Stable Isotope Lab

The lab space includes two rooms in Haenicke Hall, a mass spectrometer (Delta V Plus). The mass spec is equipped with several peripherals:

  1. Continuous flow peripherals (linked via Conflo IV):

    -Isolink-OH elemental analyzed (EA) used for δD and δ18O measurements in hydrous silicates via combustion at 1450°C and reduction of water to H2 and CO, respectively. Integration of the area under m/z 2 and 3 allows to estimate H2O wt. % of the analyte. USGS57 and 58 micas standards are used for D/H data reduction to VSMOW values.

    -Costech 4010 EA is typically used for CNS measurements. Currently in dormant state.

  2. Dual inlet measurements:

    -Laser-assisted fluorination of silicates to produce high-precision δ17O-δ18O measurements. The Fusion Teledyne 55W CO2 laser warms up a mineral grain up to the point of melting in presence of a fluorinating agent BrF5. The reaction of a silicate with BrF5 produces O2 gas and condensable byproducts (e.g., SiF4). The reaction proceeds under vacuum (~1E-03 mbar) in a stainless-steel vacuum line. A series of cryogenic traps are used to purify the resultant O2 gas.

Laser fluorination in presence of BrF5 fluorinating reagent as seen through the camera of the laser. The quartz grains are loaded in the Ni (99.95%) holder with 4mm-diameter holes. The amount of quartz shown above is 1.4 mg. The fluorination reaction liberating O2 lasted about 7 minutes with incremental increase in laser power and a slight decrease in focused area from 2mm to 1mm. We use a CO2 laser (Teledyne 50W) that was focused on a 2mm circle that is slightly offset from the position of cross hairs. With the laser focused on the grain, fluorination proceeded at high temperatures, where quartz starts to melt (you can see the blob of melt in middle bottom photo) and even vaporize - so at least at ~1700°C. Note how the last picture no quartz - which indicates 100% extraction of O2 and complete decomposition of quartz. The light powdery residue is likely AlF3, as quartz commonly contains Al as impurities at ppm levels. The progress shows the generalized reaction of BrF5+SiO2 -> SiF4 + BrF + O2. In reality, BrF5 was loaded in excess (100-200 Torr), so BrF5, BrF3, BrF, Br2 are likely present and were condensed at LN2 temperatures. Any F2 was neutralized by a reaction with hot NaCl. Note how the field of view is orangish in the last photo, likely due to SiF4, BrF3 and Br2 gases.

State of the lab (Jan 2024; “working order”):

Inside the mass spec:

Analyzer of our Delta V Plus. The flight tube and collector assembly housing are machined inside the metal block. Opened CONFLO IV is shown above the MS.

Transfer and distillation of our fluorinating agent inside a fume hood.

Chlorine in solid form — a common byproduct of dealing with fluorination reagents. Aka the lesser evil.