How to Check and Adjust the Nebulizer Needle on Agilent LC/MS Systems

Answer

This Information Applies To: Agilent 6000 Series LC/MS systems.

Issue

Checking and adjusting the nebulizer needle is part of regular maintenance or troubleshooting tasks. It is suggested when there is an issue with nebulizer spray shape or spray consistency, leading to a loss of sensitivity in the instrument.

Signs the nebulizer needle requires adjustment or replacement include:

Increased LC backpressure associated to the MSD.
Off-axis spraying.
Dripping from the nebulizer.
Reference nebulizer needle not spraying (Dual spray sources only).
When the needle appears to be corroded or damaged

Items Required

Nebulizer Adjustment Fixture (p/n GT430-20470) or Nebulizer adjustment kit (p/n G1960-67470)
Clean powder-free gloves
T6 Torx driver or 1.5 mm hex wrench.
1/4" x 5/16" open-end wrench (Qty 2)

Steps to follow

Put on clean powder-free gloves

Caution: When inserting the nebulizer into the nebulizer adjustment fixture, ensure that the nebulizer tip does not contact the fixture, or the nebulizer needle tip may be damaged.
Shine a light through the rear window of the spray chamber to illuminate the spray inside the source.
Then look through the front window to examine the spray shape and consistency or twist the source to release it from the source locking mechanism.
Lift the source out of the source body being careful to not touch the tip of the nebulizer on the source body.
Spray onto the black top of the source, or onto a piece of paper, and examine the spray shape and consistency. If the spray shape is not conical or consistent, then move onto step 3 to check the needle adjustment in the nebulizer using the adjustment fixture.
Mount the nebulizer assembly into the nebulizer adjustment fixture as shown in Figure 1. Slide the heads of the two spring loaded socket head cap screws through the mounting holes of the nebulizer. Then twist the nebulizer clockwise to hold the nebulizer assembly firmly in the fixture.
If the socket head cap screws are too loose, then gently tighten these screws to hold the nebulizer firmly.

Figure 1. Inserting and tightening the nebulizer assembly into the nebulizer adjustment fixture
Insert the magnifier into the top port and the flashlight in the side port of the fixture, see Figure 2.

Figure 2. The nebulizer, magnifier (top), and flashlight (left) inserted into the fixture
Turn on the flashlight and, while looking down the magnifier, adjust the height of the magnifier until the tip of the nebulizer is clearly in focus.
Check the needle position of the nebulizer needle in relation to the nebulizer assembly tip. See Table 1 for the correct needle position depending on the type of nebulizer in use. The distance shown in this table is the distance that needle tip protrudes from the tip of the nebulizer assembly in inches. Please note the scale shown in the magnifying lens is also in inches, with one Division = 0.001 Inches. See Figure 3 for images of correctly adjusted nebulizer needles. If adjustment is required, go to step 10

Figure 3. Example of correctly adjusted ESI nebulizer needle
1. Side view of ESI Nebulizer with 0.003 inches distance marked in red, 2. Example of a centered needle.
If the needle tip looks pitted, clogged with salt, corroded, or is not square and has jagged edges then the needle will need to be replaced. See Nebulizer Needle Replacement in an Agilent Jet Stream or Standard Electrospray Ion Source for full instructions.

Table 1: Correct distance from the tip of the nebulizer body to the end of the needle.

Nebulizer Distance (inches)

Microflow nebulizer Assembly 0.003

Tested ESI nebulizer Assembly 0.003

Tested APCI nebulizer Assembly 0.000 (flush)
If the needle distance looks correct, reverse the position of the magnifier and flashlight so the flashlight is in the top port, and the magnifier is in the side port of the fixture.
While looking through the magnifier, move the magnifier in or out of the fixture until the end of the nebulizer is in focus. Check that the needle tip is centered (concentric) with the tip of the nebulizer assembly. If adjustment is required, go to step 10.
The Nebulizer lock screw can be either a T6 Torx or 1.5 mm hex bolt. Using either a T6 Torx driver or 1.5 mm hex wrench, loosen the lock screw on the head of the nebulizer assembly.
Using the 1/4" end of the open-end wrench, rotate the needle assembly while looking down the magnifier. Turning the nut with either push the needle out or drawn it into the nebulizer tip. Adjust the needle so that the distance matches the specified distance for your nebulizer type in Table 1. See Figure 4.

Figure 4. Adjusting the nebulizer needle and then locking it in place with the lock screw.
As with step 7, reverse the position of the magnifier and flashlight, and check that the needle tip is also centered (concentric) with the tip of the nebulizer assembly (see Figure 3, Right Image). If it is a long way off center after optimizing the distance, then the needle may need to be replaced. (See Nebulizer Needle Replacement in an Agilent Jet Stream or Standard Electrospray Ion Source).
Once the position of the needle has been optimized, carefully tighten the lock screw loosened in step 8, while checking that the position of the needle has not moved during tightening. The nebulizer needle adjustment is now complete.