Solvent extraction of amino acids

Smirnova, S.V, Torocheshnikova, I.I., Formanovsky, A.A., Pletnev, I.V, Solvent extraction of amino acids into a room temperature ionic liquid with dicyclo-hexano-18-crown-6. Anal. Bioanal. Chem., 378,1369-1375,2004. 

Svetlana V. Smirnova was born in Yartsevo, Smolensk region, Russia. She graduated from MSU Chemistry Department, having specialization in analytical chemistry. She holds MS and PhD degrees from MSU. Her PhD thesis was devoted to the solvent extraction of amino acids. She works at the MSU Chemistry Department as an assistant professor (since 2002) and an associate professor (since 2005) giving the lectures and practice courses in analytical chemistry. Her scientific interests lie in the area of application of ionic liquids in extraction processes. She is the coauthor of more than 20 scientific publications. 

Micellization of R4N" A is also a problem in the organic phase. Such anion exchange is also a powerful technique used in the solvent extraction of amino acids under appropriate pH conditions so that the amino acid (Am) is in a form (Am ) (see Section 5.2.3.1.2) ready for anion exchange, for example using a quaternary ammonium compound ... 

The distribution ratios obtained were compared to the corresponding distribution ratios between water and Toctanol. The authors also calculated solvent parameters of [C4Cilm][PFg] (Section 9.3). It was shown that phenolate-ion associates with [C4CiIm][PFg] more strongly than other ions. The authors also mention the possibility of extraction of amino acids into [C4CiIm][PPg] in the presence of crown ether dibenzo-18-crown-6, though at rather moderate efficiency. 

The above consideration of the similarity and dissimilarity of ILs and conventional extraction solvents ignores one particularly striking feature of ILs. In sharp contrast to common solvents immiscible with water, ILs are capable of ion exchange. We exemplify this very important ability by considering the extraction of amino acids on the basis of our work [24],... 

The most interesting point is that extraction of amino acids into IL occurs without addition of a counterion. Typically, for amino acid extraction into conventional solvents (including extraction with crown ether), a hydrophobic counterion is required. Moreover, in most cases, even the presence of such a counteranion does not provide an efficient recovery. 

Extraction is an essential step when analyzing solid samples. In some cases homogenization with a solvent suffices, but in others the sample must first be coimninuted. Water, solutions of acetic acid or sodium chloride, or more complex saline solutions are used as solvents. Mixtures of water and methanol or water and ethanol are also employed. The choice of solvent depends on the degree of selectivity desired in the extraction and whether the extraction yield is intended for quantitative analysis. Optimization of the extraction procedure is required in all cases, to fit the nature of the sample to be analyzed and the range of molecular weights of the peptides to be separated. For example, water has been used as the extraction solvent for cheese (33) and legumes (34). Saline solutions have been utilized to extract peptides from meat (35-38) and flour (39,40). Benedito de Barber et al. (41) examined differences in the extractability of amino acids and short peptides in various solvents (1M acetic acid, 70% ethanol, and distilled water) they concluded that extraction with 1M acetic acid yielded the maximum amino acid and peptide contents. 

In polar solvents, the structure of the acridine 13 involves some zwitterionic character 13 a [Eq. (7)] and the interior of the cleft becomes an intensely polar microenvironment. On the periphery of the molecule a heavy lipophilic coating is provided by the hydrocarbon skeleton and methyl groups. A third domain, the large, flat aromatic surface is exposed by the acridine spacer unit. This unusual combination of ionic, hydrophobic and stacking opportunities endows these molecules with the ability to interact with the zwitterionic forms of amino acids which exist at neutral pH 24). For example, the acridine diacids can extract zwitterionic phenylalanine from water into chloroform, andNMR evidence indicates the formation of 2 1 complexes 39 such as were previously described for other P-phenyl-ethylammonium salts. Similar behavior is seen with tryptophan 40 and tyrosine methyl ether 41. The structures lacking well-placed aromatics such as leucine or methionine are not extracted to measureable degrees under these conditions. 

The amino acid analyser using fluorescamine as the detecting reagent has been used to measure 250 picomoles of individual amino acids routinely [262], and dansyl derivatives have been detected fluorometrically at the 10 15 M level [260]. Where the amounts of amino acid are high enough, the fluorescamine method, with no concentration step, can be recommended for its simplicity. At lower concentrations, the dansyl method, with an extraction of the fluorescent derivatives into a non-polar solvent, should be more sensitive and less subject to interferences. For proteins and peptides, the fluorescamine method seems to be the most sensitive available method. 

Amino acids Solvent extraction of 2,4-dinitro phenol AAS and TLC [267]... 

The potential for the preservation of lipids is relatively high since by definition they are hydrophobic and not susceptible to hydrolysis by water, unlike most amino acids and DNA. A wide range of fatty acids, sterols, acylglycerols, and wax esters have been identified in visible surface debris on pottery fragments or as residues absorbed into the permeable ceramic matrix. Isolation of lipids from these matrices is achieved by solvent extraction of powdered samples and analysis is often by the powerful and sensitive technique of combined gas chromatography-mass spectrometry (GC-MS see Section 8.4). This approach has been successfully used for the identification of ancient lipid residues, contributing to the study of artifact... 

Practically motivated, the aim was to develop methods for recovery and determination of amino acids in the context of analytical chemistry and biotechnology. Amino acids are hydrophilic compounds, which therefore are difficult targets for conventional solvent extraction. Extraction to an organic solvent may be enhanced by the addition of lipophilic cationic or anionic extractants, forming extractable complexes with amino acids, or by the use of macrocyclic compounds, which form stable hydrophobic host-guest complexes. The most popular reagents from the latter group are crown... 

High distribution ratios and almost quantitative recovery were observed for all amino acids. In contrast to conventional solvents, the extraction of the most hydrophilic amino acids such as Gly is quantitative. Recovery of Trp, Leu, Ala, Gly, Lys, and Arg is 96, 93, 92, 95, 94, and 92%, respectively. Also, amino acids, including highly hydrophilic, can be extracted with high efficiency from the mixture. For example, the recovery of Trp, Val, Gly from their equimolar mixture is equal to 99, 94, and 93%, respectively. Extraction was performed by adding 3 mL of IL with crown ether concentration 0.10 mol L with a 3 mL aqueous solution of amino acids (5 10 mol/L each 1.8 pH) and shaking for 15 min. 

FDNB reacts with all free -NH2 groups, including e-amino groups. Following acid hydrolysis of the dinitrophenylated protein, a separation of the dinitrophenylated N-terminal amino acid from the rest of the hydrolysis products can be achieved by organic solvent extraction of the hydrolysate. A more modern procedure utilizes dansyl chloride instead of FDNB. This method requires less protein, because dansylated amino acids can be identified via fluorescence measurements. 

Solvent extraction has long been established as a basic unit operation for chemical separations. Chapter 7 summarizes the effects of temperature, pH, ion pairs, and solvent selection on solvent extraction for biomolecules. Solvent extraction of fermentation products such as alcohols, aliphatic carboxylic acids, amino acids, and antibiotics are discussed. Enhanced solvent extraction using reversed micelles and electrical fields are also discussed. Solvent-extraction equipment and operational considerations are adequately covered in this chapter. 

Solvent extraction of penicillin from fermentation broths has been well documented in the literature. Penicillin G and penicillin V can be efficiently extracted with amyl acetate or butyl acetate at pH 2.5-3.0 and at 0° to 3°C.33 Schiigerl1 systematically reviewed solvent extraction of different forms of penicillin from fermentation broths. Figure 1 shows an integrated process for the extraction of penicillin G from clarified broth of Penicillium chryso-genurn fermentation.1 Penicillin G is converted to 6-amino penicillanic acid and phenylacetic acid at pH 8 in a 10 L Kiihni extractor by penicillin G-amidase immobilized in an emulsion liquid membrane. The 6-amino penicillanic acid is subsequently converted to ampicillin at pH 6 and the enzyme is recycled. 

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