 | Most readers available today operate with either one, eight, or twelve channel detectors (which reduces speed) or use an imaging process to map the entire microtiter plate (which reduces sensitivity and the individual signals can overlap). The reader from Carl Zeiss includes a miniature lens array containing 96 parallel micro-objectives. The 96 individual rays are mapped on a CCD surface sensor for fluorescence and luminescence measurements, while for absorption the detection takes place via a specially developed array containing 96 photodiodes. A motorized filter revolver makes it possible to switch automatically between various excitation and emission wavelengths.
This arrangement results, firstly, in higher measurement speed than with one, eight or twelve channel readers. Secondly, the miniature lens array offers considerably improved sensitivity in comparison with readers which map the entire microtiter plate. This detector also means that for the first time in UHTS it is possible to perform genuine kinetic measurements for different measurement modes, as 96 wells can be handled fully synchronously from the liquid-adding through to the detection stage.
A special miniature lens array has been developed for each detection type to provide maximum sensitivity with minimum disturbing effects. The 96 individual channels mean that a microtiter plate with 384 wells can be read in 4 steps and a plate with 1,536 wells in 16 steps without the signals of neighboring wells overlapping. So the readout time for a 1,536-well microtiter plate, e.g. for fluorescence measurement with typical specimen intensities, is only 20 seconds! | | |