Headspace-programmed temperature vaporization

The low concentration levels of the compounds in environmental samples impose specific requirements in terms of sample injection for GC analysis. In addition to the common injection techniques of capillary GC (split, splitless, on-column, and programmed temperature vaporized (PTV) injection), some other sample introduction methods coupled to GC such as solid-phase microextraction (SPME), headspace, etc., have favored the versatility of GC and reduced the time required for sample preparation. These techniques have an advantage over the conventional injection methods, which is that a preconcentration step prior to GC... 

Poy, F. and Cobelli, L. (1985) Automatic Headspace and Programmed Temperature Vaporizer (PTV) Operated in Cryo-Enrichment Mode in High Resolution Gas Chromatography. / Chrom. ScL, 23(3), 114-119. 

Dynamic-HeadSpace (D-HS) is a highly sensitive sampling technique which is commonly used in this context. However, due to its cost (requires using a thermal desorber and a Programmed Temperature Vaporizing (PTV) injector) and complexity of implementation, the use of passive techniques have been developed, in particular, HeadSpace-Solid-Phase Micro-Extraction (SPME). 

Figure 11.5 shows an example of detection of TNT headspace vapor at room temperature in MS mode and in MS/MS mode. In the latter example, the detector is programmed to trigger an excitation waveform when an ion signal at m/z 227 (TNT) is observed. The observation of fragment ions at m/z 210 and 197 is positive identification of TNT. 

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