Ion-pair solvent extraction

Tokeshi M, Minagawa T, Kitamori T (2000) Integration of a microextraction system on a glass chip ion-pair solvent extraction of fe(ii) with 4,7-di-phenyl- 1,10-phenanthrolinedisulfonic acid and tri-n-octylmethylammon-ium chloride. Anal Chem 72 1711-1714... 

Hudson, R.J.M., D.T. Covault, and F.M.M. Morel. 1992. Investigating of iron coordination and redox reactions in seawater using 59Fe radiometry and ion-pair solvent extraction of amphiphilic iron complexes. Afar Chem. 38 209-235. 

Hudson, R. J. M., Covault, D. T., and Morel, F. M. M. (1992) Investigations of Iron Coordination and Redox Reactions in Seawater Using Fe Radiometry and Ion-Pair Solvent Extraction of Amphiphilic Iron Complexes, Mar. Chem. 38, 209-235. 

M. Maeda, A. Tsuji, Fluorescence and chemiluminescence determination of steroid and bile acid sulphates with lucigenin by flow injection analysis based on ion-pair solvent extraction, Analyst 110 (1985) 665. 

M. Maeda and A. Tsuji, Fluorescence and Chemiluminescence Determination of Steroid and Bile Acid Sulphates with Lucigenin by Flow Injection Analysis Based on Ion-Pair Solvent Extraction. Analyst, 110 (1985) 665. 

Tokeshi, M., Minagawa, T., and Kitamori, T., Integration of a microextraction system on a glass chip Ion-pair solvent extraction of Fe(II) with 4,7-diphenyl-l,10-phenanthrohnedisulfonic acid and tri- -octylmethylammonium chloride, Ano/yficoZ Chemistry, 72, 1711-1714, 2000. 

Figure 12.3 Schematic of microchannel device for ion pair solvent extraction. Reproduced by permission of the American Chemical Society [2].

To obtain accurate results it is necessary to use reference materials [7] and adequate procedures for the calibration of an ISME [8], The response of the ISME is connected with the stability of the ion pair complex, because the stability of the complex is affected by the solvent used for ion pair complex extraction. In PVC matrix membranes, the PVC and plasticizer mixture plays the same role as the solvent for the ion pair complex, because it affects the stability of this complex. From this point of view, the PVC matrix membrane assures a response value more than 55 mV/decade. The response value of the liquid membrane electrode is generally less than the Nemstian one. Usually it shows responses in the 50-55 mV/decade range. But a response having the 50 mV/decade value assures good accuracy and also the reliability of the analytical information. 

Extraction using ion association (ion-pair). Neutral complexes can be formed through ion association (ion-pair) and extracted from the aqueous solution into an organic solvent. Ion associations with inorganic extracts encompass a wide range of extraction schemes. General sub-groups include... 

For anionic surfactants colorimetric methods utilize the formation of an ion pair between the surfactant anion and a cationic dye. Similarly to two-phase titration, colorimetric determination is based on the fact that the ion pair is extractable into organic solvent, while the dye by itself is not. A characteristic example of the analysis of anionic surfactant is the determination of alkylsulfates and alkyl(aryl)sulfonates as their complex with methylene blue extracted into chloroform [31]. The absorbance of chloroform extract is measured at 625 nm versus chloroform background. This methods allows one to analyze alkylsulfates and alkyl(aryl)sulfonates separately. Alkylsulfates, in contrast to sulfonates, are easily hydrolyzed by hydrochloric acid. The products of hydrolysis do not interact with methylene blue and are not transferred into chloroform. Some other cationic dyes, such as dimidium bromide, can also be used. In fact, the use of the latter allows one to achieve much higher sensitivity than that obtained with methylene blue. 

In ion-pair extraction frequently used anions are halides, thiocyanide, and tributylphosphate. Ion-pairs are extracted from relatively acidic aqueous solutions to relatively polar organic solvents such as alcohols, ethers, esters, and ketones (Table 42). 

One application of solvent extraction in SFA is the determination of anionic surfactants in water, where methylene blue ion pairs are extracted into chloroform. Another is the determination of histamine in blood serum here, interference is removed by extraction into butanol and back-extraction into an aqueous phase prior to the measurement of histamine by the formation of a fluorescent compound with o-phthalaldehyde. 

Key to the current discussion is the ability of transition metab to form charged complexes. As charged and relatively stable entities, complex ions can act as cations or anions and form coordination compounds or tightly associated ion pairs. These ion pairs may be solids, or they may form stable neutral species that can be extracted into an organic solvent such as chloroform. Thb b indeed the basb of the cobalt thiocyanate test for cocaine, in which a pink solution of aqueous cobalt thiocyanate is added, along with hydrochloric acid, to the unknown powder. If cocaine or a related substance, such as procaine, b present, a blue color results. In one modification of the test, thb blue ion pair b extracted into a chloroform layer as further evidence for the formation of a tightly associated ion pair. ... 

Like the two-phase titration methods (Chapter 16), almost all of the colorimetric methods rely on the formation of an ion pair by the anionic surfactant and a cation, in this case a dye. The ion pair is extractible into an organic solvent, while the dye alone is not, so the color of the organic phase is directly proportional to the surfactant concentration. This approach is suitable for determination of low concentrations and has been used most often for environmental analysis. 

Extraction and flotation separation of POMs as ion-pair with a bulky cation of Astrazone Violet (AV) with different organic solvents is investigated. Conditions for separation of dye excess from ion-pair PMo TiO j with polymethine dye AV ai e found. 

An alternative to the formation of neutral metal chelates for solvent extraction is that in which the species of analytical interest associates with oppositely charged ions to form a neutral extractable species.6 Such complexes may form clusters with increasing concentration which are larger than just simple ion pairs, particularly in organic solvents of low dielectric constant. The following types of ion association complexes may be recognised. 

The lipophilicity of the TRISPHAT anion 8 also confers to its salts an affinity for organic solvents and, once dissolved, the ion pairs do not partition in aqueous layers. This rather uncommon property was used by Lacour s group to develop a simple and practical resolution procedure of chiral cationic coordination complexes by asymmetric extraction [134,135]. Selectivity ratios as high as 35 1 were measured for the enantiomers of ruthenium(II) trisdiimine complexes, demonstrating without ambiguity the efficiency of the resolution procedure [134]. 

The measurement of log and log Pi by dual-phase potentiometric titration has been described by Avdeef [33], Briefly, the method is based on the shift in the apparent pK upon addition of the partition solvent In absence of ion-pair extraction, the apparent pK (PoK) is related to the aqueous pK by the equation below ... 

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. ... 

Several extractions are required when the distribution constant is small. The addition -of salts, pH adjustment, ion-pairing reagents, etc., can be used to isprove the distribution of organic solutes into the extracting solvent. 

Extractive alkylation is used to derivatize acids, phenols, alcohols or amides in aqueous solution [435,441,448,502]. The pH of the aqueous phase is adjusted to ensure complete ionization of the acidic substance which is then extracted as an ion pair with a tetraalkylammonium hydroxide into a suitable immiscible organic solvent. In the poorly solvating organic medium, the substrate anion possesses high reactivity and the nucleophilic displacement reaction with an alkyl halide occurs under favorable conditions. 

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