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


Last modified: Thursday, January 19, 2012, 11:44 AM