[Babcock_Hall]

What is the best time to remove the syringe from a manual injector?  I have viewed a couple of videos online.  In one, the syringe was removed immediately, but in the other, the syringe was not removed until the run was completed and the injector rotated back to the load position:  http://www.rajaha.com/hplc-injection/  One result from Google book suggested that the answer was somewhat dependent upon whether one was filling the sample loop partially or completely.

[tomek]

I used to withdraw syringe after turning the injector to inject position just after the run had started. It was on JASCO HPLC and I was told by the people who set this up to do it like this. Now we have upgraded to an autosampler. Make sure you're using syringe with flat end otherwise you're risking sratching the rotor.

[Babcock_Hall]

Yes, we use needles with a flat end.  I assume using other needles may lead to leaks, or to scratching something internal, or to both.

[Arkcon]

The key is consistency.  Some people leave the syringe in place, and the loop in inject position for the whole run.  The loop adds dead volume.  Some people sit ch the loop back to load once one loop volume has been swept through.  It is safest to remove the syringe at this time.  They then haven't added dead volume for the whole run.  Now, if the two people compare results, retention times will shift.