Prominences are a very strong candidate to display non-MHD effects due to partial ionization, since they are dense and relatively cool objects, in which the ionisation degree is not fully known but it is assumed to be around 50%. To measure observationally the diffusion velocity between different species we need to measure simultaneously the velocities of ionised and neutral atoms in approximately the same position. In prominences the dense material is accumulated in filamentary structures called threads, whose width is under 0.3" (from observations with space telescopes in H$\alpha$). Since prominence plasma properties are very similar to the chromospheric plasma, we need to use chromospheric lines with good spectral resolution. We present the results for the observations carried in the Vacuum Tower Telescope (VTT) in the Observatorio del Teide (Canary Islands, Spain): high-cadence simultaneous observations of a CaII and HeI lines. The Doppler velocity shows a high correlation between both lines, with deviations close to the random noise. The implications of these results are discussed.