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.