The chemical analysis of cultural heritage (CH) organic materials is challenging due to their complex composition and ethical constraints that limit sampling from the artefact. For chemical analysis, sensitive, portable, non-invasive and non- or minimally destructive analytical techniques are preferred. Currently, no reliable handheld laser ablation (LA) and mass spectrometry (MS)-based analytical technique is available that allows direct analysis of organic materials on the solid surface of a CH object.We present a novel, custom-designed handheld, optical fibre-guided, laser-based pen-type sampling probe (hereafter, laser pen probe) prototype that can be connected via a flexible, over 1 m-long, non-heated transfer line to an atmospheric pressure chemical ionisation high-resolution mass spectrometer (APCI-HRMS). An easily removable harness has been designed around the cylindrical focuser unit (connected via a 2 m long optical fibre to the 355 nm ns-pulsed Nd:YAG laser). Due to this unique design, the laser beam angle of incidence and the focal distance are always correctly ensured. This enables performing controllable, precise, and repeatable sampling directly on the solid surface of the object with minimal damage under ambient conditions. Measurements with the handheld laser pen probe-APCI-HRMS can be performed on horizontal and vertical material surfaces, as well as on various shapes of objects, resulting in an identifiable mass spectrum of the analysed material.This study evaluates the usability of a handheld laser pen probe coupled with APCI-Fourier transform ion cyclotron resonance (FT-ICR)-MS for minimally invasive molecular characterisation of CH materials, as demonstrated on two paint mock-ups and two authentic artefacts.This handheld laser pen probe connectable to the APCI-HRMS system is primarily developed for the analysis of CH materials, however, it can also be used in other fields (e.g., forensics, material sciences, physics, etc.).

Analyzing cultural heritage (CH) materials, particularly organic substances, is challenging due to their complex chemical composition. A key requirement in such analyses is the use of analytical techniques that cause minimal damage to the artifact while providing the maximum amount of chemical information about the materials. Chromatographic and mass spectrometric (MS) techniques give valuable information about components of the organic materials, but these typically require a microsample from the object, along with specific preparation and instrumental conditions. For CH artifacts, techniques that work directly on the surface, thereby causing minimal damage, are far more desirable. We have developed a 355 nm optical fiber-coupled laser ablation (LA) atmospheric pressure chemical ionization (APCI)-MS system that enables the analysis of organic material directly from the solid surface of the artifact under ambient conditions with minimal surface damage. In this study, we coupled LA with APCI-Fourier transform ion cyclotron resonance (FT-ICR)-MS. The main aim was to evaluate the effectiveness of the developed LA-APCI high-resolution (HR)MS system for the analysis of five handmade mock-up materials of different paint and varnish layers and one real-life sample. The results demonstrate the analytical potential of the LA-APCI-HRMS technique, as high-quality and identifiable mass spectra were obtained for most of the analyzed materials. In the future, the developed LA-APCI-HRMS technique could be applied not only to cultural heritage but also to other fields (e.g., forensics, material science, etc.).

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. The main aim of this work was to investigate the performance of LA-APCI-MS by analysing the pulsed 355 nm Nd:YAG laser's impact on hand-made painting materials (oil and acrylic paints and varnish) by characterising the area and volume of laser-ablated craters (measured with an optical microscope and 3D profilometer) obtained with different laser energies and the number of pulses at 90 degrees, 70 degrees, and 45 degrees incidence angles and evaluating the corresponding MS signals obtained with APCI-MS. The areas of the craters of all the samples obtained with different laser energies and a number of laser pulses at 90 degrees, 70 degrees, and 45 degrees incidence angles were between 4.1.104 to 4.2.105 mu m2 and volumes 6.9.104 to 4.3.106 mu m3. From a cultural heritage perspective, these craters were visually barely noticeable. For analysed materials, the optimal laser pulse fluence (energy density) for achieving maximum MS signals ranged from 1.8 to 2.7 J/cm2.

The process by which clay influences the preservation and retention of absorbed lipids in archaeological pottery is not well understood. Although properties such as porosity and calcium content are frequently suggested as primary factors in lipid retention, their exact influence remains unclear. To investigate this, replicate clay ceramics were manufactured using varying proportions of illitic/illite-smectitic clay, mixed with two different tempers (sand and chalk), and fired at 800 degrees C in an oxidizing atmosphere. This study aimed to assess the impact of these compositional variations on the preservation and retention of selected fatty acids, palmitic acid (C16:0) and oleic acid (C18:1), often discovered in archaeological lipid residue analysis, in both heat-degraded (100 degrees C for 14 h) and undegraded forms. Gas chromatography-mass spectrometry (GC-MS) was used for quantification, employing calibration curves generated from standard solutions of fatty acid methyl esters (FAME). Two methylation techniques were utilized: acid-catalyzed methylation (ACM) and solvent extraction using a mixture of dichloromethane (DCM) and methanol (MeOH), followed by m-(trifluoromethyl)phenyltrimethylammonium hydroxide (TMTFTH) methylation. A comparison of the two techniques revealed that prior solvent extraction using a combination of DCM-MeOH may have limited the amount of C16:0 and C18:1 methylated by TMTFTH, causing inconsistent results in quantification compared to ACM. From the ACM technique, results showed that sandtempered briquettes, whether degraded (for C16:0) or non-degraded (for C16:0 and C18:1), have minimal influence on fatty acid yield while degradation significantly affects the yield of C18:1. In contrast, C16:0 and C18:1 recovery from chalk-tempered briquettes is proportional to clay content and inversely proportional to the chalk content. This holds both for degraded and non-degraded briquettes. This work highlights the importance of considering and investigating the mineralogical composition of clay and non-clay minerals for predicting the lipid yield from ancient ceramics.

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.

Recent clinical success with targeted covalent inhibitors points to new possibilities for development of protein kinase (PK)-targeted drugs by exploiting reactive cysteine residues in and around the ATP-binding site. However, more than 300 human PKs lack cysteine residues in the ATP-binding site. Here, we report the first covalent bisubstrate PK inhibitor whose electrophilic warhead reaches outside the ATP-binding site and reacts with a distant cysteine residue. A series of covalent inhibitors and their reversible counterparts were synthesized and characterized. The most potent reversible inhibitor possessed picomolar affinity and its cysteine-reactive counterpart revealed high value of kinact/KI ratio (6.2 × 107 M-1 s-1) for the reaction with the catalytic subunit of cAMP-dependent PK (PKAc). Under optimized conditions, fluorescent dye-labeled covalent inhibitors demonstrated PKA-selectivity in the cell lysate and reacted with several proteins inside live cells, including PKAc. The disclosed compounds serve as leads for targeting PKs possessing an analogously positioned cysteine residue.

Attenuated total reflection-Fourier transform-infrared spectroscopy (ATR-FT-IR) analysis of 100 adhesive samples from different prehistoric composite artefacts, pottery, and amorphous lumps across Eastern Europe and Urals were conducted with the aim to establish a fast analytical screening method for adhesive assignment. The ATR-FT-IR analysis allowed the identification of major chemical components of the adhesive samples that were assigned to three main groups: birch bark tar without major additives, birch bark tar with additives, and minor/non-birch bark tar samples. ATR-FT-IR spectra were further analyzed using principal component analysis (PCA)-based discriminant analysis (DA) that allowed additional refinement of adhesive classifications. The ATR-FT-IR results and the DA classification were confirmed by analyzing a selection of samples with gas chromatography-mass spectrometry (GC-MS). Results demonstrate that ATR-FT-IR coupled with DA classification allows fast and reliable preliminary identification of the major components in archaeological adhesives and their further classification. As such it is a considerable and faster alternative to more laborious GC-MS analysis, especially in the case of very small samples.

Attenuated total reflection-Fourier transform-infrared spectroscopy (ATR-FT-IR) analysis of 100 adhesive samples from different prehistoric composite artefacts, pottery, and amorphous lumps across Eastern Europe and Urals were conducted with the aim to establish a fast analytical screening method for adhesive assignment. The ATR-FT-IR analysis allowed the identification of major chemical components of the adhesive samples that were assigned to three main groups: birch bark tar without major additives, birch bark tar with additives, and minor/non-birch bark tar samples. ATR-FT-IR spectra were further analyzed using principal component analysis (PCA)-based discriminant analysis (DA) that allowed additional refinement of adhesive classifications. The ATR-FT-IR results and the DA classification were confirmed by analyzing a selection of samples with gas chromatography–mass spectrometry (GC–MS). Results demonstrate that ATR-FT-IR coupled with DA classification allows fast and reliable preliminary identification of the major components in archaeological adhesives and their further classification. As such it is a considerable and faster alternative to more laborious GC–MS analysis, especially in the case of very small 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. For testing the capabilities of these aminoacridines as matrix materials, four samples related to cultural heritage materials-stearic acid, colophony resin, dyer's madder dye, and a resinous case-study sample from a shipwreck-were analyzed with MALDI(-)-MS. A novel algorithm (implemented as an executable Python script) for MS data analysis was developed to compare the five matrix materials and to help mass spectrometrists rapidly identify peaks originating from the sample and matrix material. It was determined that all five of the studied aminoacridines can successfully be used as matrix materials in MALDI(-)-MS analysis. As an interesting finding, in several cases, the best mass spectra were obtained by using a relatively small amount of matrix material mixed with an excess amount of sample. 3- and 4-aminoacridine outperformed the other aminoacridines in the ease of obtaining acceptable spectra, average number of ions identified in the mass spectra, and low dependence of the sample-to-matrix mass ratio on experimental results.

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. The bodies were submitted for osteological and archaeothanatological study, radiological investigation, AMS radiocarbon dating, chemical and textile analyses, 3D modelling, entomological as well as aDNA investigation. Here we synthesize the results of one of the most extensive multidisciplinary analyses of ancient Egyptian child mummies, adding significantly to our knowledge of such examples of ancient funerary practices.

The rationale and need for a joint master degree programme in analytical chemistry A large fraction (estimated from 25 to 70% by different surveys) 1 of the chemistry master's degree holders are employed within the area of analytical chemistry worldwide and it has been demonstrated that there is a shortage of well-educated analytical chemists in Europe. 2 The need for educated chemists is even more serious in emerging economies, such as China, India, Mexico, Brazil and Vietnam, where chemical industry is booming: "…strong growth and huge domestic demand is attracting global firms in expanding their presence in the area". 3The growing need for qualified chemical analysis specialists is also well indicated by the active attendance in practitioner-oriented training courses Europe-wide, e.g. the TrainMiC programme, 4 as well as the popularity of the respective MOOCs. 5,6 Partly, this shortage has been caused by the significant changes that have, during the recent years, taken place worldwide in the areas of measurements, testing and chemical analysis.Some examples: an increase of importance of quality assurance (quality management system, accredited according to international standards, e.g.ISO/ IEC 17025:2017 7 or GLP, is now a must in laboratories) and metrology 8 aspects (estimating measurement uncertainty, as the main quality characteristic of analytical results is now a must), emergence of new analytical techniques and more stringent requirements by legislation.A number of novel analytical techniques have become widespread in modern analytical chemistry: LC-MS for trace organic contaminants, ICP-MS for trace elements, different sensors, etc.Up to now, the higher education sector in the whole world has generally been unable to respond adequately to the changing needs of the chemical industry and analysis community. 2This is demonstrated, e.g. by the fact that around two-thirds of European chemical companies have difficulties in filling vacancies. 2The reasons are, above all, lack or insufficient coverage of the following topics in the master programmes focusing on analytical chemistry: metrology and quality topics (such as traceability, 4 TrainMiC -Training in Metrology in Chemistry (http://www.trainmic.org/) 5MOOC: Massive Open Online Course. 6See, e.g.http://each.ut.ee/EACH/measurement-uncertainty-online-coursemooc-successfully-finished/ and https://sisu.ut.ee/measurement/what-ourparticipants-say 7 ISO/IEC 17025:2017 General requirements for the competence of testing and calibration laboratories.ISO, IEC, 2017. Metrology is the science of measurements and addresses first of all the correctness and quality of measurement procedures and measurement results.Metrology in chemistry is metrology applied to analytical chemical measurement.

Matrix-assisted laser desorption/ionization (MALDI) is a mass spectrometry (MS) ionization technique suitable for a wide variety of sample types including highly complex ones such as natural resinous materials. Coupled with Fourier transform ion cyclotron resonance (FT-ICR) mass analyser, which provides mass spectra with high resolution and accuracy, the method gives a wealth of information about the composition of the sample. One of the key aspects in MALDI-MS is the right choice of matrix compound. We have previously demonstrated that 2,5-dihydroxybenzoic acid is suitable for the positive ion mode analysis of resinous samples. However, 2,5-dihydroxybenzoic acid was found to be unsuitable for the analysis of these samples in the negative ion mode. The second problem addressed was the limited choice of calibration standards offering a flexible selection of m/z values under m/z 1000. This study presents a modified MALDI-FT-ICR-MS method for the analysis of resinous materials, which incorporates a novel matrix compound, 2-aminoacridine for the negative ion mode analysis and extends the selection of internal standards with m/z <1000 for both positive (15 different phosphazenium cations) and negative (anions of four fluorine-rich sulpho-compounds) ion mode. The novel internal calibration compounds and matrix material were tested for the analysis of various natural resins and real-life varnish samples taken from cultural heritage objects. Copyright © 2017 John Wiley & Sons, Ltd.

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.chem.ut.ee/IR_spectra/) and is meant to be a useful tool for researchers in the field of conservation and materials science.

A wide range of anthropogenic pollutants that possess serious environmental and health risks are known. One type of these harmful substances that have become a focus of interest during the past decade are perfluoroalkyl acids (PFAAs), which are extensively used in industry for different purposes. Due to the harmful effects that these compounds might cause in living organisms, EFSA and EU CONTAM panel have issued a monitoring program for PFAAs in foodstuffs. This has given rise to intense research dedicated to the analysis of PFAAs over the past few years. This work focuses on chromatographic analysis of three PFAAs in fish. The analytes, perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), and perfluorooctanesulfonic acid (PFOS), are commonly associated with the production of fluoropolymers. Fluorinated alcohols are used as eluent components, and their possible advantages as eluent modifiers in LC-MS analysis of PFAAs, alternative retention mechanism and enhanced ionization efficiency, are examined. The analyzed fish samples originating from Estonian fresh and marine waters had low contents of PFAAs.

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. No significant ageing products have been detected. The ability of the aged DHB solution to act as a MALDI matrix was tested with two materials widely used in art and conservation - bone glue (a proteinaceous material) and shellac resin (a resinous material) - and good results were obtained. A number of peaks in the mass spectra measured from the DHB solution were identified, which can be used for internal calibration of the mass axis.

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. This complexity further increases with aging. Ten different solvents and two-component solvent mixtures were tested for sample preparation. The most suitable solvent mixtures for the MALDI-FT-ICR-MS analysis were dichloromethane-acetone and dichloromethane-ethanol. The obtained MALDI-FTMS mass spectrum contains nine clusters of peaks in the m/z range of 420-2200, and the obtained APCI-FTMS mass spectrum contains three clusters of peaks in the m/z range of 380-910. The peaks in the clusters correspond to the oxygenated derivatives of terpenoids differing by the number of C(15)H(24) units. The clusters, in turn, are composed of subclusters differing by the number of oxygen atoms in the molecules. Thorough analysis and identification of the components (or groups of components) by their accurate m/z ratios was carried out, and molecular formulas (elemental compositions) of all major peaks in the MALDI-FTMS and APCI-FTMS spectra were identified (and groups of possible isomeric compounds were proposed). In the MALDI-FTMS and APCI-FTMS mass spectrum, besides the oxidized C(30), triterpenoids also peaks corresponding to C(29) and C(31) derivatives of triterpenoids (demethylated and methylated, correspondingly) were detected. MALDI and APCI are complementary ionization sources for the analysis of natural dammar resin. In the MALDI source, preferably polar (extensively oxidized) components of the resin are ionized (mostly as Na(+) adducts), whereas in the APCI source, preferably nonpolar (hydrocarbon and slightly oxidized) compounds are ionized (by protonation). Either of the two ionization methods, when used alone, gives an incomplete picture of the dammar resin composition.