  We show that the uncertainty relation as expressed in the
Robertson-Schrodinger generalized form can be used to detect the mixedness of
three-level quantum systems in terms of measureable expectation values of
suitably chosen observables when prior knowledge about the basis of the given
state is known. In particular, we demonstrate the existence of observables for
which the generalized uncertainty relation is satisfied as an equality for pure
states and a strict inequality for mixed states corresponding to single as well
as bipartite sytems of qutrits. Examples of such observables are found for
which the magnitude of uncertainty is proportional to the linear entropy of the
system, thereby providing a method for measuring mixedness.
