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4: The Vocabulary of Analytical Chemistry

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  • If you browse through an issue of the journal Analytical Chemistry, you will discover that the authors and readers share a common vocabulary of analytical terms. You probably are familiar with some of these terms, such as accuracy and precision, but other terms, such as analyte and matrix, are perhaps less familiar to you. In order to participate in any community, one must first understand its vocabulary; the goal of this chapter, therefore, is to introduce some important analytical terms. Becoming comfortable with these terms will make the chapters that follow easier to read and to understand.

    • 4.1: Analysis, Determination, and Measurement
      The first important distinction we will make is among the terms analysis, determination, and measurement. An analysis provides chemical or physical information about a sample. The component in the sample of interest to us is called the analyte, and the remainder of the sample is the matrix. In an analysis we determine the identity, the concentration, or the properties of an analyte. To make this determination we measure one or more of the analyte’s chemical or physical properties.
    • 4.2: Techniques, Methods, Procedures, and Protocols
      Suppose you are asked to develop an analytical method to determine the concentration of lead in drinking water. How would you approach this problem? To provide a structure for answering this question, it is helpful to consider four levels of analytical methodology: techniques, methods, procedures, and protocols.
    • 4.3: Classifying Analytical Techniques
      The analysis of a sample generates a chemical or physical signal that is proportional to the amount of analyte in the sample. This signal may be anything we can measure, such as volume or absorbance. It is convenient to divide analytical techniques into two general classes based on whether the signal is proportional to the mass or moles of analyte, or is proportional to the analyte’s concentration
    • 4.4: Selecting an Analytical Method
      A method is the application of a technique to a specific analyte in a specific matrix. Ultimately, the requirements of the analysis determine the best method. In choosing among the available methods, we give consideration to some or all the following design criteria: accuracy, precision, sensitivity, selectivity, robustness, ruggedness, scale of operation, analysis time, availability of equipment, and cost.
    • 4.5: Developing the Procedure
      After selecting a method, the next step is to develop a procedure that accomplish our goals for the analysis. In developing a procedure we give attention to compensating for interferences, to selecting and calibrating equipment, to acquiring a representative sample, and to validating the method.
    • 4.6: Protocols
      Earlier we defined a protocol as a set of stringent written guidelines that specify an exact procedure that we must follow if an agency is to accept the results of our analysis. In addition to the considerations that went into the procedure’s design, a protocol also contains explicit instructions regarding internal and external quality assurance and quality control (QA/QC) procedures.
    • 4.7: The Importance of Analytical Methodology
      The importance of the issues raised in this chapter is evident if we examine 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 system’s health. Without careful planning, however, a poor experimental design may result in data that has little value.
    • 4.8: Problems
      End-of-chapter problems to test your understanding of topics in this chapter.
    • 4.9: Additional Resources
      A compendium of resources to accompany this chapter.
    • 4.10: Chapter Summary and Key Terms
      Summary of chapter's main topics and a list of key terms introduced in the chapter.