Tobias Pusterla reveals the next generation of monochromators and explores the advantages they bring to end users.
Microplate reader detection is based either on filters or grating-based monochromators. Typically, filters grant higher detection sensitivity because of increased transmission of light, whereas monochromators offer higher flexibility as wavelength selection can be adjusted for different fluorophores.
Double monochromators represented the state-of-the-art for flexible microplate reader detection until 2013 when BMG Labtech launched the Clariostar reader with LVF monochromator technology. Despite its name, the LVF monochromator uses neither a concave grating nor does it mechanically break up the light. Instead, it uses special adjustable filters, so-called linear variable filters (LVF), to select wavelengths. LVFs are defined as filters whose spectral properties vary linearly from one end of the filter to the other. The units consist of two LVFs that form the rising and falling edge of a filter. By moving the LVF slides relative to each other, the system separates light into distinct wavelengths and continuously adjustable bandwidths. The Clariostar reader consists of two LVF monochromators, one for excitation and one for emission. In addition, a linear variable dichroic mirror slide is used to separate the excitation from the emission light and further reduce undesired wavelengths.
LVF monochromators transmit more light than grating-based monochromators since, like filters, LVF slides allow for more than 80% light transmission. This enables filter-like sensitivity.
In grating-based solutions, bandwidths are limited to a maximum of 20-25 nm. The Clariostar allows continuously adjustable bandwidths up to 100nm. The broader the bandwidth, the more light and the higher the sensitivity.
Although some microplate readers include both filters and monochromators, these cannot be combined as each uses a separate light path. In the Clariostar, LVF monochromators and filters share the same light path as the slides holding the LVFs also incorporate slots for fixed filters. LVF monochromators and filters can hence be combined in one measurement.
These LVF monochromators have several advantages over grating-based systems.
For more information visit www.scientistlive.com/eurolab
Tobias Pusterla is with BMG Labtech in Germany.
