New Ag₃ PO₄ comparison material for stable oxygen isotope analysis.

Area of Science:

• Geochemistry
• Analytical Chemistry

Background:

• A critical need exists for a silver phosphate (Ag3PO4) reference material for stable oxygen isotope measurements.
• Currently, no such certified reference material is available from major distributing authorities.

Purpose of the Study:

• To calibrate a new Ag3PO4 stable isotope comparison material developed at the University of Natural Resources and Life Sciences (BOKU).
• To provide a much-needed reference standard for stable oxygen isotope analysis in Ag3PO4.

Main Methods:

• Four laboratories (BOKU, UWA, UH, UFZ) analyzed Ag3PO4 using high-temperature conversion elemental analyzers coupled with continuous flow isotope ratio mass spectrometers.
• Measurements were normalized using a three-point linear regression with reference materials IAEA-601, IAEA-602, and NBS127, setting the working gas δ18O to 0‰.

Main Results:

• The mean δ18O value of the BOKU Ag3PO4 material was determined to be 13.71‰ on the VSMOW-SLAP scale, with a combined uncertainty of ±0.34‰.
• The uncertainty is comparable to existing phosphate and sulfate comparison materials, indicating high reliability.
• Consistent results across laboratories suggest the effectiveness of standardized instrumentation, reference materials, and normalization procedures, with negligible matrix effects.

Conclusions:

• The BOKU Ag3PO4 material is validated as a suitable alternative comparison material for stable oxygen isotope analysis.
• This new reference material is now accessible to isotope research laboratories, aiding in the calibration of their analytical instruments.