Video-taped sample evaporation in hot chambers simulating gas chromatography split/splitless injectors. I. Thermospray injection.
The processes in devices imitating vaporising injectors were visualised and video-taped using perylene as a fluorescent marker for non-evaporated samples. The observations in the context of thermospray injection are summarised. Partial evaporation inside the needle turns the solvent into a propellant which nebulises the sample liquid at the needle exit. Evaporation in the vaporising chamber occurs from fine droplets suspended in the gas phase. Empty injector liners are best suited; packings with glass wool or obstacles in the liner, like the cup, have no significant effect on the process observed. Non-evaporated (matrix) material forms aerosol particles which may enter the column together with the vapours, but most of them are transferred to the liner wall. Since solute material may be carried along, this is a possible source of matrix effects.
Improved Techniques for Sampling and Sample Introduction in Gas Chromatography
In this work, we present a technique for the preparation of tailor-made sorbent phases for thick film open tubular traps. Solid or liquid polymers are dispersed in a polydimethylsiloxane (PDMS) pre-polymer, which is cross-linked in situ after coating. The technique is evaluated by preparing thick film open tubular traps with PDMS containing solid or liquid poly(ethylene glycol) (PEG). A significant increase in retention for polar analytes is observed, even when only 7.5% PEG is present. The increase in retention for 3-chloro-1,2-propanediol is more than tenfold. The preparation method is simple and no solvents are required. Also, the concept provides great flexibility in terms of phase composition.
New split injection technique in capillary column gas chromatography
Abstract The main sources of discrimination in split injection arise from the change in the splitting ratio caused by variation in the composition of the gas phase and non-uniform distribution of the solvent in the total gaseous sample plug formed during evaporation. Taking this into account, a new split injection technique, characterized by interruption of the carrier gas flow during the sample evaporation period, has been developed whereby the formation of a sample plug with uniform solvent distribution is enhanced. The applicability of the method is discussed and results obtained on two common kinds of sample and under different injection conditions are given.