3: The Vocabulary of Analytical Chemistry
- Page ID
- 127184
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)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.
- 3.1: Analysis, Determination, and Measurement
- The page distinguishes between analysis, determination, and measurement in the context of examining samples. Analysis involves obtaining chemical or physical information about a sample's analyte. Determination involves identifying or measuring the properties of an analyte. Measurement is the act of quantifying these properties. An example given is the analysis of drinking water for fecal coliform bacteria, where the concentration is determined by counting bacterial colonies after incubation.
- 3.2: Techniques, Methods, Procedures, and Protocols
- This page discusses the process of developing an analytical method to determine lead concentration in drinking water by considering four levels of analytical methodology: techniques, methods, procedures, and protocols. Techniques involve chemical or physical principles like those used in graphite furnace atomic absorption spectroscopy (GFAAS). A method applies these techniques to specific analytes in specific matrices, while procedures offer written directions for method application.
- 3.3: Classifying Analytical Techniques
- The page discusses analytical techniques used to measure the amount of analyte in a sample, dividing them into two classes: total analysis techniques, which respond to the absolute amount of analyte, such as gravimetry and titrimetry, and concentration techniques, which respond to analyte concentration, like spectroscopy and electrochemistry.
- 3.4: Selecting an Analytical Method
- The page discusses the criteria for selecting analytical methods for determining analyte concentrations, using lead in drinking water as an example. It explains different methods' principles, like gravimetric methods, complexation titrimetry, and atomic absorption spectroscopy, and the importance of factors like accuracy, precision, sensitivity, selectivity, robustness, and scale of operation.
- 3.5: Developing the Procedure
- The page outlines the process of developing a procedure for analytical methods, focusing on compensating for interferences, calibration, sampling, and validation.
- 3.6: Protocols
- A protocol is a set of stringent written guidelines crucial for agency approval of analytical results. It includes procedures for internal and external QA/QC to ensure accuracy. The EPA's protocol for trace metal analysis using atomic absorption spectroscopy involves calibration with a method blank and three standards. Calibration is verified through ICV and ICB samples, needing results within ??10% accuracy.
- 3.7: The Importance of Analytical Methodology
- Environmental monitoring programs aim to evaluate the current state and long-term trends of environmental systems, but without careful planning, they may generate low-value data. The Chesapeake Bay Monitoring Program exemplifies such challenges. Initiated in 1984 to study nutrients and pollutants, it initially employed EPA-approved analytical methods not sensitive enough for unpolluted waters, leading to ineffective data outcomes.
- 3.8: Problems
- The page discusses various analytical chemistry processes related to sample preparation and analysis. It outlines methods for digesting solid samples, methods for concentration determination, and considerations when interferents are present. It also addresses evaluating sensitivity, selectivity, and method suitability for different analytes and interferents. Examples include analyzing calcium in water with zinc interference and determining reduced glutathione in blood.
- 3.9: Additional Resources
- The page provides information about IUPAC's web-based compendium of analytical terminology and references to papers and texts discussing various schemes for classifying analytical methods. It lists works covering performance characteristics, debates on sensitivity, and analytical procedures for specific analytes, including notable textbooks and compilations. Additionally, it mentions a review of analytical methodology's significance in regulatory environments.
- 3.10: Chapter Summary and Key Terms
- The chapter emphasizes the importance of mastering the vocabulary specific to analytical chemistry, differentiating terms such as analyte, matrix, technique, method, procedure, and protocol. It discusses key criteria for selecting analytical methods, including accuracy, precision, sensitivity, and more, highlighting the need to balance these interdependent factors.