Resistive Heating Autosamplers

Two approaches to autosampling with resistively heated filaments are available, one in which multiple filaments are used and one in which a common filament is used. The former uses up to 14 different filament interfaces, each of which is connected sequentially to the gas chromatograph for pyrolysis. The computer permits individual control of each filament, so each sample may be analyzed using a different program. Like the Curie-point systems, the samples may be placed directly onto the heating filament. 

In the other version, a common coil filament is used, into which samples placed into quartz tubes are dropped. The quarts tubes are delivered from a carousel, which can hold up to 35 samples. Different pyrolysis conditions may be programmed for 

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There are several advantages of the resistively heated filament pyrolysers compared to other types. They can achieve very short TRT values, the temperature range is large, and Teq can be set at any desired value in this range. Several commercially available instruments are capable of performing programmed pyrolysis, and autosampling capability is also available (such as the CDS AS-2500). 

Different practical constructions of a Curie point pyrolyzer are commercially available. In these systems, the sample is put in direct contact with the ferromagnetic alloy, which is usually in the shape of a ribbon that can be folded over the sample forming a sample holder. The sample and its holder are maintained in a stream of inert gas in a similar way as for resistively heated filaments. The housing where the sample and its ferromagnetic holder are introduced is also heated to avoid the condensation of the pyrolysate but without decomposing the sample before pyrolysis. Autosample capabilities for Curie point pyrolyzers are also commercially available (e.g. DyChrom modelJPS-330) [11, 12]. 

In the interest of efficiency, autosamplers have become increasingly important in analytical laboratories. Autosampling systems are now available for all three types of pyrolysis equipment furnaces. Curie point, and resistively heated filament... 

Pyrolyzers have been adapted to provide automatic, imattended control of Py-GC. An early system used precoated pyrolysis wires held in quartz tubes on a turntable. These were sequentially loaded, accurately positioned in the induction coil, pyrolyzed, analyzed by capillary GC, and ejected. An alternative has used an automatic solids injector for samples enclosed in iron foil, and a furnace system has enabled sampling of the Martian surface. Autosampling systems based upon conventional pyrolyzers are now commercially available for resistively heated filaments, microfurnaces, and Curie-point pyrolyzers. One such system... 

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