Organic Solvent Mixtures

Some neurotoxic effects of exposures to organic solvent mixtures are not anticipated. Solvent mixture exposures to lipophilic/hydrophilic mixtures have been shown to impair color vision in those exposed to paints and lacquers, printers, and workers in microelectronics plants. I81-83 The authors of these studies did not offer any hypothesis for the observed effects. 

Moderate hearing losses have been noted in workers exposed to organic solvents J84l Synergistic hearing loss effects have been reported in workers 

Much qualitative and quantitative information about the neurotoxic effects of exposures to organic solvents has been gathered from studies on paintersJ86-95 Solvent-based paints typically contain aliphatic and aromatic hydrocarbons, alcohols, ketones, and esters. A partial, but representative, list of these and their K)w values are given in Table 18.4. As can be seen from this list, a number of lipophilic and hydrophilic chemicals are present in almost all paints. 

The quantities of solvents in paints vary with desired characteristics (e.g., drying time desired) and application (building interiors, automotive surfaces, and architectural applications). Other solvents, including chlorinated hydrocarbons and terpenes, for example, are also formulated into paints. Virtually all solvent-based paints contain mixtures of lipophiles and hydrophiles. The exposures of painters to low levels of solvents (sufficiently low enough so that they do not experience acute symptoms at the time of exposure and below the TLVs for the individual solvent molecules) enables one to ascribe neurotoxicological reactions to low level mixture exposures. 

The neurological health of painters has been extensively studied. Painters have been found to suffer from impaired behavioral effects, I86 87 93 sensory and sensorimotor neuropathies, t89l psychiatric function,I90,91,94 and learning and memory deficiency 92 problems. In the studies just cited, as well in many other similar ones, exposures were generally low level, occurring over a period of years, and exposures were to mixtures of lipophilic and hydrophilic chemicals. Other studies on exposures to single 

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TABLE 8.21 Potentials of Reference Electrodes (in Volts) at 25°C for Water-Organic Solvent Mixtures Electrolyte solution of M HCl. 

Pervaporation is a relatively new process with elements in common with reverse osmosis and gas separation. In pervaporation, a liquid mixture contacts one side of a membrane, and the permeate is removed as a vapor from the other. Currendy, the only industrial application of pervaporation is the dehydration of organic solvents, in particular, the dehydration of 90—95% ethanol solutions, a difficult separation problem because an ethanol—water azeotrope forms at 95% ethanol. However, pervaporation processes are also being developed for the removal of dissolved organics from water and the separation of organic solvent mixtures. These applications are likely to become commercial after the year 2000. 

Reverse phase chromatography is finding increasing use in modern LC. For example, steroids (42) and fat soluble vitamins (43) are appropriately separated by this mode. Reverse phase with a chemically bonded stationary phase is popular because mobile phase conditions can be quickly found which produce reasonable retention. (In reverse phase LC the mobile phase is typically a water-organic solvent mixture.) Rapid solvent changeover also allows easy operation in gradient elution. Many examples of reverse phase separations can be found in the literature of the various instrument companies. 

Tokunaga R, Takahata S, Onoda M, Ishi-i T, Sato K (1974) Evaluation of the exposure to organic solvent mixture. Comparative studies on detection tube and gas-liquid chromatographic methods, personal and stationary sampling, and urinary metabolite determination. Internationales Archiv Arbeitsmedizin 33 257-267. 

The future development of micellar RPC will probably depend on the development of applications for which micellar mobile phases offer a significant advantage over the conventional use of aqueous-organic solvent mixtures and an increase in the efficiency... 

Later, Torii et al. found that the tin-aluminum-mediated allylation can be carried out with the less expensive allyl chloride, instead of allyl bromide, when a mixture of alcohol-water-acetic acid was used as the solvent.77 When combined with stoichiometric amounts of aluminum powder, both stoichiometric and catalytic amounts of tin are effective. As reported by Wu et al., higher temperatures can be used instead of aluminum powder.78 Under such a reaction condition, allyl quinones were obtained from 1,4-quinones, followed by oxidation with ferric chloride. Allylation reactions in water/organic solvent mixtures were also carried out electrochemically, with the advantage that the allyltin reagent could be recycled.79... 

In 1991, Whitesides etal. reported the first application of aqueous medium Barbier-Grignard reaction to carbohydrate synthesis through the use of tin in an aqueous/organic solvent mixture (Eq. 8.48).106 These adducts were converted to higher carbon aldoses by ozonolysis of the deprotected polyols followed by suitable derivatization. The reaction showed a higher diastereoselectivity when there was a hydroxyl group present at C-2. However, no reaction was observed under the reaction conditions when there was an /V-acctyl group present at the C-2 position. 

Interactions of such glassy polymeric particles should resemble the collisions of hard spheres. Phase diagrams of the type shown in Fig. 36 have been obtained for various polymer-organic solvent mixtures [85,94,345-353]. 

Carmona, F.J., Gonzalez, J.A., Carcia de la Fuente, I., Cobos, J.C., Bhethanabotla, V.R., Campbell, S.W. (2000) Thermodynamic properties of n-alkoxyethanols + organic solvent mixtures. XI. Total vapor pressure measurements for n-hexane, cyclohexane or n-hcptanc + 2-ethoxyethanol at 303.15 and 323.15 K. J. Chem. Eng. Data 45, 699-703. 

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 ... 

A particularly ingenious approach is that of triphase catalysis which was developed by Regen (1979). The catalyst is a quaternary ammonium residue which is covalently bound to an insoluble polystyrene resin, and reactions of anionic reagents are carried out in a two-phase water-organic solvent mixture. 

Stoltenburg-Didinger G, Altenkirch H, Wagner M. 1990. Neurotoxicity of organic solvent mixtures Embryotoxicity and fetotoxicity. Neurotoxicol Teratol 12 585-589. 

It is quite often possible to prepare hydroxypyridinone complexes directly by one-pot synthesis from the appropriate hydroxypyranone, amine, and metal salt 90-92). They can also be prepared by reacting complexes such as P-diketonates with hydroxypyridinones (see e.g., Ce, Mo later). Several maltolate complexes, of stoichiometry ML2, ML3, ML4, or MOL2, have been prepared by electrochemical oxidation of the appropriate metal anode, M — a first-row d-block metal (Ti, V, Cr, Mn, Fe, Co, Ni), In, Zr, or Hf, in a solution of maltol in organic solvent mixtures 92). Preparations of, e.g., manganese(III), vanadium(III), or vanadium(V) complexes generally involve oxidation... 

Until recently, the most detailed kinetic investigations of phase transfer free radical polymerizations were those of Jayakrishnan and Shah (11, 12). Both of these studies have been conducted in two phase aqueous/organic solvent mixtures with either potassium or ammonium persulfate as the initiator, and have corroborated our earlier conclusions (2, 3)... 

Nyssen, G.A., Miller, E.T., Glass, T.F., Quinn, C.R., II, Underwood, J., and Wilson, D.J. Solubilities of hydrophobic compounds in aqueous-organic solvent mixtures, Unviron. Monit. Assess., 9(1) 1-11, 1987. 

Solutes have differing solubilities in different liqnids dne to variations in the strength of the interaction of solnte molecnles with those of the solvent. Thus, in a system of two immiscible or only partially miscible solvents, different solutes become unevenly distribnted between the two solvent phases, and as noted earlier, this is the basis for the solvent extraction technique. In this context, solvent almost invariably means organic solvent. This uneven distribution is illustrated in Fig. 1.3, which shows the extractability into a kerosene solution of the different metals that appear when stainless steel is dissolved in aqueous acid chloride solution. The metals Mo, Zn, and Fe(III) are easily extracted into the organic solvent mixture at low chloride ion concentration, and Cu, Co, Fe(ll), and Mn at intermediate concentration, while even at the highest chloride concentration in the system, Ni and Cr are poorly extracted. This is used industrially for separating the metals in super-alloy scrap in order to recover the most valuable ones. 

In order to select a carrier solution composition which would provide an overall maximum response for MS detection, two modifiers were selected, acetonitrile and methanol, and two buffers, i.e. ammonium acetate (10 mmol pH 7.5) and ammonium formate (10 mmol L pH 7.5). Biotin and fluorescein-biotin were dissolved in various binding buffer-organic solvent mixtures ranging from 90 10 (v/v) to 50 50 (v/v) at two concentration levels (0.01 ng 1 ng pL ) and 20 pL were injected and analyzed by MS in full-scan and SIM mode. The maximum response was found with 50% methanol, which was about a factor 2x higher than for 10% methanol. Since the proteins can denaturate or protein-ligand complexes can dissociate at relatively low percentages of organic modifier in further experiments only 10% methanol is used in the carrier solution. 

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