apci tuning issue & nebulizer needle and ferrule connection

Hi. Our lab has a HPLC/APCI-MS instrument running for couple of years. Recently, the tuning became an issue - no peaks coming out but noise. Usually after changing the APCI tuning mix, flushing and after 2-3 of dual tuning came out okay.

When I check the nebulizer spray it looks fine. 

So I thought the nebulizer needle was corroded so decided to change it. But then I thought the old nebulizer needle should be compressed by the ferrule at the end of the needle holde it but it was loose and the needle came out easily. Does this mean the old needle wasn't compressed by the ferrule? Can this cause the issue?

I would like to ask if anyone had this issue or advise. Thank you.

  • The nebulizer needle should be held in place by a compressed ferrule but as you said the spray was good, the loose grip of the needle is unlikely to be the cause. So, a no signal problem could be any part of the MS but you did the right thing by starting with the source. Did you also change the corona needle? Does the spray shield look very dirty? Perhaps that needs a clean? When was the last time you cleaned the capillary? Sorry for more questions than answers, but this type of problem could go in many directions...

  • Hi dannymobbs. Thank you so much for your reply.

    I totally understand the many things can affect the MS. To answer your questions - yes, we changed the corona needle, always clean the needle and source ever sequences.

    As you mentioned the spray shield, we normally wipe the surface of the tick cap but not the surface small cap that's inside the spray shield. (should we try this? I know from the manual it said to use a mesh cloth to gently clear the end but no solvent). 

    And the capillary has been over a year after we changed to a new one. But if you suspect this might be, I can try cleaning the old one. May I ask how you do so? I tried once and had a hard time drying the inside of the capillary.

    Thank you so much!

  • It’s definitely worth trying to clean the capillary. I attach here the printed instructions from the animation contained on the Resource Guide which ships with the instrument. The Alconox powered cleaner referenced is part number 5190-1401. Pay attention to step 3 - keep the concentration as stated. Also - step 10, take this as gospel - do NOT sonicate in Alconox for more than 15 minutes. Finally - be fastidious with the cleaning (of the measuring cylinder and of course the capillary) with water after the Alconox treatment. Any remaining detergent will cause problems. Once it is clean you can gently blow out the capillary with a clean air stream or let the capillary stand upright on a clean paper towel. Then you can reinstall the capillary and pump the MS down. 

  • Thank you very much and for providing the material. I have never seen this so easy step-by-step manual for troubleshooting.

    I will try by nex week and also let you know. 

    Thank you.

  • No worries - good luck with capillary cleaning. Just take your time and you'll be fine. Small correction to my last text - please replace '...or let the capillary stand upright on a clean paper towel' with '...or let the capillary stand upright on a lint free cloth'. Non lint free items shed particles which could get sucked into the manifold. My apologies...

  • Hi dannymobbs,

    Thank you for your leaving your kind comment on the correction. We took out the capillary but realized the powder had expired. So we replaced it with the older one which was previously cleaned (assuming the current was dirty).

    I have a few general questions but I think they are also follow-ups for this procedure (also I wanted to double-check too)

    1) there was a scratch-looking band around the metal part of the capillary on the outer side (which is facing outward when inserted) - seems like a band aligned with when the capillary cap is attached. It doesn't seem like a manufactured band but looks like something sharp carved the metal part. Is this something hurting the capillary?

    2) when pumping down the MS (by power on it starts by itself), does the MS do the baking itself? why I am asking is because I realized when it becomes nearly vacuum after an hour, I heard hot N2 flow going into the MS (even N2 generator was working more frequently to make N2). When I go to the chemstation, it shows MS status ON at that time, so I changed to stand-by. Then let it stay for at least overnight.

    3) when pumping down, the MS light is orange, but sometimes it changes to red then changes back to orange quickly. Is this normal?

    4) How critical is it to do the MS baking after the MS vent down? Seems we haven't done that every time after we start the MS..

    5) When pumping down the MS, does the other LC system (quad pump, autosampler) need to be ON too? Or is it okay just to leave them OFF and let the MS pump down itself?

    I think that's all right now. But I would really appreciate your advice! Thank you.



  • Hi,

    1. The scratch is created by the canted coil spring which sits inside the capillary cap. Its certainly not ideal that this 'band' is present but the ultimate test will be if you observe ions in the tune (which were missing before) and then if the tune goes to completion with the correct mass axis calibration, peak widths and adequate abundances. However, I think you should be prepared to replace this capillary with a brand new one.
    2. If the system pumps down normally then the source will heat up and the quadrupole will heat to 100oC. The MS requires nitrogen to be flowing in order to go ready so the fact that you saw the MS in the ON state is good so far. An overnight equilibration is recommended - you did the right thing to leave it overnight (see 4 below).
    3. Red normally means error, but we would need to see the logbook to comment. If it happens again, go to the Method & Run Control view. Then go to the View menu item then Logbook > Current Logbook. Attach a screen shot here clearly showing the error message. Do the LC modules also go into the error state.
    4. When you vent the MS to do maintenance (or for a lab shutdown), a thermal equilibration of at least 11 hours (overnight) is a must, once pumped down, before you tune.
    5. You can leave the LC modules off while the MS pumps down then equilibrates.

    Hope this helps....

  •  Hi Thank you so much for the detailed anwsers.

    The image with black line shows the starting of the MS pump down.

    Sorry I am using my phone to upload and hard to make them in order. Please see the date and time.

  • The 'drying gas pressure control timeout (1401) suggests that you don't have sufficient nitrogen pressure at the MS. You need 80-100psi. If the gas pressure on your generator (or at the regulator if you are using 'house' nitrogen) is set correctly, then it could be a clogged gas filter - the grey cylindrical fitting between the gas supply and the MS. This is a consumable and needs replacing periodically.

    Also, I only see that error on the 18th March. The entries from the 22nd do not show this error - do you still have problems? Can you turn on the MS? If yes, can you tune?

  • I see. Yes the N2 generator pressure was set to 100 psi. Then it should be the universal big trap.. 

    The drying gas pressure seemed okay yesterday so I did some tuning. Baked out the MS since morning and around late afternoon, did a 5 min tune mix flushing. Compared to the previous capillary, the inserted old but previously cleaned one was able to do the negative tuning. It came out like it should be. But the positive tuning is showing noise only and no peaks. 

Was this helpful?