Condensed-phase carbon isotopic standards for compound-specific isotope analysis

Area of Science:

• Analytical Chemistry
• Isotope Geochemistry
• Organic Chemistry

Background:

• Compound-specific isotope analysis requires high-quality internal standards.
• Accurate carbon isotope ratio determination is essential for various scientific disciplines.
• Existing methods for preparing standards may suffer from fractionation and contamination.

Purpose of the Study:

• To develop a robust protocol for preparing isotopically characterized internal standards.
• To ensure minimal isotopic fractionation and contamination during standard preparation.
• To provide reliable standards for compound-specific isotope analysis, particularly for fatty acids.

Main Methods:

• A protocol for loading fatty acids and methyl esters into flame-seal vials was developed.
• Careful procedures were implemented to minimize isotopic fractionation and contamination.
• Carbon isotope analysis was performed using international standards (NIST RM8541:USGS24) for absolute value determination.

Main Results:

• The developed protocol yields high isotopic precision with an average standard deviation of 0.09/1000 (delta 13CPDB).
• Absolute carbon isotope ratios were accurately determined against a certified international standard.
• The procedure is versatile and applicable to various volatile organic compounds.

Conclusions:

• A reliable protocol for preparing isotopically characterized internal standards has been established.
• The standards are suitable for day-to-day quality control in isotope analysis.
• This method aids in assessing derivative carbon addition during fatty acid methylation.