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48 Modern Analytical Chemistry

3 F Protocols

Earlier we noted that a protocol is a set of stringent written guidelines, specifying an
exact procedure that must be followed if results are to be accepted by the agency
specifying the protocol. Besides all the considerations taken into account when de-
signing the procedure, a protocol also contains very explicit instructions regarding
quality assurance and quality control internal and external quality assurance and quality control (QA/QC) procedures. 10
Those steps taken to ensure that the Internal QA/QC includes steps taken to ensure that the analytical work in a given
work conducted in an analytical lab is laboratory is both accurate and precise. External QA/QC usually involves a process
capable of producing acceptable results;
also known as QA/QC. in which the laboratory is certified by an external agency.
As an example, we will briefly outline some of the requirements in the Envi-
ronmental Protection Agency’s Contract Laboratory Program (CLP) protocol for
the analysis of trace metals in aqueous samples by graphite furnace atomic ab-
sorption spectrophotometry. The CLP protocol (Figure 3.7) calls for daily stan-
dardization with a reagent blank and three standards, one of which is at the labo-
ratory’s contract required detection limit. The resulting calibration curve is then
verified by analyzing initial calibration verification (ICV) and initial calibration
blank (ICB) samples. The reported concentration of the ICV sample must fall
within ±10% of the expected concentration. If the concentration falls outside this
limit, the analysis must be stopped and the problem identified and corrected be-
fore continuing.
After a successful analysis of the ICV and ICB samples, standardization is rever-
ified by analyzing a continuing calibration verification (CCV) sample and a contin-
uing calibration blank (CCB). Results for the CCV also must be within ±10% of the
expected concentration. Again, if the concentration of the CCV falls outside the es-
tablished limits, the analysis must be stopped, the problem identified and corrected,
and the system standardized as described earlier. The CCV and the CCB are ana-
lyzed before the first and after the last sample, and after every set of ten samples.
Whenever the CCV or the CCB is unacceptable, the results for the most recent set
of ten samples are discarded, the system is standardized, and the samples are reana-
lyzed. By following this protocol, every result is bound by successful checks on the
standardization. Although not shown in Figure 3.7, the CLP also contains detailed
instructions regarding the analysis of duplicate or split samples and the use of spike
testing for accuracy.

3 G The Importance of Analytical Methodology

The importance of analytical methodology is evident when examining the results
of environmental monitoring programs. The purpose of a monitoring program
is to determine the present status of an environmental system and to assess long-
term trends in the quality of the system. These are broad and poorly defined
goals. In many cases, such studies are initiated with little thought to the ques-
tions the data will be used to answer. This is not surprising since it can be hard
to formulate questions in the absence of initial information about the system.
Without careful planning, however, a poor experimental design may result in
data that has little value.