Laserchrom HPLC - Technical Support Centre

The syringe in an autosampler has two primary functions:

to draw sample from the vials
to pump the wash solution.

So we already know where the air must have come from!

If the sample level in the vial is too low for the amount required for the injection(s) that have been programmed, air will be drawn in once the level goes below the tip of the needle. This can also occur if the needle depth is set too high.

Air will also be drawn in if the wash solution runs out, or if it is not degassed prior to use. It is easy to forget this, because the wash solution can last for weeks, and it only stays degassed for a day or so at most. If air is repeatedly drawn in from the wash solution, check if it has a sinter filter on the end of the solvent line, and if so, check if it is blocked. (Simply remove the sinter and see if the problem goes away. If it doesn't have a sinter filter, it should! It keeps the autosampler free from particles, and it keeps the solvent line on the bottom of the bottle!

Run a few wash cycles, and the air should be eliminated automatically into the autosampler waste bottle. Alternatively, manually remove the syringe and expel the air. fill it with eluent and refit.