Re-determination of R(¹³C/¹²C) for Vienna Peedee belemnite (VPDB).

Area of Science:

• Geochemistry
• Analytical Chemistry
• Metrology

Background:

• The carbon isotope-delta scale, defined by Vienna Peedee belemnite (VPDB), is crucial for linking isotopic measurements to the International System of Units (SI).
• Accurate determination of the R_VPDB(¹³C/¹²C) ratio is essential for data processing in clumped isotope analysis, ¹⁷O correction, and isotopic composition conversions.

Purpose of the Study:

• To establish a highly accurate value for the R_VPDB(¹³C/¹²C) isotope ratio with minimal uncertainty.
• To facilitate precise carbon isotope measurements and related calculations in various scientific disciplines.

Main Methods:

• Errors-in-variables regression was employed, comparing isotope delta values traceable to VPDB (measured by isotope ratio mass spectrometry) with isotope ratios traceable to the SI.
• Gravimetric mixtures of ¹²C- and ¹³C-enriched d-glucose were utilized and measured by multicollector inductively coupled plasma mass spectrometry.

Main Results:

• A new value for R_VPDB(¹³C/¹²C) was determined to be 0.0111105 ± 0.0000042 (expanded uncertainty, k=2).
• This result shows excellent agreement with existing consensus values and independent measurements.

Conclusions:

• The newly determined R_VPDB(¹³C/¹²C) value offers a tenfold improvement in uncertainty compared to previous measurements.
• This enhanced precision will significantly benefit carbon isotope science, improving data processing and inter-laboratory comparability.