Ion-pair extraction —

A. BiAndstritm, Preparative Ion Pair Extraction An Introduction to Theory and Practice, Apotekarsocieteten/HAssle LAkemedel, Stockholm, Sweden, 1974, pp. 155-156. 

The ion pair extraction by flow injection analysis (FIA) has been used to analyze sodium dodecyl sulfate and sodium dodecyl ether (3 EO) sulfate among other anionic surfactants. The solvating agent was methanol and the phase-separating system was designed with a PTFE porous membrane permeable to chloroform but impermeable to the aqueous solution. The method is applicable to concentrations up to 1.25 mM with a detection limit of 15 pM [304]. 

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 ... 

The change in the apparent plQ (poKJ with varying water/organic phase ratios is an effective way to characterize ion-pair extraction (Fig. 16.1). 

Schreuder, R. H., Martijn, A., Poppe, H., and Kraak, J. C., Determination of the composition of ethoxylated alkylamines in pesticide formulations by high-performance liquid chromatography using ion pair extraction detection, /. Chromatogr., 368, 339, 1986. 

Thomas et al. [31] used a colorimetric method for the estimation of miconazole nitrate in creams. The method is based on the ion-pair extraction with bromocresol purple solution and measurement of the solution at 410 nm. 

Zhujun Z., Mullin J.L., Seitz W.R., Optical sensor for sodium based on ion-pair extraction and fluorescence, Anal. Chim. Acta 1986 184 251. 

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 potentially tautomeric side-chain thiol systems exist mainly in the thiol form in liquid solution and in the gas phase, as found by IR and NMR spectroscopy and by a study of ionization potentials.126 Upon alkylation using the ion-pair extraction method, only the S-alkylated compounds were obtained. The synthesis, reactions, and properties of some selenides of thiophene, furan, and selenophene have been reviewed.127... 

The use of basic organic dyes for ion pair extraction-photometric determination has been described.87 After ammonia treatment, an orange-red color with CUS04 and H2O2 (Deniges) can be quantitated.88 A water insoluble violet complex (X max. 620 nm) with 2-picoline-Cu(II) has also been reported.89... 

Ethoxylated alkyl amines in pesticide formulations were separated using two different columns a cyano-modified silica column to determine the alkyl distribution and an amino-modified column to determine the ethylene oxide distribution [88]. The detection, specific for ethoxylated amine, was performed with a post-column ion-pair extraction system and fluorescence detection. 

Determination of two esterquats used as substitution products of DTDMAC, such as diethylester dimethylammonium chloride (DEED-MAC) and diesterquaternary (DEQ) (Fig. 4.2.8) in sewage water samples was carried out by the same ion-pair extraction procedure for the analysis of DTDMAC reported elsewhere [103,111] followed by microbore HPLC-ESI-MS analysis [116] and quantification employing commercial blends. 

There is a recent trend towards simultaneous CE separations of several classes of food additives. This has so far been applied to soft drinks and preserved fruits, but could also be used for other food products. An MEKC method was published (Lin et al., 2000) for simultaneous separation of intense sweeteners (dulcin, aspartame, saccharin and acesulfame K) and some preservatives (sorbic and benzoic acids, sodium dehydroacetate, methyl-, ethyl-, propyl- and isopropyl- p-hydroxybenzoates) in preserved fruits. Ion pair extraction and SPE cleanup were used prior to CE analysis. The average recovery of these various additives was 90% with good within-laboratory reproducibility of results. Another procedure was described by Frazier et al. (2000b) for separation of intense sweeteners, preservatives and colours as well as caffeine and caramel in soft drinks. Using the MEKC mode, separation was obtained in 15 min. The aqueous phase was 20 mM carbonate buffer at pH 9.5 and the micellar phase was 62 mM sodium dodecyl sulphate. A diode array detector was used for quantification in the range 190-600 nm, and limits of quantification of 0.01 mg/1 per analyte were reported. The authors observed that their procedure requires further validation for quantitative analysis. 

Method A ( ion-pair extraction technique) TBA-HS04 (38.4 g, 0.11 mol) is added to aqueous NaOH (2 M, 100 ml) and the mixture stirred at room temperature for 5 min. The aqueous solution is added to the methylene compound (0.1 mol) in CHC1, (100 ml) and the two-phase system is stirred until the aqueous phase is neutral. The organic phase is separated and evaporated. 

A Brandstrom, Preparative Ion Pair Extraction , Apotekarsocieten, Hassle Lakemedel, 1974. 

The first examples of the application of phase-transfer catalysis (PTC) were described by Jarrousse in 1951 (1), but it was not until 1965 that Makosza developed many fundamental aspects of this technology (2,3). Starks characterized the mechanism and coined a name for it (4,5), whilst Brandstrom studied the use of stoichiometric amounts of quaternary ammonium salts in aprotic solvents, "ion-pair extraction" (6). In the meantime Pedersen and Lehn discovered crown-ethers (7-9) and cryptands (10,11), respectively. 

The reaction to form the palladium complex is similar to that reported for amine salts, although here, because a bidentate chelating ligand is used, no chlorine atoms are retained in the complex, and the system is easy to strip. Also, as both reactions involve initial ion pair extraction, fast kinetics are observed with 3-5 min contact time to reach equilibrium at ambient temperature. The extraction conditions can be easily adjusted in terms of acidity to suit any relative metal concentrations and, because the reagent is used in the protonated form, good selectivity over base metals, such as iron and copper,... 

In the case of metal ions present as anionic complexes in the donor phase, solvating or ion-pairing extractants can be used as carriers. Here the metal ions and counterions are cotransported across the membrane from the donor to the acceptor phase. By using a complexing or reducing agent in... 

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