So how many times do you need to rinse a syringe?
Well, I can tell you the answer for the experiment we did. Let me first refresh your memory on specifically what we did.
Sequence of manual syringe rinsing:
- 20 µL draw of a 500 ppm hydrocarbon standard and expel it
- 20 µL draw of acetonitrile – eject into sample vial – test via GC-FID
- Repeat step 2 many times
Each “rinse” was tested via GC-FID.
How many 20 µL acetonitrile rinses were needed to show no signal (FID)?
The answer is 4.
I want to thank everyone that commented when I posed the question. Most people were right on track with about 4 rinses. It is also funny that people tended to do“extra”rinsing regardless of what they thought was required. I still do this with about 6 to 10 rinses depending on the situation.
I wanted to share some helpful hints from people who commented:
- Use more than one rinse solvent especially in situations were analytes have a wide range of polarity
- Use more than one rinse vial
- Use the same solvent for rinsing as is used for the sample and standard solutions
Here is a chromatogram of a 50 ppm hydrocarbon standard followed by chromatograms of consecutive rinses. The 50 ppm chromatogram can be used as an intensity reference because the y-axis is the same for all chromatograms.
