Thermo-Conversion Elemental Analyzer (TCEA) Standard Operating Procedures

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Phase 1: Perform  TCEA Maintenance

1. Replace the graphite crucible every 75-100 samples.
2. Remove the reactor and clean the glassy carbon tube and glassy carbon grains after every 200-250 samples.

Phase 2: Warm-Up the day prior to running

1. Close SGE valve at MS source & turn on Conflo He dilution.
2. Make sure SGE valve for gas bench, GC, or LC valve is also closed.
3. Clean glassy carbon tube and glassy carbon grains if needed (see below).
4. Set the temperature controller ramp rate.

1. On Jumbo controller (one on the right) press and hold in the P button for 5 seconds, until the Pb.1 option shows, and release button immediately.:
2. Now press the P button multiple times to cycle through the options, until you reach rasd.:
3. Use the Up and Down buttons to select ramp rate. Note the units are °C/min. Never heat or cool in increments > 5°C/min. Ramp rate guidelines: At 1°C/min it takes roughly 20 hours to heat from room temperature to working temperatures of ca. 1400°C. Typically, heat overnight at 1-2°C/min. Cool at 3°C/min.:

5. Set He flow to 0.6 bar.
6. Set Jumbo controller to ramp up to the desired operating temperature overnight.

1. Press P twice to get to SP.
2. Use the up and down buttons to set the desired operating temperature.
3. Once the temperature is set wait roughly 2-3 seconds for the display to blink off and back on. Immediately press P again. The present temperature of the reactor should show.
4. Watch the cycling yellow lights of the controller and observe that they are applying power to the heating element. Also, confirm that the element is heating and at the selected rate.

Phase 2: The day of the run

0. If running phosphates, procure dry ice (located in 137 Sinsheimer and in the hallway across from 339 PSB, delivered every Tuesday and Friday).
1. Set He and Purge He carrier gas flow to 1.7 bar.
2. Open the CO tank and regulator valves in the fume hood. Check both the cylinder valve and the regulator valve are open. (Temporary: attach the Variac power supply to the automatic shutoff valve on the CO line in the fume hood. This is to bypass a defective circuit powering this valve).
3. Open CO gas tanks by opening the valves below the peripheals benchtop.
4. Close the isolation valve on the zero blank autosamper (ZBA).
5. Load samples and vent the ZBA carousel cavity

1. Open the vent valve on the top of the ZBA.
2. Open the three knurled set screws to open the ZBA lid.
3. Press the manual advance on the ZBA controller and be sure the carousel port is advancing past the drop hole. Adjust the carousel position with the manual advance jog switch on the back of the ZBA controller.
4. Load samples.
5. Close the lid being sure to check that the o-ring is seated properly and firmly tighten the three knurled set screws.
6. Open the in-line Purge line valve (slide barrel towards ZBA) and turn up the auxillary He flow to 1.5 bar. Test that He is flowing using the leak detector or flow meter.

6. Allow the ZBA sample cavity to vent for 5 minutes:

1. Then close the valve.
2. Close the in-line Purge line valve (slide barrel away from ZBA) and turn down the auxillary He flow by backing off on the auxillary He regulator by many turns.

7. Set the 4-port valve under the benchtop so that the TCEA is going to the desired mass spectrometer.
8. Set the communication switch box: Select Sherlock/Columbo EA/TCEA communication switch box according to the instrument being used.
9. On the Conflo, turn the dilution on.
10. Turn off source at the computer and then open the SGE valve at the mass spectrometer source. Be sure the other peripheral SGE valves are closed.
11. Check that the vacuum pressure is between 7-e7 to 3e-6 mBar range, and then turn the source back on. If outside this range, close the source SGE valve and see the lab manager.
12. Select CO gas on the mass spectrometer software, and monitor mass 28 background. If it is less than 1000 mV, then turn off dilution.
13. Open the Instrument Control software module and scan mass 28 for background stability. Wait until the background trace flattens out and stabilizes, then stop scan.
14. Return to Acquisition software and begin a standard on-off sequence for CO. You should achieve better than 0.1‰ precision for the standard on off δ¹⁸O.
15. While the standard on-off are going, prepare a sequence file for the run.
16. If running phosphates, crush up some dry ice and add it to ethanol, to make a dry ice-ethanol slush. Add this to slush to a small glass dewar (found at the back of the TCEA peripheral). Place the coiled 1/16 stainless steel line into the trap, such that the coil is at the bottom of the dewar.
17. Turn the 2-way valve, that is downstream of the coil at the back of the TCEA peripheral, such that gas from the TECA travels towards the mass spectrometer and not to waste.
18. Start sequence.
19. Log use on the SIL web-based form.
20. Monitor at least the first few standards to ensure instrument is performing properly.

Run Shutdown:

1. Close SGE valve at the mass spectrometer source.
2. Close CO valve on front of the peripheral benchtop. Close CO valves at the gas cylinder and regulator located in the fume hood. Shut off the Variac too (if necessary).
3. Turn on the Conflo III dilution (Isodat software).
4. Set the temperature controller ramp rate to 3°C/min:

1. On Jumbo controller (one on the right) press and hold in the P button for about 5 seconds, until the Pb.1 option shows, and release button immediately.
2. Now press the P button multiple times to cycle through the options, until you reach rasd.
3. Use the Up and Down buttons to select ramp rate. Note the units are °C/min. Never heat or cool in increments > 5°C/min. Ramp rate guidelines: At 1°C/min it takes roughly 20 hours to heat from room temperature to working temperatures of ca. 1400°C. Typically, heat overnight at 1-2°C/min. Cool at 3°C/min.

5. Set He carrier flow to 0.6 bar.
Note: Be very careful that the pressure doesnt drop below this flow rate. The carrier flow drops very slowly and operators have allowed the flow to drop to zero, at which point the furnace control is shut-off and resulting in rapid cooling of the furnace. Once the pressure reaches 0.6 bar, be sure that if you can increase the pressure by turning up the regulator, to confirm the pressure is not still dropping. Rapid uncontrolled cooling can cause very expensive repair and instrument down-time.
6. Set Jumbo controller to ramp down to room temperature:

1. Press P twice to get to SP.
2. Use the up and down buttons to set the furnace temperature to 23°C.
3. Once the temperature is set wait roughly 2-3 seconds for the display to blink off and back on. Immediately press P again. The present furnace temperature should be displayed.
4. Confirm that the heating element is cooling at the selected rate.

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Maintenance Procedures:

1. Replace the graphite crucible every 75-100 samples. A crucible can be removed if the temperature of the furnace is in standby conditions (i.e., with the furnace temperature at 600°C), but not at operating temperature!
2. Remove the reactor and clean the glassy carbon tube and glassy carbon grains after every 200-250 samples.

1. Clean the glassy carbon grains. Using a Kim-Wipe, roll the glassy carbon grains in the Kim-wipe between your fingers to wipe off the carbon ash.
2. Clean the glassy carbon tube. Using a Kim-Wipe, wipe off as best as possible the carbon ash and other residues from the outside of the glassy carbon tube. Wad up a Kim-wipe into a roll and insert it into the glassy carbon tube. Using a 3/16 wooden dowel, push the Kim-Wipe forwards and backwards inside the glassy carbon tube a few times to remove the residues (carbon deposits).

3. Reassemble the glassy carbon tube reactor.

1. Add Silver to the base of the glassy carbon tube. Insert the glassy carbon tube onto the reverse flow assembly inside the TCEA unit and put in silver wool from the top. You want about 0.5 cm of silver wool in the bottom. Recycle old wool if it doesnt look too tarnished. Use a 3/16 wood dowel to compact the silver wool into position at in the glassy carbon tube. Remove glassy carbon tube from the reverse flow assembly.
2. Add glassy carbon chips to the glassy carbon tube such that the chips are 28.5 - 29 cm. from the top of the glassy carbon tube.
3. Add a graphite crucible (if running solid samples).

4. Clean the alumina tube by wadding Kim-Wipes and using a wooden dowel to pass the Kim-Wipes back and forth inside the alumina tube.
5. Reassemble the reactor column.

1. Remove the cooling fan at the bottom of the TCEA furnace, and carefully place it on the bench outside the furnace cavity.
2. Insert the alumina tube into the TCEA furnace and secure it below in the reverse flow assembly.
3. Insert the glassy carbon tube inside the alumina tube, and press down over the o-ring fitting of the reverse flow assembly. The top of the glassy carbon tube will be about 1 cm below the top of the alumina tube.
4. Attach the top connection (Zero Blank Autosampler for solid samples, injection port for liquid samples) to the alumina tube. Use the strap wrench to tighten the top knurled nut. Be sure to hold the bottom reverse flow assembly and push it up into the top connection to ensure a secure connection.

Note: Failure to achieve a leak tight connection at this point likely means you will need to cool the furnace down the following day, and will loose 1-2 days without any analyses.


5. Place the bottom stainless steel spring below the reverse flow assembly. This is critical in that the reverse flow assembly would otherwise pop off when at operational He carrier gas flow pressures.
6. Position the fan in its slot at the bottom of the furnace cavity and replace the front door of the furnace.

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NEWS & EVENTS

November 2009

UCSC's SIL retires its 15 year-old dual-inlet Optima following a very productive career that generated over 40,000 data points.

November 2009

Two Tsavo Lions In Famed Killings Get Partial Reprieve according to UCSC Graduate Student Justin Yeakel as inteviewed on NPR's All Things Considered. Listen here:

July-August 2009

SIL co-director Christina Ravelo (Ocean Sciences) sails as co-chief scientist on Integrated Ocean Drilling Project (IODP) Expedition 323 to investigate Bearing Sea Paleoceanography.

December 2008

SIL co-director Christina Ravelo (Ocean Sciences) gives the 2008 Emiliani Lecture at the American Geophysical Union Meeting in San Francisco on "Lessons from the Pliocene Warm Period and the Onset of Northern Hemisphere Glaciation".

September 2008:

UCSC SIL has been funded by the National Science Foundation for a new Dual-Inlet Isotope Ratio Mass Spectrometer with individual acid drip system for very small calcium carbonate samples.

July 2008:

SIL co-director Jim Zachos (Earth and Planetary Sciences) recieves prestigious Humbolt Research Award. See Humbolt Award for details.

May 19, 2006: UCSC Stable Isotope Laboratory Symposium

In recognition of the new continuous flow instruments added to the UCSC stable isotope facility a Symposium is being run to highlight the new analytical capabilities.