100
80
60
40
20
0
10
20
30
40
50
60
Exposure Time (min)
Figure 1. Loss of trichloroethylene from a field sample stored in an uncovered core
barrel liner held in a plastic bag.
tection Agency (U.S. EPA 1986) has recommended
less some additional form of biological preserva-
the use of Methods 5035 and 5021. These new
tion is used. At the time these documents were
methods were published on 13 June 1997 as part
published, two chemical preservation procedures,
of the third update of the Test Methods for Evalua-
MeOH immersion and acidification to a pH of 2
tion of Solid Waste (i.e., the SW-846). The guidance
with sodium bisulfate, received the most attention.
associated with these methods and supporting
Moreover, it was recommended that MeOH pres-
information available from the American Society
ervation be used only when samples were antici-
for Testing and Materials (ASTM) D 4547-98, Stan-
pated to contain concentrations of VOCs in excess
dard Guide for Sampling Waste and Soils for Volatile
of 0.2 mg/kg, and acidification when the concen-
Organic Compounds, address all of the facets of the
trations were expected to be less than this value.
total measurement process from collection to
Once the samples are preserved, the preanalysis
analysis. D 4547-98 is a revision of D 4547-91. A
holding period could be extended up to 14 days
synopsis of the options that are currently recom-
after sample collection. Other means of biological
mended by these guidance documents for sample
preservation, such as lowering the storage tem-
perature to below 0C, although briefly men-
collection and preparation, but not necessarily
preservation, are (1) the immediate in-field trans-
tioned, did not receive as much support as these
fer of a sample into a weighed volatile organic
chemical preservation procedures, because of in-
analysis (VOA) vial that either contains VOC free
sufficient information.
water so that a vapor partitioning (purge-and-trap
The first option described has the field person-
or headspace) analysis can be performed without
nel initiate sample preparation during the collec-
reopening or that contains methanol (MeOH) for
tion activity, and may require that they handle
analyte extraction in preparation for analysis, or
solutions and weigh the sample collection vessels
(2) the collection and up to two-day storage of in-
(Hewitt et al. 1995). The second option, which is
tact samples in airtight containers before initiat-
the focus of this report, allows for the transporta-
ing one of the aforementioned sample preparation
tion and storage of samples, so that preparation
procedures. In both cases samples should be held
can be performed in a laboratory setting. Cur-
at 4 2C while being transported from the sam-
rently, only one device is recommended by more
pling location to the laboratory.
than one of these documents for performing this
The preanalysis holding period associated with
task, i.e., the En Core sampler (En Novative Tech-
these two alternatives is limited to two days un-
nologies, Inc., Green Bay, Wisconsin). This study
2
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