Organic solvent concentration in the

Finally, if the organic-solvent concentration in the recycled CO2 stream is too high for the particular system considered, a small distillation tower may be needed. Preliminary studies show that a tower with only six ideal trays, operating at 50 bars, can reduce the THF percentage in the CO2 recycled stream to 0.1 % [4]. This option should also be applied if CO2 is to be used to remove the residual THF content from the solid product. 

Polymeric micelles form stable pseudostationary phases with a critical micelle concentration of virtually zero (aggregation number of 1), and are tolerant of high organic solvent concentrations in the electrolyte solution. Mass transfer kinetics are slow compared with conventional surfactant micelles, and peak distortion from mass overloading is a problem for some polymer compositions. Preliminary studies indicate that polymeric surfactants are effective pseudostationary phases in micellar electrokinetic chromatography, but only a limited number of practical applications have been demonstrated, and uptake has been slow. 

A unique application of TLC that will not be discussed in detail in this book is the determination of lipophilicity by means of reversed-phase TLC. The determination is based on the linear relationship between / values and organic solvent concentrations in the mobile phase as described by various TLC equations. The principles and methodology of this technique have been reviewed (232), and the influence of the composition of the mobile phase on the slope of the TLC equation for a series of steroids was studied (233). 

A summary of BPDE association constants for intercalation obtained from different studies is given in Table III. The wide variation in reported association constants can be attributed in part to differences in solvent conditions. The low binding constant obtained in ref. is due to the high ionic strength and high concentration of organic solvent employed in the experiments. The difference in the values of association constants reported in refs. 3 and 8 is most likely due to the difference in the organic content of the solutions used. 

One method is to run the reaction in an aqueous buffer/organic solvent biphasic system. This makes it possible to work at high substrate and product concentrations and at the pH-optimum of the enzyme. In addition, in water-immiscible solvents the non-enzymahc addition of HCN to the carbonyl group is non-existent or extremely slow. Possible disadvantages are enzyme deactivation at the interface and the presence of organic solvent dissolved in the aqueous phase [15, 17, 18]. 

The PSA operation was carried out at 30-1000 and atmospheric pressure by using a N2 carrier gas (60 ml/min). Adsorbates was butanone. Before PSA operation the adsorbents was pretreated at 400-90010 for 2 h in flowing N2. In the adsorption operation, N2 with butanone vapor (27.2 or 5.44 Torr) was passed through a column of the adsorbent (0.3 g for 27.2 Torr and 0.6 g for 5.44 Torr of butanone pressure) until there was almost no further adsorption (2 h). In the desorption operation, pure N2 was passed through the column in a countercurrent way for 2 h instead of evacuation. The concentration of the organic solvent vapor in the effluent gas was always monitored with a TCD detector to obtain breakthrough curves. Amounts of adsorption and desorption were calculated from the breakthrough curves. 

From 1 to 10 g (ca. 5-15 equivalents)—typically 3 g—of silver carbonate on Celite per mmol of alcohol are added to a ca. 0.01-0.15 M solution of the alcohol in drya benzene.b The resulting suspension is refluxed till most of the starting alcohol is consumed.0 The suspended solid is filtered, employing filter paper or a pad of Celite , and washed with benzene or other organic solvent. Concentration of the organic solution at the rotary evaporator yields the crude carbonyl compound that may need further purification. 

Figure 5. Effect of organic solvent concentration on the yield of copolymer and molecular weight of grafted chains in the pMMA-grafted dialdehydecellulose using a quartz lube. Conditions cellulose (C — 0, 29.8 mmol/100 g), 0.3 g H,0 + solvent, 10 mL MMA, 2 mL 50°C. Key to solvent O, CC/(, 1.5 h X, (CHs)t-CHCH%OH, 1.25 h A, HCON(CHs)t, 1 h <>, (CHs)2CO, 3 h.

Besides information developed in previous surveys, information about the presence and severity of hazards can be obtained from reported industrial hygiene reviews of similar facilities and from discussions with workers, medical and management personnel. Regardless of the extent of information obtained by this preliminary screening, a survey will be needed to define the relative concentration of the organic solvent vapors in the breathing zone of the worker. 

As may be seen from the above data, from concentrated solutions picric acid can be extracted by an organic solvent, while in the case of dilute solutions it remains in the aqueous phase. 

The reduction of the capacity factors with increasing organic modifier concentration in the eluent was weaker when methanol was used compared to acetonitrile, and this was attribnted to its lower polarity [5]. Even if methanol or acetonitrile are the most common organic modifiers, an unusual solvent, tetramethylene oxide [16], was recently tested in the IPC of sulfides and aromatic sulfonated compounds and proved to play an important role in adjusting retention. 

The solntions that contain an organic solvent usually in the form of emnlsifiable concentrates and field application dilutions of such concentrates, represent the greatest potential challenge to the barrier effectiveness of polymeric gloves. Many of the solvents can severely degrade or permeate the glove materials when in nndilnted form. 

Afanasev and Skobochkina [299] obtained other equations which may describe under some approximations the rates of reactions in mixed solvents. They also considered the increase in the rate constant with organic solvent concentration in organic... 

Enzymatic synthesis of cellulose has been achieved by cel-lulase. For example, incubation of fS-cellobiosyl fluoride with a cellulase from Trichoderma viride can produce cellulose in 54% yield with DP around 22 after 12h. In addition, change of the reaction conditions (substrate concentration or organic solvent concentration) enabled the selective synthesis of the water-soluble celloohgosaccharides (118). 

The retention times of analytes are controlled by the concentration(s) of the organic solvent(s) in the mobile phase. If a relatively small entropic contribution to the retention is neglected, theoretical considerations based either on the model of interaction indices [58], on the solubility parameter theory [51,52] or on the molecular statistical theory [57], lead to the derivation of a quadratic equation for the dependence of the logarithm of the retention factor of a solute. A, on the concentration of organic solvent. aqueous-organic mobile phase ... 

Reaction mixtures are complex multicomponent systems, and their phase behavior is dictated by the composition of the mixture and operating conditions. Organic solvents present in the reaction medium as reagents may act as cosolvents and result in solute solubility enhancement (as discussed in Section 4.2). For example, the decrease in reaction rate observed at high ethanol concentrations for the lipase-catalyzed esterification of myristic acid + ethanol in SCCO2 has been, in part, attributed to the solubility enhancement of water, resulting in drying of the enzyme... 

The relationships between capacity factor, k , and organic modifier concentration in the mobile phase, and the effect of the column temperature on k for the antibiotics studied have been used to define k as a function of T and V (volume fraction) on the basis of a small number of experimental measurements for a given combination of column, organic solvent, and type of antibiotic. From calculated values of k, resolution values, Rs, may be estimated for adjacent band-pairs under all conditions. The method developed enables the optimization of RP-HPLC separations of the p-lactam antibiotics in the absence of difficult theoretical calculations, using a small number of experimental data, including the influence of the organic solvent in the mobile phase (isopropanol) and the column temperature. 

Fig. 5-5. Dependence of the retention of aromatic sulfonic acids on the organic solvent content in the mobile phase. - Separator column IonPac NS1 (10 pm) eluent 0.002 mol/L tetrabutylam-monium hydroxide/acetonitrile flow rate 1 mL/min detection UV (254 nm) injection volume 50 pL solute concentrations 40 mg/L each of toluene-p-sulfonic acid monohydrate and naphthaline-2-sulfonic acid.

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