9910157319
Thermogravimetric Analysis (TGA): How Helpful in Drug Development
What is the Thermogravimetric Analysis (TGA)?
Thermogravimetric Analysis (TGA) is a technique used to measure the change in the mass of a material as a function of temperature or time, under a controlled atmosphere. The primary purpose of TGA is to assess the thermal stability, and composition and provide the loss on drying of a sample by monitoring its mass loss or gain when heated or cooled.
Principle of Thermogravimetric Analysis (TGA)
In TGA, a small sample (typically a few milligrams) is placed on a highly sensitive balance and subjected to a controlled temperature program in a furnace or oven. The temperature is usually increased at a constant rate, and the change in the mass of the sample is continuously recorded. The mass change is plotted as a function of temperature or time, yielding a TGA curve.
Key Components of TGA Instrumentation
The following are the key components of the TGA:
- Balance: A high-precision balance to measure the mass of the sample with high sensitivity.
- Furnace/Heater: A temperature-controlled environment where the sample is heated or cooled, typically with a programmable heating rate.
- Sample Holder: A platform or pan where the sample is placed, which is usually made from materials that do not interfere with the analysis (e.g., platinum, alumina).
- Gas Flow System: An optional feature where the sample is exposed to different atmospheres (e.g., inert gas like nitrogen, oxygen, or air) to observe how the sample reacts under various conditions.
Applications of TGA
The following are the different applications of the TGA:
- To find out low on drying of the pharmaceuticals such as during standard qualification
- Determination of Thermal Stability: TGA can determine at what temperature a material will begin to decompose or undergo other thermal changes.
- Composition Analysis: By observing the pattern of mass loss, TGA can help identify the presence of specific components, such as moisture, volatiles, additives, and fillers.
- Study of Decomposition Mechanisms: TGA can be used to investigate the degradation processes of polymers, composites, and other materials under heating.
- Quantification of Organic/Inorganic Content: TGA can be used to quantify the organic content in materials (e.g., polymers) by measuring the weight loss upon heating, which can be correlated with the amount of organic material.
- Polymer Characterization: Understanding thermal transitions and the degradation behavior of polymers, resins, and elastomers.
TGA Data Interpretation
- TGA Curve: The primary output is a plot of mass vs. temperature or mass vs. time. The typical features of a TGA curve include:
- Weight Loss Steps: Indicating the loss of volatile components, solvents, or degradation of the material.
- Plateaus: Where the mass remains relatively constant as the sample undergoes no significant thermal decomposition.
- Final Mass: Some materials (e.g., inorganic materials like metals or ceramics) may leave a residual mass at the end of the experiment (e.g., ash).
Derivatives of TGA (DTG): The derivative of the TGA curve, called the DTG (Derivative Thermogravimetric) curve, is often plotted to highlight the rate of mass loss. Peaks on the DTG curve indicate the temperature at which the fastest rate of mass loss occurs.
Case Study:
- A polymeric material might show a weight loss at a specific temperature range (e.g., 250–350°C) due to the decomposition of the polymer backbone.
- If the sample contains inorganic fillers, such as silica, a residual weight percentage may remain after the complete thermal decomposition of the organic material.
Conclusion:
Thermogravimetric analysis is a versatile and valuable technique for characterizing the thermal properties and composition of pharmaceuticals. I hope this article has helped you understand TGA and its importance in pharmaceutical development. You may also want to check out other articles on my blog, such as role of HPLCMS and GCMS in pharmaceutical development.