Analysis, Determination, and Measurement
The first important
distinction we will make is among the terms “analysis,” “deter- mination,” and “measurement.” An analysis
provides chemical or physical infor- mation about a sample.
The components of interest in the sample
are called ana-
lytes, and the remainder of the sample
is the matrix. In
an analysis we determine
the identity, concentration, or properties of the analytes. To make this determina- tion we measure one or more of the analyte’s chemical
or physical properties.
An example helps clarify the differences among an analysis, a determination, and a measurement. In 1974, the federal government enacted the Safe Drinking
Water Act to ensure the
safety of public
drinking water supplies. To comply with this act municipalities regularly monitor their drinking
water supply for potentially
harmful substances. One such substance
is coliform bacteria.
Municipal water de- partments collect and analyze samples
from their water supply. To determine the
concentration of coliform bacteria, a portion
of water is passed through
a mem- brane filter.
The filter is placed in a dish containing a nutrient broth and incu- bated. At the end of the incubation period the number of coliform bacterial
colonies in the dish is measured by counting (Figure
3.1). Thus, municipal water departments analyze samples of water to determine the
concentration of coliform bacteria by measuring the number of bacterial colonies that form during
a speci- fied period of incubation.
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