Question

In microscale extractions you are instructed to remove the lower phase using a pastuer pipette even when the organic phase is the top phase. Explain why this results in better phase separation than removing the top phase directly with the pastuer pipette

Answer 1

Assuming that most of us use cone shaped seperating funnel for phase seperation. High density phase will be lower and low density phase will be top. If we try to remove the top phase the crosss section (surface area between two layer junction) between top and lower is very high and chances are there that along wiyh top phase some amount of lower phase will also come out with pastuer pipette (even when a small pressure is apllied is enough). In contrast if we try to remove the lower phase the bottom cross section is very low compare to the middle of funnel. Chances are very less to come top phase along with lower phase. Moreover reducing lower phase brings slowly move down top phase, reflects even more better seperation.

Hence in microscale extractions you are instructed to remove the lower phase using a pastuer pipette even when the organic phase is the top phase for better phase separation than removing the top phase directly with the pastuer pipette.

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