variation of liquid injection

[jiangds06]

intent to inject 1ul, what is the variation of autosampler injection volume?

[Arne]

that really depends. Anywhere from <1 % to 5% I would guess. Just inject a standard repeatedly and measure it's peak area to get an idea of injection volume variation. Use an internal standard to correct for these effects.

[BHolmes]

Depends on the size of your syringe, injection volume, and your sample. If you use a 10uL syringe for 1uL injection, you are only using 10% of the total syringe volume which is not ideal. To ensure high precision you want to use around 20-80% of the total syringe volume. So for your target injection of 1uL, I would suggest you use a 5uL syringe for 20% of total syringe volume. The sample you inject is going to affect precision as well, a viscous sample is going to have a lower precision than a less viscous sample.

In the end, the best way to measure precision for injection volume is to actually inject some samples on your system and determine the %RSD of peak areas for a set of replicate injections.

Hamilton is major manufacturer of instrument syringes, here is their general statement on syringe accuracy and precision http://www.hamiltoncompany.com/download ... rmance.pdf

[James_Ball]

intent to inject 1ul, what is the variation of autosampler injection volume?

What type of autosampler are you using? Is it Agilent that uses steps to set the volume or more of the Leap type that used a screw drive and stepper motor? The stops on the Agilent type should deliver very reproducible results if you have a good syringe, the stepper motor drive ones will depends on the accuracy of the stepper motor and its counter.