Method Statement PAHs by GC/FID
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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 polyaromatic
hydrocarbons (PAHs) in soils and waters by solvent
extraction/concentration followed by analysis of extracts by gas
chromatography with flame ionisation detection (GC/FID).
Principle
Target PAHs are extracted from an aliquot of the test sample with
dichloromethane (in triplicate). An activated silica gel
chromatographic stage then separates the PAHs from other co-extracted
polar and non-polar species (e.g. NSO's and aliphatic hydrocarbons).
The purified extracts are then concentrated and analysed by GC/FID.
Soil samples
0.1 to 10 g aliquots of dried and ground samples are taken then
extracted by sonication with three lots of dichloromethane. The three
extracts are combined and reduced in volume to circa 1 ml before
passage through an activated silica chromatography stage. The PAHs
are eluted in the second fraction from this column. This fraction is
then reduced in volume to 1 ml for analysis by GC/FID.
Water samples
10ml to 1l aliquots of the shaken sample are taken then extracted
by liquid/liquid techniques with dichloromethane. The extracts are
combined then passed through the same clean up/analysis procedure as
for the soils.
Performance
Characteristics
Substances Determined
This method is suitable for the analysis of the 'EPA 16' PAHs.
These are naphthalene, acenaphthene, acenaphthylene, fluorene,
phenanthrene, anthracene, pyrene, fluoranthene, chrysene, benz(a)
anthracene, benzo(b)/(k) fluoranthene, benzo(a)pyrene,
dibenz(ghi)perylene, indeno(1,2,3,-cd)pyrene and dibenz(a.h)
anthracene. Other PAHs may be determined by the method provided
suitable standards and validation have been performed. It should be
noted that the FID detector is not specific for PAHs and therefore
false positives are possible as identification is based upon the
selective clean up and retention time only.
Range of Application
Limit of Detection
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
40 CFR Part 126:
Guidelines establishing test procedures for the analysis of
pollutants under the clean water act. Section Method 610 –
Polynuclear Aromatic Hydrocarbons.
P.W. Brooks et.al. Org.
Geochemistry. Vol. 12, No. 6 pp519-538 1988.
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