Sampling and identification of natural dyes in historical maps and drawings by liquid chromatography with diode-array detection

Multi-Analytical Techniques for the Study of Burial Clothes of Polish King Sigismund III Vasa (1566-1633) and His Wife Constance Habsburg (1588-1631)

The subjects of this research are the burial clothes of Polish King Sigismund III Vasa and his wife Constance, which were woven and embroidered with silk and metal threads. Fragments of the textiles underwent spectroscopic, spectrometric, and thermogravimetric analyses. The hydrofluoric acid extraction method was improved to isolate various classes of dyes from the textile samples that had direct contact with human remains. High-performance liquid chromatography, coupled with diode array and tandem mass spectrometry detectors with electrospray ionization (HPLC-DAD-ESI-MS/MS) facilitated the detection and identification of colorants present in the textiles. Cochineal, indigo-, madder-, orchil-, and tannin-producing plants were identified as the sources of dyes used. Scanning electron microscopy with an energy-dispersive X-ray detector (SEM-EDS) was employed to identify and characterize the silk fibers and mordants and the metal threads. The presence of iron, aluminum, sodium, and calcium in the silk threads suggests their potential use as mordants. The analysis of the metal threads revealed that most of them were made from flattened gilded silver wire, with only a few being cut from a sheet of metal. Typical degradation mechanisms of metal threads were shown, resulting from both burial environment and earlier manufacturing process, and the use of the textiles in clothing, i.e., a significant loss of the gold layer was observed in most of silver gilt threads, caused by abrasion and delamination. The results of the thermal analysis confirmed the presence of silk and silver threads in the examined textiles.

A Mass Spectrometry-Based Approach for Characterization of Red, Blue, and Purple Natural Dyes

Effective analytical approaches for the identification of natural dyes in historical textiles are mainly based on high-performance liquid chromatography coupled with spectrophotometric detection and tandem mass spectrometric detection with electrospray ionization (HPLC-UV-Vis-ESI MS/MS). Due to the wide variety of dyes, the developed method should include an adequate number of reference color compounds, but not all of them are commercially available. Thus, the present study was focused on extending of the universal analytical HPLC-UV-Vis-ESI MS/MS approach to commercially unavailable markers of red, purple, and blue dyes. In the present study, HPLC-UV-Vis-ESI MS/MS was used to characterize the colorants in ten natural dyes (American cochineal, brazilwood, indigo, kermes, lac dye, logwood, madder, orchil, Polish cochineal, and sandalwood) and, hence, to extend the analytical method for the identification of natural dyes used in historical objects to new compounds. Dye markers were identified mostly on the basis of triple quadrupole MS/MS spectra. In consequence, the HPLC-UV-Vis-ESI MS/MS method with dynamic multiple reaction monitoring (dMRM) was extended to the next 49 commercially unavailable colorants (anthraquinones and flavonoids) in negative ion mode and to 11 (indigoids and orceins) in positive ion mode. These include protosappanin B, protosappanin E, erythrolaccin, deoxyerythrolaccin, nordamnacanthal, lucidin, santalin A, santalin B, santarubin A, and many others. Moreover, high-resolution QToF MS data led to the establishment of the complex fragmentation pathways of α-, β-, and γ- aminoorceins, hydroxyorceins, and aminoorceinimines extracted from wool dyed with Roccella tinctoria DC. The developed approach has been tested in the identification of natural dyes used in 223 red, purple, and blue fibers from 15th- to 17th-century silk textiles. These European and Near Eastern textiles have been used in vestments from the collections of twenty Krakow churches.

Analysis of Natural Dyes from Historical Objects by High Performance Liquid Chromatography and Electromigration Techniques

Based on material published between 1989 and 2018 in this paper high performance liquid chromatography and electromigration techniques used in studies of natural dyes that can be found in historical objects are rewieved. Different aspects of analysis have been discussed: the stationary and mobile phase, the choice of sample solvent, methods of extraction and detection, including sensitivity parameters, such as LOD and/or LOQ. The discussed dyes have been divided into three categories (a) red antraquinone dyes along with dyes extracted from bark and tree juices, (b) yellow flavonoid dyes and saffron and (c) blue indigoid dyes. The main markers (chromophores or auxochromes) typical for each dye source were presented which allows to identify specific species of source plants and animals. The first part of the study involved the analysis of most critical findings when it comes to HPLC or represented an significant analytical approach. The second part of the study is focused on different aspects of electromigration techniques application in analysis of natural dyes with special attention paid on such parameters as the running buffer/mobile phase composition and sample solvent. Detection methods along with LOD and LOQ comparison in HPLC and electromigration techniques were also discussed. Methods of sample preparation, such as hydrolysis and extraction, used in HPLC and electromigration techniques were also briefly discussed.

Novel methodology for the extraction and identification of natural dyestuffs in historical textiles by HPLC-UV-Vis-ESI MS. Case study: chasubles from the Wawel Cathedral collection

High-performance liquid chromatography coupled with spectrophotometric and electrospray mass spectrometric detection (HPLC–UV–Vis–ESI MS) was used for characterization of natural dyes present in historical art works. The gradient program was developed for identification of 29 colorants of various polarities. Dual detection system (UV–Vis and ESI MS) allowed differentiation of all compounds, even if they were not completely separated. This enabled examination of more color compounds over a substantially shorter time in comparison with previously recommended methods. Moreover, for extraction of colorants from historical textiles a two-step sequential procedure was proposed, excluding evaporation used in earlier procedures. The developed method was successfully applied to identification of indigotin, carminic, kermesic, flavokermesic, dcII, dcIV, dcVII, and ellagic acids as well as luteolin, apigenin, and genistein in red, violet, and green fibers taken from three selected historical chasubles which belong to the collection of the Wawel Cathedral treasury (Cracow, Poland). Italian textiles from the fifteenth and sixteenth centuries, of which chasubles were made, were dyed with a limited number of dyestuffs, consistently used for all batches of fabrics. The obtained results also allowed confirmation of the structure of the so-called “dcII” component of cochineal as a C-glucose derivative of flavokermesic acid.

Determination of natural colorants in plant extracts by high performance liquid chromatography

The determination of the colouring compounds apigenin (1), lawsone (2), juglone (3) and indigotin (4) in plant extracts using HPLC - UV/VIS methods is reported. The methods were applied to the analysis of 1-4 in ethanolic and propylene glycolic extracts originating, respectively, from chamomile (Chamomilla recutita [L] Rauschert, Asteraceae), henna (Lawsonia inermis L., Lythraceae), walnut (Juglans regia L., Juglandaceae) and natural indigo (Indigofera sp., Fabaceae). In the case of the indigo extracts, an optimized acid hydrolysis was applied. HPLC separations were performed on a Hypersil ODS RP18 column using linear gradient elution programs. The detection limits for 1-4 were 0.11, 0.6, 0.10, 0.089 ?g mL-1, respectively. The procedure did not involve any sample ?clean -up? methods. The amounts of the colouring compounds ranged from 0.006 mg mL-1 (3) to 0.13 mg mL-1 (4) in the ethanolic extracts and from 0.22 mg mL-1 (2) to 1.44 mg mL-1 (4) in propylene glycolic extracts. The proposed HPLC methods are advantageous in terms of sample preparation and the selective separation of the compounds. The plant dye extracts are commonly used in hair colouring formulations. The results indicate that the methods developed may serve for the quantitative control of dying plants and cosmetic products.

Simultaneous identification of natural dyes in the collection of drawings and maps from The Royal Chancellery Archives in Granada (Spain) by CE

A simple and rapid capillary electrophoretic method with UV detection (CE-UV) has been developed for the identification of five natural dyes namely, carmine, indigo, saffron, gamboge and Rubia tinctoria root. The separation was performed in a fused-silica capillary of 64.5 cm length and 50 microm id. The running buffer was 40 mM sodium tetraborate buffer solution (pH 9.25). The applied potential was 30 kV, the temperature was 25 degrees C and detections were performed at 196, 232, 252, 300 and 356 nm. The injections were under pressure of 50 mbar during 13 s. The method was applied to the identification of carminic acid, gambogic acid, crocetin, indigotin, alizarin and purpurin in the collection of drawings and maps at the Royal Chancellery Archives in Granada (Spain). The method was validated by using HPLC as a reference method.