A shadow of ink: Test papers soaked in 4:7-diphenyl-1:10-phenanthroline as a carrier of elemental information for spectrochemical investigations of manuscripts by XRF, LA-ICP-MS and SIMS

In this study, X-Ray Fluorescence Spectrometry (XRF), Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) and Secondary Ion Mass Spectrometry (SIMS) have been used to assess the transfer of ions between iron-gall inks and indicator papers soaked in 4:7-diphenyl-1:10-phenanthroline. Such indicators are commonly used in the conservation practice to detect Fe(II) ions and diagnose a presence of ink corrosion phenomena in historical manuscripts. For this purpose four different model inks with variable Fe:Cu proportions were prepared on the basis of gall nuts extract mixed with FeSO4.7H2O, CuSO4.5H2O and Gum Arabic. Obtained results indicate that apart from the main components of inks (S, Fe and Cu) also other elements can migrate to indicator test papers. Collected XRF and LA-ICP-MS data were consistent in their potential for reconstructing major elemental composition of model inks on the basis of indirect analysis with indicator test papers. LA-ICP-MS extended the range of learning into the trace elemental composition, while SIMS allowed observations of structurally significant fragment ions (ML2+, ML+, M+) where L = 4:7-diphenyl-1:10-phenanthroline and M = Fe or Cu ions.