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)

General Information

Status
Published
Publication Date
22-Apr-1997
Current Stage
6060 - Document made available
Completion Date
23-Apr-1997

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SLOVENSKI STANDARD
SIST EN 61619:1998
01-november-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
ICS:
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.

---------------------- Page: 1 ----------------------
NORME
CEI
INTERNATIONALE
IEC
61619
INTERNATIONAL
Première édition
STANDARD
First edition
1997-04
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
chromatography
 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

sous quelque forme que ce soit et par aucun procédé, électronique any form or by any means, electronic or mechanical, including

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
International Electrotechnical Commission 3, rue de Varembé Geneva, Switzerland
Telefax: +41 22 919 0300 e-mail: inmail@iec.ch IEC web site http: //www.iec.ch
CODE PRIX
Commission Electrotechnique Internationale
PRICE CODE V
International Electrotechnical Commission
Pour prix, voir catalogue en vigueur
For price, see current catalogue
---------------------- Page: 2 ----------------------
61619 © IEC: 1997 – 3 –
CONTENTS
Page

FOREWORD .................................................................................................................................. 5

Clause

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

Annexes

A Test mixtures ......................................................................................................... 39

B General informations .............................................................................................. 53

C Bibliography ........................................................................................................... 62

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61619 © IEC: 1997 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
––––––––
INSULATING LIQUIDS –
CONTAMINATION BY POLYCHLORINATED BIPHENYLS (PCBs) –
METHOD OF DETERMINATION BY
CAPILLARY COLUMN GAS CHROMATOGRAPHY
FOREWORD

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

organizations.

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.
---------------------- Page: 4 ----------------------
61619 © IEC: 1997 – 7 –
INSULATING LIQUIDS –
CONTAMINATION BY POLYCHLORINATED BIPHENYLS (PCBs) –
METHOD OF DETERMINATION BY
CAPILLARY COLUMN GAS CHROMATOGRAPHY
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

least).
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

least).
---------------------- Page: 6 ----------------------
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).

---------------------- Page: 7 ----------------------
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

resolution.
6.1.1 Injector
Either an “on-column” injector or a “split/splitless” injector may be used.
---------------------- Page: 8 ----------------------
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

follows:
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.
RAW DATA
INTEGRATED PEAK DATA (AREA OR HEIGHT)
CALCULATE ERRT FOR EACH PEAK
IDENTIFY PEAKS WITHIN WINDOWS
COMPARED TO LIBRARY FILES ALL PROBABLES OR ALL POSSIBLES
CALCULATE PCB CONCENTRATION
FOR EACH PEAK BY THE INTERNAL STANDARD METHOD
SUM PCB CONCENTRATIONS FOR EACH PEAK
TOTAL PCB CONCENTRATION
---------------------- Page: 9 ----------------------
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.
8.3
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
---------------------- Page: 10 ----------------------
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

materials.

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 =
---------------------- Page: 12 ----------------------
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
ng/ml
ng/ml
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.
---------------------- Page: 13 ----------------------
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

elution).

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 (11.7.2.2) 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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