Extraction by Ion Pairs

Kotrebai, M., Birringgr, M., Tyson, J.F., Block, E. and Uden, P.C. (1999) Identification of the principal selenium compounds in selenium-enriched natural sample extracts by ion-pair liquid chromatography with inductively coupled plasma - and electrospray ionisation-mass spectrometric detection. Anal. Comm., 36, 249-252. 

D Incan, E., Phase transfer catalysis and extraction by ion pairs. Stereoselectivity of the Horner-Emmons reaction. Tetrahedron, 33, 951, 1977. 

Liquid-liquid extraction by ion-pair formation involves formation of an uncharged species as exemplified below for a case in which a tertiary amine like trioctylamine (TOA) or triisooctylamine (TIOA) is used as the solvent to extract the anionic metal complex represented by B. ... 

Extraction of Sc and that of U are two important examples of liquid-liquid extraction by ion-pair formation brought about in the presence of a mineral acid using a tertiary amine of high molecular weight, nemely, trioctylamine. 

Selectivity of separation in liquid-liquid extraction by ion-pair formation is achieved by making the required variations in parameters like pH used for complexation, the complexing ligand, and concentration of the extractant effected by mixing with differing amounts of a suitable diluent which aids extraction. Most difficult separations, for example, those of acids like malonic, ascorbic, tartaric and citric in Organic Chemistry have been achieved by this separatory technique. 

In the examples considered above, use has been made of liquid anion-exchangers for extraction by ion-pair formation. Use can also be made of liquid cation-exchangers for extraction by ion-pair formation and the mechanism of such an extraction is represented below. 

Recovery and Purification. The dalbaheptides are present in both the fermentation broth and the mycelial mass, from which they can be extracted with acetone or methanol, or by raising the pH of the harvested material, eg, to a pH of 10.5—11 for A47934 (16) (44) and A41030 (41) and actaplanin (Table 2) (28). A detailed review on the isolation of dalbaheptides has been written (14). Recovery from aqueous solution is made by ion pair (avoparcin) or butanol (teicoplanin) extraction. The described isolation schemes use ion-exchange matrices such as Dowex and Amberlite IR, acidic alumina, cross-linked polymeric adsorbents such as Diaion HP and Amberlite XAD, cation-exchange dextran gel (Sephadex), and polyamides in various sequences. Reverse-phase hplc, ion-exchange, or affinity resins may be used for further purification (14,89). 

High-performance liquid chromatography (HPLC) with a micellar mobile phase or with a selective pre-column or reaction detection system has also been used to determine alkylenebis(dithiocarbamaes). ° Zineb and mancozeb residues in feed were determined by ion-pair HPLC with ultraviolet (UV) detection at 272 nm. These compounds were converted to water-soluble sodium salts with ethylenediaminetetra-acetic acid (EDTA) and sodium hydroxide. The extracts were ion-pair methylated with tetrabuthylammonium hydrogensulfate (ion-pair reagent) in a chloroform-hexane solvent mixture at pH 6.5-8.S. The use of an electrochemical detector has also been reported. ... 

Reactions of trident and ambident anions of hydroxy compounds with alkylating reagents were also studied.121 The ion-pair extraction method was found to be superior alkylating agents were methyl iodide (soft) and dimethyl sulfate (hard). Upon alkylation by ion-pair extraction the 5-methyl-substituted selenolene-2-one system gives mainly C-alkylation with the soft acid, methyl iodide, and mainly O-alkylation with the hard acid, dimethyl sulfate. 

The extraction of an anionic surfactant from river water has been performed by ion-pair LLE with the methylene blue cation [15—17] a recovery in river water of 96.7% and a detection limit of 0.05 mg L-1 have been reported. 

M. Puttemans, L. Dryon, and D.L. Massart, Extraction of organic acids by ion-pair formation with tri-iV-octylamine , Anal. Chim. Acta, 1984,161, 221. 

Aboul-Enein and Al-Duraibi (1998) employed dansyl chloride in a fluorescence assay for PUT, SP, SPD, and their acetylated derivatives by ion-pair reverse-phase chromatography. This assay could be applied to the separation of free and acetylated polyamines in biological samples. Dansyl chloride has also been used as the fluorescence reagent in the determination of polyamines in urine by Molins-Legua and colleagues (1999). Derivatization was carried out within the C18 cartridges that were used during the SPE extraction procedure. Recoveries were 80-95% for all four polyamines analyzed and the hmit of detection was 10 ng/ml. 

Finally, another development is the use of A -alkylamides that selectively extract platinum from strong acid media, presumably by ion pair formation between the protonated amide and the chloroanions ... 

Vitamin Bg has been traditionally extracted by using acid hydrolysis (chloridric acid or sulfuric acid) at high temperature followed by enzymatic hydrolysis with takadiastase or phosphatase to release the phosphorilated vitamers. In the 1990s, a rapid method was proposed involving the transformation of all the vitamers into pyridoxol and then analyzed by ion pair chromatography [620], The following researches anyway focused the attention on separation and determination of all the different forms of vitamin B. ... 

Recovery and Purification. The dalbaheptides aie present in both the femieiilalioii broth and the mycelial mass, from wliicli they can be extracted with acetone or methanol, or by raising the pH of the harvested material. A detailed review on the isolation of dalbaheplides has been written. Recovery from aqueous solution is made by ion pair (avoparcin) or butanol (teicoplanin) extraction. 

Clarification of extracts can be accomplished with Carrez reagents (44). Purification has been performed by solid phase or partition. Wu et al. (47) absorbed saccharin onto ODS-4 cartridges and then eluted with methanol phosphate buffer. Puttemans et al. (28,50) extracted saccharin from soft drinks and yogurt by ion-pair extraction with tri-n-octylamine and back-extraction to an aqueous phase with perchlorate. Tereda and Sakabe (48) used cetrimide and Sep-Pak Cl8 in the cleanup of saccharin in coffee drink. The column was preconditioned with methanol, water, and 5 mM cetrimide. The sample, diluted in phosphate buffer pH 3.0 containing cetrimide was poured into the cartridge, washed with water, and eluted with acetonitrile water (1 1, v/v). Moriyasu et al. (40) added n-propylammonium bromide to the extract, passed it through a Bond Elut Cl 8 column, and eluted the sweetener with a mixture of methanol-water (4 6, v/v). The eluate was passed through a Bond Elut SAX column and washed with 0.5% phosphoric acid and water, and the sweetener was eluted with 0.3 N hydrochloric acid. 

R. El Harrak, M. Calull, R. M. Marce and F. Borrull, Determination of naphthalene-sulphonates in water by on-line ion-pair solid-phase extraction and ion-pair liquid chromatography with diode-array UV detection , Int. J. Environ Anal. Chem. 69 295-305 (1998). 

Field, J.A., D.J. Miller, T.M. Field, S.B. Hawthorne, and W. Giger. 1992. Quantitative determination of sulfonated aliphatic and aromatic surfactants in sewage sludge by ion-pair/supercritical fluid extraction and derivatization gas chromatography / mass spectrometry. Anal. Chem. 64, 3161-3167. 

Akyuz, M. and S. Ata. 2006. Simultaneous determination of aliphatic and aromatic amines in water and sediment samples by ion-pair extraction and gas chromatography-mass spectrometry. J. Chromatogr. A 1129 88-94. 

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