The invention relates to a liquid receptacle (22) comprising a bottom (1) and sidewalls for holding a liquid. The bottom (1) encompasses a flat sensor surface (3) that is in contact with the liquid when the receptacle is filled, a light-incident area (2) that is located below the sensor surface (3) and is suitable for focusing light (13) onto the sensor surface (3), a light emergence area (5), and a cover area (4) that is suitable for reflecting light from the sensor surface (3) such that the light can emerge through the light emergence area (5). The invention further relates to a method for qualitatively or quantitatively determining an analyte in such a liquid receptacle (22). In said method, excitation light (13) is focused onto the sensor surface (3) via the light-incident area (2) such that a luminescent marker which characterizes the analyte is excited, and the generated luminescence is then reflected onto the cover surface (4) and is detected after emerging through the light emergence area (5). The invention also relates to an analysis device comprising a holder for a liquid receptacle, a light source (10) that is disposed such that the light (13) thereof can be focused onto the sensor surface (3) of the liquid receptacle (22) via the light-incident area (2), and a detector (17) which is arranged in such a way as to be able to detect the light (9) emerging from the light emergence area (5) of the liquid receptacle (22).