Presampling - Field Sampling: Principles and Practices in Environmental Analysis - page 52

equipment, including any needed chemicals. Note that chemical storage must be well
separated from sample storage to prevent cross-contamination. Any storage building
designated for chemicals needs to have ventilation and an explosion-proof fan for moving
air through and removing fumes.
In a rural or farming-type setting buildings may already be at the field and available for
use. Such buildings may already have electricity, water, and bathroom facilities and be
suitable for use as the office and field laboratory. However, it is preferable to have a
separate sample storage building. Farm buildings are used to store all manner of
chemicals, from fertilizers to pesticides to antibiotics to disinfecting chemicals. Fumes
from any of these sources can be absorbed by field samples, contaminating them and
causing complications in analytical procedures later. This could result in the analytical
results showing contamination that is not in the field but is actually in the storage
building. In a worst-case situation a recomendation may be made for a field to be
remediated for a contaminant that it does not contain.
The importance of a separate room that has never been used before for sample storage
cannot be overemphasized. Even if a room or building has been thoroughly cleaned and
has no smell or other evidence of contamination it can still be there. Colorless and
odorless contamination can be contained in cracks and dust in the walls, floor, and ceiling
and can be just as detrimental to samples as any other contamination.
3.2. FIELD OFFICE LABORATORY
Many field sampling situations will call for setting up a small laboratory at the field
office. This should not be a table in a corner of a busy area or where samples for
shipment to commercial analytical laboratories are stored. This is an area that needs to be
in its own room with running water, electricity, an explosion-proof exhaust fan, and
sufficient bench space to allow for setting up instruments and working with samples.
The laboratory will be provided with a minimal amount of common laboratory
equipment. Any work done in any laboratory will require purified water, which can either
be distilled in the laboratory or purchased. Another source is water that has gone though
several ion exchangers and reverse osmosis processes and is called deionized (DI) water.
Distillation equipment is usually bought, while DI/reverse osmosis equipment can be
rented. This water will be used for preparing solutions and for final cleaning of
glassware.
Soil samples will require drying and sieving. Drying is usually done by placing a thin
layer of the soil sample on a clean surface, such as a piece of plastic, and allowing it to
air dry. It will always be more convenient to dry the sample using an oven.
Unfortunately, drying a soil sample at even slightly elevated temperatures causes
irreversible changes, thus soil samples should never be mechanically dried before
analysis.
In most cases a #10 and #200 sieve will be sufficient for most sieving needs. It is good
to have a receiving can or pan to place under the sieve to catch sieved material. Typically
sieves are constructed of brass with soldered-in mesh. This means that sieved samples
can pick up metals such as copper, zinc, lead, and silver during sieving. Stainless steel