Quantitative analysis can be classified based on the method used to measure the amount of a substance. Here are the main types explained:
1. Gravimetric Analysis
- Principle: Measure the mass of a substance or its derivative to find the amount present.
- How it works: The substance is converted into a solid of known composition, which is weighed.
- Example: Precipitating and weighing barium sulfate to determine sulfate in water.
2. Volumetric Analysis (Titration)
- Principle: Measure the volume of a solution of known concentration required to react completely with the substance.
- How it works: A titrant is added to the sample until the reaction is complete (often indicated by a color change).
- Example: Using NaOH to determine the amount of HCl in a solution.
3. Spectrophotometric Analysis
- Principle: Measure the amount of light absorbed by a solution, which is proportional to the concentration.
- How it works: A spectrophotometer shines light through the sample and measures absorbance.
- Example: Determining the concentration of copper ions in water using a colored complex.
4. Electrochemical Analysis
- Principle: Measure the electric current or potential related to the amount of substance.
- Methods include:
- Potentiometry: Measures voltage (e.g., pH measurement).
- Coulometry: Measures total electric charge passed to determine substance.
- Example: Determining the concentration of metal ions using ion-selective electrodes.
5. Chromatographic Analysis
- Principle: Separate components of a mixture and measure their quantity.
- How it works: The sample is passed through a stationary phase, and components are detected as they elute.
- Example: Measuring caffeine content in a soft drink using HPLC.
Summary:
Quantitative analysis can be done by measuring mass, volume, light absorption, electrical signals, or separation of components. Each method is chosen based on the substance and accuracy needed.