M. Járó - L. Költő szerk.: Archaeometrical research in Hungary (Budapest, 1988)
Analysis - TIMÁR-BALÁZSY Ágnes: Investigation of dyes on textiles from the collections of Hungarian museums
Gas chromatography is not applied widely in the examination of plant and animal dyes. The only gas chromatogram that is available is of fustic and madder; this was published by Masschelein—Kleiner and Maes [49]. High pressure liquid chromatography (HPLC) was used by Roelofs for tracing 10 different kinds of yellow dyes [57]. The method of identifying and separating dyes of anthraquinone structure by HPLC was worked out by Wouters [58]. HPLC was applied by Walker and Needles for analysis of natural dyes [56]. The advantage of thin-layer chromatography over spectroscopic investigations is that besides being an analytical method it is also a method for separating. That is why it is suitable for analysing mixtures of dyes, as well. The equipment for thin-layer chromatography seems tobe the cheapest among instrumental analytical methods. This is the reason I decided to use this method in the first line in my daily work on dye identification. 3.3.1. Preparation of the sample 2-10 mg of the reference material of analytical purity and 2—50 mg of the dyed yams were treated hot by 1 drop of 10% hydrochloric acid. As for the dyed fibre, the aim was to break the bond between the dye and the mordant. In the case of the vegetable drug the acidic treatment aimed at separating the dye — present in the form of glycoside — from glucose, while the dye of analytical purity was treated in order to bring about similar conditions. 1 ml of methyl alcohol was added to the solution. From the sample prepared in this manner 10—30 pi amount was applied to the layer by capillary action. 33.2. Application of thin-layer chromatography After comparing the various thin-layer chromatographic conditions from the special literature [59] the following systems were chosen for investigation both the known and the unknown samples: A. Chromatographic conditions for identifying athraquinones and some other natural dyes (See Tables A/1-2): Adsorbent layer: Cellulose acetate 300 AC— 10 (Macherey-Nagel) Eluent: ethyl acetate: tetrahydrofuran: water = 6:35:45 Detection: spraying with 0.5M alcoholic KOH and illumination by UV/350 B. Chromatographic conditions for flavonoides and other natural dyes (See Tables B/l-4): Adsorbent layer: Kieselgel 60 DC-Alufolien (Merck) Eluent: chloroform: ethyl acetate: methyl ethyl ketone: formic acid = 15:5:3:1 Detection: spraying with 1% Naturstoffreagens (2-amino-diphenyl borate)* UV/350 C . Chroma tographic conditions for cam tin OÍ cfes (See Table C ) : Adsorbent layer: Kieselgel 60 F 2 s4 DC-Alufolien Eluent: benzol: methyl alcohol: diethyl ether = 85:5:10 Detection: I. spraying with 5% Rhodanin in ethyl alcohol II. spraying with 25% ammonia + UV/254
