Integrating liquid chromatography mass spectrometry into an analytical protocol for the identification of organic colorants in Japanese woodblock prints

Marc Vermeulen,Marco Leona,Emily M K Müller,Diego Tamburini,Elena Basso,Silvia A Centeno

doi:10.1038/s41598-020-77959-2

Abstract

Three Japanese woodblock prints from the Edo period (1603–1868) underwent a scientific investigation with the aim of understanding the changes in the colorants used in Japanese printing techniques. A multi-analytical approach was adopted, combining non-invasive techniques, such as fiber optic reflectance spectroscopy (FORS), Raman spectroscopy, multispectral imaging (MSI), and macro X-ray fluorescence (MA-XRF) with minimally invasive surface-enhanced Raman spectroscopy (SERS). The results enabled many of the pigments to be identified and their distribution to be studied, apart from two shades of purple of organic composition. Consequently, the potential of high-pressure liquid chromatography tandem mass spectrometry (HPLC–MS/MS) was explored for the first time with application to Japanese woodblock prints. The intrinsic sensitivity of the instrument and an effective extraction protocol allowed us to identify a mixture of dayflower (Commelina communis) blue and safflower (Carthamus tinctorius) red in purple samples constituted of 2–3 single fibers. In addition to the innovative integration of MA-XRF and HPLC–MS/MS to investigate these delicate artworks, the study concluded on the use of traditional sources of colors alongside newly introduced pigments in late Edo-period Japan. This information is extremely important for understanding the printing practices, as well as for making decisions about display, conservation, and preservation of such artworks.

Highlights

Three Japanese woodblock prints from the Edo period (1603–1868) underwent a scientific investigation with the aim of understanding the changes in the colorants used in Japanese printing techniques
One of the aims of this study was to test the feasibility of such sampling and subsequent HPLC–MS/MS analysis, in order to identify the sources of the organic colorants used to obtain particular hues, such as purple shades, which may prove challenging with other techniques
The observation of the purple areas did not present any variation in color, as it would be expected for mixtures of blue and red

Summary

Introduction

Three Japanese woodblock prints from the Edo period (1603–1868) underwent a scientific investigation with the aim of understanding the changes in the colorants used in Japanese printing techniques. Driven by research questions such as the lightfastness of colors, the chronology of the use of certain pigments[11,12,14], the introduction of new materials in Japan[4,11], the understanding of the creation sequence of prints[4,13,15], and the transition between the Edo period and the Meiji e ra[4], researchers have developed analytical protocols with particular attention to the investigation of Japanese woodblock p rints[1,4,5,14,15] While SERS is very sensitive to detect many colorants, the technique presents some limitations, especially for yellow colorants or some complex m ixtures[28,31]

Objectives

Methods

Results

Conclusion