Characterisation of laser-ablated craters of different painting materials and evaluation with modified LA-APCI-MS system.

The cultural heritage materials (CH) are the most difficult to analyse as they are complex, aged multicomponent mixtures. For the analysis of the composition of organic substances, chromatographic and mass spectrometric (MS) techniques are preferred, but they usually require a small sample piece from the object (risking damaging the artefacts) and additional sample preparation. We have developed a novel flexible laser ablation (LA) coupled to the atmospheric pressure chemical ionisation-MS (LA-APCI-MS) method that could analyse solid organic material directly on the object under atmospheric conditions without removal of the sample piece and sample preparation with minimal visual damage to the surface.

Laser-based analytical techniques in cultural heritage science - Tutorial review.

This tutorial review combines the fundamentals of the design and operation of lasers with their usage in applications related to conservation and cultural heritage (CH) science - as components of analytical devices for the study of the chemical composition of materials. The development of laser instruments and their fundamental physical background, including a short explanation of their properties and parameters, are briefly summarised, and an overview of different laser-based analytical techniques is given. The analytical techniques covered in this tutorial are divided into three groups based on their technical aspects and properties: (1) vibrational spectroscopy, (2) elemental analysis, and (3) different molecular mass spectrometric techniques.

Quantitative mineralogical analysis of clay-containing materials using ATR-FT-IR spectroscopy with PLS method.

A universal method for quantitative analysis of clay components, in terms of mineral composition, using ATR-FT-IR spectroscopy (in the mid-IR and far-IR regions) combined with partial least squares (PLS) regression technique (ATR-FT-IR-PLS) is reported. For the PLS method development, altogether 222 samples covering natural clay sources and various archaeological/cultural heritage artefacts were used as calibration and validation standards. This is the largest calibration set used for creating an ATR-FT-IR-PLS method for clay minerals.

Quantitative GC-MS Analysis of Artificially Aged Paints with Variable Pigment and Linseed Oil Ratios.

In this study, quantitative gas chromatography-mass spectrometry (GC-MS) analysis was used to evaluate the influence of pigment concentration on the drying of oil paints. Seven sets of artificially aged self-made paints with different pigments (yellow ochre, red ochre, natural cinnabar, zinc white, Prussian blue, chrome oxide green, hematite + kaolinite) and linseed oil mixtures were analysed. In the pigment + linseed oil mixtures, linseed oil concentration varied in the range of 10 to 95 g/100 g.

Experimental and Computational Study of Aminoacridines as MALDI(-)-MS Matrix Materials for the Analysis of Complex Samples.

Monoaminoacridines (1-, 2-, 3-, 4-, and 9-aminoacridine) were studied for suitability as matrices in the negative ion mode matrix-assisted laser desorption/ionization mass spectrometry (MALDI(-)-MS) analysis of various samples. This is the first study to examine 1-, 2-, and 4-aminoacridine as potential matrix material candidates for MALDI(-)-MS. In addition, spectral (UV-Vis absorption and fluorescence), proton transfer-related (basicity and autoprotolysis), and crystallization properties of these compounds were characterized experimentally and/or computationally.

Multidisciplinary investigation of two Egyptian child mummies curated at the University of Tartu Art Museum, Estonia (Late/Graeco-Roman Periods).

Two ancient Egyptian child mummies at the University of Tartu Art Museum (Estonia) were, according to museum records, brought to Estonia by the young Baltic-German scholar Otto Friedrich von Richter, who had travelled in Egypt during the early 19th century. Although some studies of the mummies were conducted, a thorough investigation has never been made. Thus, an interdisciplinary team of experts studied the remains using the most recent analytical methods in order to provide an exhaustive analysis of the remains.

Quantitative non-destructive analysis of paper fillers using ATR-FT-IR spectroscopy with PLS method.

A quantitative non-destructive express method of determining fillers -kaolin and chalk- in paper was created using attenuated total reflectance Fourier transform infrared (ATR-FT-IR) spectroscopy in the mid-IR and far-IR region (3800-245 cm) combined with partial least squares (PLS) data analysis. Altogether, 30 two-component (cellulose pulp + kaolin and cellulose pulp + chalk) reference paper samples with known different filler concentrations and one reference paper sample without any fillers were prepared for calibration and validation. The reference values of filler concentrations in the prepared papers were determined by gravimetric analysis via dry ashing (for establishing accurate concentrations of fillers in paper) and ATR-FT-IR microspectroscopy (for evaluating homogeneity of the papers).

MALDI-FT-ICR-MS for archaeological lipid residue analysis.

Soft-ionization methods are currently at the forefront of developing novel methods for analysing degraded archaeological organic residues. Here, we present little-used soft ionization method of matrix assisted laser desorption/ionization-Fourier transform-ion cyclotron resonance-mass spectrometry (MALDI-FT-ICR-MS) for the identification of archaeological lipid residues. It is a high-resolution and sensitive method with low limits of detection capable of identifying lipid compounds in small concentrations, thus providing a highly potential new technique for the analysis of degraded lipid components.

Identification and classification of textile fibres using ATR-FT-IR spectroscopy with chemometric methods.

The possibility of classification of single- and two-component textile materials using ATR-FT-IR spectra and chemometric methods, principal component analysis (PCA) and discriminant analysis, was assessed. Altogether 89 textile samples belonging to 26 different types (11 one- and 15 two-component textiles) were investigated. It was found that PCA classification using only two or three principal components (PCs) enables identifying different one- and two-component textiles, although with two important limitations: it was not always possible to distinguish between the cellulose-based fibres (cotton, linen and in some cases viscose) and it was only partly possible to distinguish between silk and wool.

ATR-FT-IR spectral collection of conservation materials in the extended region of 4000-80 cm⁻¹.

In this paper, a spectral collection of over 150 ATR-FT-IR spectra of materials related to cultural heritage and conservation science has been presented that have been measured in the extended region of 4000-80 cm(-1) (mid-IR and far-IR region). The applicability of the spectra and, in particular, the extended spectral range, for investigation of art-related materials is demonstrated on a case study. This collection of ATRFT-IR reference spectra is freely available online (http://tera.

2,5-Dihydroxybenzoic acid solution in MALDI-MS: ageing and use for mass calibration.

2,5-Dihydroxybenzoic acid (DHB) is one of the most widely used and studied matrix compounds in matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. However, the influence of ageing of the DHB solution on the MALDI mass spectra has not been yet systematically studied. In this work, the possible changes occurring in the acidified acetonitrile/water solution of the MALDI matrix compound DHB during 1-year usage period have been monitored with MALDI-Fourier transform ion cyclotron resonance mass spectrometer (MALDI-FT-ICR-MS) and attenuated total reflectance Fourier transform infrared (ATR-FT-IR) spectroscopy.

Analysis of dammar resin with MALDI-FT-ICR-MS and APCI-FT-ICR-MS.

Comprehensive analysis of high-resolution mass spectra of aged natural dammar resin obtained with Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR-MS) using matrix-assisted laser desorption/ionization (MALDI) and atmospheric pressure chemical ionization (APCI) is presented. Dammar resin is one of the most important components of painting varnishes. Dammar resin is a terpenoid resin (dominated by triterpenoids) with intrinsically very complex composition.

ATR-FT-IR spectroscopy in the region of 550-230 cm(-1) for identification of inorganic pigments.

A comprehensive study of ATR-FT-IR spectra of 40 inorganic pigments of different colours widely used in historical paintings has been carried out in the low wave number spectral range (550-230 cm(-1)). The infrared spectra were recorded from mixtures of pigment and linseed oil. It is demonstrated that this spectral range - essentially devoid of absorption peaks of the common binder materials - can be well used for identification of inorganic pigments in paint samples thereby markedly extending the possibilities of pigment identification/confirmation by ATR-IR spectroscopy into the realm of pigments having no absorptions in the mid-IR region.

ATR-FT-IR spectroscopy in the region of 500-230 cm(-1) for identification of inorganic red pigments.

It is demonstrated that micro-ATR-FT-IR in the low wave number range (500-230 cm(-1)) can be well used for identification of pigments in paint samples thereby markedly extending the possibilities of pigment identification by ATR-IR spectroscopy into the realm of pigments having no absorptions in the mid-IR region. Reference spectra of pigments can be conveniently obtained by mixing them with linseed oil in approximately 1:1 mass ratio. Vermilion (or cinnabar), read lead, different red iron oxide pigments and cadmium red can be identified.