A standard-free variant of spectral laser microanalysis of the material of gold alloys for determining the standard of fineness of the specimens investigated has been implemented experimentally. A good correspondence of the results of measurements of the concentrations of gold in the materials analyzed to the specified data is shown. The basic stages and characteristic features of the procedures of the standard-free analysis are considered.Introduction. Articles made from gold alloys as well as native gold are the objects of routine technological, criminalistic, art, and other investigations. The methods and equipment used to analyze the material of gold alloys were considered to a quite satisfactory extent in [1]. The most widespread traditional method of determining the content of gold in alloys is assaying. The main drawbacks of this method are the following: the absence of information on doping components; a comparatively large mass of the laboratory sample, usually exceeding 200 mg; the slow operation of the analysis (not less than 2 h), and the necessity of recovering wastes. The most rapid method of determining the content of gold in alloys remains assaying on an assay stock. This technique has still another important advantage, that is, the mass of the sample used is fairly small (0.01-0.10 mg). The main disadvantages are the impossibility of determining the content of the remaining elements in the material and the necessity of having a highly competent operator. The simplest technique is the measurement of the material density (densitometry). Usually pure metals are suitable for the purpose. Moreover, this method cannot be used for investigating hollow specimens and articles with fragments made from other materials. Analysis of the composition of precious metals can be performed by the classical methods of "wet" chemistry. Although highly accurate, these techniques are very laborious in the case of a complete elemental analysis, and the main thing is that they require a relatively high expenditure of material.An effective investigation of the composition of the alloys of precious metals is ensured by the methods of spectral analysis: atomic absorption analysis involving a flame or electrothermal atomizer and an emission or mass spectrometric analysis with an inductively confined plasma. The procedure of measurement with the aid of the indicated methods eventually requires that the test sample be converted into a solution or a finely divided powder, although laser samples can be used for initial sampling. Here, among the drawbacks are a comparatively large expenditure of the material (except for electrothermal atomizers) and the high labor content of the full cycle of the procedure. One of the most promising methods that makes it possible to carry out a nondestructive analysis is the xray fluorescent one (XF). However, XF spectrometers yield quantitative information on the composition of the surface layers of a sample (on the order of several micrometers) and, moreover, the geometric shape of the investig...

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UDC 535.33A technique of layer-by-layer laser microanalysis of the materials of easel-painting works employing a twopulse scheme of substance excitation and registration of the spectrum from one double pulse is suggested. With paintings from the Nesvizh Portrait Gallery as examples, the effectiveness of the method in identification and attribution of paintings is shown.Keywords: pigments, layer-by-layer laser spectrum microanalysis, double pulse.Introduction. At the present time, in studying paintings, methods of art expertise are more often supplemented with methods of natural sciences. Comprehensive technical-technological investigation of a work of art that encompasses each structural element of the picture (base, primer, drawing, paint layer, protective coating) includes overall examination of the work by luminescent methods on exposure to UV and IR irradiation and by the x-ray graphical method as well as studying the paint materials used. The materials used in painting a picture are very diverse and are determined by the time of creation of a picture, the tradition of the artistic school, and also by the artistic individuality of a painter -his style and technique. Accumulation of information on the materials that were used at different times by various painters and the creation of a database are essential for the success of the investigations carried out.The most difficult problem in studying a work of art is determination of the pigments and binders that enter into the primer and paint layers. Pigments are identified by methods of microchemical analysis, petrography, and various physical methods, for example, x-ray structural analysis, as well as different kinds of spectral analysis (IR Fourier spectroscopy to identify the binder and an emission analysis to identify pigments). The x-ray structural analysis has some limitations because the intensity of a spectrum depends on substance absorption, which, in turn, influences the sensitivity of the method. Therefore, registration of even a relatively high content of pigment with low absorptivity is difficult when this pigment is mixed with a highly absorptive component [1]. The spectral electric-discharge emission method allows one to rather exactly determine the chemical composition of a sample but needs a great amount of it. Moreover, it is extremely difficult to perform a layer-by-layer analysis by this method.In the present work, we suggest a method of two-pulse laser spectrum microanalysis of the chemical composition of easel-painting materials. Its advantage over the electric-discharge method of spectral analysis lies in the fact that it needs no special preparation and it is local and provides the possibility of layer-by-layer examination of the chemical composition of the materials of the work studied.Experimental Technique. Model samples have a multilayer structure with known chemical composition of each layer. As the base for the two samples prepared by us, a linen canvas was used primed by titanium white on an oil binder. The paint layer of the first...

Laser ablation in liquid media is proposed as a new sample preparation technique in elemental composition analysis of art pigments using inductively coupled plasma optical emission spectroscopy (ICP-OES). Solid samples are transformed to colloidal solutions of nanosized analyte particles. This makes the technique compatible with convevtional solutionbased standardization. The dissociation of particles in solution is improved, which increases the accuracy of quantitative ICP measurements.

535.33The ability to use laser ablation for preparation of art pigment samples in quantitative analysis of their elemental composition by atomic emission spectroscopy of inductively coupled plasma is shown. The proposed technique enables one to eliminate errors associated with both the influence of strong acids and the stoichiometric disruption in a sample. Introduction.A study of the technical features underlying art works (stratigraphic structure, color palette, materials, ratio of materials in each structural element, etc.) can provide the information required to define the period and site of creation of a work and its authenticity [1] and can identify the optimal method for minimizing losses during restoration. Despite the development of highly sensitive physicochemical analytical methods, the identification of art materials remains one of the most complicated steps in the technical study of art works owing to the uniqueness of each specimen. Laser spectral microanalysis is currently used more and more often to identify inorganic pigments because it does not require preliminary sample preparation and enables the elemental composition in each structural fragment of the work to be determined. The art pigments used by the master cannot always be unambiguously identified from the observed elemental composition because several elements occur in different pigments. Not only the elements present but also their quantitative contents must be determined. Atomic emission spectroscopy of inductively coupled plasma (ICP-AES) is currently one of the most accurate methods for quantitative determination of the elemental composition of various substances [2][3][4].The most important step in the quantitative analysis of the elemental composition of a substance using ICP-AES is sample preparation. The principal goal is to dissolve the determined elements and to avoid losses of components because the analyzed samples are introduced as solutions. Classical methods for chemical dissolution (destruction and mineralization) do not always dissolve completely the samples even if closed autoclave and microwave oven systems are used. Incomplete dissolution of the sample (formation of a precipitate) leads to a loss of part of the sample during its preparation. This is largely responsible for an increase in the total uncertainty of the resulting quantitative data.Mineral pigments differ in their ability to dissolve in acids. This is explained by their chemical structure from the viewpoint of materials science. Mineral pigments can be transition-metal oxides, hydroxides, and salts. The chromophores in these pigments are fragments of a crystal lattice consisting of cations with variable valence (e.g., Fe, Mn, Cu, Ni, Cr) that are bonded to OH groups, O atoms, and H 2 O molecules [1]. Hydroxides and basic or amphoteric oxides dissolve readily in acids. Therefore, lead and zinc white pigments; azurite; malachite; red-lead; verdigris; Paris green; zinc, barite, and strontium yellows; massicot; and others are capable of dissolving. The reaction...