title: A Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry Method for the Identification of Anthraquinones: the Case of Historical Lakes.
abstract: This study deals with the identification of anthraquinoid molecular markers in standard dyes, reference lakes, and paint model systems using a micro-invasive and nondestructive technique such as matrix-assisted laser desorption/ionization time-of-flight-mass spectrometry (MALDI-ToF-MS). Red anthraquinoid lakes, such as madder lake, carmine lake, and Indian lac, have been the most widely used for painting purposes since ancient times. From an analytical point of view, identifying lakes in paint samples is challenging and developing methods that maximize the information achievable minimizing the amount of sample needed is of paramount importance. The employed method was tested on less than 0.5 mg of reference samples and required a minimal sample preparation, entailing a hydrofluoric acid extraction. The method is fast and versatile because of the possibility to re-analyze the same sample (once it has been spotted on the steel plate), testing both positive and negative modes in a few minutes. The MALDI mass spectra collected in the two analysis modes were studied and compared with LDI and simulated mass spectra in order to highlight the peculiar behavior of the anthraquinones in the MALDI process. Both ionization modes were assessed for each species. The effect of the different paint binders on dye identification was also evaluated through the analyses of paint model systems. In the end, the method was successful in detecting madder lake in archeological samples from Greek wall paintings and on an Italian funerary clay vessel, demonstrating its capabilities to identify dyes in small amount of highly degraded samples. Graphical Abstract ᅟ.
authors: Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Via Giuseppe Moruzzi, 3, 56124, Pisa, Italy.
authors: Francesca
authors: F
authors: Sabatini
authors: Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Via Giuseppe Moruzzi, 3, 56124, Pisa, Italy.
authors: Anna
authors: A
authors: Lluveras-Tenorio
authors: Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Via Giuseppe Moruzzi, 3, 56124, Pisa, Italy. ilaria.degano@unipi.it.
authors: Ilaria
authors: 0000-0002-3585-8555
authors: I
authors: Degano
authors: Department of Biochemistry and Microbiology University of Chemistry and Technology, Technicka 5, 166 28, Prague 6, Czech Republic.
authors: Stepanka
authors: S
authors: Kuckova
authors: Department of Biochemistry and Microbiology University of Chemistry and Technology, Technicka 5, 166 28, Prague 6, Czech Republic.
authors: Iva
authors: I
authors: Krizova
authors: Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Via Giuseppe Moruzzi, 3, 56124, Pisa, Italy.|ICVBC-CNR, Via Madonna del Piano 10 - Edificio C, 50019, Sesto Fiorentino, Florence, Italy.
authors: Maria Perla
authors: MP
authors: Colombini
keywords: Anthraquinones; LDI; MALDI; Organic lakes; Singly charged double cation adducts; ToF