Prior to this invention various fluorometers have been used in a wide variety of applications for measuring the fluorescence of fluorescently excitable materials. For example, fluorometers are used in junction with fluorescent assays to detect and measure the quantities of immunological and non-immunological substances.
In carrying out fluorescent assays, microtest plates (or microtitration plates, as they are also called) and strips of microtest wells are often used. Microtest plates are formed with a multiplicity of wells which are joined together in a molded one-piece structure for containing microliter quantities of fluid samples in liquid or solid form. Examples of a microtest plate and microtest wells in strip form are described in U.S. Pat. No. 4,154,795 which issued to A. C. Thorne on May 15, 1979.
The use of microtest plates and microtest strips of wells in fluorescent and other types of assays offers several important advantages. First, they permit the mass preparation of a large number of test sample solutions at the same time. Second, they are more convenient to handle as compared with individual test tubes. Third, they can easily and inexpensively be washed. Fourth, they are inexpensive and disposable. Fifth, they are customarily formed from plastic materials which are not fragile like glass. Sixth, they can be made from a material having an ability to attract certain molecules such as protein molecules so that they can serve as a solid phase in an immunoassay.
Some fluorometers are not sufficiently sensitive to measure the fluorescence of the small, microliter quantities of the relatively low fluorescent samples which are prepared with the microtest plate and strip equipment described above. Other fluorometers, while having sufficient sensititvity, are usually unsuitable for measuring the fluorescence of substances in microtest wells because they are designed to direct the exciting light and/or the sample's emitted light through a wall of the sample-holding vessel. As a result, the microtest plates and strips, which are customarily molded from plastic materials having a substantial level of native fluorescence, are excessively excited to produce spurious light emissions which interfere with and impair accurate measurements of the intensity of the light emitted by the fluorescently excited test sample itself.