Resin extraction techniques

Isolation. Isolation procedures rely primarily on solubiHty, adsorption, and ionic characteristics of the P-lactam antibiotic to separate it from the large number of other components present in the fermentation mixture. The penicillins ate monobasic catboxyHc acids which lend themselves to solvent extraction techniques (154). Pencillin V, because of its improved acid stabiHty over other penicillins, can be precipitated dkecdy from broth filtrates by addition of dilute sulfuric acid (154,156). The separation process for cephalosporin C is more complex because the amphoteric nature of cephalosporin C precludes dkect extraction into organic solvents. This antibiotic is isolated through the use of a combination of ion-exchange and precipitation procedures (157). The use of neutral, macroporous resins such as XAD-2 or XAD-4, allows for a more rapid elimination of impurities in the initial steps of the isolation (158). The isolation procedure for cephamycin C also involves a series of ion exchange treatments (103). 

The caprolactam obtained must meet die specifications of permanganate number, volatile bases, hazen color, UV transmittance, solidification point, and turbidity in order to be used for repolymerization alone or in combination witii virgin CL.5 Reported CL purification methods include recrystallization, solvent extraction, and fractional distillation. One solvent extraction technique involves membrane solvent extraction. Ion exchange resins have been shown to be effective in the purification of aqueous caprolactam solutions. In one such process,... 

Exudate collection in trap solutions usually requires subsequent concentration steps (vacuum evaporation, lyophilization) due to the low concentration of exudate compounds. Depending on the composition of the trap solution, the reduction of sample volume can lead to high salt concentrations, which may interfere with subsequent analysis or may even cause irreversible precipitation of certain exudate compounds (e.g., Ca-citrate, Ca-oxalate, proteins). Therefore, if possible, removal of interfering salts by use of ion exchange resins prior to sample concentration is recommended. Alternatively, solid-phase extraction techniques may be employed for enrichment of exudate compounds from the diluted trap solution (11,22). High-molecular-weight compounds may be concentrated by precipitation with organic solvents [methanol, ethanol, acetone 80% (v/v) for polysaccharides and proteins] or acidification [trichloroacetic acid 10% (w/v), per-... 

Principles and Characteristics In the Parr bomb extraction technique (see also Section 8.2.1.2), a Teflon-tetrafluoroethylene fluorocarbon resin lined vessel is used for sample containment. A sample (typically 1 g) is heated in a small volume of solvent at T, t, p of choice. 

Headspace solid phase microextraction (HS-SPME). With this extraction technique, it is possible to concentrate volatile compounds thus allowing their detection even at trace levels, as in the case of volatile and semi-volatile terpenes in archaeological findings [7,31]. Chapter 10 outlines how resinous materials are investigated using HS-SPME-GC/MS. 

Mercury was determined after suitable digestion by the cold vapour atomic absorption method [40]. Lead was determined after digestion by a stable isotope dilution technique [41-43]. Copper, lead, cadmium, nickel, and cobalt were determined by differential pulse polarography following concentration by Chelex 100 ion-exchange resin [44,45], and also by the Freon TF extraction technique [46]. Manganese was determined by flameless atomic absorption spectrometry (FAA). 

Toxic nitrophenols (4-nitrophenol, 2-nitrophenol, and 2,4-dinitrophenol) present in air samples are sampled on silica gel or XAD-2 polymeric resin, extracted, and analyzed by the HPLC/DAD technique [240], Nitrophenols are also determined in rain and snow precipitations through HPLC/ UV analysis after SPE [241]. 

A large discrepancy between the two concentration techniques was found for the copper results. The average difference was 72 27 ngl-1. Bruland and Frank analysed the Chelex column effluent by the solvent extraction technique, and found 63 and 135ngl-1 as the copper content for the samples at 25 m and 2500 m, respectively. These values are almost equal to the difference between the Chelex and solvent extraction results. Therefore, they concluded that about 60% of the copper in seawater (unfiltered and unacidified) is not removed by the Chelex technique. As Riley et al. suggested, copper in seawater is not liberated by the Chelex resin because of association with colloids and fine particulates [62]. In order to avoid this error, acidification and heating of seawater is necessary prior to the Chelex treatment. According to the results of Bruland and Franks, acidification and storage followed by solvent extraction appears to be superior to the Chelex resin concentration for the quantitative determination of copper in seawater [15]. Similar problems have been pointed out by Eisner and Mark, Jr. [63] and Florence and Batley [64]. 

C18-bonded silica gel (chapter 2.3.5 64)), Hyphan (chapter 2.3.6 71,72>) tetra-ethylenepentamine plus toluene diisocyanate resin (chapter 2.3.879>), ethylene diamine triacetic add (chapter 2.3.9 85>), and solvent extraction techniques using the systems ammonium pyrrolidine dithiocarbamate/chloroform (chapter 2.3.3 55)), ammonium pyrrolidine dithiocarbamate + diethyldithiocarbamate/Freon TF (chapter 2.3.670)), trifluoroacetone/toluene (chapter 2.3.668)), and dithizone/chloroform (chapters 2.3.7 78) and 2.3.8 80)). 

A useful method for the separation ofhydrazoic acid is by a column extraction technique using a mixed-bed ion-exchange resin, a strongly acidic resin in the [H form], and a weakly basic resin in the (OH" form). All cations and most anions are held on the column while hydrazoic acid runs through the column. Other cations and anions elute as water. Weak acids, e.g., boric, silicic, and carbonic will also run through the column. The technique has not been applied to the analysis of explosive azides however, it has been used for the analysis of alkali azides and for the preparation of standard solutions of hydrazoic acid [18]. 

There are several methods available for the extraction of bile salts from serum or plasma. The most convenient methods utilize some form of liquid-solid extraction. An early procedure involved the anion-exchange resin, Amberlyst A-26 (S8), but considerable time and effort was required to perform column chromatography and to concentrate the eluate from the column. The introduction in 1972 of the neutral resin, Amberlite XAD-2, improved the ease of extracting bile acids and their conjugates from serum samples (M6). Further improvement occurred in 1977 with the description of a batch extraction technique using the related neutral resin, Amberlite XAD-7 (B5). With this technique, serum is diluted in 0.1 M sodium hydroxide to release bile acids from albumin and mixed with resin for 1 hour. After washing the resin in dilute alkali, bile acids are eluted with methanol, which cdn be removed on a rotary evaporator (B5). 

A number of alternative approaches are available as technical solutions for the above-mentioned problems (e.g., Hamer, 1982 Lilly, 1982 Meiorella et al., 1981) vacuum membrane retractive and extractive fermentation, and biphasic processing (Mattiasson, 1983 Reisinger et al., 1987) and ion-exchange resin culture techniques. Experimental tests of dialysis culture processes are described in the literature for ammonium-lactate fermentation of whey (Stieber et al., 1977), and an improved mathematical model was later developed (Stieber and Gerhardt, 1979) incorporating P inhibition. Recently,... 

A key to successful chromatographic analysis lies in proper sample preparation. Ideally, it is preferred to dissolve the sample in a suitable solvent and analyze that solution directly, provided the presence of dissolved polymer does not complicate the chromatographic analysis. These cases are indeed rare. Normally, filtration or precipitation followed by final filtration is desirable to remove interferences in sample components (polymers) and higher-molecular-weight components. This approach works well when the polymers are, first, soluble, and second, can be precipitated with an antisolvent. Less soluble polymers, such as highly crystalline resins, require extraction to remove the components of interest from the resin matrix. Numerous extraction techniques (supercritical fluid extraction, solvent extraction, resin dissolution followed by antisolvent precipitation, etc.) are also available [14]. 

---