Peptide mass mapping as an effective tool for historical mortar analysis

• Ageing effects on protein additives in mortars were studied using two MS techniques.
• MALDI–TOF MS was used for rapid and sensitive identification of additives.
• LC–MS/MS provided sequence information for unambiguous identification of proteins.
• The complementarity of MALDI–TOF MS and LC–MS/MS allows for their convenient combination.

Recently, peptide mass mapping using MALDI–TOF MS (Matrix-Assisted Laser Desorption/Ionization – Time of Flight Mass Spectrometry) was shown to be an effective tool for protein analysis in such challenging insoluble materials as historical mortars.The first aim of this study was to investigate the influence of ageing on the performance of peptide mass mapping analysis using MALDI–TOF MS. Therefore, analyses were performed on model mortar samples with different compositions after 5 years of ageing.The second goal of this work was to analyse peptide fragments using LC–MS/MS (Liquid Chromatography coupled to tandem Mass Spectrometry), which represents a new approach. The use of this method led to obtaining the sequence information that allowed for unambiguous identification of the proteins present. Our study proved the complementarity of both approaches; therefore, their combination is highly beneficial.