I'm using my GCMS for pesticides analysis in wine. When I inject manually the standards (and not the samples), it happens that some residues of analytes from the previous injections stay in the syringe altering the real concentration injected in the column. I'm working with n-hexane as solvent. What can i use to clean my syringe and avoid the problem?
This looks like a trial and error problem - it probably won't be the same for the different standards. I would try washing the syringe several times inbetween with different solvents, going from polar ones (maybe even from water or EtOH as this should be what your pesticides are soluble in) back to hexane. Then do a test injection with just n-hexane to see how it looks.
Hi Gianluca,
maybe these links will also be helpful to you:
https://www.researchgate.net/post/GC-MS_washing_solvents_for_the_plunger_needle
https://www.researchgate.net/post/Whats_the_best_wash_solvent_for_cleaning_the_syringe_and_column_used_to_inject_PAHs_in_a_GC-MS
Regards
Markus
Which pesticides? Hexane is good for the chlorinated pesticides but not really very good for any of the other classes. You need more polar solvents for most of the pesticides that you'd actually encounter in wine. Try acetone, acetonitrile or methanol as a rinse solvent and see if that doesn't help.
As I also work with similar substances I can recommend you to wash your syringe first 15 times with methanol and after that 15 times with n-hexane. Since we often had the same problem we tried different things whereat the method I described was the best. I hope this will help you.
You can rinse the syringe with both polar and non-polar solvents. After rinsing, it is advisable to random check the effectiveness of cleaning by taking a blank run before you start with the actual analysis.
Alexandra Klimm i tried with different solvents, from water to n-hexane, decreasing the polarity but your method seems valid too!
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