The PTV Cold Injection System

There are many advantages of cold split and splitless sample injection  

The PTV cold injection technique is mainly used for residue analysis in the areas of pesticides, pharmaceuticals, polyaromatic hydrocarbons, brominated flame retardants, dioxins and PCBs. However, the enrichment of volatile halogenated hydrocarbons, the direct analysis of water and the formation of derivatives in the injector also demonstrate the broad versatility of the PTV type injector (Bergna et al., 1989 Mol et al., 1993 Blanch et al., 1994). 

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A special form of the PTV cold injection system consists of the column and insert connected via a press-fit attachment. Total sample transfer is possible in the same way as the classical PTV injection, but no spht is present to allow flushing of the injection area after evaporation. Injectors of this type can be used only for total sample transfer (e.g. a SPI (septum-equipped programmable injector). Figure 2.69). 

All other PTV adjustments of time and temperature are completely unchanged compared with total sample transfer Of particular importance for the split injection using the PTV cold injection system is the fact that the sample is injected into the cold injector (see also Section 2.2.7.5). The choice of start temperature of the G C oven is now no longer coupled to the boiling point of the solvent because of the solvent effect and is chosen according to the retention conditions (Tipler and Johnson, 1989). 

Figure 2.72 The course of an analysis with large quantities of solvent using the PTV cold injection system filled with a 1 cm Chro-mosorb plug lOOpL PCB solution (200pg/ jL). After the dead time, a broad solvent peak is registered. After the solvent peak is eluted, the split valve is closed and the PTV heated up. A smaller roughly triangular solvent peak is produced from adsorbed material. After...

Trimethylsulfonium hydroxide, derivatization agent for esterification and methylation, for example, free fatty acids, phenylureas, and so on. TMSH was used successfully to save on extra steps for the derivatization in the insert of the PTV cold injection system. 

Like cold on-column injection the PTV has a low thermal mass, so can be heated and cooled quickly. However, unlike cold on-column the sample is injected into an injector liner and not direct onto the column. Unlike conventional split/spUtless injection, the aim is to make use of volatility selectivity of the system rather than to inhibit it. By selecting an appropriate starting temperature, the anal34es condense in the liner if desired the solvent may be flushed away through... 

For sample introduction in HTGC, split, splitless, on-column injection, or combinations of the latter, the programmable temperature vaporizing (PTV) injector are suitable. Howeveq with the exception of cold on-column injection, none of these introduction systems fulfill the requirements of an adequate HTGC injection device and guarantees reliable results. 

All heated injector systems are well-known sources of error, due to the possibility of artifact formation, and in many cases, split, splitless, or PTV injection provides discrimination of high-boiling compounds by thermal degradation. Only cold on-column injection ensures quantitative sample transfer from the injection port into the capillary column without thermal stress of the samples or discrimination of high-boiling compounds. 

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