TG-GC-MS - Evolved Gas Analysis with Chromatographic Pre-Separation - product brochure
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TGA-GC-MS Coupling Evolved Gas Analysis with Chromatographic Pre-Separation Analyzing & Testing

Thermogravimetry and Thermogravimetry (TGA) and Simultaneous Thermal Analysis (STA) Thermogravimetry (TGA) and Simultaneous Thermal Analysis (STA), which is primarily simultaneous TGA-DSC (Differential Scanning Calorimetry), are widely applied analytical methods for the research and quality control of all kinds of inorganic and organic materials and products. Often, it is not sufficient to determine only the mass and enthalpy changes resulting from a thermal treatment; additional information may be required about the volatile products evolved during chemical reactions, thermally induced...

Evolved Gas Analysis Gas Chromatography (GC) – Mass Spectrometry (MS) GC is a high-resolution method for separating volatile and semivolatile compounds. The gas mixtures are separated based on the differences in component distribution between a stationary phase (e.g., inner coating of a capillary) and a mobile phase (purge gas; e.g., helium). Gas components with low affinity for the stationary phase but higher affinity for the mobile phase will be rapidly carried away by the purge gas, whereas gases with a high affinity for the stationary phase will follow with a relatively significant time...

TGA/STA-GC-MS Coupling Since the gas separation in the GC column takes a certain amount of time – the duration of which depends upon sample characteristics, column flow rate, column length, and stationary and mobile phase – it is not possible to couple into the GC with a continuous online sample gas flow. Our solution, therefore, was to develop a direct coupling in a quasi-continuous mode using heated automatic valves, which allow for softwarecontrolled gas sampling (flow-through sampling loop) and gas injection, even at short intervals, within the NETZSCH Proteus® software. Sample...

Valve Box The NETZSCH valve box contains a heated double loop system. Operation of the valve is completely controlled by the NETZSCH Proteus® software. This system allows either continuous injections (i.e., recurrent injections at defined intervals and with a definable number of occurrences) to the GC column or event-controlled injections. Maximum Flexibility To achieve a higher concentration in evolved gas species, an optional cooling trap can be placed between the injector system and the GC column. Additionally, it is also possible to directly inject the gas mix into the mass...

TGA/STA-GC-MS Coupling Gas chromatography comes into play when MS has reached its limitations in determining the properties of complex gas mixtures. 4 Transfer line to the GC-MS Mass spectrometer Valve-based gas injector and temperature controller

State-of-the-art Quadrupole-MS >1000 u High-speed sampling; up to 20000 u/s Various ionization techniques available (EI, CI, PI, depending on MS type) Tool-free servicing, e.g., simplified ion source maintenance Stand-alone MS measurements Transfer System Heated adapter system (up to 400°C) Heated transferline (max. 350 °C) with inert glass-lined steel capillary NETZSCH Box – Valve-Based Gas Injector Double-loop system for short injection intervals Software integrated in Proteus® Special insulation design for constant temperature (up to 350 °C) to prevent cold spots Easy GC integration via...

THE THREE MEASUREMENT MODES QUASI-CONTINUOUS, EVENTCONTROLLED AND CRYO TRAP ARE EXPLAINED WITH THE HELP OF THE SAME MATERIAL: POLYCARBONATE (PC) 100 During the entire TGA run, the gases produced were sampled at intervals of 4 min in the GC column, which was kept at a constant temperature of 200°C. As soon as the mass loss started, the total ion current (TIC) detected several peaks. Analysis of the MS spectra for each injection gave a mixture of compounds released during pyrolysis. Eight different compounds were identified. Due to the increased temperature of the column, not all peaks were...

Event-Controlled Mode One injection to the column was automatically conducted as soon as the DTG peak (peak in the first derivative of the TGA curve) was detected by the software. The GC column was heated from 40°C to 300°C at 5 K/min to separate the compound mixture. Nine compounds could clearly be identified. To do so, the mass spectra of each peak were compared to the NIST library. The identification of phenol is shown below as an example. Total ion chromatogram for polycarbonate measured in the event mode; peaks labeled with identified compounds. Name CO2 Phenol 4-Methylphenol...

Multi-Injection and Cryo Trap Mode During the TGA measurement, the outer jacket of the cryo trap is cooled with liquid nitrogen to trap outgassing compounds (cooling phase, left image) to increase concentration. After the gas collection has completed, the trap is immediately heated with the built-in heating cartridge (heating phase, right image) at high heating rates to ensure sharp gas injection to the column. Column in Heating Cartridge Cooling Phase Heating Phase Gaseous coolant out in Liquid coolant Functional principle of the cryo trap In principle, the detection limit of by-products...

Evaluation of the GC-MS-TIC Chromatograms TIC *106/Counts 1.080 min The GC-MS software enables easy evaluation of the mass spectra for each peak in the chromatogram. An easy zoom-in function allows for enlargement of the peaks. The NIST search generates a compound list including retention time, score and compound name. Each measured spectrum can be displayed in comparison to the NIST spectrum.

This example shows a thermogravimetric measurement (TGA, green) on polystyrene with the event-controlled mode. One gas portion was injected on the column at the DTG peak (black) at 418°C. Separation of the compounds released over the GC column with a temperature ramp of 15 K/min yielded the three main compounds styrene, the styrene dimer and styrene trimer, which are in good correlation with literature data. Unlimited Applications TGA curve (green) for polystyrene (PS) under inert conditions; mass loss rate (DTG, black) Total ion chromatogram for polystyrene (PS), measured in the event...