The search for the physical origin of shear banding has motivated many theoretical and experimental studies and yet no consensus has emerged. Thanks to the 1-2 shear cell and its spatially-resolved measurements taken along the velocity-gradient direction, it is now possible to elucidate the shear banding behavior of WLM solutions quite precisely. A combination of measurements of sample transmission, coherent scattering and incoherent scattering will be used to determine whether concentration gradients are present in a couple of shear banding WLM solution while simultaneously decreasing the associated uncertainties of the measurements and shedding light to the basis of this phenomenon.