From our mentor-by-literature Neal Anderson, a comment on saving samples from your extractions:
Understand the partitioning of the desired product in each phase during every stage of the extraction process. Collect each "spent" phase, label the container, and store until it is clear that the extract can be discarded without losing yield or valuable process history that could be collected by analysing the extract.This is one that I suspect that most non-process organic chemists follow; even in graduate school, I was loathe to toss the layers of any extraction until I knew that I had isolated the desired product in the expected yield. However, I suspect that it is the "valuable process history" that is most important. Going back and being able to understand why you're doing the extraction and watching impurities drop out is worthwhile.