A definitive analytical spectroscopic study of Indian yellow, an ancient pigment used for dating purposes

Author(s)

de Faria, Dalva L. A. ; Edwards, Howell G. M. ; Careaga, Valeria ; Walt, Nicholas ; Maier, Marta S.

• Document type: Journal article
• Source: Forensic Science International; v. 271, p. 1-7, FEB 2017.
• Web of Science Citations: 9

Abstract

The Raman spectrum of tartrazine has been mistakenly reported as being that of Indian yellow in the literature, which has serious consequences for the identification of this pigment in art works regarding their authentication. Unlike tartrazine, Indian yellow (a natural mixture of the magnesium and calcium salts of euxanthic acid) exhibits in its Raman spectrum a strong fluorescent background when visible excitation is used, however, excitation in the near infrared (1064 nm) permitted the observation of the Raman bands from the raw pigment with the main features placed at 1346, 1368, 1425, 1441 and 1626 cm(-1). Indian yellow identification was assured by H-1 and C-13 Nuclear Magnetic Resonance characterization and the complete assignment of the proton and carbon resonances was accomplished using heteronuclear single quantum correlation (HSQC), heteronuclear multiple bond correlation (HMBC), nuclear overhauser effect spectroscopy (NOESY) and H-1-H-1 correlation spectroscopy (COSY). Scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) and X-ray fluorescence (XRF) analyzes were also conducted on a genuine sample of this historical pigment. (C) 2016 Elsevier Ireland Ltd. All rights reserved. (AU)

• FAPESP's process: 12/13119-3 - Vibrational spectroscopy in condensed phases
• Grantee: Mauro Carlos Costa Ribeiro
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 11/13760-8 - Impact of microenvironment chemical composition on heritage objects: mechanisms and monitoring
• Grantee: Thiago Sevilhano Puglieri
• Support Opportunities: Scholarships in Brazil - Doctorate