What is the sensitivity of TG? How small a mass change can it detect?

TG Sensitivity and Mass Change Detection Capabilities

Modern thermogravimetric analyzers exhibit exceptional sensitivity, typically capable of detecting mass changes as small as 0.1 micrograms (μg) under optimal conditions. This represents approximately 0.001% of a standard 10-milligram sample, demonstrating the technique's remarkable precision for quantifying subtle mass variations during thermal transitions. The actual detectable mass change depends on several instrumental and experimental factors; high-performance microbalances in research-grade TGA instruments achieve even greater sensitivity, down to 0.01 μg, in controlled environments.

Factors Influencing Practical Detection Limits

Instrumental and Environmental Considerations

The theoretical sensitivity of TGA is influenced by multiple factors, including balance design, environmental stability, and experimental parameters. Microbalances with electromagnetic compensation systems provide the highest sensitivity but require strict vibration isolation and thermal stability. Buoyancy effects, gas flow turbulence, and static electricity can all introduce noise that elevates practical detection limits above theoretical capabilities. For analyzing materials such as ceramic precursors or certain Plastics, these factors must be carefully controlled to achieve the best possible detection limits.

Sample-Specific Considerations

The practical detection limit varies with material properties and sample characteristics. Highly dense materials typically allow better signal-to-noise ratios than low-density powders. Decomposition reactions with rapid mass loss are more readily detected than gradual processes, such as slow desorption. For additive manufacturing materials, including metal powders used in Powder Bed Fusion or polymers used in Material Extrusion, sample homogeneity significantly affects measurement precision and the ability to detect subtle transitions.

Application-Specific Detection Capabilities

High-Sensitivity Applications

For precise quantification of minor components, such as moisture content in Aluminum Alloys powders or residual solvent in Resins, TGA can reliably detect concentrations as low as 0.01% with proper method optimization. This sensitivity is crucial for quality control in Aerospace and Aviation applications, where trace moisture affects powder flow characteristics and final part properties. The technique also excels at detecting minor polymer additives, filler content, and the effectiveness of thermal stabilizers.

Comparison with Complementary Techniques

While TGA provides exceptional mass change sensitivity, it cannot identify the chemical nature of evolved gases. For complete characterization, we often combine TGA with Fourier-transform infrared spectroscopy or mass spectrometry to identify decomposition products. For elemental composition analysis rather than mass changes, techniques like OES or EDS remain more appropriate for materials such as Stainless Steel or Titanium Alloy.