At home, the colour can be extracted by pouring hot water on the flowers. However, in the lab, we have the option of using various solvents.
Using acetone and ethanol, which are common organic solvents, the blue dye can be extracted by soaking the flowers in them. It is observed that the tone of the extract in acetone is slightly different from that of ethanol and water. This could be due to the extraction of the non-polar pigment(s) from the flower, since acetone is a less polar solvent as compared to ethanol and water. The advantage of using acetone or ethanol (as compared to water) is that the solution can be concentrated using the rotary evaporator, since these organic solvents have lower boiling points. As the solution become more concentrated, so will the intensity of the colour of the dye.
It is worth noting that the acetone extract decolourises after a couple of days. Also, if the flowers had been kept (in a refrigerator) for a few weeks, the extract would appear more greenish. It is important that the flowers should be kept in the refrigerator, in a ziplop bag, to prevent it from drying up.
Extraction can be done more efficiently by grinding the petals gently in a mortar and pestle. However, in doing this, would produce small solid particles, which can be simply removed by filtration. One trick in doing a simple filtration quickly, is to use a small ball of cotton instead of a filter paper.
The dye has appeared to be stable in ethanol after storing it for a few weeks. Thus, this solution can be kept until it is ready for use.
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