The injector liners tend to get contaminated over a period of time due to injection of dirty samples. Due to adsorption on liner walls there is loss of some sample components and as a result there is a drop in sensitivity accompanied with broadening of the chromatographic peaks. The degree of deterioration of signals depends on the level of contamination of injected samples and can even become apparent even after 10 -15 injections. In such cases back flushing of columns is of little help. You may consider modification of the sample extraction and preparation stages but this can be time consuming.
An alternate option would be to clean or replace the liners. This is a time-consuming process as shown in the video and can interrupt the analysis sequence.
The interruptions are likely to be more frequent when you are engaged in pesticide residue analysis in fruit and vegetable specimens. In such cases you may have to remove liners for cleaning or replacement at shorter intervals. In such situations an automated liner exchange system can give you a lot of peace of mind. It makes possible liner exchange any time during the sampling sequence or at defined intervals thereby saving your valuable time and also saving you from cumbersome sample cleanup steps during sample preparation. Such an assembly comprises of programmable temperature vaporizing (PTV) inlet in combination with an autosampler. Every liner is fitted with a transfer adapter and an electrical gripper. A number of liners are sequentially picked up at predefined intervals and exchanged . The adapters provide a gas tight seal for contamination free storage and exchange.
Several commercial automated liner exchangers are available in the market which can be used for cool on-column inlet replacement .The injector top and the transfer adapter remains cool during the liner transfer .This results in minimal septum bleed or bleeding at the O-rings. The automated liner exchange has no significant effect on the performance of the gas chromatogram.
Gerstel automated liner exchange (ALEX) system is popular automated liner exchange which can be used with the Agilent GC and MS systems .
The time-saving provided by such liner exchangers assumes great significance in industrial and commercial laboratories which handle large sample batches unattended.