1. What is Extinction Coefficient?

The extinction coefficient (ε) is a measure of how strongly a chemical species absorbs light at a particular wavelength. It is a fundamental parameter in spectroscopy and is used to determine concentrations of substances in solution according to Beer's Law.

2. How Does the Calculator Work?

The calculator uses the Beer's Law relationship:

Where:

• \( \varepsilon \) — Extinction coefficient (M⁻¹ cm⁻¹)
• \( \text{slope} \) — Slope of absorbance vs. concentration plot (absorbance/M)
• \( \text{path length} \) — Length of the light path through the sample (cm)

Explanation: The slope is obtained from a calibration curve plotting absorbance against concentration, and the path length is typically 1 cm for standard cuvettes.

3. Importance of Extinction Coefficient

Details: The extinction coefficient is crucial for quantitative analysis in spectroscopy, allowing researchers to determine unknown concentrations of analytes, characterize compounds, and study chemical reactions.

4. Using the Calculator

Tips: Enter the slope from your absorbance vs. concentration calibration curve in absorbance/M units, and the path length of your cuvette in cm. Both values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is Beer's Law?
A: Beer's Law states that absorbance is directly proportional to concentration: A = εcl, where A is absorbance, ε is extinction coefficient, c is concentration, and l is path length.

Q2: What are typical extinction coefficient values?
A: Extinction coefficients vary widely depending on the compound and wavelength. They can range from less than 100 M⁻¹ cm⁻¹ for weak absorbers to over 100,000 M⁻¹ cm⁻¹ for strong chromophores.

Q3: How do I obtain the slope for this calculation?
A: Prepare standard solutions of known concentrations, measure their absorbance, and plot absorbance vs. concentration. The slope of the best-fit line is used in this calculation.

Q4: Does extinction coefficient depend on wavelength?
A: Yes, extinction coefficient is wavelength-dependent. It should be reported at the specific wavelength where measurements were taken.

Q5: What factors affect extinction coefficient accuracy?
A: Temperature, solvent, pH, instrument calibration, and sample purity can all affect the accuracy of extinction coefficient determinations.