Sample Transport and Storage - Field Sampling: Principles and Practices in Environmental Analysis - page 202

this regard, some method of making the sample containers tamper-proof should be found.
One approach to this problem is to use fragile labels that are applied to a sample
container when filled out, so that tampering will damage them. If the individual
containers are not made tamper-proof, boxes or other containers of lots of samples can be
made tamper-proof by the use of seals or locks that indicate when they have been opened.
Another area of security is that the sample numbers be secure so that a sample can
always be identified. Sample identification numbers must be placed on the containers in
such a way that they cannot be erased or removed. Sometimes a little thought beforehand
is helpful in avoiding the loss of numbers. Labels inside a sample container with the
sample are not recommended in any case because they are a source of contamination and
often decompose (e.g., paper labels placed inside containers of moist soil will often
degenerate in several days). Under certain conditions labels on the outside can also be
lost. For instance, labels placed on the outside of soil drying cups often fall off during
drying. Lot containers, however, such as coolers used for shipping samples, will have
labels and other paperwork inside them. These are sealed in plastic bags and do not come
in contact with the samples.
There are several ways to avoid many labeling problems. Choose labels with high-
quality adhesive and write on them with indelible, nonsmearing ink. Place labels on areas
of the sample container that will receive little or no abrasion. One interesting place for a
label is on the bottom of sample bottles or containers. Often the middle of the bottle
bottoms are indented, and thus not subject to abrasion. A second reason this is a good
place is that dirty, wet fingers, water, and solvents can get on the top and sides of bottles
but often do not reach bottle bottoms. Some sample bags have fold-over tops secured by
tabs. The folded area is a good place to put a sample label. A third approach is to use
permanent markers to directly mark the sample container.
Samples must be secure from pests. During transport and storage in the field, samples
may attract rodents and other animals that can destroy or contaminate samples. Even
samples kept for only a short time may be attractive nesting and hiding places for rats and
mice. Rodents will attract snakes, and soon there is a whole host of animals in with the
samples. Even without opening the sample containers such intrusions may cause
contamination because some sample containers are porous and can allow contaminants
from animals to enter.
Samples will need to be protected from the deleterious effects of microorganisms in
addition to large animals. Because microorganisms can rapidly change the nature of
components in a sample, controlling their activity is important. Microbial activity is
minimized at low temperatures, and so storage at 4°C is sometimes required. Also,
limiting the time between sampling and analysis will limit the development of this type of
problem.
Sample security means that samples are not exchanged for one another and two
different batches of samples are not intermixed. Samples must have designated space
during transportation and storage. Keeping samples in their designated transportation and
storage space will assure that they are not mixed with other samples, which is particularly
important when different samples or different sample batches require different analysis or
different analytical procedures. Once a sample has started an analytical procedure—
extraction, for instance—it is usually not possible to use that same sample or extract in