Absolute ¹³C/¹²C Isotope Amount Ratio for Vienna Pee Dee Belemnite from Infrared Absorption Spectroscopy

Area of Science:

• Geochemistry
• Analytical Chemistry
• Metrology

Background:

• Stable isotope ratio measurements rely on reference standards, historically the Vienna Pee Dee Belemnite (VPDB) scale.
• The original VPDB standard is depleted, and current reference materials face issues of exhaustion and compositional instability.
• This mirrors challenges in metrology, such as the redefinition of the International System of Units.

Purpose of the Study:

• To report an accurate, independent measurement of the stable carbon isotope ratio of VPDB.
• To validate infrared absorption spectroscopy as a fundamentally accurate method for isotope analysis.
• To support ongoing efforts to redefine the VPDB scale and advance SI-traceable isotope measurements.

Main Methods:

• Utilizing infrared absorption spectroscopy for direct measurement of the stable carbon isotope ratio.
• Employing a calibration-free approach to enhance accuracy and traceability.
• Comparing results with values derived from mass spectrometry.

Main Results:

• An accurate value for the stable carbon isotope ratio was determined using infrared absorption spectroscopy.
• The results align with recently reported mass spectrometry data, validating the new approach.
• The findings support the development of SI-traceable isotope analysis.

Conclusions:

• Infrared absorption spectroscopy provides a reliable, calibration-free method for stable carbon isotope ratio determination.
• This advancement aids in establishing SI-traceable isotope standards and improving CO2 source apportionment.
• The method holds potential for enhancing isotopic tracer studies and mass balance calculations.