Sample Transport and Storage - Field Sampling: Principles and Practices in Environmental Analysis - page 203

other analytical procedures.
At every step between the field and the final analysis an accounting of where the
sample is or has been needs to be kept. It is essential that there be no doubt about the
authenticity of the sample. It must be impossible for a sample to be contaminated,
switched for another sample, or mixed with another sample. In part this means that
samples are never left in the hands of persons not responsible for their transport and
storage. It also means having a detailed, well-documented chain of custody (discussed
below).
Security can also be thought of in terms of not allowing any sample to exit the
container and contaminate or be contaminated by its surroundings. This is dangerous for
the persons handling the samples and leads to contamination of the sample, making it
useless. Great care must be taken in making sure that the sample is well sealed in the
proper container. When several containers are packaged together this means that they
cannot interact with each other, either to break open an adjacent container or to exchange
components. Often a good approach is to have the samples double-contained. This would
be a plastic bag inside a plastic bag or a bottle inside a plastic bag. In addition, the
containers packaged together should be cushioned from each other by packing material.
A summary of security concerns is given in Table 8.1.

TABLE 8.1 Security Considerations for Field Samples

Container
integrity

Handling and package containers to minimize breakage

Sample numbers Apply sample numbers in several places using high-quality labels and

permanent markings.

Pests Samples must be secure from pests.

Sample mixing Set up protocols that prevent mixing of samples from different batches or

mixing of batches.

Sample leakage Package samples to prevent leakage during transportation and storage.

8.2. CONTAINERS

Sample containers must have three characteristics. First, the container material must be
compatible with the sample and the component or components of interest in the sample.
The container must not take away from or absorb any component in the sample, and it
must not add any component to the sample. This could be considered negative and
positive contamination of a sample. Characteristics of sample containers are covered in
more detail in Chapters 3 and 5.
The second characteristic is that the sample container be chosen so that it will not lose
components during shipment or transport. Losing components might take place by
breaking the container or by diffusion of material out of the container. Diffusion could be