🤔 Problem
The needle shows no or smaller helium flow, indicating that the needle may be clogged.
First of all, remember to perform the following good practices to prevent clogging of the needle at all times:
Replace the septa of the «Flushing» position after each batch of samples.
Soak the needle in some milli-Q water after each use in order to prevent build-up of acid and debris from septa at the needle.
Clean potential acid drops on every septa after acid addition (before sampling).
🌱 Solution
Check visually (e.g. with a magnifier or under a microscope for potential debris and acid blocking the needle tip- and sideholes and carefully remove it with a fine tip, e.g. with a pin.
If no waste is visible, try any of the following actions:
soak the needle in some milli-Q water and flush the needle with helium to dry it. If the blocking persists, soaking in ethanol instead can be helpful, though extra thorough drying should be performed afterwards.
try to carefully clean the two holes in the double-walled headspace needle with a thin wire
flush the needle under higher pressure (e.g. 3 mbar) in order to remove potential remnants of septa or other acid inside the needle
switch the capillaries, connecting the sample-out capillary to the sample-in at the back of the CHS2 to flush out particles from the side hole, applying either normal or higher (eg. 3 mbar) pressure. Make sure not to flush any liquid back into the CHS2, e.g. by disconnecting the capillary connection at the CHS2 that will lead the gas back into the CHS2.
depending on the shape of the the needle’s tip, that may also lead to increased debris getting stuck in the in the sampling needle. It is possible to bend the very tip of the needle over the capillary with pliers. However, this has to be done very carefully in order not to bend or break the needle. The goal of this is for the needle tip to be in front of capillary rather than leavin the capillary in the needle exposed to the septa.
If none of the aforementioned actions help, swapping-out the needle might be probably the most reasonable solution.