Client Operated Instrument

The TA Discovery thermogravimetric analyzer (TGA) 5500 with the Pfeiffer quadrupole mass spectrometer accessory allows for the thermal analysis of materials and their evolved gases. Thermogravimetric analysis is an analytical technique that measures the amount and rate of weight change in a material, either as a function of increasing temperature or isothermally as a function of time, in a controlled atmosphere. It can be used to detect phase changes due to decomposition, oxidation, or dehydration. Users who wish to be trained should contact the lab to schedule training. Instrument time is reserved through ChemFOM. 

Key Features and Specifications

Theory of Operation

The Discovery TGA 5500 has a vertical thermobalance which is mounted above the furnace. The null balance consists of a horizontal balance beam, also referred to as an arm. On either end of the beam, there is an attachment for the sample pan or the reference tare pan using platinum wires. The tare pan offsets the weight of the sample pan, thereby approximately balancing the sample pan mass and reducing the drive force required to maintain equilibrium. The balance is kept in a null position through meter movement. The meter movement consist of a taut band that supports a wire coil to which the balance beam is mounted and a field assembly comprising a permanent magnet and magnetically soft iron armature to create a constant strength magnetic field. Electrical current supplied by a meter coil drive passes through the wire coil and interacts with the magnetic field to apply torque to the balance beam to maintain the null position. Displacement of the null balance from the null position is sensed by a displacement sensor. The electrical current in the coil when the null balance is in the null position is directly proportional to the sum of the forces acting on the balance arm and is a measure of the sample weight when all of the extraneous forces have been eliminated or accounted for.  

The Discovery TGA 5500 furnace uses quartz halogen lamps as the heat source. Four IR lamps are arranged in a circular pattern surrounding the quartz tube that encloses the sample area.The sample area is enclosed by a cylinder inside of the quartz tube. This cylinder absorbs radiation from the lamps and heats the sample, pan, and thermocouple. Temperature is measured and controlled by a thermocouple assembly under the sample pan. The thermocouple assembly includes a second thermocouple to protect the furnace from excessive temperature. Purge gas enters the sample area through a tube within the quartz tube, passes through a hole in the wall of the absorber across the sample pan, and through another hole in the wall of the absorber, finally exiting through a second tube in the quartz tube. Rapid cooling of the furnace is accomplished by air that enters the furnace chamber through the bottom of the furnace.  

The Pfeiffer ThermoStar MS is an accessory to the TA TGA Discovery 5500 that allows the for the characterization of evolved gases during thermal analysis. Evolved gas is transferred from the TGA to the mass spectrometer through a heated transfer line which is maintained at 200°C. A 0.15 mm quartz capillary is used to introduce the evolved gases into the mass spectrometer. The ThermoStar includes a cross beam ion source, with either a tungsten or iridium coated yttrium oxide filament. Mass separation is achieved through the use a quadrupole mass filter, with a mass range of 1-300 amu and a mass accuracy of 0.5 amu. Ions are detected via the dual detectors using either the Faraday cup or secondary electron multiplier detector. The mass spectrometer is capable of parts per billion sensitivity depending on the analyte. Data collection can be initiated directly from the TGA software, and the resulting MS data can be combined with its corresponding TGA results for direct overlaying and comparison.

Link to manufacturer's brochure: https://www.tainstruments.com/pdf/brochure/BROCH-DTGA-HP750.pdf