Beer-Lambert Law Calculator & Guide

Beer-Lambert Law Calculator & Guide

Your Complete Resource for Understanding Spectrophotometry Principles

Interactive Calculator

Enter any three values to calculate the fourth

Understanding the Beer-Lambert Law

The Beer-Lambert Law (also called Beer's Law) is a fundamental principle in spectroscopy that describes how light is absorbed by matter. This relationship is crucial for quantitative analysis in chemistry, biochemistry, and environmental science.

A = ε × c × l

Where:

  • A = Absorbance (unitless)
  • ε = Molar absorptivity (L·mol⁻¹·cm⁻¹)
  • c = Concentration (mol·L⁻¹)
  • l = Path length (cm)

Practical Applications in Modern Science

The Beer-Lambert Law finds applications across numerous scientific disciplines:

  • Pharmaceutical analysis: Determining drug concentrations
  • Environmental monitoring: Measuring pollutant levels
  • Biochemical research: Quantifying DNA, RNA, and proteins
Real-World Example: Measuring Protein Concentration

The Bradford protein assay uses the Beer-Lambert Law. If A = 0.85, ε ≈ 43000 L·mol⁻¹·cm⁻¹, l = 1 cm:

c = A / (ε × l) = 0.85 / (43000 × 1) ≈ 1.98×10⁻⁵ M

"The Beer-Lambert Law remains the cornerstone of quantitative absorption spectroscopy..." — Principles of Instrumental Analysis

Further Reading