Solvent mixtures for

H) was determined for each solute, in each solvent mixture, for 10 different linear velocities ranging from 0.02 cm/sec. to 0.6 cm/sec. Three measurements were taken at each velocity, which produced a minimum of 180 values of (H) for each solute. Each data set was then fitted to each dispersion equation and the respective constants... 

A variety of reaction mixtures can be analyzed by this simple technique, although a suitable solvent or solvent mixture for the development of the slide must be determined for the particular compounds involved. 

Mixed solvents are generally unsatisfactory for use in the determination of polymer molecular weights owing to the likelihood of selective absorption of one of the solvent components by the polymer coil. The excess of polarizabilit f of the polymer particle (polymer plus occluded solvent) is not then equal to the difference between the polarizabilities of the polymer and the solvent mixture. For this reason the refractive increment dn/dc which would be required for calculation of K, or of i7, cannot be assumed to equal the observed change in refractive index of the medium as a whole when polymer is added to it, unless the refractive indexes of the solvent components happen to be the same. The size Vmay, however, be measured in a mixed solvent, since only the dissymmetry ratio is required for this purpose. 

The remainder of this section deals primarily with selectivity optimization in isocratic liquid chromatography and with gradient elution Before entering these subjects proper, however, a discussion of the relevant chromatographic properties of solvents is in order as a framework for the intuitive selection of the preferred solvent or solvent mixtures for selectivity optimization. 

Vandenburg et al. [37,489] have described the use of Hildebrand solubility parameters in a simple and fast solvent selection procedure for PFE of a variety of polymers. Hildebrand parameters for several common solvents and polymers are presented in Tables 3.2 and 3.34, respectively. When the proper solvent mixture for the polymer was determined, PFE resulted in essentially the same recoveries as the traditional extraction methods, but used much less time and solvent. PFE can be used to give very fast extractions and appears to offer the greatest flexibility of solvents and solvent mixtures. The method is ideal for a laboratory which analyses a large number of different polymers. 

Another specific effect of some consequence arises from the use of aqueous organic solvent mixtures. For the cobalt system, dry solvents induce CO hydrogenations which are stoichiometric for water (13a) (within 2% material balance) according to the reaction ... 

Select solvent mixtures for crystallization of drug or active ingredient [Karunanithi et al. (2006)]. See also chapters 2 and 4. 

The distribution of solutes between the two phases can be estimated by measurement of the relative solubility of the reagent in each phase of the system under given physical conditions. Water and 1-octanol have become a standard solvent mixture for this [21], although other pairs of solvents may be used to produce, for example, a scale of preference for fluorous versus organic solvents, as described below. The quantity P, known as the partition coefficient, is defined as... 

The influence of the substrates 1-octene and morpholine was measured by repeating the cloud titrations with addition of these substances to determine the appropriate composition of the solvent mixture for the reaction. While the addition of 1-octene has almost no effect on the TMS systems the addition of morpholine leads to a decrease of the miscibihty gap (Fig. 14). As morphoHne itself is semi-polar and can be used as a mediator a smaller amount of s3 is needed to obtain a homogeneous system. 

Uses Solvent mixtures for nitrocellulose and polyvinyl resins in organic synthesis. 

The selection of a solvent for a new separation problem, even today, is a matter of trial and error. The application of theory (2) with the additional application of the solubility parameters (6J-65) makes it possible to estimate the composition of appropriate solvent mixtures for the separation of relatively simple compounds. In order to calculate the necessary solvent strength, however, a set of experimental data concerning the behavior of the sample components, the adsorbent, and the elution strength of the eluents with the specific adsorbent are necessary. Others (J5) recommend a graphical method as a time-saving alternative to bi th calculation and the trial-and-error approach to obtain a first approximation of the eluent composition appropriate for the separation of a givin sample. 

Besides the core business of paint removal they also started to supply solvent mixtures for de-lacquering to other companies. 

HPLC Separations. SAMPLE PREPARATION FOR INJECTION. Isolated residue organics were dissolved in water/acetonitrile solvent mixtures for reverse-phase HPLC separations as follows sample was dissolved in a minimum volume of acetonitrile and diluted with water until... 

We theorize that the broadness of the second peak in the ibuprofen separation is due to the higher concentration of that enantiomer in the injection mixture. Further tests are being performed to optimize the solvent mixture for this separation, which should also help to reduce the broadness of this peak... 

Phthalimide protection is stable towards acids and bases, but can be cleaved with strong nucleophiles, such as hydrazines or sulfides, or by reduction with sodium boro-hydride [230]. More sensitive towards nucleophilic attack than unsubstituted phthalimide is tetrachlorophthalimide [33]. This group has been successfully used as N(a) protection of amino acids in the solid-phase synthesis of peptides (deprotection N2H4/DMF (15 85), 40 °C, 1 h coupling DIC/HOAt/amino acid (1 1 1), 3 equiv. of each, DMF, 25 °C, 4 h [294]). Typical conditions for the removal of phthaloyl protection on cross-linked polystyrene include treatment of the resin with hydrazine hydrate [295,296], with methyl hydrazine [297], or with primary aliphatic amines [298] in DMF, EtOH, or solvent mixtures for several hours at room temperature or above [296,299,300]. Illustrative examples are sketched in Figure 10.15. It has been claimed that the hydrazinolysis of polystyrene-bound phthalimides proceeds more readily in DCM or DCE than in DMF [301]. 

Table 11.6.2 Solvent Mixture for Extracting Isoflavones from Soy Foods"...

Table 4-1. Solvent mixtures for thin layer chromatograpy of phenolic compounds...

Electrochemical binding assays have also been applied for testing computational predictions which render the highest stabilization energy for the pre-polymerization mixture of several formulations traditionally used in non-covalent MIPs [119]. The batch binding assays and voltammetric detection confirm the theoretically best monomer-porogen solvent mixture for preparation of a recognition material for the dopamine metabolite homovanillic acid. 

Almost any solvent is possible for a recrystallization. Table 13.1 shows some of the most frequently used solvents in the pharmaceutical industry. Mixtures of solvents, binary or even ternary, are also common. The burden of checking many solvents and solvent mixtures for use in recrystallizations can be mitigated with automated high-throughput screening tools. A drug s solubility is tested in each solvent and reasonable solvent mixture at various... 

The problems associated with the separation of phosphate esters are the tendency of the spots to diffuse difficulty of reproducing RF values variability of RF values with complexity of the mixture being resolved and distance of solvent travel proper purification and equilibration of the filter paper effect of inorganic ions in natural mixtures and the choice of suitable solvent mixtures for desired separations. The problem of detecting the separated spots is somewhat simpler. In addition to methods applicable to the detection of reducing sugars (e.g., use of aniline salts fructose esters are detected by naphthoresorcinol-acid), methods depending on phosphomolybdate formation are most commonly used. Hanes and Isher-... 

Conductometric analysis using a 2-propanol/toluene/water solvent mixture in the titration of fresh and used oil samples (Armitage et al., 1987, Pawlak, 1980) and benzene/alcohol solvent mixture for the titration of phenolates and sulfonates (Labre and Briant, 1960) have been found to give satisfactory results however, benzene is a class A carcinogen and is no longer used in most laboratories. 

CA) and ethanol (Dehydrated Alcohol, USP Pinctillians, US Industrial Chemical Co., Tuscola, IL) were used to prepare solvent mixtures for all the experiments. 

Figure 3.20 Nomogram illustrating the solvent strength of various binary solvent mixtures for LSC. Vertical (dashed) line illustrates a series of iso-eluotropic solvents (see text). Figure taken from ref. [358]. Reprinted with permission.

When each of the various types of LC was discussed earlier in this chapter, the mobile phase was one of the topics included, but a more comprehensive discussion of these liquids, their properties, and their optimal use in LSC and BPC is needed. This section will describe several ways to select the best solvent mixture for a separation. A more comprehensive discussion on the optimization of selectivity has been given by Glajch and Kirkland.63... 

To use the selectivity parameters in selecting solvent mixtures for LC, Snyder assumes additivity in proportion to the volume fractions of the solvents ... 

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