Abstract
The autumnal leaf color change is a familiar phenomenon to most students living in temperate climate zones. The extraction and analysis of the pigments of the autumn leaves provide an engaging way to study the phenomenon utilizing both simple as well as more sophisticated analytical methods. In this laboratory experiment, students extract the red and yellow pigments, that is, anthocyanins and carotenoids from leaves and separate them from each other by liquid–liquid extractions. From the separated phases, anthocyanin and carotenoid concentrations can be evaluated visually or spectrophotometrically. The anthocyanins are analyzed by a rapid and simple ultra-performance liquid chromatography–tandem mass spectrometry method to discover which of the six most common groups of anthocyanins are present in the sample. The simplicity of the experiment setup allows it to be used as an introduction to mass spectrometry since the results can be easily interpreted without complicated data processing. The experiment provides opportunities for learning outside the classroom, as the samples can be collected from the nearby parks or forests and analyzed using more sophisticated methods on a student visit to a university or other research institution. The sample preparation followed by the visual analyses of the phases is however simple enough to be performed in a regular school laboratory.
Highlights
The autumnal leaf color change of most temperate deciduous trees is a beautiful phenomenon that can be utilized for teaching purposes from its chemical point of view
The red pigments are analyzed further by ultra-performance liquid chromatography combined with tandem mass spectrometry (UPLC−MS/MS) to classify them into the six common subgroups of natural pigments
Spectroscopy has been used for quantitative and qualitative purposes in several laboratory experiments on anthocyanins and carotenoids.[4−10] All of this can be done with samples familiar to the students from everyday life, such as berries, fruits, flower petals, and leaves
Summary
The autumnal leaf color change of most temperate deciduous trees is a beautiful phenomenon that can be utilized for teaching purposes from its chemical point of view In this experiment, the yellow and red pigments are extracted from the autumn leaves and quantified spectrophotometrically. The red pigments are analyzed further by ultra-performance liquid chromatography combined with tandem mass spectrometry (UPLC−MS/MS) to classify them into the six common subgroups of natural pigments. This experiment combines chemistry and biology, and provides students out-of-classroom learning experiences, since the plant samples can be collected by the students from the nearby parks, forests, or gardens, and can be analyzed in collaboration with university or any other institution with the suitable instrumentation. Working with anthocyanins and carotenoids makes the experiments colorful and visually attractive, and more interesting
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