Caution on the use of NBS 30 biotite for hydrogen-isotope measurements with on-line high-temperature conversion systems.

Rationale: The supply of NBS 30 biotite is nearly exhausted. During measurements of NBS 30 and potential replacements, reproducible δ(2)HVSMOW-SLAP values could not be obtained by three laboratories using high-temperature conversion (HTC) systems. The cause of this issue has been investigated using the silver-tube technique for hydrogen-isotope measurements of water.

Pressure baseline correction and high-precision CO2 clumped-isotope (∆47) measurements in bellows and micro-volume modes.

Rationale: CO(2) 'clumped-isotope' measurements (tracking enrichment of (16)O(13)C(18)O, reported as ∆(47) values, on CO(2) derived from carbonate minerals or the atmosphere) are becoming central to a wide range of geochemical investigations. We present a novel approach to address problems with instrument stability, external precision, and the analysis of small samples that have hampered the advancement of Δ(47) measurements.

Methods: We measured Δ(47) values on CO(2) gases introduced via dual inlet to an isotope ratio mass spectrometer.