Microparticles identification

Identification of metal particles dispersed in pictorial or decorative layers in works of art is often difficult for microscopy techniques because of (i) their presence as highly diluted components and concentrated in microparticles that, in turn, are included in binding media and attached to priming and protective layers (ii) the coexistence of metals with priming, ground or pigmenting layers in the samples and (iii) the presence of products resulting from the alteration of metals. 

Domenech A, Domenech-Carbo MT, Sauri MC, Gimeno JV, Bosch F (2005) Identification of curcuma and safflower dyes by voltammetry of microparticles using paraffin-impregnated graphite electrodes. Microchim Acta 152 75-84. 

Domenech A, Domenech-Carbo MT, Mas X, Ciarrocci J (2007) Simultaneous identification of lead pigments and binding media in paint samples using voltammetry of microparticles. 

Livesay s patent (Ref 4) claims that expls and small arms propints can be codified for post-use identification by incorporation of microparticles of (unspecified) Sr oxides or salts of 0.1 wt % into recoverable fireproof carrier particles of a unique characteristic size (1—250 microns) and shape so that the total (micro plus carrier) particle has a d of > 3g/cc and an incineration temp of 400—500°... 

This approach allowed the identification of 390 proteins among which 34% were localized to the plasma membrane. The microparticles obtained from the two different ways of stimulation did not show significant variation in their proteome (Miguet et al. 2005). 

These results have been compared to a systematic analysis of a classical plasma membrane protein preparation, generated by ultracentrifiigation (100,000 g on sucrose). This plasma membrane isolation has allowed the identification of 292 proteins, and only 69 proteins were located to the plasma membrane (24 vs. 34% for the microparticles preparation). Moreover, 75 plasma membrane proteins were identified specifically in the microparticles preparation, and only 9 were identified only in the plasma membrane preparation. These results are summarized in Figure 6. 

Domenech-Carbo et al. also showed the voltammetry of immobilized microparticles to be valuable in the unambiguous identification of dyes such as Curcuma and Safflower in microsamples of works of art and archaeological artifacts (see also Section 6.4.1) [140]. Here, the use of square-wave voltammetry in aqueous acetate or phosphate buffers led to the appearance of well-defined oxidation peaks ofthe dyes in the potential region of +0.65 to +0.25 V (versus Ag AgCl). 

Fourier transform infrared (FT-IR) spectroscopy can be used to characterize drug substances, polymer blends, polymer complexes, dynamics, surfaces, and interfaces, as well as chromatographic effluents and degradation products. It provides information about the complexation and interactions between the various constituents in the PECs. It is capable of qualitative identification of the structure of unknown materials as well as the quantitative measurement of the components in a complex mixture. FT-IR spectra of physical mixture and PEC can be determined by FT-IR spectrophotometer using KBr disc method in the range of 4000 to 250 cm h Since the stability and drug substance is very important in several applications, determination of their physicochemical stability is crucial. The FTIR spectra of polyacrylic acid, PVP, metformin hydrochloride, and PEC microparticles of metformin were shown in Figure 56.8. The FTIR spectra of polyacrylic acid and PVP have shown... 

In the last decade confocal laser scanning microscopy (CLSM) was shown to be a helpful tool for various further tasks of microparticle characterization (Lamprecht et al., 2000a, b, c). It minimizes the light scattered from out-of-focus structures, and permits the identification of several compounds through use of different fluorescence labels. Therefore, CLSM can be applied as a non-destructive visualization technique for microparticles. Moreover, CLSM allows visualization and characterization of structures not only on the surface, but also inside the particles, provided the carrier matrices are sufficiently transparent and can be fluorescently labeled by collecting several coplanar cross-sections, a three-dimensional reconstruction of the inspected objects is possible. Figure 6.13 shows the application of CLSM to investigatation of the cross-sectional structures of spray-dried powders of maltodextrin (MD) with a dextrose equivalent value of DE = 2 and 20. Florescein sodium salt was dissolved in the feed solution as a fluorescent probe of the carrier... 

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