How to Determine the Extinction Coefficient

The extinction coefficient, also known as the molar absorptivity or absorption coefficient, refers to the absorbance value of the test solution to light. As an important parameter of optical properties, its measurement is crucial for understanding the structure, properties, and functions of materials.

 

The measurement of the extinction coefficient is based on the Beer-Lambert Law, which states that the absorbance (A) of a solution is directly proportional to its concentration (c), the path length of the light (l), and the molar extinction coefficient (ε) when a monochromatic light passes through a homogeneous, non-scattering solution. The mathematical expression is A = εcl. The extinction coefficient ε is a characteristic constant of the solution, related to the wavelength of the incident light, the properties of the solution, temperature, and other factors.

 

The most commonly used method to determine the extinction coefficient is spectrophotometry. The spectrophotometer measures the absorbance of the solution at different wavelengths. Combined with known concentration and path length, the extinction coefficient can be calculated. This method is simple to operate and highly accurate, making it widely used in fields such as chemistry and biology.

 

Analysis Workflow

1. Reagent Preparation

Prepare the test solution and a series of standard solutions with known concentrations. Ensure that the solution is homogeneous and bubble-free during this process.

 

2. Instrument Debugging

Turn on the spectrophotometer and preheat it to a stable state. Use a blank solution (such as the solvent) as a reference and zero the spectrophotometer.

 

3. Standard Product Measurement

Measure the absorbance of a series of standard solutions with known concentrations at a suitable wavelength according to the characteristics of the test substance, and record the data. Plot a standard curve with concentration as the horizontal axis and absorbance as the vertical axis. Obtain the slope and intercept of the standard curve through linear regression.

 

4. Sample Measurement

Measure the absorbance of the test solution and record the data.

 

5. Data Processing

Calculate the concentration of the test solution based on the standard curve. Then, use the Beer-Lambert Law to calculate the extinction coefficient.

 

MtoZ Biolabs combined with spectrophotometry, can efficiently and accurately detect the extinction coefficient of biological products. It also offers other services related to the characterization of biological products.