Varian ProStar 400, Operation Manual

Page: 35 / 63

I
NSTALLATION
ProStar 400 AutoSampler
9
Injection volume
Due to the reduced solvent velocity near the wall of the tubing
(loop), it takes more than the nominal loopvolume to fill the loop
reproducibly. For flushed loop injections the ProStar 400
takes
twice the loop volume from the sample vial for a sample loop
equal to or larger than 100 µL and three times the loop volume
for a sample loop smaller than 100 µL.
Sample consumption formula (dispenser controlled)
The minimum amount of sample needed for N injections per vial:
Flushed loop injections for 100 µL loop or larger:
rest pre-flush 2N x loop (N-1) x 4 (µL)
Flushed loop injections for loop smaller than 100 µL:
rest pre-flush 3N x loop (N-1) x 4 (µL)
Example: 3 flushed loop injections out of a standard sample vial
using a 20 µL loop and 30 µL pre-flush volume, minimum sample
volume needed is:
200 µL + 30 µL + 3 x 3 x 20 µL + 2 x 4 µL = 418 µL
Sample consumption for headspace pressure controlled loopfill
If the sample loop is filled on a time basis by sample headspace
pressure (see
Injection Principle on page 14 and Operation on
page 17), sample consumption has to be determined
experimentally since the flow is dependent on the viscosity. (For
water, the flow rate is approximately 1 mL/min.) Make sure that
programmed fill time is sufficient to flush the loop with at least
twice its volume.
If more injections are to be taken from the same vial, please note
that a volume equal to max. 20% of the headspace in the vial
after loopfill may flow to waste during analysis time due to
expansion of the headspace back to atmospheric pressure.