# Beware the Artifact: Generation of Ellagic Acid and Related Species During Atmospheric Solid Analysis Probe (ASAP) Measurements of Iron Gall Inks and Tannins in the Negative Ionization Mode

## TL;DR

This study shows that ellagic acid and related compounds can form during ASAP mass spectrometry of iron gall inks and tannins, affecting results in the negative ionization mode.

## Contribution

The paper identifies new breakdown products and radical ion species of gallic acid and ellagic acid during ASAP measurements.

## Key findings

- ASAP measurements of gallic acid produce dimeric adducts and condensation products under varying conditions.
- Iron III ions cause dehydrogenation of gallic acid species to ellagic acid during ASAP analysis.
- New breakdown products and radical ion species of gallic acid and ellagic acid were identified.

## Abstract

A detailed comparative analysis of the results of atmospheric solid analysis probe (ASAP) mass spectrometry of inks, tannins, and gallic acid (GA) in the negative ionization mode was performed. Results obtained for tannin by ASAP have been compared with those obtained with electrospray ionization (ESI). Apart from the GA ion, measurements frequently also yielded anions corresponding to association products and condensation products. At zero collision energy, pure GA gave a dimeric adduct (m/z 339); the formation of ions at m/z 303 and 304 was favored by increased temperatures and collision energies. In the case of inks, the subsequent dehydrogenation of such species to ellagic acid (EA) (m/z 301) was attributed to the oxidative effect of the iron III ion. On the basis of the results, a modification of the “standard ink protocol” has been suggested. Furthermore, several yet non‐described breakdown products and radical ion species of GA and EA ions were identified.