Hello, I am currently doing a research about essential oil extracted using soxhlet extraction from guava (Psidium guajava L.) and my solvent is n-hexane. I am just wondering what should be the color of the solution after rotary evaporator? Because currently, we have a crude like greenish color.
Hi,
My Interpretation of Extract Colour:
A greenish hue in the extract usually indicates the presence of chlorophyll and other pigmented non-polar substances. This is common when using n-hexane as the extraction solvent due to its non-polarity. It is important to note that the colour of the extract does not necessarily reflect its quality or efficacy. However, if the objective is to obtain a clear or colourless essential oil, additional purification steps may be required. For example, techniques such as winterization, distillation, or chromatography can be used to remove chlorophyll and other pigments. In conclusion, the greenish hue observed in the guava leaf extract after concentration using a rotary evaporator indicates the extraction of chlorophyll and possibly other pigmented, non-polar compounds by n-hexane. The colouration is a direct result of the chemical properties of the guava leaves and the non-polar solvent. If the presence of these compounds is unwanted for your application, additional purification steps should be considered. Hydro destillation is also sometimes done.
I mostly agree with Phil. Using a Soxhlet equipment and n-hexane as the extraction solvent, a HEXANE EXTRACT is obtained containing the essential oil PLUS all compounds soluble and partially soluble in n-hexane, i.e. waxes, triglycerides, fatty acid esters, sterols, triterpenes, some carotenoids, etc., including low polarity chlorophylls. That's why the hexane extract (sometimes called "oleoresin") is greenish in color. If you want to obtain the pure essential oil, you must carry out distillation by steam distillation.
Dear mark,
It's simply Anthocyanins. The same happens when you leave a glass of guava juice with residue that runs down the sides and dries on wood or plastic.
Best regards.
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