Method for ultra-low-level analysis of gold in rocks

Area of Science:

• Geochemistry
• Analytical Chemistry

Background:

• Analyzing ultralow gold concentrations (<10 pg/g) in geological samples is critical for understanding ore genesis, crustal mobility, planetary differentiation, and plume volcanism.
• Existing methods often have detection limits in the nanogram per gram range, insufficient for these research areas.

Purpose of the Study:

• To develop and present a novel, rapid, and user-friendly method for the precise quantification of gold at picogram per gram levels in geological matrices.
• To achieve significantly lower detection limits than currently available methods for gold analysis.

Main Methods:

• The method involves hydrofluoric acid-aqua regia acid digestion of geological samples.
• Chromatographic separation of gold from matrix elements using diisobutyl ketone (DIBK) on an inert resin.
• Analysis of separated gold using inductively coupled plasma-mass spectrometry (ICP-MS).

Main Results:

• The developed method achieves an analytical detection limit of 2 parts per trillion (pg/g).
• The method is reliable for a wide range of gold concentrations, from picograms to micrograms per gram.
• Analysis of four geostandards (GXR1, GXR4, CH-3, SARM 7) showed >95% accuracy, with results within error of published values.

Conclusions:

• This new ICP-MS based method provides a highly sensitive and accurate means for analyzing ultralow gold concentrations in geological samples.
• The method's speed, ease of use, and wide applicability make it suitable for high-throughput analysis in various geological research fields.