Labs 1-3: Spearmint and peppermint oils
TLC & distinguishing spearmint oil from peppermint oil
Is there relatively simple, low-cost technique to distinguish spearmint oil from peppermint oil? Thin-layer chromatography (TLC) might be such a technique. Your task is to find out.
In your first and second laboratory sessions you will address the following questions:
- What is thin-layer chromatography?
- What is a “mobile phase”?
- What is an “Rf value,” and how is it determined?
- How are the components of a mixture “detected” on the TLC plate?
- What are the major components of spearmint oil and peppermint oil?
- How will you devise a test – a procedure - to determine whether TLC can be used to distinguish between these two oils?
- What kind of data can you collect
- What controls do you need for your procedure?
In your second and third sessions you will refine your procedure, settle on a specific protocol, and collect data to answer the question: “can TLC be used to reliably distinguish between peppermint and spearmint oils?”
Here are some resources for you to explore:
- The Chemguide has a nice description of TLC.
- More detailed descriptions of TLC and its use are available in two texts in the lab:
- High-performance thin-layer chromatography for the analysis of medicinal plants
- Plant drug analysis - a thin layer chromatography atlas
- The spearmint (Mentha spicata) and peppermint (Mentha piperita) plants are both found in the U.S. They are described in "The herb hunters guide American medicinal plants of commercial importance."
- Other resources for exploring the content of spearmint, peppermint, and other plants (wintergreen?) are: