Derivative spectrometry

The principle of derivative spectrometry consists of calculating, by a mathematical procedure, derivative graphs of the spectra to improve the precision of certain measurements. This procedure is applied when the analyte spectrum does not appear clearly within the spectrum representing the whole mixture in which it is present. This can result when compounds with very similar spectra are mixed together. 

Interest in this procedure manifests itself in three situations in which the absorbance is altered  

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Derivative spectrometry improves the precision of analysis when compounds with very similar spectra are present in the mixture. The derivative spectral curves, in the mathematical sense, amplify the weak variations in the slopes of the initial spectrum (called the zeroth order spectrum). These derivative plots show greater variations than when in absorbance units (Fig. 11.27). 

Dead time, 7 Dead volume, 13 DEAE cellulose, 88 Deconvolution (spectrum), 215 Deflection equation, 297 Degrees of freedom, 168 Derivative spectrometry 215 Deshielding, 139 Deuterium arc lamp, 199 Diffuse peak, 324 Diffuse reflection, 180 Diffusion coefficient, 5, 102 Diffusion current, 362 Diode array, 200 Distribution isotherm, 9 Double beam, 169 DTGS, 175... 

Deoxyschizandrin, synthesis of 1278, 1280 Deprotonation 92-105 energy of 3, 97-100 Depsides 942-944 Derivative isotherm summation 944 Derivative spectrometry 929, 984 Derivatization, pre-analysis 985-991 DesMarteau sulfonimide, as electrophilic fluorinating agent 647 Desulfurization 1079 Detoxification, of phenoUc compounds 1361-1363... 

First-derivative spectrometry and pyridoxal-4-phenylthiosemicarbazone as a reagent (in aqueous 30% DMF) was used to determine Cu and Co in steel [20]. 

Although the direct spectrometric determination of certain amino acids in food by derivative spectrometry in appropriate spectral regions or by specific reaction with suitable reagents after unfolding of the protein structure has been attempted, amino acid analysis typically requires hydrolysis of the proteins followed by separation of the liberated amino acids. 

O Haver TC and Begley T (1981) Signal-to-noise in higher order derivative spectrometry. Analytical Chemistry 53 1876-1878. 

Chromatographic systems have been developed for the reversed-phase TLC separation of lipophilic vitamins on RP-18 as stationary phase. A mixture of lipophilic vitamins (A acetate, E, E-acetate, and D3) was separated using acetonitrile-benzene-chloroform (10 10 1, v/v) as mobile phase (Table 3). The applied chromatographic conditions do not permit the separation of vitamin E and vitamin E-acetate. Derivative spectrometry was used to determine vitamin A acetate in mixtures of other lipophilic or water-soluble vitamins. Spectrophotometric analysis of lipophilic vitamins enables determination of vitamin A-acetate in the presence of vitamins E, E-acetate, and D3 and also C, Bi, and nicotinamide. 

Thlsky G, Maryring L, Kruezer H 1978 High-resolution, higher-order UV/Vis derivative spectrometry. Angew Chem Int Ed 17 785-799... 

The first mass spectrometric investigation of the thiazole ring was done by Clarke et al. (271). Shortly after, Cooks et al., in a study devoted to bicydic aromatic systems, demonstrated the influence of the benzo ring in benzothiazole (272). Since this time, many studies have been devoted to the influence of various types of substitution upon fragmentation schemes and rearrangements, in the case of alkylthiazoles by Buttery (273) arylthiazoles by Aune et al. (276), Rix et al. (277), Khnulnitskii et al. (278) functional derivatives by Salmona el al. (279) and Entenmann (280) and thiazoles isotopically labeled with deuterium and C by Bojesen et al. (113). More recently, Witzhum et al. have detected the presence of simple derivatives of thiazole in food aromas by mass spectrometry (281). 

Mass Spectrometry A prominent peak m the mass spectra of most carboxylic acid derivatives corresponds to an acyhum ion derived by cleavage of the bond to the car bonyl group... 

The mass of an electron is very small compared with the total mass of the molecule. Consequently, the relative molecular mass of a molecule (M,.) is almost the same as that of the derived molecular ion (M +). For practical purposes in mass spectrometry, = M/+, and is written, M +. 

By high-resolution mass spectrometry, ions of known mass from a standard substance can be separated from ions of unknown mass derived from a sample substance. By measuring the unknown mass relative to the known ones through interpolation or peak matching, the unknown can be measured. An accurate mass can be used to obtain an elemental composition for an ion. If the latter is the molecular ion, the composition is the molecular formula. 

Mass spectral fragmentation patterns of alkyl and phenyl hydantoins have been investigated by means of labeling techniques (28—30), and similar studies have also been carried out for thiohydantoins (31,32). In all cases, breakdown of the hydantoin ring occurs by a-ftssion at C-4 with concomitant loss of carbon monoxide and an isocyanate molecule. In the case of aryl derivatives, the ease of formation of Ar—NCO is related to the electronic properties of the aryl ring substituents (33). Mass spectrometry has been used for identification of the phenylthiohydantoin derivatives formed from amino acids during peptide sequence determination by the Edman method (34). 

Mass Spectrometry. As of 1996, ms characteristics of pyrazoles and derivatives had not been described in depth. The fate of unsubstituted pyrazole (23) in the mass spectrometer operated in the electron ionization mode may be depicted as follows ... 

Pikromycin. Pikromycin (19, R = OH, R = H), the first macroHde discovered (77,78), is produced by S.felleus. Pikromycin is identical to amaromycin and albomycetin (79—81) and may be identical to proactinomycin (82—84). The stmcture of pikromycin was deterrnined from chemical degradation, mass spectrometry, nmr, and x-ray crystallography (85—90). Its aglycone, pikronoHde (20, R = OH), was produced by S. vene elae (36). A derivative, kromycin (22, R = OH), was formed from pikromycin under acidic conditions (87,88,91) and more drastic conditions produced an intramolecular spHoketal of pikronoHde named kromin (89,91). 10,11 -Oihydropikromycin (21, R = OH, R = H), was also produced by S. vene elae (92). 

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