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50 Modern Analytical Chemistry

These concerns are illustrated by the Chesapeake Bay monitoring program.
This research program, designed to study nutrients and toxic pollutants in the
Chesapeake Bay, was initiated in 1984 as a cooperative venture between the fed-
eral government, the state governments of Maryland, Virginia, and Pennsylvania,
and the District of Columbia. A 1989 review of some of the problems with this
program highlights the difficulties common to many monitoring programs. 11
At the beginning of the Chesapeake Bay monitoring program, little attention
was given to the proper choice of analytical methods, in large part because the
intended uses of the monitoring data were not specified. The analytical methods
initially chosen were those standard methods already approved by the EPA. In
many cases these methods proved to be of little value for this monitoring project.
Most of the EPA-approved methods were designed to detect pollutants at their
legally mandated maximum allowed concentrations. The concentrations of these
contaminants in natural waters, however, are often well below the detection limit
of the EPA methods. For example, the EPA-approved standard method for phos-
phate had a detection limit of 7.5 ppb. Since actual phosphate concentrations in
Chesapeake Bay usually were below the EPA detection limit, the EPA method
provided no useful information. On the other hand, a nonapproved variant of
the EPA method commonly used in chemical oceanography had a detection limit
of 0.06 ppb. In other cases, such as the elemental analysis for particulate forms of
carbon, nitrogen, and phosphorus, EPA-approved procedures provided poorer
reproducibility than nonapproved methods.

3 H KEY TERMS

accuracy (p. 38) measurement (p. 36) rugged (p. 42)
analysis (p. 36) method (p. 36) selectivity (p. 40)
analytes (p. 36) method blank (p. 45) selectivity coefficient (p. 40)
calibration (p. 47) precision (p. 39) sensitivity (p. 39)
calibration curve (p. 47) procedure (p. 36) signal (p. 37)
concentration techniques (p. 38) protocol (p. 37) standardization (p. 47)
detection limit (p. 39) quality assurance and quality technique (p. 36)
determination (p. 36) control (p. 48) total analysis techniques (p. 38)
matrix (p. 36) robust (p. 42) validation (p. 47)

3 I SUMMARY

Every discipline has its own terminology. Your success in studying ple, time, cost, and the availability of equipment. These criteria are
analytical chemistry will improve if you master the language used not mutually independent, and it often is necessary to find an ac-
by analytical chemists. Be sure that you understand the difference ceptable balance among them.
between an analyte and its matrix, a technique and a method, a In developing a procedure or protocol, consideration is given
procedure and a protocol, and a total analysis technique and a to compensating for interferences, calibrating equipment and
concentration technique. standardizing the method, obtaining an appropriate sample, and
An analytical method is selected on the basis of criteria such as validating the analysis. Poorly designed procedures and protocols
accuracy, precision, sensitivity, selectivity, robustness, ruggedness, produce results that are insufficient to meet the needs of the
the amount of available sample, the amount of analyte in the sam- analysis.