Microplate readers scan, analyze and obtain numerical results from chemical reactions conducted within microplates. The most common assay (examination and determination as to characteristics) types are absorbance, fluorescence and luminescence. Microplate readers are generally configured to accept one of the three common microplate size configurations – either 96, 384, or 1536 well microplates.
As stated above, the most common assay types used by microplate readers are absorbance, fluorescence and luminescence. Absorbance is the conversion of radiant energy to a different form of energy by interaction with matter. This is also known as photometric. Fluorescence is the molecular absorption of light energy by a molecule, with immediate emission of less energetic photons (longer wavelength). Luminescence does not require light to excite molecules. The energy is provided by chemical (chemiluminescence) or biochemical (bioluminescence) reactions.
When working with microplate readers, there are a number of key performance specifications to determine before making the selection. These include wavelength range, accuracy, and response time. Wavelength range is the range in which microplate readers can measure the distance between two adjacent peaks (or troughs) of a wave. Accuracy is the agreement between a mean measured value and a true or accepted value as quantified by error. Accuracy is related to determinate errors and quantified by bias. Response time is the amount of time required from introduction of the sample into the reader until the analysis is complete.
Some microplate readers offer a number of features, which can help to maintain or drive reactions. These features include integral shakers, integral dispensers and temperature control. Integral shakers serve to agitate the reactant material to speed up processing and facilitate readings. Microplate readers with integral dispensers can add additional reactants to the microplates being analyzed to again speed up reactions, or to provide secondary readings to compare with the primary results, without removing the microplate and thereby contaminating potential results. Microplate readers with temperature control can maintain specified temperatures to ensure that critical reactions continue unmolested, or drive reactions if the pace is not meeting expectations.