Absorbance Readers

Published On January 11, 2019 | By admin | Technology

Researchers and scientists in biotechnology, pharmaceutical, agricultural, and even in food industries endeavor to develop routine laboratory processes and adeptness by automated handling of samples. An absorbance reader helps in minimizing the operational time, saves cost, and lets the users dedicate time for analysis of data and generation of various insights.

Absorbance readers, also known as plate readers or microplate readers are the bioanalytical instruments used in physical, chemical, and most important biological laboratories to measure the absorbance of a sample. These instruments are widely used in the areas of target validation, drug discovery, quality control, detection, process control, and manufacturing processes in the industries, clinical laboratories, and also in the academic research institutions. It is generally considered as a multidisciplinary instrument that is used for performing, measuring, and analyzing several types of assays.

How does an Absorbance Reader work?

Absorbance is the ability of any substance to absorb light rays of a specific wavelength. Absorbance detection has been in the field of research for more than four decades. The absorbance readers detect the signals by measuring the absorption of light. These readers work on the Beer Lambert’s law. A light source illuminates the samples in the microtitre plate with a specific wavelength. The wavelength is controlled by a filter or a monochromator. The molecules in the samples are excited upon illumination. The amount of intensity of the light rays are transmitted through the sample is measured by the detector on the other end of the sample.

Generally, the amount of light transmitted in turn the amount of intensity of light absorbed is a measure of the concentration of the sample placed. The measured absorbance of the sample is called the Optical Density (OD). Absorbance is calculated as per Beer-lamberts’ law whose equation is:

A λ = log10 (I0/I)

Where I refer to the intensity of light at a specified wavelength denoted by λ, which has passed through the sample also called transmitted light intensity and I0 denotes the intensity of the light before it enters the sample.

Types of absorbance readers:

Calorimeters, spectrophotometers, and Nanodrop are all modifications of absorbance readers. There are various modifications in the absorbance readers: ELISA readers generally have a very low footprint and have various technologies like Unlimited LED sources, etc. A few ELISA readers have the ability to perform auto-check and auto zero! Modular microplate readers have come with various options like reading absorbance, fluorescence, Time-resolved FRET, etc.

Applications of absorbance readers:

The range of applications of absorbance readers includes assays for checking the enzyme activities, nucleic acid quantification assays, ELISAs, Protein, and cell growth assays, interactions between proteins, reporter assays, molecular interactions, quantifications of ATP, immunological assays, immunochemistry assays, screening of targets and compounds in drug discovery and many more.


Many absorbance readers have been miniaturized according to the users’ expectation. From the days when the absorbance readers used quartz cuvette to glass cuvette, the absorbance readers have evolved to use microtitre plates. Thus, absorbance readers have become an integral part of every research lab, making the lives of the scientist easier.

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