Absorbance

Last Updated: July 15, 2018

Definition - What does Absorbance mean?

Absorbance in chemistry is a logarithmic measure of the amount of light or radiation a particular substance absorbs. Absorbance is determined by measuring the light waves that pass through a solution. The light that enters the solution but does not pass through or transmit is the value that is absorbed by the solution.

The amount of transmitted light for a particular solution is compared to a standard measure to calculate the logarithmic measure. In other words, it is a determination of what percentage of the light passes through the substance.

Measuring a solution's absorbance can be used as a tool to determine the concentration of specific chemicals in a solution. Absorbance may also be used to assess the purity of a solution.


WorkplaceTesting explains Absorbance

Absorption spectrometry is a technique used for chemical analysis of substances. Using this method, examiners can measure the absorption of radiant energy (light) in a solution. This measurement can then be used to determine what chemicals are present in the solution and whether the solution contains any contaminants. Thus, the method may be used both for diagnostic testing and quality assurance.

Measuring absorption is one of the methods used for breath alcohol and drugs of abuse testing methods.

For example, blood alcohol levels are measured by assessing the molecules in a breath sample based on their light absorption. The ethanol alcohol in the breath of a person who has been drinking will go through a series of chemical changes when exhaled into a breath alcohol test unit. This resulting chemical absorbs light at a different rate than that of the pure, baseline solution, indicating a positive result.

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