Slag Sample is a Mission Item in Borderlands 2.
They are needed during the mission Wildlife Preservation
The scientist Patricia Tannis requests you gather 10 of these Slag Samples to help her with the research.
Slag Mutation is a volatile, brutal science that flies in the face of human ethics. Needless to say, Dr. Tannis is extremely interested in it, and asks that you get some samples of the slag serum Hyperion is using on the wildlife.
A sample of Slag, a volatile byproduct of Eridium manufacturing.