Home
Back
Beer's Law Equation:
| From: | To: |
The molar extinction coefficient (ε) is a measure of how strongly a chemical species absorbs light at a particular wavelength. It is a fundamental parameter in UV-Vis spectroscopy that quantifies the absorption characteristics of a substance.
The calculator uses Beer's Law equation:
Where:
Explanation: Beer's Law states that absorbance is directly proportional to the concentration of the absorbing species and the path length of light through the sample.
Details: The molar extinction coefficient is crucial for quantitative analysis in spectroscopy, determining concentration of unknown samples, characterizing molecular properties, and studying chemical kinetics and equilibrium.
Tips: Enter absorbance value (typically between 0.1-1.0 for accurate measurements), concentration in mol/L, and path length in cm (usually 1.0 cm for standard cuvettes). All values must be positive numbers.
Q1: What is the typical range for molar extinction coefficients?
A: Values range from near 0 for non-absorbing compounds to over 100,000 L/mol·cm for strongly absorbing chromophores like dyes and conjugated systems.
Q2: Why is absorbance typically measured between 0.1-1.0?
A: This range provides optimal accuracy. Below 0.1, noise becomes significant; above 1.0, detector saturation and stray light effects can occur.
Q3: Does molar extinction coefficient vary with wavelength?
A: Yes, ε is wavelength-dependent. It is typically reported at the absorption maximum (λmax) of the compound.
Q4: What factors affect the accuracy of ε calculation?
A: Concentration accuracy, path length precision, instrument calibration, sample purity, and proper blank correction are critical factors.
Q5: Can this calculator be used for any wavelength?
A: Yes, but ε values are specific to each wavelength. The calculated ε applies only to the wavelength where absorbance was measured.