Beer-Lambert Absorbance Calculator
Use the Beer-Lambert Law (A = ε·c·l) to convert between absorbance, concentration, and path length. Includes common extinction coefficients for DNA, RNA, proteins, and dyes.
Parameters
Microfluidic channels are typically 0.005–0.05 cm (50–500 µm)
Result
| Parameter | Value |
|---|---|
| Absorbance (A) | 0.5000 |
| ε at 260 nm | 6,600 L mol−¹ cm−¹ |
| Concentration (c) | 75.758 µM |
| Path length (l) | 1 cm |
About the Beer-Lambert Law
The Beer-Lambert Law describes the relationship between the absorbance of light through a solution and the concentration of the absorbing species. It is the foundation of UV-Vis spectrophotometry and is used daily in biology and chemistry labs to quantify nucleic acids, proteins, dyes, and metabolites.
The Equation
where A is the measured absorbance (dimensionless), εis the molar extinction (absorption) coefficient (L mol−¹ cm−¹), cis the molar concentration (mol L−¹), and l is the optical path length (cm). Rearranging for any unknown is straightforward.
Beer-Lambert in Microfluidics
In microfluidic channels, path lengths are typically 50–500 µm (0.005–0.05 cm), which is 100–200× shorter than a standard 1 cm cuvette. This dramatically reduces absorbance readings at the same concentration, requiring either higher concentrations, more sensitive detectors, or longer on-chip optical paths (e.g. Z-shaped detection cells) to achieve adequate signal-to-noise.
Limitations
The Beer-Lambert Law is valid for dilute, homogeneous solutions where the absorbing species do not interact. It breaks down at high concentrations (typically A > 2) due to detector saturation, molecular interactions, and stray light. It also assumes monochromatic light and that fluorescence and scattering are negligible.
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