Troubleshooting "Metering Home failed" Error in Agilent Autosamplers

Created by Max Schütte over 2 years ago | Last modified by Paubudge over 1 year ago

This Information Applies To: Agilent Autosamplers G1313A, G1329A/B, G4226A, G1367A/B/C/D/E, G7129A/B/C.

Issue:

If during initialization or during a sequence, the "Metering Home Failed" error occurs, this article will guide through the procedure of identifying the cause. Sometimes, this error may also appear as "Cannot Find Metering Sensor".

Steps to follow:

Often the reason is a blockage in the injection system. Remove the capillaries into and out of the metering device (Figure 1).

Figure 1. Loosening the two capillaries of the Metering Device: the blue sample loop and the capillary coming from the injection valve
Reset your autosampler (switching it off and on).
1. If the sampler still does not initialize correctly, showing the same error message, the metering device should be disassembled and inspected (you can ask for help from an Agilent Customer support Representative). Check the condition of the plunger and the plunger seal and replace if worn or damaged. Also, the rotor seal of the injection valve should be inspected. If the sampler does not initialize correctly and plunger, metering seal and the rotor seal are fine, call your Agilent Support representative for further help.
2. If the sampler initializes without the capillaries connected, perform several injections with maximum injection volume (capillaries disconnected). Make sure to have paper towels or beakers ready to collect any mobile phase flow at the metering device or capillaries. This purging procedure may serve to clean the metering device and flush out any particulates it may contain.
Reconnect the capillary that is coming from the injection valve to the metering device.
In continuation, purge the system stepwise to flush out any particulates. Start with the metering device: Purge the system using a small flow rate (injector in mainpass mode). Use paper towels to collect the mobile phase flow at the metering device outlet.

Warning: Beware the sharp needle tip: Avoid touching it so as not to get pierced.

Reconnect the loop capillary to the top of the metering device and flush the loop capillary and the needle. For this action, the needle has to be placed above the needle seat (via Injector Steps in the Lab Advisor Software) and the autosampler has to be in the mainpass mode. Apply a moderate flow rate and, with the purge valve closed, collect the solvent coming out of the needle end. Afterwards, in the Injector Steps view of the Lab Advisor, select Reset to reset your autosampler.

You may also flush the loop and the needle stepwise (otherwise carry on with step 5). Therefore, disconnect the loop from the needle (check your manual for "Exchanging the Needle Assembly" for further reference) and, depending on your module, follow either step 4.a (G7129X), 4.b (G1313A, G1329X) or 4.c (G1367X, G4226A):
1. For the Infinity II model G7129X:
  Using Lab Advisor, go to the Service & Diagnostics section, click the Autosampler, and choose Injector Steps. Next, click Needle up for the Vialsampler to lift the needle (see Figure 2) up fully.
  
  Figure 2. Lab Advisor Injector Steps - Needle Up
  
  Remove the safety cover (Figure 3), then lift and flip the wash port to the left into the service position (Figure 4).
  
  Figure 3. Removing the Safety Cover
  
  Figure 4. Flipping back the Wash Port
  
  In the Injector Steps view, click Needle Into Sample to move down the needle assembly and place the needle above the seat. Now you may loosen the loop capillary from the needle assembly end and, closing the purge valve, flush the loop. Remember to collect the solvent flowing out the loop end.
  
  Next, reconnect the loop capillary to the needle assembly. Mind the correct angle of the connection: The straight, uncovered part of the capillary should be oriented horizontally as can be seen in Figure 1 to enter the guiding cut-out of the safety cover's right side. With the needle still positioned above the needle seat, purge through loop and needle, collecting the flow out of the needle (be cautious not to pierce yourself).
  
  Afterwards, in the Injector Steps view click Needle Up, flip back the wash port, reinstall the safety cover and click Reset. Go on with step 5.
2. For the G1313A and G1329X Autosamplers:
  
  In the Lab Advisor software, under Service & Diagnostics, click the Autosampler and click Maintenance Positions. Click Change Needle and then click Start moving the safety flap (Figure 5) away from the needle and positioning the needle approx. 15 mm above the needle seat. Now remove the front cover of the autosampler.
  
  Figure 5. Front view of the G1313X and G1329X Autosampler: 1 - Safety cover, 2 - safety flap
  
  Next, click Down until the needle screw is aligned with the hole in the safety cover (Figure 6) and loosen the loop capillary from the needle assembly (Figure 7).
  
  Figure 6. Alignment of the Needle Screw with the hole in the Safety Cover
  
  Figure 7. Loosening the Loop Capillary.
  
  Flush the loop by closing the purge valve. Remember to collect the solvent flowing out the loop end. Afterwards, reconnect the loop capillary to the needle assembly and move up the needle sufficiently (by clicking Up). Flush through both loop and needle, collecting the flow coming out of the needle tip (be cautious not to pierce yourself). Next, click End to reposition the safety flap around the needle. Replace the front cover of the autosampler and reset the module. Go on with step 5.
3. For the G1367X and the G4226A:
  
  In the Lab Advisor Software, under Service & Diagnostics, click the Autosampler and click Maintenance Positions and then Change Needle/Seat.
  
  Next, open the front and remove the side door of the module. Turn the needle carrier 90 ° clockwise so that it is easily accessible and flip open the leak guide (Figure 8).
  
  Figure 8. Needle Carrier Arm of the G1367 and G4226 modules. 1 - Leak guide. 2 - Wrenches to loosen the Needle Assembly. 3 - Holder Clamp
  
  Next, attach a 5/16-inch wrench to hold the position at the needle assembly and use a 1/4-inch wrench to loosen the fitting of the loop capillary (Figure 8). Lastly, pinch the holder clamp, pull it back (Figure 8) and remove the loop capillary from the needle assembly (be cautious not to pierce yourself).
  
  Flush the loop, then re-attach the needle assembly, flip back the leak guide and flush both the loop and the needle. End the maintenance position via Lab Advisor and reset your Autosampler. Go on with step 5.
Disconnect the seat capillary from port 5 in the injection valve (Figure 9).

Figure 9. Injection valve ports, standard configuration - Connections: 1 - From pump; 2 - To metering device; 3 - Plug; 4 - To waste; 5 - From needle seat; 6 - To analytical column
Close the purge valve, thus flushing through the metering device, the sample loop, the needle, and the needle seat. Make sure to collect the solvent coming out of the open needle seat capillary end (autosampler in mainpass mode).
Also inspect the waste tubing at port 4 (Figure 9) of the injection valve for any kind of obstruction or hindrance of flow (e.g. connect it to the outlet of the purge valve and see if you can flush it without issues).
Reconnect all the capillaries, re-establishing your module's initial configuration.