Barrier between Single and Multiple Sample Absorbance Instruments
As spectroscopic instruments evolved from single sample test tube instruments to multisample microplate readers, new technological barriers were encountered. One example of such a barrier was in the lamps that provide the incident of light directed at the sample (I0). The first lamps provided less energy over a limited range of wavelengths, thus inhibiting the use of a microplate reader.
Halogen, tungsten, and deuterium lamps had to be used in combination to cover most of the UV to far red spectrum. High energy xenon flash lamps overcame this barrier, providing a single light source with more energy over a broader spectral range. This advancement propelled microplate readers to the next level, allowing for a larger range of assays at lower concentrations.
Another technological barrier in microplate readers is the inability to instantly capture a full absorbance spectrum from the ultraviolet to the near infrared. Recent technology used for wavelength selection, such as filters and monochromators, allows for absorbance measurements of one wavelength or a band of wavelengths in less than one second per well (Figure 1).
But if a broad range of wavelengths or if multiple wavelengths at a high resolution were to be measured, which are both common on a single sample cuvette instrument, the time spent using either technology is greater than two minutes per well. This would equate to more than three hours for a 96-well microplate, thereby making instantaneous, high-resolution full-spectrum measurements impractical on a microplate reader.