Organic acid separation

The aqueous alkaline extract is heated to ioo° to remove ether and volatile impurities. The solution is then cooled with ice and acidified with 25 per cent sulfuric acid, and the organic acid separated. The water layer is distilled from a 2-1. flask until no more oily solution comes over, The distillate is saturated with salt and the acid layer is separated. This water layer together with the low boiling fraction from distillation of the crude trimethylacetic acid is distilled and the distillate salted out as before. 

Carbohydrates and organic acids separation (e.g., fructose/glucose, citric acid,... 

Here, we review two organic acid separations the first being citric acid from fermentation broth and the second separates saturated from unsaturated free fatty acids. 

Fung, Y.-S., Gong, F., and You, T.-Y. (2004). Sensing beverage tastes from organic acids separated by capillary electrophoresis and assessed by pattern recognition. Chem. Sens. 20(Suppl. B), 480 81. 

Different capillary columns are available for organic acid separation and analysis. In our laboratory, the gas chromatography column in all GC-MS applications is crosslinked 5% phenyl (poly)methyl silicone, 25 m internal diameter 0.20 mm stationary phase film thickness 0.33 pm (Agilent HP-5, DB-5, or equivalent). Several instrument configurations are commercially available, which allow for positive identification of compounds by their mass spectra obtained in the electron impact ionization mode. A commercially available bench-top GC-MS system with autosampler (Agilent 6890/5973, or equivalent) is suitable. Software for data analysis is available and recommended. The use of a computer library of mass spectra for comparison and visualization of the printed spectra is required for definitive identification and interpretation of each patient specimen. 

These results show that sorption is a technical possibility for succinic acid separation. In particular, sorption remains an excellent candidate for in situ separation. However, targets for capacity, regeneration, and concentration were not met in these preliminary studies. Additional process tests focusing on regeneration and succinic acid concentration will be required. Therefore, these and other economic considerations not reported here have favored membrane or crystallization methods such as described in the referenced patents (3,26-28) these approaches were continued in the larger succinic acid fermentation project (29,30). The sorption data are presented as a baseline for other researchers in the examination of organic acid separation schemes. 

Diphenyl carbonate from dimethyl carbonate and phenol Dibutyl phthalate from butanol and phthalic acid Ethyl acetate from ethanol and butyl acetate Recovery of acetic acid and methanol from methyl acetate by-product of vinyl acetate production Nylon 6,6 prepolymer from adipic acid and hexamethylenediamine MTBE from isobutene and methanol TAME from pentenes and methanol Separation of close boiling 3- and 4-picoline by complexation with organic acids Separation of close-boiling meta and para xylenes by formation of tert-butyl meta-xyxlene Cumene from propylene and benzene General process for the alkylation of aromatics with olefins Production of specific higher and lower alkenes from butenes... 

Fig.. . 12. Separation of a range of simple organic acids. Separation conditions 27 cm x 75 pm,. 5.0 s injeaion, 0.5 mM TTAB-5.0 mM phthalate-50 mM MES. pH 5.2.. 50°C, -.5 kV. Reproduced with permission from [19].

Organic acids can be detected in the parts per billion range. With preconcentration, this limit can be further decreased. A typical ion-exclusion chromatogram of organic acids separation is presented in Fig. 1. 

The separation of underivatized VFA is now commonly accomplished on specialty capillary GC columns. These have replaced packed GC columns which were frequently used in the Capillary fused silica columns designed for organic acid separation are of... 

Most environmental samples require some pretreatment, usually in the form of filtration and centrifugation, before these are injected via a sample loop. lEC separation of organic acids is achieved on cation exchange columns which are characterized by their particle diameter, substrate crosslinking, ion exchange capacity, type of functional group, and hydrophobicity. The most commonly used columns are comprised of fully sulfonated, crosslinked divinylbenzene/polystyrene copolymers (e.g., HPICE-AS6 or -ASl, Dionex). However, a comparison smdy found other columns to be equally as effective for organic acid separation. Unmodified silica gel columns... 

GC methods employ an extraction step prior to injection on GCs equipped with polar columns which facilitate organic acids separation. Matrix interferences from inorganic anions, metals, and solvents are mostly eliminated by the extraction step. GC methods used for analysis of rain or air samples should also be suitable for the analysis of groundwater samples. 

For membrane solvent extraction, Schlosser et al. [114] provided a comprehensive review for organic acid separation and recovery. Large-scale utilization of membrane solvent extraction [107,115,116] modules in pharmaceutical/chemical plants is used. Lopez and Matson [115] demonstrated enzymatic resolution of diltiazem precursor using hydrophilic polyacrylonitrile hollow fibers and an aqueous-organic interface on the outside surface of these fibers. Klaassen and Jansen [116] and Porebski et al. [107] illustrated the use/ performances of modules of porous hydrophobic PP hollow fibers in chemical plants achieving aqueous-to-organic and organic-to-aqueous solvent extraction, respectively. 

New ion exclusion columns with bifunctional cation exchange sites offer more selectivity for organic acid separations. 

In general, organic acid separations can be optimized by changing the pH, because the eluent pH influences the degree of dissociation and, consequently, the solute retention. 

Figure 5.17 Effect of soivent addition on organic acid separation. Separator column lonPac ICE-AS6 eluent 0.4mmol/L heptafluor-obutyric acid/acetonitrile flow rate 1 mL/min ...

Figure 7.19 Overlay of seven organic acids separated on Sequant ZIC-pHILIC under gradient conditions. Column dimensions ...

In addition to anion-exchange and ion-exclusion chromatography, organic acids in fruit juices can also be separated by reversed-phase chromatography in the ion-suppression mode. A suitable stationary phase for this type of application is Acclaim OA, a polar-embedded stationary phase optimized for hydrophilic organic acid separations. This column is compatible with 100% aqueous mobile phases and has excellent hydrolytic stability at low pH values. Retention,... 

Sanderson G W, Selvendran R R 1965 Organic acids in tea plants. Nonvolatile organic acids separated on silica gel. J Sci Food Agr 16 251-258... 

The cost of recovery of sucdnic add will be of prime importance in determining whether a cost-effective process will allow succinate-derived chemicals to compete with petrochemicals. Most succinate fermentations need to be run at or near a neutral pH and require the addition of a salt to maintain pH. Removal of the salt to achieve the isolation of the desired add is one of the challenges of developing a low-cost separation process. Various approaches toward the recovery of organic adds have been tried, but it is beyond the scope of this chapter to review organic acid separation technology. Some work has focused specifically on succinic acid and that is what will be covered here. 

Fig. 4.1 Chromatogram of (9-acetylated menthyl esters of organic acids separated on a WCOT glass capillary column (25 mxO.3 mm i.d.) coated with SP-1000, under isothermal conditions (temperatures in parentheses) (a) synthetic / 5-lactic acid (150°C) (b) synthetic / 5-glyceric acid (200°C) (c) / -lactic acid isolated from urine (150°C) and (d) / -glyceric acid isolated from urine (200°C). (Redrawn with modifications from Kamerling etal.y 1977)...

Organic acids separated by paper or thin-layer chromatography can be introduced after elution either directly on an insertion probe or via the GC. 

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