Laboratory extraction

Definition and verification of the process parameters when making the transition from laboratory measurements to a laboratory extraction system and ultimately to a pilot extraction plant, are reported in [471 - 473] and will be discussed below as an example of the process development. 

As with sampling, laboratory extraction equipment must be clean. In addition, extraction equipment must be compatible with the analyte of interest. It also must not add any of the analyte or an interfering analyte to the sample during extraction. This is particularly important because of the low levels of analyte being determined and because most laboratories will not have new, disposable equipment. 

Analytical techniques to evaluate potential lubricating oil stocks are essential to a refiner s planning program. When sulfuric acid was the sole chemical used to refine burning oils and lubricants, it was a simple matter to carry out acid-treating experiments on a small scale in the laboratory, and results so obtained were quite reliable. With the advent of solvent treating, analytical techniques were developed which consisted of single or multiple-batch laboratory extractions in conjunction with correlations based on plant experience (17). 

SCFs are widely used in small-scale laboratory extraction and analysis and are already established for large-scale extraction of caffeine from coffee, flavors from hops, and many other such uses with plant sizes up to 50,000 tons per year throughput. A Philip Morris semicontinuous denicotinization plant is said to employ pressure chambers of 1.5-m diameter and 5-m height. The outlet gas is passed through activated carbon and recycled. ... 

Steinberg et al. (1987) studied the persistence of 1,2-dibromoethane (EDB) in soils and found that low amounts of the organic were released with time, particularly if EDB had not been freshly added to the soil (Fig. 6.3). They suggested that the slow release rate was due to EDB being trapped in soil micropores where release is influenced by extreme tortuosity and/or steric restrictions. It was estimated that based on a radial diffusion model, 23 and 31 years would be required for a 50% equilibrium in EDB release to occur from two Connecticut soils. The previous studies point out that while sorption of pesticides is usually rapid and often reversible in the laboratory, extraction from field soils is extremely slow and often requires multiple extractions or even chemical dissolution of the soil matrix. 

To apply IRS, one needs to know i, of the samples. Extraction of optical properties has been studied by many researchers.69-73 The majority of methods are based on diffusion theory or variants of it. Our laboratory extracts optical properties from biological tissue routinely in other wavelength ranges, and a similar method could be employed for this purpose.73... 

More than seven replicates may be analyzed however, all of the obtained results must be used in the calculation, unless there is a well-justified reason to discard any of them. MDLs are specific to a given matrix, method, and instrument, and greatly depend on the analyst s technique. The better the analytical precision, the lower the calculated value of the MDL. Laboratories are required to perform MDL studies at least once a year (APHA, 1998 EPA, 1999d). However, the MDLs may be determined more often if there is a change in the laboratory extraction, analysis, or instrumentation. For trace element analyses, the MDL studies are performed in reagent water only, as a metal-free solid matrix that would successfully emulate natural soils does not exist. 

In the tenth official proficiency test, five laboratories did not find divinyl sulfoxide (CAS 1115-15-7) in the decontamination solution sample Dl The chemical should have been recovered from the organic extract of the sample. Concentration of the extract, if undertaken, could have helped two laboratories identify this chemical. In one laboratory, false sample preparation was the probable reason for missing it. The laboratory extracted the sample with dichloromethane, evaporated the extract to dryness, dissolved the evaporation residue, and finally sily-lated it. Usually, organic solvents should not be evaporated to dryness in the recovery of a volatile chemical, and this might be the reason for missing the chemical. Perhaps for this same reason the laboratory missed ethyl 2-methoxyethyl methylphospho-nate (CAS 170082-62-9) in the Dl sample. 

In the fourth official proficiency test, two laboratories failed to find propyl propylphosphonate (CAS 21921-97-1) and 0-propyl propylthiophos-phonate (CAS registry number unknown) in the water sample. The laboratories followed the ROPs but with slight modifications. One laboratory cation exchanged a portion of the water sample, and after evaporating it to dryness, silylated the residue with 1 % ferf-butyldimethylchlorosilane (CAS 18162-48-6)/MTBSTFA (10%) in toluene. The other laboratory extracted a portion of the water sample with dichloromethane, evaporated the water phase to dryness, and dissolved the evaporation residue in diazomethane/ether solution. Another portion of the water sample was extracted with ethyl acetate and evaporated to dryness and the evaporation residue was dissolved in acetone. The acetone solution was then itself evaporated to dryness and silylated with BSTFA/pyridine in acetonitrile. A third portion of the water sample was adjusted to the same pH as the blank water sample and extracted with dichloromethane. After that, the pH was reduced... 

L. C. Craig and D. Craig, Laboratory extraction and countercurrent distribution . 

TABLE 5. Nonpolar Acyl Lipid Composition of Laboratory Extracted Wheat Germ Oil. ... 

Complete information is important in order to assist in the initial selection of container closure components, design laboratory extraction studies for components, and to establish a linkage, or correlation, between potential leachables (i.e., extractables) and observed leachables in a particular drug product. Such a correlation is required by regulatory guidances for certain dosage forms. ... 

FIGURE 9.3 Scheme for laboratory extraction of pectins. With permission from Voragen et al. (1995). 

For special cases such as these, and also in some of the earlier CSIRO survey work, laboratory extraction and titration was employed to estimate alkaloid content results were expressed as percentage of dry plant material assuming a mean molecular weight of 3(X) 119, 20. Quantitative determination was also used in the survey of Solarium species for alkaloids, a colorimetric procedure being applied which was based on solasodine as the standard [23]. In addition, a GLC method was developed by CSIRO workers for assaying pyrrolizidine alkaloids [124] vicinal hydroxyls were first converted to the corresponding alkyl boronate derivatives and other hydroxyls protected by trifluoroacetylation, then the derivatised alkaloid mixture was separated on a chiral-phase column. 

Most laboratory extractions are done wiith a separatory funnel and done one or more times, changing the extracting solvent each time. These are called batch extractions. For the following equations, let D = distribution ratio A = amount of solute originally present X = amount not extracted volume of water and V = volume of organic. 

However, most laboratory extraction problems involve extractions of a limited amount of sample - a batch extraction. The apparatus described in this chapter are simple, efficient, and economical for laboratory use and require small volumes of solvent. Small solvent volumes are advantageous because of (1) lower initial solvent costs, (2) less time spent removing the solvent when the extraction is finished, and (3) less solvent to worry about disposing of according to EPA regulations. 

A.C.Sm., gave a positive field test for alkaloids (1), but laboratory extraction failed to give significant amounts of alkaloid. 

In the rotary annular contactor [D2, L2, T2] shown schematically in Fig. 4.27 [T2], the organic and aqueous phases flow countercurrently by gravity in the annular space between a rotating itmer cylinder and a stationary outer cylinder. Taylor-instability vortices generated in the annulus promote dispersion and interfacial area. This is one of the simplest of the mechanically a tated contactors, and it has been developed for possible application to fuel reprocessing. In laboratory extractions of uranium from nitric add with TBP in kerosene, Davis [D2] obtained values as low as 7.5 cm for the column hei t equivalent to a theoretical stage. The rotor speed varied from 1200 to 2000 r/min, with annular widths of 0,1 to 0.35 cm and a stator diameter of 2.2 cm. The residence time per theoretical stage was 10 s or less. 

Ayres, A.L. J.J. Dooley. Laboratory extraction of cottonseed with various petroleum hydrocarbons, J. Am. Oil Chem. Soc. 1948,75, 372-379. 

Massoia essential oils prepared from barks of various origins were analyzed after laboratory extraction. Table I summarizes the compositional analysis... 

The rare earth oxides obtained as a by-product from the commercial extraction of monazite have long served as starting materials for the preparation and purification of compounds of the rare earths. While such residues are still readily available, they are becoming of greater value industrially and, furthermore, it is often difl cult to obtain the desired complete details of the large scale extraction processes. For these reasons the laboratory extraction of monazite is more often carried out at the present time than formerly. 

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