Chromatography Forum

Hi! I have an old waters 600 HPLC that is set up for semiprep operation with a manual injector with a 2 ml sample loop, and I don't want to ruin that setup, but it would be nice to have a second manual injector with an analytical sample loop and a switch between them.

I'm pretty sure I've seen this configuration implemented somewhere, but I would like some information on how to do this practically.

Could 2 injectors just be put in series, and the one not used set to 'load' so that it is bypassed? Or should the flow be switched.

Thanks in advance!

I'd just swap loops...

Swapping the loops would certainly be the cheapest, but somewhat inconvenient unless you are doing it infrequently.
I don't think there would be any problem with putting two injectors in series. That would add some extra-column volume to the system, but if the prep injector is first (i.e., upstream), that shouldn't matter too much. The exception would be if you are running gradients, in which case it would increase the dwell volume.

Gotcha. Maybe I'll thumb screw nuts on my sample loops, should make it pretty quick to exchange. I might try the two-in-a-row system at a later point.

Thank you for your quick replies!