Toxic organic solvent

The immobilization of reagents onto sorbents often results in increase of their sensitivity and, in some cases, selectivity, allows to simplify the analysis and to avoid necessity of use of toxic organic solvents. At the same time silicas are characterized by absence of swelling, thenual and chemical stability, rapid achievement of heterogeneous equilibrium. 

The aqueous micellai solutions of some surfactants exhibit the cloud point, or turbidity, phenomenon when the solution is heated or cooled above or below a certain temperature. Then the phase sepai ation into two isotropic liquid phases occurs a concentrated phase containing most of the surfactant and an aqueous phase containing a surfactant concentration close to the critical micellar concentration. The anionic surfactant solutions show this phenomenon in acid media without any temperature modifications. The aim of the present work is to explore the analytical possibilities of acid-induced cloud point extraction in the extraction and preconcentration of polycyclic ai omatic hydrocai bons (PAHs) from water solutions. The combination of extraction, preconcentration and luminescence detection of PAHs in one step under their trace determination in objects mentioned allows to exclude the use of lai ge volumes of expensive, high-purity and toxic organic solvents and replace the known time and solvent consuming procedures by more simple and convenient methods. 

A BDS patent [106] was awarded for the use of biocatalysts belonging to the group of Pseudomonas, Flavobacterium, Enterobacter, Aeromonas, Bacillus, or Corynebac-terium. One of the strains P. putida was further developed by mutation of the parent strain to obtain organic solvent-resistant mutants [107], The mutated strains were screened by selective cultivation in the presence of 0.1% to 10% by volume (v/v) of concentrations of a toxic organic solvent. The specific mutated strains obtained were P. putida No. 69-1 (PERM BP-4519), P. putida No. 69-2 (PERM BP-4520), and P. putida No. 69-3 (PERM BP-4521). 

Extraction efficiency is not the only factor to be examined in the choice of solvent or reagent for a particular application. Environmental, as well as economic considerations must be taken into account. Solvents such as benzene and chloroform (which have solubilities of 0.07 and 0.82 parts per 100 parts of water) might be preferred for extractive efficiency, but their use would result in large losses to the aqueous phase. Not only would this be expensive, but it would be undesirable for reasons of health the toxic organo lead salts would be removed, but an equally toxic organic solvent would be added to the effluent. Addition of a solvent recovery unit subsequent to the extraction step might render the technique uneconomic (relative to alternative effluent treatment techniques). 

The liquid-gas equilibrium line terminates at a point known as the critical point. The temperature and pressure that define the critical point are known as the critical temperature and the critical pressure. For example, nitrous oxide has a critical temperature of 36°C and a critical pressure of 72.45 bar (1051 psi). When the temperature and pressure exceed these critical values, the system becomes a supercritical fluid. Supercritical fluids have the flow properties of gases but densities similar to liquids, and supercritical fluids have no surface tension. Therefore, supercritical fluids are terrific solvents. For example, supercritical carbon dioxide is an excellent solvent for extracting caffeine from coffee without resorting to more toxic organic solvents like dichloromethane. 

Zhang and Rusling [66] employed a stable, conductive, bicontinuous microemulsion of surfactant/oil/water as a medium for catalytic dechlorination of PCBs at about 1 mA cm-2 on Pb cathodes. The major products were biphenyl and its reduced alkylbenzene derivatives, which are much less toxic than PCBs. Zinc phthalocyanine provided better catalysis than nickel phthalocyanine tetrasulfonate. The current efficiency was about 20% for 4,4 -DCB and about 40% for the most heavily chlorinated PCB mixture. A nearly complete dechlorination of 100 mg of Aroclor 1260 with 60% Cl was achieved in 18 hr. Electrochemical dehalogenation was thus shown to be feasible in water-based surfactant media, providing a lower-cost, safer alternative to toxic organic solvents. 

High consumption of expensive, high-purity gases Insufficient separation selectivity and efficiency Related long analysis time Large amounts of expensive and toxic organic solvents used as mobile phase, such as acetonitrile and methanol. 

Steam distillation has been traditionally used for isolation of essential oils, but some problems were recently reported for example, degradation of certain monoter-penes can occur because of acid-catalyzed hydration. An alternative method, useful for much smaller sample sizes, involves extraction with organic solvents, such as dichloromethane, followed by evaporation of solvent from the extract. However, this approach is not very popular when the obtained extracts are to be used in the cosmetic or food industry, because of the possible toxic organic solvent residue. 

Solvent-free sample preparation techniques attract widespread attention to reduce the use of toxic organic solvents. Solid-phase microextraction (SPME) is a solvent-free technique for sample preparation that can integrate sampling, extraction, concentration, and sample introduction into single step, resulting in high sample throughput. 

Recoidy, flie reducticxi of the amount of toxic organic solvent, such as toluene and xyloie has been attracting much attention for pesoving the Inologically mild environm The developnent of a new... 

Minimization of toxic organic solvents with high vapour pressure, and reduction in typically large volumes... 

The total content of oils, fats and waxes on fabrics can be extracted with 1,1,1-trichloroethane using the Soxhlet extractor. By comparing the fabric weight before and after extraction, the weight percentage of oils, fats and waxes can be easily calculated. It was reported that supercritical CO can be used instead of the toxic organic solvent to extract the commercial finishes from polyester, nylon and polypropylene fibres. ... 

To evaluate the possible electrochemically induced cyclization of haloamides to P-lactams, avoiding the use of toxic organic solvent, the behaviour of haloamides has been investigated in previously electrolyzed RTILs. 

Recently, supercritical fluid extraction (SFE) has been utilized for extraction and cleanup of biological samples. The procedure is quick and avoids the use of flammable or toxic organic solvents (Anitescu and Tavlarides 1998 Djordjevic et al. 1994). Packed-column GC techniques are still widely used however, HRGC has made it possible to achieve better separation of PCB congeners for quantitation (Ballschmiter and Zell 1980 Mullin et al. 1984). 

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