# Developing an Analytical Method for the Analysis of a Medicinal Plant

- Page ID
- 227261

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 Danshen 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. As students progress through the module they are introduced to chromatographic separations, solvent extractions, response surfaces, one-factor-at-a-time optimizations, central-composite designs, desirability functions, and spike recoveries.

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 included in the instructor’s manual.

- Part IV. Selecting the Solvent, Temperature, and Microwave Power
- Investigation 10: One-Factor-at-a-Time Experimental Optimizations
- Investigations 11–13: Optimizing the Solvent (Part A)
- Investigations 14: Optimizing the Solvent (Part B)
- Investigation 15: Optimizing the Temperature (Part A)
- Investigation 16: Optimizing the Temperature (Part B)
- Investigation 17: Optimizing the Microwave Power (Part A)
- Investigation 18: Optimizing the Microwave Power (Part B)

- Part V. Optimizing the Solvent-to-Solid Ratio and the Extraction Time
- Investigations 19-21: Optimizing Two Factors at Once Using a Central-Composite Design
- Investigations 22-23: Modeling the Effect of Solvent-to-Solid Ratio and Extraction Time on Extraction Yield of Danshensu
- Investigations 24-25: Modeling the Effect of Solvent-to-Solid Ratio and Extraction Time on Extraction Yield of Other Analytes

- Instructor’s Guide
- 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

- Student Handout (Word, PDF)
- Assessment Questions: For Assessment questions that accompany this module, please contact
**David Harvey**(harvey@depauw.edu)

## Contributors and Attributions

- Dr. David Harvey (DePauw University): harvey@depauw.edu. Content from ASDL.