The Thermogravimetric Analysis (TGA) is a remarkable technique used to characterize materials used in various pharmaceutical, food, environmental, and petrochemical applications. TGA measures the composition, purity, decomposition reactions, decomposition temperature and absorbed moisture content of your products.

How TGA Method Works

TGA analysis provides the understanding of change in mass of a material in terms of both time and temperature. In this method the sample is heated from ambient to 1000 degree in nitrogen or air, then the resultant weight loss is calculated which occurs due to semi volatile compounds, polymer degradation, ash content, carbon black and moisture. The loss of surface absorbed solvent can be distinguished from solvent in the crystal lattice and from degradation losses. The measurements are carried out in atmospheres having controlled humidity and oxygen concentration to reveal interactions with the drug substance, between drug substances, and between active substances and excipients or packaging materials.

What do we get from TGA?

• It is beneficial in routine analysis of content determination to get accurate understanding of sample composition.
• It helps in understanding the reactivity corrosivity of sample materials when exposed to specific environments.
• TGA analyzes the changes in size, shape and overall mass when exposed to varying temperatures.
• It gives accurate details of the mass change of the materials under test.
• It provides necessary data for a wide range of materials characterization objectives.
• Determines the stability of pharmaceutical drugs.
• Allows quantitative composition analysis.
• It determines the purity of a mineral, inorganic compound, or organic material.
• Helps in determining the water/carbon content or other residual solvents in a material.
• Allows analysis of reactions with air, oxygen, or other reactive gas.

Thermogravimetric Analysis Applications

Thermal Stability

TGA is used to evaluate the thermal stability of a material in a desired temperature range. A thermally stable material will have no observed mass change. Negligible mass loss corresponds to little or no slope in the TGA trace. TGA also gives the upper use temperature of a material. The material begins to degrade beyond this temperature.

Oxidation and Combustion

The thermogravimetric analyser causes ion combustion in the sample by heating it beyond its ignition temperature. Oxidative mass losses are the most common observable losses in TGA

Thermogravimetric kinetics

Thermogravimetric kinetics can be observed for insight into the reaction mechanisms of thermal decomposition involved in the pyrolysis and combustion processes of different materials.

TGA materials analysis

• This process uses heat to force reactions and physical changes in materials.
• TGA provides quantitative measurement of mass change in materials associated with transition and thermal degradation.
• It records change in mass from dehydration, decomposition, and oxidation of a sample with time and temperature.
• Characteristic thermogravimetric curves are given for specific materials and chemical compounds due to unique sequences from physicochemical reactions occurring over specific temperature ranges and heating rates. These unique characteristics are related to the molecular structure of the sample.

Scope

In Thermogravimetric Analysis the sample is heated at a uniform rate in an appropriate environment to measure the percent weight loss of a test sample. The loss in weight over specific temperature ranges provides an indication of the composition of the sample, volatiles, inert filler and thermal stability.

Method

TGA analysis is performed by gradually raising the temperature of a sample in a furnace as weight is measured on an analytical balance that remains outside the furnace. Thermogravimetric analysis instrument measures the changes in a sample’s weight in a particular temperature by enclosing the sample in an oven. In Thermogravimetric analysis the result obtained appears as a continuous chart record, a schematic, typical, single step decomposition reaction. We also test for moisture and ash. In this process, the sample’s mass is uninterruptedly monitored for changes. Consequently, we get an in-depth understanding of changes in mass of a particular material. ISO 11358 standards are used for TGA. It is applicable in solids and liquids.

Thermogravimetric Analysis Principle

In the basic principle of thermogravimetric analysis, the sample is heated in a given environment (air, N2, CO2, He, Ar, etc.) at controlled rate. Consequently, as a function of temperature or time the change in the weight of the substance is recorded. At a constant rate the temperature is increased for a known initial weight of the substance . The changes in weights are recorded as a function of temperature at different time intervals as thermogravimetric analysis notes. Indeed, this plot of weight change against temperature is called thermogravimetric curve or thermogram.

What are the types of Thermogravimetric Analysis(TGA)?

The three types of thermographic analysis represent different ways to apply heat to the sample, as weight change is measured over time.
• Isothermal or static thermogravimetry: Temperature is constant
• Dynamic thermogravimetry: Temperature is changed in a linear manner.
• Quasi Static thermogravimetry: A series of increasing temperatures

Vital details on TGA

• Sample size: The sample should weigh about 50 milligrams.
• Sample type and compatibility: TGA is typically used for pharmaceutical substances.
• Unique capabilities: TGA records weight loss as a function of temperature.
• Timing: Typical analysis time is about 1 hour