Sample pyrolysis

The external heat flux (q"x) from the cone heater does not exclusively determine the heat flux important for samples pyrolysis in the cone calorimeter, since the reradiation from the hot sample surface (q"eTad), the loss by thermal conductivity into the specimen and the surroundings ( I SS), and the heat flux from the flame (q Lmt) are also of the same order of magnitude.82 85 Thus, the heat flux effective with respect to pyrolysis during a cone calorimeter run (qeii) is the result of the external heat flux and the material s response (qeB = q L + < L - gCad - qLs). 

Fig. 4.7.2. Schematic diagram of a Curie-point pyrolyzer (Fischer, Germany). Note the possible modifications of the wire tip (a, b, and c) for solid samples. Pyrolysis glass injector (/), ferromagnetic wire (2), carrier gas inlet (3), impulse cable from power generator (4), induction coil (5), aluminum box (6), adapter for GC injector (7), GC inlet (8), GC septum (9), GC oven (10)...

Studies of 0/ 0 isotope variations in several vascular plant species, mosses and environmental surface bog water from temperate peat bogs (Switzerland) used as climatic archives for paleoclimatic reconstruction were reported by Menot-Combes et 8 0-values in organic material were determined by the online continuous flow method after sample pyrolysis at 1080 °C in the presence of glassy carbon in a Carlo-Erba elemental analyzer. The gases obtained (CO, N2 and H2O) were separated by passing them through a water trap and a GC column in a helium carrier gas. The isotope composition of CO was measured with a VG Prism II isotope ratio mass spectrometer relative to the VSMOW isotope standard. The overall analytical uncertainty is 0.08%o for water 8 0-values." ... 

A wood cylinder is vertically positioned in the uniformly heated zone of the reactor, through a suspension system, which is connected to a precision balance. The sample is exposed to the same radiative heat flux along the lateral surface. For each chosen radiation intensity, steady temperatures of the radiant heater are achieved within a couple of minutes (maximum heating rates of about 750K/s) but, given the thick sample, pyrolysis takes place under heat transfer control. 

A CDS Pyroprobe 100 combined with a gas chromatograph (CP 9000) was used to pyrolyze and analyze a 70 mg sample. Pyrolysis temperature was set to 500 C. Heating rate was 600°C " and pyrolysis time was 10 s. A DB 1701 column (60 mxO.25 mm, 0.25 mm film thickness) was used for the separation of monomeric volatile compounds. Further details of the procedure can be found elsewhere [18]. External calibration was used for quantification of levogtucosenone. 

The mechanical problems related to the rapid solid sample introduction or related to the introduction of solid samples with no air leak makes this type of pyrolyser more appropriate for liquid or even gas sample pyrolysis. Also, it being possible to build large furnace pyrolysers, this type is successfully used when larger amounts of sample are necessary to be pyrolysed. This is a common case for the pyrolysis of non-homogeneous samples when a few mg of sample do not represent well the average sample composition. 

Figure 8.3.1. Pyrogram of a crosslinked phenol-formaldehyde resin sample. Pyrolysis done on 0.4 mg material at 60(f C in He, with the separation on a Carbowax type column.

Cooks and co-workers [ 164,251a,b] studied the structures of modified bases of DNA with a high specificity. They used a direct introduction probe to control sample pyrolysis and measurements were performed in Cl with isobutane. The different bases of DNA were thus liberated intact from a salmon sperm DNA sample. 

The carbonaceous type residue remaining after sample pyrolysis at 500°C under an inert (nitrogen) atmosphere in a controlled manner for a specific time. ASTM D4530. 

On a heated filament (a) Filament heated directly by electric current The pyrolysis temperature can be varied during pyrolysis. Simple design The method is applicable to small samples. Pyrolysis of fibrous materials is difficult. Temperature control is limited... 

Although the applications described here have concerned diverse macromolecular samples, pyrolysis is also of utility in the analysis of smaller molecules, particularly quaternary ammonium compounds, which undergo quantitative thermal fragmentation to volatile products. For example, the specificity and sensitivity afforded by Py-GC/MS with mass fragmentography renders the technique suitable for the analysis of endogenous neurotransmitters such as acetylcholine at the l-2pmol level. However, in all cases, analytical throughput is limited by the retention times of the pyrolysis products, a condition that is particularly severe in taxonomic applications. Automation allows extended use, but direct Py-MS... 

Identifled/Investigated Material Sample Pyrolysis Experimental Conditions... 

Images of the five pyrolysis samples are shown in Figures 3.5 to 3.9. These images show that initially the clay-carbonaceous char layer is thin, but as the pyrolysis times increase, the samples are comprised of a greater fraction of char until the char dominates the structure in the 400 s and 1150 s samples. Pyrolysis residues were collected from three regions on each of the five... 

Weight of sample Pyrolysis temperature Pyrolysis gas GC column... 

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