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Chemistry LibreTexts

Instructor’s Guide

  • Page ID
    237906
  • Developing an Analytical Method: Instructor’s Guide

    Suggested Responses to Investigations & Supplementary Materials

    This module introduces students to the process of developing an analytical method using, as a case study, the quantitative analysis of eight analytes in the medicinal plant Danshensu using a combination of a microwave extraction to isolate the analytes and HPLC with UV detection to determine their concentrations. The module is divided into nine parts:

    • Part I. Context of Analytical Problem
    • Part II. Separating and Analyzing Mixtures Using HPLC
    • Part III. Extracting Analytes From Samples
    • Part IV. Selecting the Solvent, Temperature, and Microwave Power
    • Part V. Optimizing the Solvent-to-Solid Ratio and the Extraction Time
    • Part VI. Finding the Global Optimum Across All Analytes
    • Part VII. Verifying the Analytical Method’s Accuracy
    • Part VIII. Applying the Analytical Method
    • Part IX. Closing Thoughts

    Interspersed within the module’s narrative are a series of investigations, each of which asks students to stop and consider one or more important issues. Some of these investigations include data sets for students to analyze; for the data in the module’s figures, you may wish to have students use the interactive on-line versions that provide access to a cursor and the ability to pan and zoom. The on-line figures, created using Plotly (https://plot.ly/), also provide access to the underlying data in the form of a spreadsheet.

    This exercise is based loosely on work described in the paper

    “Simultaneous extraction of hydrosoluble phenolic acids and liposoluble tanshinones from Salvia miltiorrhiza radix by an optimized microwave-assisted extraction method”

    the full reference for which is Fang, X.; Wang, J; Zhang, S. Zhao, Q.; Zheng, Z.; and Song, Z. Sep. Purif. Technol. 2012, 86, 149-156 (DOI:10.1016/j.seppur.2011.10.039). Although most of the data in this exercise are drawn directly from or extrapolated from data in the original paper, additional data are drawn from other papers or generated artificially; specific details of differences between the data in the original paper and the data in this case study are discussed below as part of the suggested responses to the cases study’s investigations.

    Suggested responses are presented in normal font.

    Supplementary materials are in italic font.

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