Mixed Organic Solvents Research Articles

Japanese experience in biological monitoring.

In Japan, industrial health control is accomplished by control of the working environment, work practice management and health care. Periodical biomonitoring of workers exposed to lead and 8 popular organic solvents, including mixed solvents, became mandatory as of October 1, 1989, with an ordinance issued by the Ministry of Labor. This ordinance states that the results of measurements of lead and the 8 solvents in each work place must be classified into 3 categories, named distributions 1, 2 and 3 based on the biological level of the determinant, and then must be reported to the Labor Standards Inspection Office. Distribution 3 encompasses workers having concentration levels above the BEIs of ACGIH except for the concentration of lead in the blood. The National Federation of Industrial Health Organizations surveyed the state of biological monitoring in Japan by a questionnaire to the laboratories. The total number of cases examined in the fiscal year 1990 was about 110,000 for the biomonitoring of lead, and about 520,000 for the monitoring of urinary metabolites of the 8 organic solvents. The ratio of the number of workers in distribution 3 to that of the total workers examined was 0.4% for urinary delta aminolevulinic acid and 0.2-3.5% for the urinary metabolites of each organic solvent. Similar results were obtained from 7 major laboratories. To achieve large-scale biological monitoring in future, a method is necessary for evaluating the exposure or health risks of workers exposed to mixed organic solvents by estimating their urinary metabolites.

Ultrasonic and Viscometric Studies of Yttrium Soap; in Mixed Organic Solvents

Ultrasonic and Viscometric Studies of Yttrium Soap; in Mixed Organic Solvents

Chromatography of Anions on Alumina Thin Layers: Effect of Transition Metals on CI--Br--I- and No-2-NO-3 Separations

Abstract Chromatographic behaviour of eighteen anions on thin layers of alumina and alumina mixed with silica gel (1:1, 1:2 and 2:1) has been studied using mixed acidic organic solvent systems containing formic acid. Though the addition of silica gel to alumina enhances the mobility and clarity of detection of anions, but it causes the increased tailing for Fe(CN)3- 6, Cr04 2- and Cr2O4 2-. Formic acid is responsible for the differential migration of anions. All the anions remained at the starting line (RF = 0) in pure organic solvents. Formic acid-Ketone systems gave better results compared to formic acid-alcohol systems. Development time increases with the increase of viscosity/mol. wt. of organic solvents. The mutual separation of C1, Br−, Br−, I− and NO− 2 and NO− 3 were achieved on pure alumina using formic acid-acetone solvent systems. The effect of transition metals (Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn) on C1−-Br−-I− and NO− 2-NO− 3 separations has been studied.

Autonomic and peripheral nervous system dysfunction in workers exposed to mixed organic solvents.

To assess possible solvent-induced dysfunction of the autonomic and peripheral nervous systems, 11 solvent-exposed workers and 11 age-matched unexposed controls were examined using the coefficient of variation in electrocardiographic R-R intervals (CVRR) and the distribution of nerve conduction velocities (DCV). Two components of CVRR, i.e., the C-CVRSA and C-CVMWSA, were also examined, which are considered to reflect parasympathetic and sympathetic activities, respectively. The workers had been occupationally exposed to toluene and/or solvent mixtures such as thinners, for 35-360 months. In the solvent-exposed workers, the CVRR and C-CVRSA were significantly reduced compared with unexposed controls. Similarly, the faster velocities of the DCV and median nerve conduction velocities were significantly slowed. The reduction in the CVRR was significantly correlated with duration of exposure in the solvent-exposed workers. These data, despite the small sample size and the variety of organic solvents, suggest that organic solvents may affect both the faster myelinated nerve fibers and autonomic nervous activity (principally, parasympathetic component).

Transfer of cesium ion from the aqueous phase into the mixed organic phase of a two-phase water/nitrobenzene-carbon tetrachloride extraction system

Standard Gibbs energies of transfer of cesium ion from water to nitrobenzene and nitrobenzene-carbon tetrachloride mixture have been evaluated from electrochemical measurements. From the results the conclusion can be drawn that with increasing dielectric permitivity of organic mixed solvents the value of the Gibbs transfer energy of Cs+ ion decreases.

The conductance behaviour of mixed organic electrolytes for a non-aqueous Li/MnO 2 battery

This paper reports a study of the electric performance of mixed organic solvents of propylene carbonate—1,2-dimethoxyethane—tetrahydrofuran and dimethyl sulphoxide—1,2-dimethoxyethane. The effects of the dielectric constants of the solvents, lithium perchlorate concentration, the viscosity of the solutions and the mixture ratio of the solvents upon ion electric conductivity are presented and discussed.

Dose-related subclinical neurobehavioral effects of chronic exposure to low levels of organic solvents.

One hundred eight-seven workers (mean age +/- SD; 42 +/- 8.8 years) in two paint manufacturing plants were examined to determine if sustained low-level exposure to mixed organic solvents resulted in the painters' syndrome (a psycho-organic syndrome). The test battery consisted of a medical and occupational questionnaire, the Present State Examination, the Zung Depression Scale, the Scandinavian Questionnaire 16, a neuropsychological battery, and vibration thresholds. Solvent exposure, expressed as total hydrocarbon of combined selected solvents, was quantitated using 13-15 years of personal breathing zone samplings. Linear regression analysis controlling for several confounding variables demonstrated significant correlations between increasing exposure to mixed organic solvents and neurobehavioral performance for vibration threshold and several neuropsychological tests. Dose-related effects of chronic solvent exposure on neurobehavioral outcomes (all subclinical) were shown, but "typical" symptoms characteristic of the painter's syndrome were not found.

Neurobehavioural effects of industrial mixed solvent exposure in chinese printing and paint workers

Neurobehavioural symptoms and performance tests were evaluated in a group of 78 workers exposed to mixed organic solvents (printers, paint sprayers and paint production workers) and a referent group of 145 unexposed subjects (nonproduction factory workers and volunteer postal workers). Both groups were administered a structured symptoms questionnaire and eight neurobehavioural tests for psycho-motor function, visual and auditory memory. An excess of symptoms of fatigue, irritability, depression, poor memory, sleep disturbances and symptoms suggestive of autonomic dysfunction was found in the exposed group. Neurobehavioural test performance was generally worse, and performance on tests of psycho-motor function (choice reaction test and digit symbol) and auditory memory (digit span and associate learning) was significantly poorer in the exposed group. The findings support the view that apparently healthy and actively employed workers exposed to mixed solvents show neurobehavioural deficits.

Effects of occupational exposure to organic solvents upon cognitive performance

Twenty-three individuals exposed to mixed organic solvents were compared with 23 nonexposed controls on a number of cognitive performance tasks. Solvent exposure resulted in a significantly poorer performance on the forward digit span test, copying of a complex figure, and on semantic memory tests which also measure individual's ability to integrate linguistic information into cohesive units. These tasks rely heavily upon short-term memory and its integrative operations in higher cognitive function. Acute exposure effect was also observed for the linguistic integrative task.

Conductometric studies and thermodynamics of dissociation and micellization of praseodymium and neodymium linoleates in mixed organic solvents

The results show that the praseodymium and neodymium linoleates behave as a weak electrolyte in dilute solutions (60% benzene+40% methanol v/v) below the critical micellar concentration, and the conductance result can be explained on the basis of Ostwald's formula and Debye‐Huckel's theory of weak electrolytes. The dissociation constant and thermodynamic parameters for dissociation and micellization processes of lanthanide linoleates are also evaluated. The micellization process has been found to be predominant over the dissociation process.

Ultrasonic measurements and other allied parameters of yttrium soaps in mixed organic solvents

The ultrasonic measurements of yttrium soaps were made in a mixture of 70% benzene and 30% dimethylsulfoxide (v/v) to determine the critical micelle concentration, soap-solvent interaction and various acoustic and thermodynamic parameters. The values of the CMC decrease with increasing chainlength of fatty acid constituent of the soap molecule and are in agreement with the values obtained from other micellar properties. The various acoustic parameters (intermolecular free-length, adiabatic compressibility, apparent molar compressibility, specific acoustic impedance, apparent molar volume, molar sound velocity, solvation number, available volume and relative association) for yttrium soaps (myristate, palmitate, stearate and oleate) have been evaluated by ultrasonic velocity measurements.

Light scattering measurements of anisotropic viscoelastic coefficients of a main-chain polymer nematic liquid crystal

Abstract We report the first systematic measurements of elastic coefficients and viscosities that clearly demonstrate the distinction between rigid and semiflexible behaviour of a main-chain polymer nematic liquid crystal, a solution of poly-γ-benzyl glutamate (PBG) in mixed organic solvents. Quasi-elastic Rayleigh scattering studies show a crossover which occurs at a molecular chain length near the persistence length of PBG as the chain length increases. The results are in qualitatively good agreement with recent theoretical predictions for semiflexible chains. It is seen that bending distortions of an individual polymer play an important role in the fundamental nature of nematic elasticity and viscosity.

Microgels as soluble enzyme supports in organic media

The enzymes α-chymotrypsin, sulfatase, and esterase have been conjugated to soluble carboxyl-bearing microgels with a water-soluble carbodiimide. Enzymatic activity towards several substrates has been observed in mixed aqueous-organic and organic solvents. Michaelis-Menten parameters for the enzyme-polymer conjugates have been determined and are compare with the results from native enzyme preparations in water and enzymes immobilized on insoluble supports.

Solvolysis rates in mixed organic solvents

Solvolysis rates in mixed organic solvents

Solvolysis rates in mixed organic solvents

Solvolysis rates in mixed organic solvents

Preparation and Preliminary Evaluation of Eudragit RL and RS Pseudolatices for Controlled Drug Release

AbstractEudragit RL and RS pseudolatices were prepared by the solvent change technique, which consisted of dissolving the polymer in a water miscible organic solvent or in a mixed water miscible organic solvent system, followed by dispersian in deionized water under mild agitation. The organic solvent (s) was removed from the aqueous organic solution to leave a stable Eudragit latex.Eudragit pseudolatex coated theophylline pellets were prepared in a fluidized-bed coating machine. The effects of polymer type and coating level, plasticizer concentration, and PH of the dissolution medium on drug release were investigated. The higher content of quaternary ammonium groups attached to the polymer backbone make the coatings produced from Eudragit RL too water sensitive; and hence unsuitable for controlling theophylline release. On the other hand, Eudragit RS films retarded theophylline release. On the other hand, Eudragit RS films retarded theophylline release over a wide pH range. Release of the drug was found ...

The Preparation of III-V Semiconductors in Aqueous Solution

AbstractIndium arsenide colloids have been prepared by passing arsine through an aqueous solution of the metal nitrate. Similar experiments with gallium solutions produced an extremely fine precipitate which has been tentatively identified as amorphous gallium arsenide. Attempts to precipitate aluminium arsenide from aqueous solutions or mixed organic solvent systems were unsuccessful. The materials were characterised by transmission electron microscopy, X-ray powder diffraction and and optical absorption spectroscopy.

17O‐nmr studies of the conformational and dynamic properties of enkephalins in aqueous and organic solutions using selectively labeled analogues

The synthesis of Leu-enkephalin selectively 17O-enriched in Gly2 and Gly3 is reported. The 17O-nmr chemical shifts of [17O-Gly2, Leu5]- and [17O-Gly3, Leu5]-enkephalins in H2O are almost identical and independent of the pH. Since hydrogen bonding is the dominant factor governing the chemical shifts of the peptide oxygen, it can be concluded that the hydration state of both oxygens is identical and independent of the pH. The 17O chemical shifts of the [17O-Leu5]-enkephalin terminal carboxyl group at pH approximately 1.9 and 5.6 are very different in H2O but very similar in CH3CN/DMSO (4:1) solution. This suggests that the protonation state of the carboxyl group at both pH values in CH3CN/DMSO solution is the same and consequently that Leu-enkephalin exists in the neutral form at pH approximately 5.6. In this organic mixed solvent system both Gly2 and Gly3 oxygen resonances exhibit a significant shift to high frequency by the same extent (delta delta approximately 30 ppm). It is concluded that both peptide oxygens are not hydrogen bonded to an appreciable extent and that no specific 2----5 hydrogen bonding exists to an appreciable extent. This conclusion is in agreement with the energy of activation for molecular rotation, as determined from T1 measurements, which was found to be almost identical for both [17O-Gly2, Leu5]- and [17O-Gly3, Leu5]-enkephalins in CH3CN/DMSO (4:1) mixed solvent.

Electrode processes in mixed solvents: Correlations between electrochemical rate constants and gibbs energy of transfer

Relationships have been established between the cathodic and anodic rate constants of electrode processes and the Gibbs energy of transfer, Δ tr of the reactant for ion transfer and Δ Δ G tr = Δ G tr,Ox-Δ G tr,Red for electron-transfer reactions in aqueous + organic mixed solvents. These dependences are different from those obtained for electrochemical reactions in pure solvents, this being explained quantitatively by the various compositions of the surface and bulk phases. The correlations obtained offer diagnostic criteria which are useful in the understanding of the mixed-solvent influence on the mechanism of electrochemical reactions occurring under such conditions. Equations have been devised which describe three ways of electroreduction in two-solvent systems: (i) removal of surface molecules by an activated complex, a mechanism similar to that in the presence of neutral organic inhibitors; (ii) selective resolvation with adsorbed organic molecules; and (iii) electron transfer outside the surface phase. Satisfactory agreement was found between the experimental results and the calculated data for selected electrochemical processes in mixed solvents.

Sulfur solubility in pure and mixed organic solvents

Sulfur solubility in pure and mixed organic solvents