Procedure for measureing CO2 isotopic values, in mixtures of 200-3000 ppm CO2, in balance N2. These mixtures are for the calicte precipitation experiments

Really important steps in ALL CAPS
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PUT A PLASTIC TUB OR CARBOARD BOX with padding under the glass converter, just in case...

Verify the fluorination line is well pumped down

Attach the N2 regulator to the gas cylinder

Attach the brass adapter to the regulator (regulator outlet to 1/4in. tubing, actually a hose barb fitting turned on a lathe.)

Attach the cylinder/regulator assembly to the fluorination line at the sample chamber fitting, using  stiff 1/4in. plastic flex tubing, and two double ended Ultra-Torr fittings (one is already there for the chamber.)

WITH THE MAIN GAS CYLINDER VALVE SHUT, turn up the regulator to a pressure well above atmospheric, say 1.5, and pump using the fluorination line waste trap side. Pump on the entire line to the gas cylinder valve until at background high vacuum.

!!!TURN (UNSCREW) THE REGULATOR ALL THE WAY DOWN!!!

Shut all Nupro valves between the gas cylinder and the MS inlet.

Set regulator for 1.1 atmosphere. Be aware that with "gauge pressure" type gauges, a one atmosphere indication is relative to actual atmospheric P, i.e. two atm relative a to good vacuum. The current guage dial is ideal, and shows negative pressure relative to actual atmospheric P.

Open the Nupro valves between the cylinder and the last shut valve just downstream of the collection finger, proceeding in order from upstream to down.

Close the first Nupro valve.

Put LN2 at the two metal loops and the yield measurement finger, and wait 15 minutes for the CO2 to freeze.

Open the Nupro just upstream of the MS inlet and pump away N2 until at background P.

Close the Nupro just upstream of the MS inlet.

Remove LN2 at the two loops, and heat to collect CO2 at the measurement finger.

Get yield. If adequate, measure CO2 isotopic values. If inadequate, proceed with further collection cycles.

For 200 ppm, may have to do 4-5 cycles. For additional cycles, use only the first two loops to freeze the CO2, then transfer to the already cold measurement finger.