Solvent residue

Solvent extraction removes chlorophyll and other pigments to give a light-colored product but increases processing costs. Furthermore, solvent extraction removes p-carotene and reduces vitamin A activity (89) (see Terpenoids Vitamins). Supercritical CO2 extraction at 30 and 70 MPa (4,350 and 10,150 psi) and 40°C removed 90 and 70% carotene and lutein, respectively, from alfalfa LPC (96). This process avoids organic solvent residues and recovers valuable by-products. 

Supercritical Fluid Extraction. Supercritical fluid (SCF) extraction is a process in which elevated pressure and temperature conditions are used to make a substance exceed a critical point. Once above this critical point, the gas (CO2 is commonly used) exhibits unique solvating properties. The advantages of SCF extraction in foods are that there is no solvent residue in the extracted products, the process can be performed at low temperature, oxygen is excluded, and there is minimal protein degradation (49). One area in which SCF extraction of Hpids from meats maybe appHed is in the production of low fat dried meat ingredients for further processed items. Its apphcation in fresh meat is less successful because the fresh meat contains relatively high levels of moisture (50). 

From the third reactor the polymer is then run into a devolatilising ( stripping ) vessel in the form of thin strands. At a temperature of 225°C the solvent, residual monomer and some very low molecular weight polymers are removed, condensed and recycled. The polymer is then fed to extruder units, extruded as filaments, granulated, lubricated and stored to await dispatch. 

The optimization of empirical correlations developed from the ASPEN-PLUS model yielded operating conditions which reduced the steam-to-slurry ratio by 33%, increased throughput by 20% while maintaining the solvent residual at the desired level. While very successful in this industrial application the approach is not without shortcomings. The main disadvantage is the inherent assumption that the data are normally distributed, which may or may not be valid. However, previous experience had shown the efficacy of the assumption in other similar situations. 

Seed oils and waxes are more commonly extracted by SFE. It is the most suitable technique for non-polar compounds such as oils and waxes instead of other organic solvents, and it avoids the presence of solvent residues after extraction. Both extraction methods, the classical and SFE, stiU need the additional purification step of the extract, increasing the cost of the final product. 

In the following, we write the protic solvents conventionally as SH, where H is the proton and S is the solvent residue. They include many compounds with -OH and >NH groups, also some others (Table 8.1). All these solvents are polar, have... 

Throat cut, almost fatally, by shards of a test tube from which a polymeric residue was being cleared. Explosion apparently almost immediate were there also miscible solvent residues ... 

Many of the properties of a polymer depend upon the presence or absence of crystallites. The factors that determine whether crystallinity occurs are known (see Chapter 2) and depend on the chemical structure of the polymer chain, e.g., chain mobility, tacticity, regularity and side-chain volume. Although polymers may satisfy the above requirements, other factors determine the morphology and size of crystallites. These include the rate of cooling from the melt to solid, stress and orientation applied during processing, impurities (catalyst and solvent residues), latent crystallites which have not melted (this is called self-nucleation). 

One of the most studied technologies is supercritical fluid extraction with SC-CO2. The advantages of SC-CO2 include its low processing temperature, which minimizes thermal degradation the ease of separation with no solvent residue left in the final product and minimization of undesirable oxidation reactions. 

Kimura ET, Ebert DM, Dodge PW. 1971. Acute toxicity and limits of solvent residue of sixteen organic solvents. Toxicol Appl Pharmacol 19 699-704. 

Lesage, S., Jackson, R.E., Priddle, M.W., and Riemann, P.G. Occurrence and fate of organic solvent residues in anoxic groundwater at the Gloucester landfill, Canada, Environ. Sci. Technol, 24(4) 559-566, 1990. 

Changing the pump fluid The interior section will be extracted from the pump and the contaminated pump fluid poured out. The interior section and the pump body are then cleaned with pure petroleum ether (naphtha). The interior section and pump body of mercury pumps should have been cleaned beforehand with a clean brush use a bottle brush for the nozzle bores. Ensure that all the nozzle orifices are properly cleaned. It is advantageous to evaporate all solvent residues in a drying kiln. Then the inside section is inserted once again and the fresh pump fluid is installed through the forevacuum port. It is necessary to ensure that the upper nozzle cover is not moistened with pump fluid Do not install too much pump fluid ... 

Limit tests for solvent residues and other volatile impurities in drug substances. 

The current BP methods for determination of solvent residues in pharmaceuticals remaining from the manufacturing process rely on direct injection of the sample dissolved in a suitable solvent (often water) and are based on packed column GC. Some examples are given in Table 11.4. 

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