A spectrometer (1) comprises a light source (2), a monochromator (3) with at least one diffraction grating (4), a monochromator housing (5), an order sorting filter (7), a microplate receptacle (12) and a controller (6). The order sorting filter (7) of the spectrometer (1) comprises a substrate (23), a first optical thin film (24) and a second optical thin film (25), wherein, in a spatially partly overlapping and interference-free manner, the first optical thin film (24) is arranged on a first surface (26) and the second optical thin film (25) is arranged on a second surface (27) of the substrate (23). A spectrometer (1) equipped with a respective order sorting filter is used in a scanning method for detecting the absorption spectrum of samples examined in wells (14) of microplates (13).