Improved Standard Addition Method for Measuring Stable Isotopic Compositions and Its Application to Sulfur Isotope...

Area of Science:

• Geochemistry
• Analytical Chemistry
• Isotope Analysis

Background:

• Standard Addition Method (SAM) is crucial for analyzing complex natural samples.
• Traditional SAM faces limitations with significant isotopic variations due to calculation approximations and prior data requirements.

Purpose of the Study:

• To develop an improved Standard Addition Method (SAM) for accurate isotopic composition and concentration measurements.
• To overcome the limitations of traditional SAM in handling samples with high isotopic variability and complex matrices.

Main Methods:

• Proposed an improved SAM that directly calculates isotope ratios (R) instead of approximations (R*).
• Determined sample fraction using isotope compositions of standards and mixtures, eliminating reliance on concentration and volume.
• Validated the method on natural samples with substantial sulfur (S) isotope variation and low S concentration.

Main Results:

• Achieved accurate determination of sulfur (S) isotope compositions (δ³⁴S) and concentrations.
• Reduced required sample size by 80% compared to direct measurement.
• Demonstrated higher accuracy in δ³⁴S values compared to traditional SAM.

Conclusions:

• The improved SAM provides a reliable and superior alternative for isotopic analysis of challenging natural samples.
• The method enhances accuracy and efficiency in determining both isotopic composition and concentration.
• Successfully validated for sulfur isotope analysis in natural samples with wide isotopic variations.