Spectrophotometry is a technique used in quantitative analysis to measure the amount of light absorbed or transmitted by a substance at a specific wavelength. It helps determine the concentration of a substance in a solution.
Key Points:
- Principle:
- Based on Beer–Lambert Law, which states that the absorbance of light by a solution is directly proportional to the concentration of the absorbing substance and the path length of the light.
- Absorbance (A) = ε × c × l, where:
- ε = molar absorptivity
- c = concentration
- l = path length of the light through the solution
- How it Works:
- A beam of light of a specific wavelength passes through the solution.
- A detector measures the intensity of light before and after passing through the solution.
- The decrease in light intensity (absorbance) is used to calculate the concentration.
- Uses:
- Measuring concentration of colored solutions (e.g., iron, copper ions).
- Enzyme activity assays in biochemistry.
- Monitoring chemical reactions.
- Advantages:
- Highly sensitive and accurate.
- Requires very small amounts of sample.
- Quick and non-destructive.
In short: Spectrophotometry is a method to measure how much light a substance absorbs, which allows scientists to determine its concentration in a solution.