An Overview of Basic Principles of Analytical Methods - Field Sampling: Principles and Practices in Environmental Analysis - page 252

scope of this chapter and will not be discussed.
The analytical laboratory's project manger (PM) will ask the above questions of the
client. This works as a check to make sure that the test being requested will answer the
client's question. The PM maintains direct contact with the client and is responsible for
communication between the client and the laboratory. Therefore the PM is the vital link
in the initial chain of questions by both the lab and the client. While the PM does not
have to be a chemist, he or she will have a broad level of experience and knowledge of
the laboratory's methods and processes as well as a detailed knowledge of the specific
criteria of the various analytical procedures. This is especially important when it is
considered that the PM is acting as a twoway check (e.g., both on the client and his or her
requested analysis as well as on the laboratory's response, generated data, and resultant
report).
10.2. WHAT IS THE NATURE OF THE SAMPLE?
The nature of the sample or the sample matrix is part of the first general questions asked;
however, because of the profound effects this answer has on sampling and subsequent
sample preparation and analysis it important to consider it again. Indeed, it is a question
that must be asked more than once and be considered throughout the planning of the
analytical strategy. The characterization of the sample matrix will often automatically
determine many sampling and analytical parameters. For example, the sampling process
for a soil is dramatically different from that for groundwater or air. Also, the type and
nature of the sample containers are often driven by this question. Precleaned glass
containers with Teflon seals and various preservatives are needed for many organic test
methods. Alternately, for metals analysis, plastic or Nalgene-type containers are needed.
Although the three states of matter—gases, liquids, and solids—have their own
individual sampling requirements and techniques, there are several key factors in regard
to taking a sample that are universal to the sampling process. The first common point is
the consistency in sampling. Regardless of the accuracy and precision of the analytical
process used, the analytical result can be no better than the quality of the original sample
submitted for analysis. Therefore one of the primary concerns of the sampler must be the
collection of a true and representative sample. The second point is that once taken,
correct and clearly labeled documentation of the samples is essential, as is the accuracy
of the data recorded in the field information sheets (Figure 10.3) and in the project
notebook.
10.3. THE SAMPLING PROCESS
The sampling event is the first significant result-determining step in the analytical
process. The main goal of sampling is to obtain a sample that is representative of the
field. The other side of this is to maintain or preserve the sample as a valid example of
the field conditions. The possibility of error at that point and the effect of that error are
greater than within the analytical methodology [1, 2].