Topics - Film Thickness

Film Thickness In chromatography, film thickness usually refers to the thickness of the layer of stationary phase covering the surface of the support in a packed column or on the wall of a capillary column. The film thickness of the stationary phase in a chromatographic column determines the magnitude of the resistance to mass transfer in the stationary phase and, thus, the variance per unit length of the column and the column efficiency. In fact, the contribution of the resistance to mass transfer in the stationary phase to the overall variance per unit length of a column, increases as the square of the film thickness of stationary phase. Reducing the film thickness of stationary phase does increase the efficiency of the column but it also reduces the retention and separation of any pair of solutes. Thus, reducing the film thickness of stationary phase has an experimental limit, and, in practice, there is an optimum film thickness that will provide the best resolution for any given pair of substances