Method Statement PCBs by GC/MS
@(#) Uncontrolled Document pcb.html Version 1.1 Last
Revised on 12/09/02
Contents
Introduction
Principle
Performance
Characteristics
Range
of Application
Limit of
Detection
Analytical
Quality Control
References
Introduction
The performance of this method is validated in accordance with
internationally recognised procedures.
This procedure describes the determination of target
polychlorinated biphenyls (PCBs) in soils and waters by solvent
extraction/concentration followed by analysis of extracts by gas
chromatography with mass spectrometeric detection (GC/MS).
Quantitation is based upon the addition of stable isotopically
labelled internal standards added to the sample prior to extraction.
Principle
Target PCBs are extracted from an aliquot of the test sample with
dichloromethane (in triplicate), after the addition of a mixture of
carbon 13 labelled PCBs to the test sample. The extracts are then
combined and reduced in volume to 1ml. The extracts are then analysed
by GC/MS in the selected ion recording mode. This is normally
performed at a mass resolution of 5000 (10% valley definition). Clean
up and fractionation may be necessary for some samples and/or target
suites (e.g. WHO12).
Soil samples
0.1 to 10 g aliquots of dried and ground samples are spiked with
labelled internal standards then extracted by sonication with three
lots of dichloromethane. The three extracts are combined and reduced
in volume to circa 1 ml. The PCBs are then analysed by GC/MS.
Water samples
10ml to 1l aliquots of the shaken sample are taken then extracted
by liquid/liquid techniques with dichloromethane, after addition of
labelled internal standards. The extracts are combined then analysed
as for the soils.
Performance
Characteristics
Substances Determined
This method is suitable for the analysis of specific PCB
congeners, or 'totals'. Totals are normally defined by this method as
the sum of all tri-heptachlorinated congeners. This measures some 180
of the 209 possible congeners. Commonly requested suites are the
'ICES7' congeners (consisting of PCB #s 28,52,101,118,138,153,180)
and the 'WHO12'. Other PCBs may be determined by the method provided
suitable standards and validation have been performed.
Range of Application
Limit of Detection
Soils 0.01-0.1 ug/kg
Waters 0.001-0.05 ug/l
Analytical Quality
Control
Analytical quality control is maintained by a number of measures:
Multi-point calibration with
authentic standards (with defined minimum performance
characteristics)
Analysis of control samples within
each analytical batch, such as independent standards, matrix spikes
or reference materials
Analysis of reagent/method blanks
within each analytical batch
Ongoing quality assured by the use
of control charts in conjunction with warning and action limits for
the QC sample data
Participation in external
proficiency testing and interlaboratory schemes such as LGC CONTEST,
HSE WASP, CSL FAPAS
References
US EPA Method 8270,
Revision C, Semivolatile Organic Compounds by Gas Chromatography –
Mass Spectrometery (GC/MS).
‘Background Levels
of Polychlorinated Biphenyls in British Soils - II’,
Chemosphere, 19, 1457-1466 (1989).
US EPA Method 8082
‘Polychlorinated Biphenyls (PCBs) by Gas Chromatography.
‘Analysis of
Polychlorinated Biphenyls (PCB) by Glass Capillary Chromatography -
Composition of Technical Aroclor- and Clophen-PCB Mixtures’,
Fres. Zeit. fur Anal. Chem. 302, 20-31.
US EPA Method 1668, -
“Revision A: Chlorinated biphenyl congeners in water, soil,
sediment, and tissue by HRGC/HRMS”, 1999.
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