproduction réservés  Copyright - all rights reserved
Aucune partie de cette publication ne peut être reproduite ni utilisée No part of this publication may be reproduced or utilized in
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ou mécanique, y compris la photocopie et les microfilms, sans photocopying and microfilm, without permission in writing from
l'accord écrit de l'éditeur. the publisher
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Telefax: +41 22 919 0300 e-mail: IEC web site http: //
Commission Electrotechnique Internationale
International Electrotechnical Commission
Pour prix, voir catalogue en vigueur
For price, see current catalogue

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61619 © IEC: 1997 – 3 –
1 Scope and object. 7
2 Normative reference. 7
3 Definitions. 7
4 Principle. 9
5 Reagents and auxiliary materials . 9
6 Apparatus . 13
7 Sample . 17
8 Chromatograph operating conditions . 17
9 Data-processing system . 19
10 Checks of instrumental performance. 21
11 Procedure . 25
12 Test report . 35
13 Detection limit . 35
14 Precision. 37
A Test mixtures . 39
B General informations . 53
C Bibliography . 62

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61619 © IEC: 1997 – 5 –
1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of the IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, the IEC publishes International Standards. Their preparation is
entrusted to technical committees; any IEC National Committee interested in the subject dealt with may
participate in this preparatory work. International, governmental and non-governmental organizations liaising
with the IEC also participate in this preparation. The IEC collaborates closely with the International Organization
for Standardization (ISO) in accordance with conditions determined by agreement between the two
2) The formal decisions or agreements of the IEC on technical matters express, as nearly as possible, an
international consensus of opinion on the relevant subjects since each technical committee has representation
from all interested National Committees.
3) The documents produced have the form of recommendations for international use and are published in the form
of standards, technical reports or guides and they are accepted by the National Committees in that sense.
4) In order to promote international unification, IEC National Committees undertake to apply IEC International
Standards transparently to the maximum extent possible in their national and regional standards. Any
divergence between the IEC Standard and the corresponding national or regional standard shall be clearly
indicated in the latter.
5) The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with one of its standards.
6) Attention is drawn to the possibility that some of the elements of this International Standard may be the subject
of patent rights. The IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 61619 has been prepared by technical committee 10: Fluids for
electrotechnical applications.
The text of this standard is based on the following documents:
FDIS Report on voting
10/379/FDIS 10/408/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
Annex A forms an integral part of this standard.
Annexes B and C are for information only.

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61619 © IEC: 1997 – 7 –
1 Scope and object
This International Standard specifies a method for the determination of polychlorinated
biphenyl (PCB) concentration in non-halogenated insulating liquids by high-resolution capillary
column gas chromatography using an electron capture detector (ECD).
The method gives the total PCB content and is especially useful when a detailed analysis of
PCB congeners is necessary. Other methods, such as IEC 60997, may be used when a less
detailed analysis is acceptable.
The method is applicable to unused, reclaimed (including dechlorinated and chemically and/or
physically treated), or used insulating liquids contaminated by PCBs.
2 Normative reference
The following normative document contains provisions which, through reference in this text,
constitute provisions of this normative document. At the time of publication, the edition
indicated was valid. All normative documents are subject to revision, and parties to agreements
based on this International Standard are encouraged to investigate the possibility of applying
the most recent editions of the normative document indicated below. Members of IEC and ISO
maintain registers of current valid International Standards.
IEC 60475: 1974, Method of sampling liquid dielectrics
3 Definitions
For the purposes of the International Standard, the following definitions apply:
3.1 Polychlorinated biphenyl (PCB)
A biphenyl substituted by one to ten chlorine atoms.
NOTE – For legal purposes, congeners with one, two or ten chlorine atoms may be excluded from this definition.
3.2 Congener
All the chlorine derivatives of biphenyl, irrespective of the number of chlorine atoms, are
termed congeners.
NOTE – There are 209 possible PCB congeners.These are listed in table B.1. The congener numbers (IUPAC)
are for easy identification; they do not represent the order of chromatographic elution.
International Union of Pure and Applied Chemistry.

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61619 © IEC: 1997 – 9 –
4 Principle
The PCB congeners are determined by temperature programmed gas chromatography. The
chromatograph uses a high-efficiency capillary column to separate the PCBs into single or
small groups of overlapping congeners.
The sensitivity of the electron capture detector (ECD) may be reduced by the presence of
mineral oil. In this method the sample is diluted 100 times to reduce this effect to a minimum.
A sample preparation (clean-up) procedure is used to remove most of the impurities likely to
interfere with the determination.
Reference compounds are included to enable calculation of experimental relative retention
times (ERRTs) which are compared to a data file of peak ERRTs to identify individual or groups
of unresolved congeners. An internal standard is added for quantification.
Relative response factors (RRF), taken from the data files (9.1), corrected by experimental
relative response factors (ERRFs) obtained from reference compounds, are applied to
identified peaks to quantify the individual (or groups of) congeners, and the values summed to
give total PCB content.
5 Reagents and auxiliary materials
5.1 Reagents and standards
All reagents and materials, including those for clean-up, shall be free from PCB contamination
and compounds responding to the ECD.
5.1.1 Solvent
Hexane, heptane, cyclohexane or isooctane (2,2,4-trimethylpentane), high purity, free from
PCB contamination and low in compounds that respond to the ECD.
5.1.2 Hexachlorobenzene
Purity 99 % at least, used for checking detector sensitivity.
5.1.3 Insulating liquid
An insulating liquid, checked to be free from PCBs or other interfering substances, of the same
type as is present in the sample.
5.1.4 Congener 30 solution (C 30)
10 mg/l in solvent (5.1.1) purchased in solution or prepared from pure material (purity 99 % at
5.1.5 Congener 209 (DCB), decachlorobiphenyl solution
10 mg/l in solvent (5.1.1) purchased in solution or prepared from pure material (purity 99% at

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61619 © IEC: 1997 – 11 –
5.1.6 Calibration solution of selected PCB congeners
Certified calibration mixture in solvent (5.1.1) containing at least the following PCB congeners
at a concentration of 10 mg/l each: 18, 28, 31, 44, 52, 101, 118, 138, 149, 153, 170, 180, 194
and 209 (see B.3).
5.2 Commercial PCB standards (see B.4)

5.2.1 Solutions of Aroclors 1242, 1254 and 1260 in solvent (5.1.1)
Concentration required 50 mg/l or more, typically 1000 mg/l.

5.2.2 Solutions of Aroclors 1242, 1254 and 1260 in oil

50 mg/kg solutions of Aroclors 1242, 1254 and 1260 in unused insulating liquid, either
purchased as standardized solutions or prepared from pure material.
5.3 Gas chromatography gases
5.3.1 Carrier gas: helium or hydrogen, purity 99,99 % at least.
5.3.2 Make-up gas: argon/methane, 95% 5%. Alternatively, 99,99 % minimum purity
nitrogen can be used.
5.4 Internal standard/reference solutions
NOTE – Standards should be stored in a cool, dark place.
5.4.1 Internal standard solution 2 (IS 2)
2 mg/l C209 (DCB), 2 mg/l C30.
Pipette (5.8.3) 5 ml of DCB solution (5.1.5) and 5 ml C30 solution (5.1.4) into a 25 ml
volumetric flask, make up to the mark with solvent (5.1.1).
5.4.2 Internal standard solution 0,5 (IS 0,5)
0,5 mg/l C209 (DCB), 0,5 mg/l C30.
Follow 5.4.1 using a 100 ml volumetric flask.
5.5 Test mixture solution (for system evaluation)

Into a 20 ml volumetric flask: weigh, to the nearest 0,001 g, 0,50 g of 50 mg/kg Aroclor 1260,
 
plus 0,50 g of 50 mg/kg Aroclor 1254 plus 1,00 g of 50 mg/kg Aroclor 1242 solutions in
insulating liquid (5.2.2).
Add by pipette 1 ml of IS 2 solution (5.4.1) and make up to volume with solvent.
Prior to use this solution shall be treated as per 11.1.3.
5.6 Calibration – congener mix stock solution
Into a 20 ml volumetric flask: weigh, to the nearest 0,001 g, 2,0 g of insulating liquid (5.1.3) and
add 1 ml of the calibration PCB congener mix (5.1.6). Make up to the mark with solvent (5.1.1).

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61619 © IEC: 1997 – 13 –
5.7 Congener mix calibration solution (for response factors)
Submit 500 μl of solution (5.6) to the clean-up (11.1.3). The final solution is suitable for the
determination of relative factors.
Prepare a fresh solution monthly.
5.8 Glassware
5.8.1 Volumetric flasks 100, 50, 25, 10 and 5 ml (tolerance better than ± 0,4%)
5.8.2 Syringes and pipettes:
500 μl ± 5 μl syringe or pipette,
1 μl and 5 μl gas chromatography precision syringes.
5.8.3 Bulb pipettes (volumetric) 1, 2 and 5 ml class A
5.9 Columns and accessories for sample preparation
5.9.1 Commercial or self-packed solid-phase extraction columns:
3 ml silica gel column, adsorbent weight 500 mg, particle size 40 μm,
3 ml benzenesulphonic acid column, adsorbent weight 500 mg, particle size 40 μm.
5.9.2 Column adapter, for joining two columns
5.9.3 Vacuum manifold column processor – optional
6 Apparatus
6.1 Gas chromatograph (GC)
A high-resolution gas chromatograph with accurately reproducible oven temperature control,
capable, when used with the appropriate column and conditions, of resolving the test mixture
(5.5) at least as well as in figure A.1 (90 peaks observed) and of reproducing relative retention
times to within ± 0,0015.
The gas lines (carrier gas and make-up gas) shall be fitted with water vapour and oxygen traps.
The carrier gas supply system shall be capable of running with a 50 m column at maximum
efficiency using He or H carrier gas, e.g. adequate column head pressure.

The oven temperature programmer shall have a range that can be set to attain the required
6.1.1 Injector
Either an “on-column” injector or a “split/splitless” injector may be used.

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61619 © IEC: 1997 – 15 –
6.1.2 Columns
Either a cross-linked 5 % phenyl-methyl silicone, stationary phase coated onto fused silica
capillary column or a similar chemically bonded phase column. Their dimensions shall be as
length = 50 m to 60 m;
internal diameter = 0,2 mm to 0,35 mm;
film thickness = 0,1 μm to 0,25 μm.
NOTE – For suitable columns and manufacturers see B.2.
6.1.3 Detector
High-temperature Ni 63 electron capture detector (ECD) with adequate sensitivity to give a
signal-to-noise ratio greater than 20 for one picogram of hexachlorobenzene (5.1.2) injected
into the column.
The detector shall be operated within its linear range.
6.2 Data-processing system
Any data-processing system may be used with suitable software that can be programmed to
process the operations shown below.







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61619 © IEC: 1997 – 17 –
7 Sample
7.1 Sampling
Sampling shall be made in accordance with procedures described in IEC 60475.
To avoid cross-contamination of the samples, it is recommended that all the auxiliary material
used (tubing, fittings, corks, connections, etc.) be disposable (single-use) and free from
interfering compounds.
7.2 Sample preparation
Only glass or metal apparatus is suitable for sample preparation and the determination except
for disposable pipette tips and columns made of plastic. All equipment shall be free from PCBs
and interfering substances.
If the samples have a free-water phase, it shall be separated from the oil phase prior to further
analysis, for example by centrifuging. Emulsified water perceived as opacity can be removed by
adding sodium sulfate in portions and shaking until a clear sample is obtained.
The sample should be homogenized, e.g. by shaking the sample by hand for 3 min. An
ultrasonic bath may also be used for this purpose.
8 Chromatograph operating conditions
8.1 General
The operating conditions given below have been found to be adequate but they should be
optimized with each GC system so that gas chromatograms similar to the one shown in annex
A can be obtained from dilutions of the test mixture in 5.5. Using hydrogen as carrier gas, a
satisfactory separation will be obtained in 30-40 min (figure A.1). With helium carrier gas, the
separation will take longer, 55-60 min.
8.2 Injectors
Set up the injector according to the manufacturer's instructions. Typical settings for this
analysis are as follows:
Split/splitless injector
Splitless mode: T = 240 °C to 280 °C
Split mode: T = 250 °C to 280 °C, split ratio = 5:1 to 50:1
On-column injector: T = 50 °C to 110 °C according to the solvent used.
Oven temperature program
Injector mode Split Splitless On-column
Initial isothermal period 0 – 2 min 1 min 0,5 min
Initial temperature 130 °C 50 °C 70 °C
Temperature program 130 °C to 290 °C 50 °C to 130 °C 70 °C to 130 °C
at 2,5 °C/min at 40 °C/min at 40 °C/min
130 °C to 290 °C 130 °C to 290 °C
at 2,5 °C/min at 2,5 °C/min
Rest time to final temperature 5 min 5 min 5 min
Cool down to 130 °C 50 °C 70 °C

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61619 © IEC: 1997 – 19 –
8.4 Carrier gas flow rate
Adjust inlet pressure to give a flow rate through the column of 1 ml/min at 130 °C, e.g. 270 kPa
for He.
NOTE – Hydrogen carrier gas is effective in reducing column pressure head and analysis time
8.5 Electron capture detector (ECD) settings
Temperature: 300 °C to 350 °C.
Electrical control: use manufacturer’s recommended settings to give the best conditions
for linearity of the detector.
Make-up gas, flow rate: 20 ml/min to 50 ml/min, according to manufacturer's recommendations.
9 Data-processing system
The system should be prepared in readiness for the start according to the manufacturer's
instructions. Most systems require designation of a minimum of two reference points including
the internal standard DCB.
9.1 Data files
The method requires data files containing experimental data (ERRT) and data originating from
the literature. For each peak of single or coeluting congeners the following data is filed in order
of increasing ERRT (see table A.1):
experimental relative retention time (ERRT);
congener numbers;
relative response factors (RRFs).
Two sets of RRFs based on data originating from [4] are provided in table A.1. A weighted
average response factor was calculated for each peak containing coeluting congeners using
the relative proportions of the congeners found in commercial mixtures using data from [5], [6]
and [7].
"All probable"
Some congeners have never been observed in commercial PCB mixtures. So, in those cases
where more than one congener co-elutes under one chromatogram peak, the RRF of the group
of congeners is weighted by exclusion of congeners not found in commercial mixtures. Use this
data set with unknowns and mixtures of commercial products.
"All possible"
This class includes all 209 PCB congeners. This data set is included for use with dechlorinated
Table A.1 shows that where there is no co-elution (for example peak n° 48) the RRF of each
set has the same value and where there is co-elution (for example peak n° 49) there are
different values for the different sets.
RRFs in table A.1 are corrected for the instrument being used by the calibration procedure in
clause 11.
Figures in square brackets refer to the bibliography given in annex C.

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61619 © IEC: 1997 – 21 –
9.2 Co-eluting congeners
More than one congener may co-elute under a single peak, the programme should group peaks
together if they fall within the window of ± 0,0015 from the RRT. See table A.2 for individual
congener RRTs and elution order.
10 Checks of instrumental performance
When initially implementing this method and after major repairs and replacement of critical
instrumentation components (specifically EC detector and GC column), each laboratory that
uses this method shall operate a performance control programme. This should include
verification of sensitivity, resolution and linearity range. It is recommended to monitor the
performance routinely at appropriate time intervals.
10.1 Sensitivity check
The ECD shall have sufficient sensitivity to give a signal-to-noise ratio (S/N) greater than 20 for
one picogram of hexachlorobenzene injected into the column.
10.2 Linearity check
The response of the electron capture detector is proportional to the quantity of PCBs injected
only within a limited range; if the quantities of PCBs passing through the detector become
excessive, the response will cease to be linear. Determine the linear range as follows:
10.2.1 Use the stock solution of selected PCB congeners (5.6). Dilute the solution with
solvent (5.1.1) containing 100 mg/ml of insulating liquid (5.1.3) in suitable steps e.g. 1, 2, 5, 20,
50, 100 dilution. Submit 500 μl of each solution to the clean-up procedure (11.1.3) and add
10 μl of C30 solution (5.1.4) to the 5 ml collecting flask before making up to the mark with
solvent. The final dilutions are now, e.g. 10, 20, 50, 200, 500, 1 000. Each solution contains
20 ng/ml C30 and the eluate from 10 mg/ml insulating liquid. Inject a suitable quantity (the
same each time) into the GC according to the injection system using the chromatographic
conditions in clause 8.
10.2.2 The use of congeners 31, 118 and 180 that are present in major proportions in
commercial mixtures plus the internal standard C209 (DCB) is recommended.
Measure the peak area or height (R ) for the specified congeners 31, 118, 180 and 209 and
calculate the concentration (
B ) of each congener in ng/ml for each dilution.
Use the area or height of the C30 peak to check that the correct volume has been injected. The
area/height of the C30 peak for the series of injections shall not vary by more than ± 5 % of the
average for that series of injections. Tests that fall outside of this range shall be repeated.
Calculate the sensitivity factor S for each congener and each dilution:
S =

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61619 © IEC: 1997 – 23 –
Plot S versus B (see figure 1).
j j
IEC  303/97
Figure 1 – Linearity check
10.2.3 The linearity plot is a line through the data points (figure 1). This line must be within
5 % of the constant value obtained by a least square fit. The upper limit of the linear range is
the point where the plot crosses the – 5 % envelope and the lower limit level is where the line
crosses the + 5 % envelope. The linear range of the detector is defined in figure 1.
10.2.4 Relating the linear range of the ECD to amounts of commercial mixtures. The maximum
amounts of commercial mixture that may be injected to ensure they fall within the linear range
of the detector may be calculated from the respective congener (see table 1).

Table 1 – Typical amounts of the major congeners in Aroclor mixtures
 
Congener Congener
Aroclor Arocolor
number concentration
solutions concentration
1242 500 31 23
1254 500 118 32
1260 500 180 36
NOTE – The concentrations are approximate; a solution containing
 
500 ng/ml of Aroclor is a 1 in 100 solution of a 50 mg/l Aroclor standard.
10.3 Resolution check
Treat 500 μl of solution (5.5) as per 11.1.3. Using optimised chromatographic parameters,
inject a suitable aliquot in the linear range of the ECD.

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61619 © IEC: 1997 – 25 –
Calculate the resolution (R) for the pairs of congeners C28/C31 and C141/C179 (identified as
in figure A.1). Resolution R is expressed as the ratio of the distance between the maxima of
the peaks to the average of their peaks width at the base using the formula:
R = 2 Δt/(y + y )
a b
The resolution shall be at least:
28/31 0,5
141/179 0,8
2 tΔ
R =
y + y
IEC  304/97
Providing the resolution is satisfactory, this chromatogram can be used for the determination of
ERRTs (11.4).
11 Procedure
Safety precautions
Exercise normal laboratory safety precautions, wear gloves, impervious to mineral oil and light
hydrocarbon solvents. Use only small quantities of flammable solvents on the workbench;
handle larger volumes in a fume cupboard.
Ensure proper handling and disposal of PCB’s and PCB contaminated equipment according to
local regulations.
11.1 Sample treatment (clean-up)
11.1.1 Test portion
Weigh to the nearest 0,001 g, 0,9 g to 1,0 g of the test sample into a 10 ml volumetric flask.
Add 1 ml, by pipette (5.8.3) of internal standard solution IS 2 (5.4.1) or IS 0,5 (5.4.2). Make up
to the mark with solvent (5.1.1). Shake well to mix. If the sample is obviously wet, shown by the
opacity of the solution, add anhydrous sodium sulphate and shake until a clear solution is
obtained. This solution is designated solution A.
NOTE – For samples of unknown PCB content, use IS 2 (5.4.1). For better accuracy, IS 0,5 is preferred for
samples with expected PCB content less than 20 mg/kg.

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61619 © IEC: 1997 – 27 –
11.1.2 Solid-phase column preparation
Attach the sulphonic acid column (5.9.1) to the top of the silica gel column (5.9.1) using an
adapter (5.9.2).
Elute the column assembly three times with 2 ml of the solvent (5.1.1) in order to purify the
stationary phase. Do not allow the adsorbent to dry at this stage.
11.1.3 Clean-up procedure
Transfer 500 μl ± 5 μl of solution A (11.1.1) onto the top of the sulphonic acid upper column.
Add 0,5 ml solvent and apply a slight vacuum to distribute the sample evenly over the packing
of the upper column. Wait at least 30 s before elution.
The elution shall be carried out at a maximum flow rate of 2 ml/min and the columns eluted
each time until the solvent level is just above the top of the adsorbent (except for the final
Elute the column combination twice with 1 ml aliquots of solvent (5.1.1) collecting the eluate in
a 5 ml volumetric flask. Remove the sulphonic acid upper column and the adapter and elute the
silica gel column twice with 0,5 ml of solvent, collecting the eluate in the same volumetric flask.
Dilute to the volume mark with solvent (5.1.1); shake well to mix. This solution is designated
solution B and used for GC analysis.
For some samples additional clean-up techniques may be necessary (see B.5).
11.1.4 Recovery

Dilute an Aroclor solution (5.2.1) in solvent (5.1.1) to obtain a concentration of 5 mg/l.
This solution is designated solution C.
Run a 500 μl aliquot of solution C through the clean-up procedure (11.1.3). The 5 ml eluate
obtained is designated solution D.
Dilute 500 μl of solution C to 5 ml with solvent (5.1.1) to give a concentration of 0,5 mg/l

Aroclor . This solution is designated solution E.
Add 50 μl internal standard solution IS2 (5.4.1) to solution D (from clean-up) and to solution E.
Inject solutions D and E into the GC and obtain a chromatogram and area table for each

solution. Calculate the total amount of PCB for the Aroclor in each solution using the internal
standard method ( and calculate the recovery as follows:
Total PCB content (mg) solution D
% recovery=× 100
Total PCB content (mg) solution E
The calculated recovery shall be greater than 95 %.

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61619 © IEC: 1997 – 29 –
11.1.5 Commercial PCB standards
50 mg/kg commercial mixtures of PCBs in oil are used (5.2.2). If a standard of lower
concentration is required, this is prepared by diluting (by weight) with unused PCB-free
insulating liquid.
Commercial PCB standards are treated the same as the samples (11.1) and submitted to the
clean-up procedure.
11.2 Background check
Run each new batch of solvent and a blank prepared with PCB-free insulating liquid (5.1.3) as
per 11.1 through the GC to ensure that there are no spurious peaks.
A blank test portion should be run with every batch of samples and at least every 20 samples.
11.3 Determination
11.3.1 Sample and commercial PCB standard solutions, solution B (11.1.3) are injected into
the GC. The GC is run under optimized conditions (clause 8).
11.3.2 Commercial PCB standards are run with every batch of samples, at least once every
10 samples. Choose standards appropriate to the samples; typically run 10 mg/kg and

50 mg/kg standards of Aroclor 1260 in oil, (this is the

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