Solubility direct measurement

Mancozeb is a dithiocarbamate pesticide with a very low solubility in organic and inorganic solvent. In this work we have developed a solvent free, accurate and fast photoacoustic FTIR-based methodology for Mancozeb determination in commercial fungicides. The proposed procedure was based on the direct measurement of the solid samples in the middle infrared region using a photoacoustic detector. A multivariate calibration approach based on the use of partial least squares (PLS) was employed to determine the pesticide content in commercially available formulations. 

Spectrophotometric methods may often be applied directly to the solvent extract utilising the absorption of the extracted species in the ultraviolet or visible region. A typical example is the extraction and determination of nickel as dimethylglyoximate in chloroform by measuring the absorption of the complex at 366 nm. Direct measurement of absorbance may also be made with appropriate ion association complexes, e.g. the ferroin anionic detergent system, but improved results can sometimes be obtained by developing a chelate complex after extraction. An example is the extraction of uranyl nitrate from nitric acid into tributyl phosphate and the subsequent addition of dibenzoylmethane to the solvent to form a soluble coloured chelate. 

Lohse et al. have summarized the results of recent work in this area [21]. The focus of the work is obtaining the interaction parameter x of the Hory-Huggins-Stavermann equation for the free energy of mixing per unit volume for a polymer blend. For two polymers to be miscible, the interaction parameter has to be very small, of the order of 0.01. The interaction density coefficient X = ( y/y)R7 , a more relevant term, is directly measured by SANS using random phase approximation study. It may be related to the square of the Hildebrand solubility parameter (d) difference which is an established criterion for polymer-polymer miscibility ... 

Texturization is not measured directly but is inferred from the degree of denaturation or decrease of solubility of proteins. The quantities are determined by the difference in rates of moisture uptake between the native protein and the texturized protein (Kilara, 1984), or by a dyebinding assay (Bradford, 1976). Protein denaturation may be measured by determining changes in heat capacity, but it is more practical to measure the amount of insoluble fractions and differences in solubility after physical treatment (Kilara, 1984). The different rates of water absorption are presumed to relate to the degree of texturization as texturized proteins absorb water at different rates. The insolubility test for denaturation is therefore sometimes used as substitute for direct measurement of texturization. Protein solubility is affected by surface hydrophobicity, which is directly related to the extent of protein-protein interactions, an intrinsic property of the denatured state of the proteins (Damodaran, 1989 Vojdani, 1996). 

Although the pH-partition hypothesis and the absorption potential concept are useful indicators of oral drug absorption, physiologically based quantitative approaches need to be developed to estimate the fraction of dose absorbed in humans. We can reasonably assume that a direct measure of tissue permeability, either in situ or in vitro, will be more likely to yield successful predictions of drug absorption. Amidon et al. [30] developed a simplified film model to correlate the extent of absorption with membrane permeability. Sinko et al. [31] extended this approach by including the effect of solubility and proposed a macroscopic mass balance approach. That approach was then further extended to include facili-... 

Is there any other approach or concept that can directly measure protein amount in the tissue section Ten years ago, Roth et al.38 documented a novel method, named the Midwestern assay. This method is based on using two chromogens, soluble and insoluble, for the IHC staining process, to produce sequential production of soluble and insoluble reaction products. The soluble IHC product is used to measure the amount of antigen (protein) by spectrophotometry, while insoluble product indicates the localization of protein in the tissue section. Their experimental results demonstrated that soluble reac-... 

Most conventional organic contaminants are fairly hydrophobic and thus exhibit a low but measurable solubility in water. Solubility is often used to estimate the air-water partition coefficient or Henry s law constant, but this is not possible for miscible chemicals indeed the method is suspect for chemicals of appreciable solubility in water, i.e., exceeding 1 g/100 g. Direct measurement of the Henry s law constant is thus required. 

Quenching of the emissions of fluorophores sensitized by dioxetanes has also been used for chemical analysis [29, 30] but this is probably less specific and less sensitive than direct measurement of the sensitized emission of the analyte. Most analytical reactions of the dioxetanes require an organic solvent for optimal solubility and CL yields [31]. This has led to considerable interest in the development of water-soluble oxalate esters [32],... 

The direct measurement of enthalpies of solution of lanthanide trifluorides in water is hardly practicable, in view of their very small solubilities in this solvent. Enthalpies of hydration of lanthanide trifluorides have been measured (217). It should be possible to derive enthalpies of solution, at least for the hemihydrates LnF3-y2H20, by measuring enthalpies of precipitation. 

In the sorption experiments of Icopini et al. (2004), the measured isotopic contrast between Fe(II)aq and the goethite starting material was -0.8%o after Fe(II) had sorbed to the surface over 24 hours in this case, the isotopic fractionation between sorbed Fe(II) and Fe(II)aq is not the 0.8%o measured difference, but is approximately +2.1%o based on an inferred 8 Fe value for the sorbed component as calculated from Fe mass balance (Fig. 4), as was noted in that study. Measured differences in Fe isotope compositions between ferric oxide/hydroxide and Fe(II)aq during dissimilatory Fe(III) reduction and photosynthetic Fe(II) oxidation have been proposed to reflect fractionation between soluble Fe(II) and Fe(III) species, where the soluble Fe(III) component is postulated to be bound to the cell and is not directly measured (Beard et al. 2003a Croal et al. 2004). In the case of dissimilatory Fe(III) reduction, assuming a static model simply for purposes of illustration, if 50% of the Fe in a pool that is open to... 

A direct measure of nonpolar character of a hydrocarbon molecule is given either by its molar solubility in water or by its molar attraction constant (Small s number) as given by Small... 

Color is a subjective phenomenon whose esthetic value has been recognized for centuries. Since it is dependent on the light source, the object, and the observer, color is not subject to direct measurement, though instruments can measure a color for reproducibility. Colorants that provide color in polymers may be soluble dyes or comminuted pigments. 

The solubility limitation does not allow direct measuring k(i for ferrocene and Compound I. However, it is worth estimating k(i for this most reactive electron donor among ferrocenes. Using the observed ratio k6 100 x k7 for substituted ferrocenes (Table IV) and the steady-state rate constant k7 for ferrocene of 2 x 105 M 1 s- (119), the k6 should be around 2 x 107 M-1 s 1. Thus, ferrocene reacts very rapidly with Compound 1,10-fold as fast as [Fe(CN)6]4. ... 

Aqueous solubility is a direct measure of the hydrophobicity of a substance. Therefore, perhaps the most practical way of estimating the intrinsic water solubility (logS) for structurally diverse organic substances is through the use of the Yalkowsky equation [47], which uses regression-derived correlation with logPQ w and melting point (MP) for solids ... 

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