Studies of artists' organic pigments (2003)

Title: Laser desorption mass spectrometric studies of artists' organic pigments
Author: Nicolas Wyplosz
University: University of Amsterdam
Year: 2003
Type of document: PhD thesis
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From the Introduction:

The technical investigation of organic pigments in easel paintings is not without problems. Pigments have complex chemical compositions; details of their manufacturing processes are generally unknown and dramatic transformations of the colouring properties are observed with the passing of time. Characterisation of the chemical composition is greatly complicated by the particularly small size and complex arrangement of the samples available for analysis. Microscopic samples are preferably studied as paint cross-sections, but the finest methods of molecular analysis available today (chromatography and mass spectrometry) are not very compatible with this sampling method. In practice, investigation of organic pigments in cross-sections remains often inconclusive by the lack of a suitable method of analysis. This dissertation explores a new approach to the analysis of organic pigments found in easel paintings, using laser desorption mass spectrometry (LDMS). LDMS makes it possible to investigate the surface of paint cross-section with a spatial-resolution down to 10 mm utilising the analytical method of mass spectrometry.

Table of Contents:

Chapter 1 : Introduction
1.1. Introduction
1.2. Structure of an easel painting
1.3. Traditional and modern organic pigments
1.4. Categories of pigments under investigation
1.5. Deterioration of organic pigments
1.6. Investigation of organic colouring materials in conservation science
1.7. LDMS of organic colouring materials, a rationale
1.8. Thesis outline
1.9. Main results and implications for painting studies

Chapter 2: Principles and instrumentation of LDMS
2.1. Introduction
2.2. Laser Desorption Mass Spectrometry for Surface Analyses
2.3. Principles of LDMS
2.4. Instrumentation for the analysis of paint cross-section
2.5. Conclusion

Chapter 3: An experimental strategy for LDMS of paint materials
3.1. Introduction
3.2. Sample and sample mounting
3.3. Laser-sample interaction
3.4. Shot-to-shot variations
3.5. TOF-MS versus ITMS: pressure and time-scale
3.6. Ion collection in the ITMS analyser: LMCO
3.7. CID experiments with the ITMS analyser
3.8. Conclusion

Chapter 4: LDMS of flavonoids
4.1. Introduction
4.2. Flavonoid pigments
4.3. Experimental
4.4. Characterization of flavonoid aglycones with LDMS
4.5. Multiple-stage LDI–ITMS
4.6. Characterisation of flavonoid-O-glycosides
4.7. Analysis of complex samples
4.8. Analysis fibres dyed with flavonoids
4.9. Investigation of cross-sectioned samples
4.10. Conclusion

Chapter 5: LDMS of anthraquinones
5.1. Introduction
5.2. Anthraquinone pigments
5.4. LDI and MALDI of Alizarin
5.5. Alizarin lake in oil paint
5.6. Analysis of natural dyed fibres
5.7. Conclusion

Chapter 6: LDMS of indigoids
6.1. Introduction
6.2. Experimental
6.3. Analysis of synthetic indigo
6.4. Analysis of natural indigos
6.5. LDMS of indigo at the surface of dyed fibres
6.6. LDMS of indigo in oil paint
6.7. Spatially- resolved LDMS of cross-sections
6.8. Conclusion

Chapter 7: LDMS of modern synthetic pigments
7.1. Introduction
7.2. Samples
7.3. Experimental conditions
7.4. Analysis of reference samples
7.5. Acrylic polymer emulsions and oil paints
7.6. Spatially- resolved LDMS analysis of cross-sectioned paint samples
7.7. Conclusions

Chapter 8: Surface preparation of paint cross-sections
8.1. Introduction
8.2. FTIR-imaging and LD-ITMS
8.3. Evidence of smearing
8.4. A new sample preparation
8.5. Analyses after polishing
8.6. Conclusion
8.7. Acknowledgements

Bibliography