This application note presents evolved gas analysis of thermal paper, including using heart cutting technique to transfer selected group of compounds to sepa - rate sample pathway.
Similar to the concept of thermogravimetry (TGA), Evolved Gas Analysis (EGA) is a method that uses precise temperature increments to first thermally extract and then decompose materials. The difference between TGA and EGA is that mass spectral data is produced in EGA relative to temperature instead of mass loss as in TGA, so more chemical information is gained.
However, in EGA studies on complex sample matrices, one challenge is that the target analytes may possess low concentration and overlap with many high con - centration compounds that may even saturate the detector. Traditional heart cutting is a two-dimensional gas chromatography technique that serves as an effective tool to provide selectivity to resolve this issue. Here, we use the same approach to remove material, which may overwhelm the material of interest, from an EGA run.
Experimental Setup
Thermal paper, coated with a material formulated to change color when exposed to heat, is widely used at cash registers. A piece of thermal paper sample underwent EGA at 100°C per minute from 100°C to 800°C. This temperature ramping rate was 5 times faster than TGA method. A short piece of fused silica was used to connect the GC inlet to the detector. Approximately 100 µg of paper was added to a Drop-In-Sample Chamber (DISC) tube, and analyzed with a 6150 Pyroprobe coupled to a GC/MS system. The GC oven was kept at 300°C to allow evolved compounds travel immediately to the detector without chromatographic separation. The heart cutting technique was performed by combining two methods, where the beginning of the 2nd method transferred selected compounds to the vent instead of to the GC. Additionally, multi-step pyrolysis GC analysis was followed, using thermal information gained from EGA analysis to yield better resolution.
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