Schedule B3 - COAG Standing Council on Environment and Water

The removed material (including the materials retained on the sieve) should be labelled and
retained for possible future analysis.
5.1.2 Homogenising (for non-volatile constituents)
Samples for analysis of volatile contaminants should not be homogenised by stirring, grinding
or sieving. Procedures applicable to volatile analytes are described below.
To minimise the amount of reagents used and waste produced, most analytical methods require
analysis of only a portion of the sample, sufficient to provide a quantifiable response. The
amount of sample received by the laboratory is usually larger than required for a single
determination and any additional analyses for QA purposes.
Depending on the analyses required (excluding volatile analysis), a homogeneous test sample is
prepared from either the field-moist (i.e. ‘as received’) or dried sample. The analysis portions
are then taken from this test sample.
The sub-sample taken should comprise at least 25% by weight or 200 g of the sample received
by the laboratory (laboratory sample), whichever is the smaller. It must be thoroughly
disaggregated and mixed using a mortar and pestle or other appropriate apparatus. The entire
sample may be homogenised but only if no test requiring the original, untreated sample will be
needed. Further, it is advisable to keep a portion in the ‘as received’ state to check, if necessary,
that no contamination has occurred during the homogenising process. Described below are the
pre-treatment procedures to obtain homogenised field-moist and dry analysis portions.
5.1.3 Preparation of field-moist (‘as received’) analysis portions
In general, soils to be tested for organic analytes, especially rapidly degradable or otherwise
labile contaminants, should not be dried but should be analysed in a field-moist state. Where an
excessive amount of moisture can affect the extraction efficiency, the sample may be ’dried' by
mixing the analysis portion with anhydrous sodium sulfate or magnesium sulfate prior to
extraction (US EPA SW-846, Method 3540C).
Field-moist samples will often not be amenable to mechanical grinding or sieving. For those
samples which are amenable to this, and for which non-volatile analytes are to be determined,
at least 25% by weight or 200 g of the laboratory sample, whichever is the smaller, should be
thoroughly ground and mixed by hand, in a mortar and pestle, to obtain a homogeneous subsample.
For most metals and inorganics, better analytical reproducibility is obtained using air-dried soil.
However, if the sample is to be analysed for these analytes in the field-moist state and if it is
amenable to sieving, for example, sandy loam, it should also be passed through a 2 mm plastic
sieve. Ensure that there are no solid particles distinctly different from the soil; for example,
fragments of metal or coloured particles of an unusual nature. If this is the case, the sample
must be analysed in the air-dried state and pre-treated as described below.
Store the treated sample in a suitable container.
All equipment must be cleaned in a way to minimise sample cross-contamination; this can be
confirmed by analysing equipment rinsates and/or control samples.
5.1.4 Preparation of dry analysis portions (non-volatiles only)
Air-drying helps to give a representative analysis portion by producing samples amenable to
grinding, sieving and splitting. However, air-drying may modify the chemical form of some
species and hence affect the results obtained (Adam et al. 1983, Bartlett et al. 1980, Harry et al.
1981, Khan et al. 1978, Leggett et al. 1985, Specklin et al. 1989).
<strong>Schedule</strong> <strong>B3</strong> - Guideline on laboratory analysis of potentially contaminated soils 15