Cells for spectrophotometers with variable optical path lengths

A method and a device are proposed for varying optical path lengths of cells for spectrophotometers by placing parallel-plane insert plates (PPIPs) of variable thickness inside the cell. This method allows (a) the rapid adjustment of the optical path length of a standard cell (a dual PPIP set 5, 2 (2 pieces), and 1 mm thick ensures the variation of the optical path length of a 10-mm cell from 1 to 10 mm with a step of 1 mm); (b) mixing of solutions in cells; and (c) simple and quick washing of cells and PPIPs in routine spectral measurements.