Development of a novel method for unraveling the origin of natron flux used in Roman glass production based on B isotopic analysis via multicollector inductively coupled plasma mass spectrometry

The provenance of the flux raw material used in the manufacturing of Roman glass is an understudied topic in archaeology. Whether one or multiple sources of natron mineral salts were exploited during this period is still open for debate, largely because of the lack of a good provenance indicator. The flux is the major source of B in Roman glass. Therefore, B isotopic analysis of a sufficiently large collection and variety (origin and age) of such glass samples might give an indication of the number of flux sources used. For this purpose, a method based on acid digestion, chromatographic B isolation and B isotopic analysis using multicollector inductively coupled plasma mass spectrometry was developed. B isolation was accomplished using a combination of strong cation exchange and strong anion exchange chromatography. Although the B fraction was not completely matrix-free, the remaining Sb was shown not to affect the delta B-11 result. The method was validated using obsidian and archaeological glass samples that were stripped of their B content, after which an isotopic reference material with known B isotopic composition was added. Absence of artificial B isotope fractionation was demonstrated, and the total uncertainty was shown to be