While running a test calibration, the syringe heater seemed to be having electrical issues. Runs were taking up to 100 minutes, as the software was waiting for the syringe to reach 70 degrees C. The issue was investigated, and one of the pins was found to have rattled out of the block a little bit. Pin was pushed back in with a finger nail on each side of the base, contacts were cleaned, and everything has been working well since.
The initial oven hold time was reduced from 6 min to 0.5 min and the oven temperature ramp rate was increased from 15 C/min to 25 C/min. This resulted in a 26.5 min runtime compared to the previous 37.5 min runtime. A new GC runtime length was set in the PAL method parameters and the single overlap mode was set up. Next sample is now heated in the oven while GC is cooling down with the next injection happening ~2 minutes after the GC returns to ready state. In total, the runtime per sample is now in the 35-40 minute range compared to the previous runtime of 60-65 minutes per sample.
A link to the US vendor of Gerstel autosampler parts
https://webstore.gerstelus.com/
2.5 mL syringe for the autosampler: https://webstore.gerstelus.com/pc_product_detail.asp?key=61E8355807F34ACFAFC6ACA274A068AC
Plunger for the syringe: https://webstore.gerstelus.com/pc_product_detail.asp?key=1849AD6D281D4FC6909DC30826626E23
Needle for the 2.5 mL autosampler syringe: https://webstore.gerstelus.com/pc_product_detail.asp?key=26D115687E36429CAB3C1D7DCF1834E2
If experiencing carryover issues, it is recommended to check the autosampler syringe plunger. Once the plunger was replaced on 393, no further carryover was observed.
Encountered a problem with the autosampler bending needles. Bent 3 needles without getting past 3 samples(standards). Looking up troubleshooting help indicated the tension cord in the autosampler needed to be changed.
To change the tension cords:
- Instrument > Change pal configuration > release terminal
- on the pal terminal: menu > utilities > syringe > change syringe
- remove the syringe
- turn off pal autosampler
- manually raise the syringe holder to align the 3 holes with screws underneath
- be careful when removing the arm as there is a cord plugged into the back that doesn't stretch far
- once all 3 screws are undone the arm can be removed by pulling it away slightly to unplug the cord in back, then fully removing
- unscrew the screw holding the top cap in place. One end of one of the tension cords is attached to the cap.
- pull the cap off to access and undo that end of the tension cord, then set the cap aside.
- slide the syringe holder down to access and remove the other end of the tension cord
- loosen and remove the slide stop
- slide the syringe holder out to remove the back plate by unscrewing 5 screws. 3 on one side, 2 on the other
- the other tension cord is accessible once the back plate is removed. replace it with the new tension cord
- slide the syringe holder back in being sure to align the wheels on the rail. keep the cord pushed to the back of the arm to help keep things from getting tangled up
- replace the slide stop
- slide the new tension cord (longer one) through the arm so that you can access both ends, one from the top, and one from the side
- connect the tension cord to the cap and replace the cap on the arm
- stretch the tension cord down to connect it to it's place towards the bottom of the syringe holder
- reattach the arm to the pal system by plugging in the cord in back and then reattaching with the 3 screws through the 3 holds in the syringe holder
- turn pal autosampler back on and put it back into 'change syringe' mode
- replace the syringe, click 'continue'
- can now lock the terminal again.
The 1 uL syringe used for GC2 calibration, LS0265, has been discontinued. It will be replaced with1.0 µL NanoVolume syringe with 7 cm 0.63 mm OD bevel tipped needle. https://www.trajanscimed.com/collections/sge-nanovolume-syringes/products/000506
Our GC2 autosampler needle (CM5201) stock is low (PC=0). An experimental calibration was made with a cone-tipped needle (009970-041-00) found in the drawer (PC=26), and it worked fine. This needle was added to AMS (CM9044). It is 52 mm long. Our preferred side-hole needle (CM5201) is 57 mm long. When installing the shorter needle, the injection depth was changed on the remote control (Instrument > Change PAL Configuration > Release Terminal) from 25 mm to 30 mm. If the needle is changed back to the 57 mm one, the injection depth should be changed back to 25 mm. To do this, on the remote control, go to Menu > Utilities > Injectors > GC Inj1. After you make the change, press Lock Terminal on the computer screen. Update: An order was placed for six CM5201 needles, apparently that was all that John could locate. It appears they have been discontinued. They were also outrageously expensive, $78 a piece. They should be arriving soon. In the meantime, it is fine to use the 52 mm cone-tip needles. It is more likely to become clogged with septum than a side-wall needle, but it seems fine as an emergency spare.
If the GC2 software comes up strange looking after a reboot or at any other time, right-click on Desktop, go to Display Settings and change the computer display scaling to 100%. This does not require a reboot, just shut down software, open software back up on 100 % and then change the display scaling to 200%.
When a practice calibration run was started on GC2, the helium pressure in the gas lines dropped to 40 PSI on the gauges in the lab and 60 PSI on the outgoing regulator gauge at TBULK. TBULK regulator was turned up until pressure reached 110 PSI. Everything was stable until the next run started on GC2. Same thing happened, pressure dropped 40 PSI in the lab and 60 PSI in TBULK. Pressure was increased to 120 PSI on the TBULK regulator. This repeated itself one more time, and now pressure was increased to 200 PSI, and this resolved the issue. The calibration run finished successfully and no further pressure fluctuations were experienced. After the calibration run the pressure stabilized around 160 PSI.
The helium and nitrogen traps on the back of the instrument were replaced with new ones. The new traps look exactly like the old ones but they now say to "install vertically this side down". This would be an opposing orientation to the way the old ones were installed. This was discussed, and a decision was made to install the new ones in the same orientation as the old ones. Just noting this here in case strange behavior of the instrument is observed down the road. Should strange behavior occur, new traps can be installed in the opposing orientation. The plumbing would then have to be reconfigured though, as we would have to direct the gas flow in the top of the trap and out from the bottom of the trap. Strange behavior due to trap orientation highly unlikely and not expected. The flow direction of the trap remains identical to the old traps.
When using the Gerstel autosampler, the labels attached to the vials should be the small ones used in the Microbiology Label Printer. The labels should be attached to the top half of the vial. The larger Chem Lab labels impede the autosampler from inserting the vials into the oven and back into the vial rack. The AS will either have a Z-axis error and abort the sample sequence, or it will believe it hasn't injected a sample (when it may have) and then proceed on to the next sample immediately before the previous one has finished.
PFMD tracer standards yield a non-linear calibration curve. When making dilutions, you need to extract STD A very slowly using the 1 µL syringe, and pipette the samples slowly into sealed headspace vials. Since the volume of standard is so low, only a small bead will form on the tip of the syringe needle. It is best to have the tip touch the inner wall of the vial to get the bead to come off, otherwise the hexane solvent starts to evaporate and the PFMD present in the bead adsorbs onto the needle tip and doesn't remain in the vial with the needle is removed.
Issue with the a electrode prong on the syringe heater block getting stuck and not making full contact with the autosampler. The syringe block temperature never could reach the 70°C setpoint. Johanna bent the prong back into place.