TA Instrument Discovery Mass Spectrometry

1. Overview

Thermogravimetric Analysis (TGA) measures sample mass changes under controlled heating.
Evolved Gas Analysis (EGA) identifies gaseous products released during decomposition, volatilization, or oxidation in real time.
TGA-MS combines TGA with Mass Spectrometry to correlate mass loss with the chemical identity of evolved gases.

2. Principle

Evolved gases are transferred from the TGA to the MS through a heated transfer line to prevent condensation.
Ionization: Molecules are ionized (commonly by 70 eV electron impact) to form positive ions.
Mass Analysis: Ions are separated by mass-to-charge ratio (m/z) in a mass analyzer (e.g., quadrupole).
Detection: Ion currents are recorded using detectors such as a Faraday cup or electron multiplier.
Scanning Modes: Either a full m/z scan or a selective “peak jump” mode can be used to monitor specific ions over temperature or time.

3. Data Interpretation

• TGA‑MS results typically display:
  • TGA mass loss curve
  • Derivative (DTG) curve
  • Selected m/z ion signals vs. temperature
• Peaks in specific m/z channels indicate the release of particular gases (e.g., m/z 17 → NH₃, 18 → H₂O, 44 → CO₂).
• Enables assignment of mass loss events to chemical reactions or decomposition steps.

4. Example Application

Nylon 66 degradation: Mass loss occurs around 427 °C. Characteristic m/z signals (17, 18, 27, 41, 44, 55) indicate NH₃, H₂O, CO₂, and hydrocarbon fragments.
This reveals polymer chain scission and the formation of small volatile molecules.

5. Capabilities:

• Optimized for evolved gas analysis
• Mass range: 1-300 amu
• Mass resolution: >0.5 amu
• Quadruple detection system with parts per billion (ppb) sensitivity