Spectroscopic methods provide a powerful tool for studying the properties of proteins at interfaces. The protein accumulated in one adsorbed layer is frequently less than the minimum mass of protein required by a detection method. In such a case las is the case in circular dichroism spectroscopy) the sorbent material is usually supplied as dispersion. However, light scattering by the dispersed particles often interferes with the measurement of the circular dichroism of the protein. Therefore, there is a strong need for an experimental setup that enables these measurements to be made using flat surfaces. An example of such a setup is the multiplate quartz cell presented here. The potential of this multiplate quartz cell is shown by some preliminary circular dichroism measurements of IgG adsorbed on different types of surfaces. (C) 2000 Academic Press.