Absorbance microplate reader

Absorbance-based detection can be performed on the PHERAstar® FSX, CLARIOstar®, SPECTROstar® Omega, FLUOstar® and POLARstar® Omega plate readers, as well as on the dedicated SPECTROstar® Nano . BMG LABTECH was the first company to employ an UV/vis spectrometer instead of filters for absorbance detection.  Upon illumination of the sample by a high-power xenon flash lamp, BMG LABTECH´s ultra-fast UV/vis spectrometer collects the entire absorbance spectrum instead of a specific wavelength. It captures all wavelengths from 220 to 1000 nm at a resolution of 1 – 10 nm in less than 1 second per well.

Absorbance overview


Absorbance, also known as Optical Density (OD), is defined as the (logarithmic) ratio between the intensity of light hitting a sample and the intensity of that very light transmitted through the sample. While a specific wavelength of light usually selected by a filter illuminates a sample, part of this light gets absorbed. The non-absorbed light passes through the sample and is collected by a detector located opposite the light source, on the other side of the microplate well.

Since the amount of light absorbed by a sample relates to its concentration (Lambert-Beer law), absorbance has been used for the quantification of nucleic acids and proteins as well as in popular colorimetric reactions such as ELISA tests. BMG LABTECH offers a variety of absorbance microplate readers.

Absorbance products

The following plate readers can be configured to perform absorbance measurements. Choose between PHERAstar FSX - the high-throughput screening reader for fast read times, CLARIOstar with LVF monochromators™ for highest flexibility, Omega Series - our upgradable microplate readers for absorbance or any number of dectection modes and the SPECTROstar Nano - our dedicated absorbance reader with UV/vis spectrometer and additional cuvette port.

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