Identification by GC-FID and GC-MS of amino acids, fatty and bile acids in binding media used in works of art

GC-FID was used as single methodology for the identification and differentiation of proteins, lipids and ox bile from binders used in artistic paintings. The samples were hydrolyzed by HCl. Subsequently, the simultaneous formation of volatile derivatives of the amino, fatty and bile acids with ethyl chloroformate was performed quickly and safely in an aqueous medium. The derivatives were separated by capillary GC and characterized by GC-MS. The ageing of drying oils was studied, identifying pelargonic acid among other degradation products. Proteinaceous and lipoid binding media were characterized by means of the quotients between the areas of the peaks for each amino or fatty acid with respect to the area of the peak for alanine or palmitic acid. Fatty acids from ox bile were easily identified by their retention times characteristic for eicosanoic, docosanoic and pentadecanoic acids. The suggested method was applied to the analysis of binders in baroque paintings by Palomino in Valencia (Spain). Animal gelatine and linseed oil were found.     

Release of iron from ferritin by aceto- and benzohydroxamic acids

The release of iron from ferritin by aceto- and benzohydroxamic acids was studied at two different iron chelator concentrations (100 and 10 mM), at two pH values (7.4 and 5.2), and in the presence or absence of urea. Collectively, the results demonstrate that both aceto- and benzohydroxamic acids remove iron from ferritin. Aceto- and benzohydroxamic acids penetrate the ferritin shell and react directly with the iron core of the ferritin cavity probably forming mono(hydroxamate) iron(III) complexes which exit ferritin and react with the excess hydroxamate in the solution to produce bis(hydroxamate) iron(III) complexes. The sizes of both the benzohydroxamic acid and the mono(benzohydroxamate) iron(III) complex, 6 and 7 A, respectively, are larger than that of the ferritin channels which indicates the flexibility of the channels to allow the entry and exit of these molecules. The size of the hydroxamic acid influenced the effectiveness of the iron release from ferritin following the expected trend with smaller iron chelators showing greater effectiveness. Likewise, the percentage of iron removed from ferritin was pH-dependent; the percentage of iron removed at pH 5.2 was greater than that at pH 7.4. Finally, the presence of urea, capable of opening the ferritin channels, dramatically increased the effectiveness of the iron chelator in removing iron from ferritin, especially at pH 7.4.     

A Structural Study of the Iminodiacetate Moiety Conformation in N‐(1‐adamantyl)‐iminodiacetate(2‐) Copper(II) Complexes

N,N‐bis(carboxymethyl)‐1‐adamantylamine acid (H₂BCAA) or N‐(1‐adamantyl)‐iminodiacetic acid forms zwitterions that are intra‐stabilized by a ‘bifurcated’ N⁺‐H···O(carboxyl)₂ interaction. In the crystal, both half‐protonated carboxyl groups of H₂BCAA^± are involved in linear O‐H···O inter‐molecular bridges of 2.46Å. In the studied BCAA‐Cu^II derivatives, the iminodiacetate‐moiety of the BCAA chelating ligand exhibits a mer‐NO₂ conformation in [Cu(BCAA)(H₂O)₂] ( 1 ) and [Cu(BCAA)(Him)]₂ ( 2 ), but a fac‐O₂+N(apical) conformation in [Cu(BCAA)(bpy)(H₂O)]·3.5H₂O ( 3 ) [Him = imidazole, bpy =2,2′‐bipyridine]. In clear contrast, dipyridylamine (dpya), as auxiliary ligand, seems to be unable to promote the fac‐O₂+N(apical) conformation in BCAA, as reveal the structures of two new salts with the trinuclear cation [(dpya)₂Cu‐μ₂‐Cu(BCAA)₂‐Cu(dpya)₂]²⁺ and the anions [Cu(BCAA)₂]^2? ( 4 ) or NO₃^? ( 5 ), respectively.     

A novel one-dimensional cyano-bridged Ni3Fe2 ferromagnet constructed from bimetallic molecular squares

Reaction of the complex [Ni(rac-CTH)](2+) (rac-CTH = rac-5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane) with [Fe(CN)(6)](3-) leads to a novel cyano-bridged Ni(3)Fe(2) complex, [[Ni(rac-CTH)](3)[Fe(CN)(6)](2)](4). The structure consists of an alternating arrangement of [Fe(CN)(6)Ni(rac-CTH)](2) squares and trans-planar [Ni(rac-CTH)](2+) units bridged by cyanide groups to give a neutral 1D chain running along the a axis. Magnetic measurements reveal the occurrence of ferromagnetic coupling between Fe(III) and Ni(II) ions and 3D magnetic ordering at 3 K due to interchain interactions. Canting of the moments is inferred from the low value of the magnetization of the saturation below T(c).     

Identification of natural dyes used in works of art by pyrolysis–gas chromatography/mass spectrometry combined with in situ trimethylsilylation

Samples of four natural dyes from different organic families—natural madder (anthraquinonoid), curcuma (curcuminoid), saffron (carotenoid) and indigo (indigotic)—were analysed using a new procedure based on pyrolysis–gas chromatography/mass spectrometry (Py–GC/MS), which includes the on-line derivatisation of the natural dyes using hexamethyldisilazane (HMDS). In addition, a previous procedure involving the addition of a 10% H₂SO₄ aqueous solution to the dye and further separation with ethyl acetate has been tested. This procedure enhances the sensitivity of the method by extracting the colouring compounds from the rest of the compounds present in the natural dye. Two possible derivatising reagents—HMDS and tetramethylammonium hydroxide (TMAH)—were compared in order to assess their effectiveness in the proposed method. Characteristic peaks from trimethylsilyl derivatives of alizarin, quinizarin, xanthopurpurin and purpurin were obtained for madder; peaks from safranal, isophorone and trimethylsilyl derivative of crocetin for saffron; peaks from 4-(4-hydroxy-3-methoxy)phenyl-3-buten-2-one and 4-(4-hydroxy-3-methoxy)phenyl-2-butanone, which are primary pyrolysis products of curcuma, and peaks from indole, 2-methylindole and 2,3-dihydroindol-2-one, which are primary pyrolysis products of indigo, among others, were obtained. The reported procedure leads to the unambiguous identification of the four studied dyes from solid samples formed by individual dyes.Electronic Supplementary Material Supplementary material is available for this article at     

Identification of lipid binders in paintings by gas chromatography. Influence of the pigments

The influence of the presence and the type of pigments in the lipid binding media of paintings were studied by gas chromatography with flame ionization detector. The drying oils were linseed stand oil, poppy oil and sunflower oil, and the pigments studied were cadmium red, cobalt blue, tin white, lead white, chalk and plaster of Paris, commonly used in paintings. The results indicate that the stearic/palmitic ratio and the presence of pigments are quite stable during ageing. However, some differences in the oleic acid/palmitic acid ratio were found, depending on the type of pigment present in the lipid binding media. These variations are related to the drying effect of the pigments. The proposed method has been applied to the identification of drying oils in two samples from baroque paintings in the "Basilica de la Virgen de los Desamparados" of Valencia, Spain.     

Comparative electrochemistry of technetium(V) and rhenium(V) dioxo complexes

The heavy use of^99mTc in nuclear medicine and the recent development of¹⁸⁸Re radiopharmaceuticals have encouraged the comparative study of Tc and Re coordination compounds. In this work, the electrochemistry of [M^VO₂ (amine)₂]⁺ (M=Tc, Re; amine = ethylenediamine, 1,3-diaminopropane, diethylenetriamine, triethylenetetramine) complexes is studied by cyclic voltammetry and the results are compared. The voltammograms of these compounds, obtained at different pH values, show that [ReO₂(amine)₂]⁺ cations are thermodynamically stable even when protonated. On the other hand, analogous Tc compounds are not so stable and easily decompose if existing as [TcO(OH) (amine)₂]²⁺.     

Fast flow-injection fluorimetric determination of amiloride by using a solid sensing zone

A rapid and simple flow-through solid phase spectrofluorimetric system is described in this paper for the determination of the diuretic amiloride in physiological fluid (serum) and pharmaceuticals. The sensor was developed in conjunction with a monochannel flow-injection analysis system with fluorimetric transduction. Amiloride was transitorily retained on cationic exchanger gel Sephadex SP-C25 placed in the detection area into the cell. The determination is carried out without any derivatization reaction, by measuring directly the intrinsic fluorescence of the analyte and using the peak height as analytical signal. The wavelengths of excitation and emission were 291 and 419 nm, respectively. Amiloride could be determined in the concentration ranges of 10–600 and 4–250 μg l⁻¹ at a sampling rate of 24 and 30 h⁻¹, respectively with detection limits of 0.92 and 0.33 μg l⁻¹ for 100, and 600 μl of sample volume injected, respectively. The relative standard deviations for ten independent determinations were better than 0.65%. The method was satisfactorily applied to the determination of amiloride in spiked biological fluids (serum) and pharmaceutical preparations without any pretreatment of the samples.     

Electrochemical characterization of biodeterioration of paint films containing cadmium yellow pigment

The voltammetry of microparticles (VMP) methodology was used to characterize the biological attack of different bacteria and fungi to reconstructed egg tempera and egg–linseed oil emulsion paint films containing cadmium yellow (CdS), which mimic historical painting techniques. When these paint films are in contact with aqueous acetate buffer, different cathodic signals are observed. As a result of the crossing of VMP data with attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), scanning electrochemical microscopy (SECM), field emission scanning electron microscopy (FESEM), and atomic force microscopy (AFM), these voltammetric signals can be associated with the reduction of CdS and different complexes associated to the proteinaceous and fatty acid fractions of the binders. After biological attack with different fungi (Acremonium chrysogenum, Aspergillus niger, Mucor rouxii, Penicillium chrysogenum, and Trichoderma pseudokoningii) and bacteria (Arthrobacter oxydans, Bacillus amyloliquefaciens, and Streptomyces cellulofans), the observed electrochemical signals experience specific modifications depending on the binder and the biological agent, allowing for an electrochemical monitoring of biological attack.     

On the Relationship Between Two Kinds of Besov Spaces with Smoothness Near Zero and Some Other Applications of Limiting Interpolation

Using limiting interpolation techniques we study the relationship between Besov spaces \(\mathbf B ^{0,-1/q}_{p,q}\) with zero classical smoothness and logarithmic smoothness \(-1/q\) defined by means of differences with similar spaces \(B^{0,b,d}_{p,q}\) defined by means of the Fourier transform. Among other things, we prove that \(\mathbf B ^{0,-1/2}_{2,2}=B^{0,0,1/2}_{2,2}\). We also derive several results on periodic spaces \(\mathbf B ^{0,-1/q}_{p,q}(\mathbb {T})\), including embeddings in generalized Lorentz–Zygmund spaces and the distribution of Fourier coefficients of functions of \(\mathbf B ^{0,-1/q}_{p,q}(\mathbb {T})\).