Organic solvents, viii

As illustrated above there exist a large variety of techniques for preparing liposomes. From a pharmaceutical point of view, optimum liposome preparation techniques would avoid the use of organic solvent and detergents (which are difficult to remove), would exhibit a high trapping efficiency, would yield well-defined vesicles which can be produced in a reproducible way, and would be rapid and amenable to scale-up procedures (see Sec. VIII). 

Table VIII. Effect of Ragweed Organic Solvent Extracts on Lettuce and Carrot Germination...

Some results of the modification of lignin sulfonate Ultra B002 by reaction with terephthaloyl chloride are summarized in Table VI. The total hydroxyl content of the lignosulfonates as well as their derivatives are presented in Table VII. The hydrolytic resistance of selected products is evaluated in Table VIII. The results presented in Tables VI-VIII stress several advantages of the derivatives with terephthaloyl chloride. The modified lignin sulfonates were insoluble, or only very slightly soluble, in organic solvents. They were, however, soluble in dimethyl sulfoxide. Ordered structures were identified by X-ray studies (16,17). 

Mercury compounds prepared in this way (Table VIII) are strongly refractive liquids which crystallize in favorable cases. They dissolve readily in organic solvents and are stable to water. Since the mercury compounds can be obtained in a pure form (by distillation, recrystallization) they are actually isolated as an intermediate step in carbosilane synthesis. This results in the removal of all the impurities arising from the various steps in the synthesis, a factor which is particularly important in making carbosilanes of higher molecular weights, where purification becomes more difficult as the molecular weight increases and by-products tend to have an unfavorable effect on the synthesis. 

Examination of Polysulfide Fractions. Polysulfide fractions from the alloocimene, myrcene, limonene, styrene, and Thiokol LP-33 materials prepared at 140 °C have been fractionated by gel permeation chromatography. Other Thiokol products could not be examined because they were insoluble in all organic solvents used. In Tables VIII-XII the molecular weight and molecular formula of each fraction are given. Table... 

In FAAS an ideal organic solvent should possess the following characteristics (i) Low viscosity (ii) Good combustion characteristics (low background absorption and nontoxic combustion products) (iii) Low volatility (iv) Immiscibility in water (v) Not poisonous (vi) Good extraction efficiency (vii) Good nebulization efficiency (viii) Easy to handle (ix) Available in high purity form. 

The usual amide solvent systems are used for the polymers from VIII and IX while the all-hydrazide polymer from X and terephthaloyl chloride has been repiorted to be insoluble in the usual organic solvents. 

A convenient method for the preparation of polysulfides by the two-phase polycondensation in a KOH solution is known. " Polycondensation of 1,4-dibromobutane (VIII) and 1,6-hexanedithiol (IX) leading to polysulfide (X) was carried out in various organic solvent/HjO system with DC-18-C-6 catalyst. 

The dehydration of all kinds of organic solvents can be carried out by pervaporation. This process is very attractive, especially in those cases where water forms an azeotrope with the solvent at low water content. Atypical case is ethanol/water with an azeotropic composition of 96% ethanol by weight. Purification of ethanol can also be achieved via a hybrid process distillation up to 96% and pervaporation to > 99%, see figure VIII - 28. 

JW Gardner, A Pike NF de Rooij, M Koudelka-Hep, A Hierlemann, and W Gopel "Integrated Polymer Array Sensor for Detecting Organic Solvents", Conf Proc Eurosensors VIII Toulouse (F) 9/1994, and Sensors and Actuators, in press... 

The experimental data for the polymerization of itaconic acid in dioxane with initiators that are soluble in organic solvents are given Table VIII. The polymers prepared at 50 C were described as being slightly yellow in color and soluble in water, methanol, dioxane, dimethylformamide, dimethyl sulfoxide, formamide, and ethanol. Copolymers prepared at room temperature were colorless and had similar solubility behavior except that they were insoluble in cold dioxane but soluble in dioxane when heated to 70 "C. The polymers were insoluble in petroleum ether and in methyl ethyl ketone. 

A number of organic solvents may be used for extraction of the free steroids from the urine hydrolysate. Each solvent which has been used in the past has advantages as well as disadvantages. The preferred solvent appears to be diethyl ether which is widely used despite its inflammability and proneness to develop peroxide. The ease with which ether can be removed at low temperatures, its high solvent power for the steroids, and its relatively small tendency to form emulsions favor its use. Benzene and carbon tetrachloride are also widely employed as extractants. However, their use is accompanied by relatively high toxicity hazards and if they are used care should be exercised to provide adequate ventilation. The lack of inflammability of carbon tetrachloride is a point in its favor. In one of the micromethods to be described below (Section VIII), ethylene chloride was found to be advantageous. 

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