Evaluation between ultrahigh pressure liquid chromatography and high-performance liquid chromatography analytical methods for characterizing natural dyestuffs

Development and Application of Desorption Electrospray Ionization Mass Spectrometry for Historical Dye Analysis

A desorption electrospray ionization (DESI) source was built and attached to a Bruker 7T SolariX FT-ICR-MS for the in situ analysis of 14 early synthetic dyestuffs. Optimization using silk and wool cloths dyed with rhodamine B concluded that when using a commercial electrospray emitter (part number: 0601815, Bruker Daltonik), a nebulizing gas (N₂) pressure of 3.9 bar and a sprayer voltage of 4.5 kV (positive ionization mode) or 4.2 kV (negative ionization mode), a solvent system of 3:1 v/v ACN:H₂O, and a sprayer incident angle, α, of 35° gave the highest signal-to-noise ratios on both silk and wool for the samples investigated. The system was applied to modern early synthetic dye references on silk and wool as well as historical samples from the 1893 edition of Adolf Lehne's Tabellarische Übersicht über die künstliche organischen Farbstoffe und ihre Anwendung in Färberei und Zeugdruck [Tabular overview of the synthetic organic dyestuffs and their use in dyeing and printing]. The successful analysis of six chemically different dye families in both negative and positive modes showed the presence of known degradation products and byproducts arising from the original synthetic processes in the historical samples. This study demonstrates the applicability and potential of DESI-MS to the field of historical dye analysis.

Development and validation of a liquid chromatographic method with diode array detection for the determination of anthraquinones, flavonoids and other natural dyes in aged silk

A HPLC method coupled with diode array detector was developed and validated for the quantitation of alizarin, apigenin, carminic acid, curcumin, ellagic acid, emodin, fisetin, kaempferide, kaempferol, kermesic acid, morin, purpurin, quercetin and sulfuretin which are components of several natural dyes. 1- Hydroxyanthraquinone was selected as internal standard. The compounds were separated under gradient elution on a RP-column (Altima C18, 250 mm x 3.0 mm i.d., 5 μm) with a mobile phase consisting of solvent A: H₂O + 0.1% (v/v) trifluoroacetic acid and solvent B: acetonitrile + 0.1% (v/v) trifluoroacetic acid. The method was validated in terms of linearity, limits of detection and quantitation, accuracy, precision, ruggedness and robustness and applied to the analysis of silk dyed with buckthorn (Rhamnus trees), cochineal (Dactylopius coccus Costa), madder (Rubia tinctorum L.), turmeric (Curcuma longa L.) and young fustic (Cotinus coggygria Scop). Furthermore, dyed silk samples were subjected to artificially accelerated ageing conditions induced by UV radiation. The effect of the latter on the quantities of the aforementioned compounds was monitored, except for apigenin, kermesic acid and morin.

Microextraction of Reseda luteola-Dyed Wool and Qualitative Analysis of Its Flavones by UHPLC-UV, NMR and MS

Detailed knowledge on natural dyes is important for agronomy and quality control as well as the fastness, stability, and analysis of dyed textiles. Weld (Reseda luteola L.), which is a source of flavone-based yellow dye, is the focus of this study. One aim was to reduce the required amount of dyed textile to ≤50 μg for a successful chromatographic analysis. The second aim was to unambiguously confirm the identity of all weld flavones. By carrying out the extraction of 50 μg dyed wool with 25 μL of solvent and analysis by reversed-phase UHPLC at 345 nm, reproducible chromatographic fingerprints could be obtained with good signal to noise ratios. Ten baseline separated peaks with relative areas ≥1% were separated in 6 min. Through repeated polyamide column chromatography and prepHPLC, the compounds corresponding with the fingerprint peaks were purified from dried weld. Each was unequivocally identified, including the position and configuration of attached sugars, by means of 1D and 2D NMR and high-resolution MS. Apigenin-4′-O-glucoside and luteolin-4′-O-glucoside were additionally identified as two trace flavones co-eluting with other flavone glucosides, the former for the first time in weld. The microextraction might be extended to other used dye plants, thus reducing the required amount of precious historical textiles.

Spectral characterisation of a traditional Mesoamerican dye: relationship between in situ identification on the 16th century Codex Borbonicus manuscript and composition of Justicia spicigera plant extract

Characterisation of vegetal colourants in manuscripts is still a challenging task. Their identification using non-invasive techniques - since sampling is rarely possible - is valid only if there is evidence that the recorded signals are generated by compounds specific to the plant species. Otherwise, more extensive chemical characterisations are required to relate the non-invasive technique signals to the chemical composition of the dye extract and thus avoid misidentification. The case study of a traditional Mesoamerican dye found in the Codex Borbonicus is reported herein. The non-invasive identification of the colourant plant source and chemical characterisation of the coloured molecules were carried out through a multi-analytical technique approach. In situ Raman and UV-Vis emission fluorescence signals suggested the use of Justicia spicigera leaves to produce the brown paint layers of the manuscript. Analysis of the plant extract by liquid chromatography revealed that two compounds are mostly responsible for the colour, and these compounds were successfully isolated. Both contribute to the Raman spectra while only one of them is mainly responsible for the fluorescence recorded on Codex Borbonicus.

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.

Liquid chromatography: Current applications in Heritage Science and recent developments

Liquid chromatography has been widely employed in the analysis of materials in Heritage Science, due to its ease of use and relatively low-cost, starting from thin layer chromatography of organic binders in paintings, of archaeological waxes and resins, and finally of natural dyes. High performance systems employing analytical columns containing packed stationary phases gradually supplanted thin layer chromatography (TLC) in the field, since the separation, detection and quantitation of specific species contained in a sample in the field of Cultural Heritage requires selective, sensitive and reliable methods, allowing for analysing a wide range of samples, in terms of analyte types and concentration range. Today, the main applications of High-Performance Liquid Chromatography in this field are related to the separation and detection of dyestuffs in archaeological materials and paint samples by reversed-phase liquid chromatography with suitable detectors. Proteomics and lipidomics are also gaining momentum in the last decade, thanks to the increased availability of instrumentation and procedures. In this chapter, principles and theory of liquid chromatography will be presented. A short review of the instrumentation needed to perform an analysis will be provided and some general principles of sample preparation revised. More details on the detection systems, the chromatographic set-ups and specific sample treatment strategies will be provided in the individual sections dedicated to the applications to Heritage Science of the main types of liquid chromatographic techniques. In particular, the applications of thin layer chromatography will be shortly described in paragraph 4.1. The applications of Reverse Phase High Performance Liquid Chromatography (RP-HPLC) will be discussed in detail in paragraph 4.2, including the analysis of natural and synthetic dyes and pigments and the profiling of lipid materials. The possibility to perform proteomic analysis will be presented and a link to the relevant Chapter in this book provided. The most important and promising applications of ion exchange chromatography (IC) will be discussed in paragraph 4.3. Finally, size exclusion and gel permeation chromatography (GPC) will be presented in paragraph 4.4, including applications to the study of polymeric network formation in paint binders, of the phenomena related to the depolymerisation of cellulose in paper and of cellulose and lignin in wood samples. The possibility to study synthetic polymers as artists’ materials and restorers’ tools by size exclusion (SEC) or gel permeation (GPC) will also be introduced. In the conclusions, future perspectives of liquid chromatography in Heritage Science will be briefly discussed.

Development of an Abbreviated Mycophenolic Acid Area Under the Time-Concentration Curve for Renal Transplant Patients Under Enteric-Coated Mycophenolate Sodium: A Comparison With Critical Analysis of Available Equations

BACKGROUND

Enteric-coated mycophenolate sodium is frequently used in renal transplantation. The pharmacokinetic profile of mycophenolic acid (MPA) shows a broad range of time-to-maximum concentration (Tmax) that limits the use of a single MPA concentration to calculate the area under the time-concentration curve (AUC). For both research and clinical MPA monitoring, measuring a complete AUC is troublesome to the center and patients.

METHODS

We obtained 171 complete MPA-AUC12h (0, 20, 40, 60, 90, 120, 180, 240, 360, 480, 600, and 720 minutes) from 59 adult (54 ± 16 years) patients (29 men and 43 whites) who have been receiving stable doses of tacrolimus/enteric-coated mycophenolate sodium and steroids. We used the 59 curves drawn at 31 ± 4 days after transplantation to develop the abbreviated equations, and the remaining 112 curves drawn at 109 ± 59 days were used to validate them. We used 5 other proposed equations to estimate MPA-AUC (eAUC) (4 with enzyme-multiplied immunoassay technique assay and one with high-performance liquid chromatography [HPLC]) and then used these results to compare with our measured AUC, the bias, and the 10% and 30% accuracy. MPA was measured by ultraperformance liquid chromatography coupled to a tandem mass spectrometry, and AUC was calculated by the trapezoidal rule.

RESULTS

For both MPA-measuring methods, enzyme-multiplied immunoassay technique and ultraperformance liquid chromatography coupled to a tandem mass spectrometry, the Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo (HCFMUSP) equations, and others that measure MPA up to 6 hours after the dose had an acceptable low bias with more results in the 10%-30% range than those using data collected until 4 hours. A highly adequate eAUC is obtained using blood collected at 8 hours.

CONCLUSIONS

This analysis offers blood-sampling alternatives for MPA monitoring depending on the precision needed.

Surface Acoustic Wave Nebulisation Mass Spectrometry for the Fast and Highly Sensitive Characterisation of Synthetic Dyes in Textile Samples

Surface acoustic wave nebulisation (SAWN) mass spectrometry (MS) is a method to generate gaseous ions compatible with direct MS of minute samples at femtomole sensitivity. To perform SAWN, acoustic waves are propagated through a LiNbO₃ sampling chip, and are conducted to the liquid sample, which ultimately leads to the generation of a fine mist containing droplets of nanometre to micrometre diameter. Through fission and evaporation, the droplets undergo a phase change from liquid to gaseous analyte ions in a non-destructive manner. We have developed SAWN technology for the characterisation of organic colourants in textiles. It generates electrospray-ionisation-like ions in a non-destructive manner during ionisation, as can be observed by the unmodified chemical structure. The sample size is decreased by tenfold to 1000-fold when compared with currently used liquid chromatography-MS methods, with equal or better sensitivity. This work underscores SAWN-MS as an ideal tool for molecular analysis of art objects as it is non-destructive, is rapid, involves minimally invasive sampling and is more sensitive than current MS-based methods. Graphical Abstract ᅟ.

Early evidence (late 2nd millennium BCE) of plant-based dyeing of textiles from Timna, Israel

In this article, we focus on the analysis of dyed textile fragments uncovered at an early Iron Age (11^th-10^th centuries BCE) copper smelting site during new excavations in the Timna Valley conducted by the Central Timna Valley (CTV) Project, as well as those found by the Arabah Expedition at the Hathor Temple (Site 200), dated to the Late Bronze/early Iron Ages (13^th-11^th centuries BCE). Analysis by HPLC-DAD identified two organic dyestuffs, Rubia tinctorum L. and indigotin, from a plant source (probably Isatis tinctoria L.). They are among the earliest plants known in the dyeing craft and cultivated primarily for this purpose. This study provides the earliest evidence of textiles dyed utilizing a chemical dyeing process based on an industrial dyeing plant from the Levant. Moreover, our results shed new light on the society operating the copper mines at the time, suggesting the existence of an elite that was interested in these high quality textiles and invested efforts in procuring them by long-distance trade.

Characterisation of chemical components for identifying historical Chinese textile dyes by ultra high performance liquid chromatography - photodiode array - electrospray ionisation mass spectrometer

This research makes the first attempt to apply Ultra High Performance Liquid Chromatography (UHPLC) coupled to both Photodiode Array detection (PDA) and Electrospray Ionisation Mass Spectrometer (ESI-MS) to the chemical characterisation of common textile dyes in ancient China. Three different extraction methods, respectively involving dimethyl sulfoxide (DMSO)-oxalic acid, DMSO and hydrochloric acid, are unprecedentedly applied together to achieve an in-depth understanding of the chemical composition of these dyes. The first LC-PDA-MS database of the chemical composition of common dyes in ancient China has been established. The phenomena of esterification and isomerisation of the dye constituents of gallnut, gardenia and saffron, and the dye composition of acorn cup dyed silk are clarified for the first time. 6-Hydroxyrubiadin and its glycosides are first reported on a dyed sample with Rubia cordifolia from China. UHPLC-PDA-ESI-MS with a C18 BEH shield column shows significant advantages in the separation and identification of similar dye constituents, particularly in the cases of analysing pagoda bud and turmeric dyed sample extracts.

Investigation of crimson-dyed fibres for a new approach on the characterization of cochineal and kermes dyes in historical textiles

The colorant behaviour of cochineal and kermes insect dyes in 141 experimentally-dyed and 28 artificially-aged samples of silk and wool was investigated using ultra-high performance liquid chromatography coupled to photodiode array detector (UHPLC-PDA), liquid chromatography electrospray ionisation mass spectrometry (LC-ESI-MS) and image scanning electron microscopy - energy dispersive X-ray spectroscopy (SEM-EDX). Partial-least squares discriminant analysis (PLS-DA) was then used to model the acquired UHPLC-PDA data and assess the possibility of discriminating cochineal insect species, as well as their correspondent dyed and aged reference fibres. The resulting models helped to characterize a set of 117 red samples from 95 historical textiles, in which UHPLC-PDA analyses have reported the presence of cochineal and kermes insect dyes. Analytical investigation of the experimentally-dyed and artificially-aged fibres has demonstrated that the ratio of compounds in the insects dye composition can change, depending on the dyeing conditions applied and the type of fibres used. Similarities were observed when comparing the UHPLC-MS and SEM-EDX results from the dyed and aged references with the historical samples. This was verified with PLS-DA models of the chromatographic data, facilitating the classification of the cochineal species present in the historical samples. The majority of these samples were identified to contain American cochineal, which is in agreement with historical and dye identification literature that describe the impact of this dyestuff into European and Asian dyeing practices, after the Iberian Expansion in the 16th century. The analytical results emphasize the importance of using statistical data interpretation for the discrimination of cochineal dyes, besides qualitative and quantitative evaluation of chromatograms. Hence, the combination of UHPLC-PDA with a statistical classification method, such as PLS-DA, has been demonstrated to be an advisable approach in future investigations to assess closely related species of natural dyes in historical textile samples. This is particularly important when aiming to achieve more accurate interpretations about the history of works of art, or the application of natural dyes in old textile production.