Hi
The solution that i inject contains organics acids (C2 to C12), lactic acid and heptanoic acid as internal standard .
Between each injection i used to wash with ethanol absolute then water.But one day i have decided to inject the"syringe" and only lauric acid comes out.So my washing method was not enough good to remove completely the lauric acid.Now, before starting any injections i wash my syringe(glass and needle only)in watersonic bath containing 12%formic acid.It takes 2 hours to remove lauric acid.Then i start to inject and between each injection i wash with formic acid(35%)then ethanol absolute and water.
I would like to know if there is another simple way to wash my syringe and make sure that all my acids are tottally removed???
thank you for helping me

I would not expect that lauric acid sticks to the glass and the metal of the needle. How about the plunger? What is the material of the plunger?

Hi
I have just read your message.I think the plunger is zink but i 'll find out this afternoon.I've forgotten to say that i clean the plunger with a cloth soaked with 12%acid formic

Might I suggest washing with a slightly basic solvent to help solublize the acid? Maybe dilute ammonia in alcohol? The low pH would seem to hinder removing the residual acid.
Regards,
Mark

While dilute base would be an excellent idea, or even pyridine, I would really want to use methylene chloride to clean the syringe parts well, especially if I added some acetic acid to the mix. Followed by methanol and air drying.

What for do you need to remove lauric acid completely? Mostly, you need only wash syringe in your sample solution. A little carryover doesn't matter.

Just to thank you people who tried to help with "my lauric acid"