Ion-pair Extraction Research Articles

Determination of aromatic sulfonates in coastal water by on-line Ion-pair solid-phase extraction/ion-pair liquid chromatography with UV detection

A method for determining aromatic sulfonates in sea water is presented. Ion-pair solid phase extraction is coupled on-line to ion-pair liquid chromatography with UV detection. In the enrichment step, the recoveries from 100 mL of sea water were higher than 65% for most analytes. Linearity was good and detection limits were between 0.02 and 1 μgL−1. The repeatability of the method, expressed as % of relative standard deviation (n=3) was between 1 and 15%. The method was checked in coastal water near the commercial port of Tarragona, where effluents from the petrochemical industry are discharged. All the samples taken were found to contain 2-naphthalenesulfonate.

Synthesis, structure, and extraction behavior of 4,5′,4″,5‴-tetra-tert-butyltetrabenzo-24-crown-8 †‡

Isomerically pure 4,5′,4″,5‴-tetra-tert-butyltetrabenzo-24-crown-8 was synthesized by a route that eliminates any need for isomer separation. Its structure was determined using single crystal X-ray diffraction methods. Since the observed saddle-shaped conformation of the crown ether is the same as previously reported for the closely related tetrabenzo-24-crown-8, the presence of the peripheral tert-butyl groups has no apparent effect on ring structure. This structure experiences few intermolecular interactions beyond London forces, suggesting it represents a low energy conformation. Liquid–liquid distribution behavior of CsNO3 and CsClO4 between water and 1,2-dichloroethane (1,2-DCE) containing 4,5′,4″,5‴-tetra-tert-butyltetrabenzo)-24-crown-8 was investigated. Equilibrium constants corresponding to the extraction of ion pairs and dissociated ions, formation of the caesium complex, and dissociation of the ion pairs in water-saturated 1,2-DCE at 25 °C were obtained from equilibrium modeling using the SXLSQI program. 4,5′,4″,5‴-Tetra-tert-butyltetrabenzo-24-crown-8 exhibits stronger caesium binding and a similarly low tendency towards ion-pairing, in comparison with the previously characterized isomeric 4,4′- and 4,5′-di-tert-octyltetrabenzo-24-crown-8 ethers.

The effect of hydrophobic picrate on the extraction and separation of lanthanides(III) with carbamoylmethylene phosphine oxide

The effect of a hydrophobic anion, such as picrate (pic−), on the extraction and separation of Ln(III) ions with a carbamoylmethylene phosphine oxide (CMPO) from aqueous nitric acid solutions into benzene has been examined in the present study. The metal extraction with the CMPO was greatly enhanced by adding a small amount of pic−, which did not coordinate with the metal ions but only played the role of a counter-anion in the ion pair extraction. Furthermore, the separation of the Ln(III)-series was also improved, which is a great advantage of the anion effect: On the contrary, a synergism by using two extractants, both of which can coordinate with a metal ion, generally decreases such selectivity. From analyses of the distribution data of Ln(III) ions and picric acid, the mechanism of the cooperative effect was clarified. The strong cooperative effect originates from the difference in the hydrophobicity between pic− and NO3−. Indeed, the Eu(III)–CMPO complex cation paired with pic− was much less hydrated than that paired with NO3−; besides, the binding number of CMPO to the Ln(III) ions also seemed to be affected by the hydration. From these results it is concluded that the metal ions can be dehydrated by the effect of hydrophobic pic−, to a great extent, when its ion pairs are formed. This can be the origin of the great enhancement of the extractability by adding pic−. Metal dehydration can also produce the improved selectivity for the Ln(III) ions, i.e., the coordination of the CMPO can be performed more effectively with much fewer water molecules hydrated to the metal ions, and, thus, the inherent selectivity of the extractant can be exhibited more clearly. Metal dehydration can be induced under the influence of pic−, which is quite inert in coordination, electrostatic interaction, and hydration properties.

Separation of chromium(VI) and chromium(III) with crown ether by means of ion-pair extraction.

A new method for the separation of chromium (VI) and chromium (III) with dicyclohexyl 18-crown-6 (DC18C6) in 1,2-dichloroethane was developed by means of solvent extraction. In this process, CrVI as HCrO4- was extracted as an ion-pair complex with the potassium-crown ether complex cation in the organic phase within 1 min. The extracted species was ascertained to be [K(DC18C6)]+ · [HCrO4]-. When mixtures of CrVI and CrIII were extracted under the optimum condition, CrVI alone was extracted quantatively, whereas CrIII remained in the aqueous phase. After extraction, CrVI in the organic phase was quantatively back-extracted by a 0.1 M NH3 solution. Then, each of the concentrations of CrVI and CrIII could be determined by means of inductively coupled plasma atomic emission spectromrtry (ICP-AES). Cations, such as iron (III), zinc (II) and cadmium (II), interfered with this extraction. The present method was applied to recover CrVI trace in the presence of CrIII in real samples, and clarified to be applicable to CrVI determination in natural water samples.

Ion-Pair Extraction and Flame Atomic Absorptiometric Determination of Copper in Standard Reference Materials

The ion-pair extraction of univalent copper with 3,6-dithiaoctane in the presence of each of 15 univalent anions into a small volume of chloroform at a pH of less than 7 was studied. Of these anions, picric acid, Bromothymol Blue, and cobalt(III)-dihydroxyazobenzene complex gave a quantitative extraction of copper (>99%) and Bromocresol Green, EO, PO, and Co-5-Br-PAPS complex a constant, but a slightly lower, extraction (85–95%) at their corresponding pH ranges, respectively. The direct nebulization of 50 μL of the chloroform extract into a fuel-lean air–acetylene flame gave a sensitive signal height without any background correction from chloroform. The present method was successfully applied to the determination of copper in three standard botanical, one standard zoological, and four standard geological reference materials.

Extractive spectrophotometric methods for determination of diltiazem HCl in pharmaceutical formulations using bromothymol blue, bromophenol blue and bromocresol green

Three simple and sensitive extractive spectrophotometric methods have been described for the assay of diltiazem hydrochloride either in pure form or in pharmaceutical formulations. The developed methods involve formation of coloured chloroform extractable ion-pair complexes of the drug with bromothymol blue (BTB), bromophenol blue (BPB) and bromocresol green (BCG) in acidic medium. The extracted complexes showed absorbance maxima at 415 nm for all three methods. Beer's law is obeyed in the concentration ranges 2.5–20.0, 2.5–10.0 and 2.5–12.5 μg ml −1 with BTB, BPB and BCG, respectively. The methods have been applied to the determination of drug in commercial tablets and capsules. Results of analysis were validated statistically and through recovery studies.

Ion-Pair Extraction and “One-Drop” Flame Atomic Absorptiometric Determination of Silver in Sargasso

Ion-pair extraction of silver with 3,6-dithiaoctane in the presence of a univalent anion into a small volume of chloroform at pH less than 6 was studied. Univalent anions tested were 5 inorganic and 9 colored organic anions and 2 cobalt complex anions. Of these anions, perchlorate, tetraphenylborate and picrate anions and three alkyl oranges, Bromocresol Green, Bromothymol Blue, 5-Br-PAPS and cobalt-dihydroxyazobenzene complex gave a quantitative extraction (>99%) of silver. The direct nebulization of 50 μL of the chloroform extract into a fuel-lean air-acetylene flame gave a highly sensitive signal intensity without any background correction from chloroform. The present method was applied to the determination of silver in a certified botanical sample, NIES-CRM No. 9 Sargasso. The results were very satisfactory and reproducible.

Interpretation by the Solvophobic Theory on the Linear Additive Representation of the Logarithm of Ion-Pair Extraction Constant with Individual Contributions of Cation, Anion, and Organic Solvent

A theoretical basis was given for the linear additive representation of the logarithm of ion-pair solvent extraction constant (Kex) in terms of logarithmic values of three individual extraction constants (Kcation, Kanion, and Ksolvent) for cations, anions, and organic solvents constituting ion-pair extraction systems. The differences in extractability between cations and between anions were quantitatively discussed according to the thermodynamic cycle model of 1:1 ion-pair extraction. The increment of log Kcation and log Kanion of hydrophobic ions is explained by taking the increment of the free energy change of the hydration (ΔGhyd) of the ions into account. The order of the extractability of inorganic cations and anions was also interpreted using literature data of ΔGhyd of each inorganic ion. The free energy change of the solvation of a hypothetical ion-pair having a shape of spherical was calculated on the basis of the solvophobic theory. The difference in extracting powers of some extracting organic ...

A case of suicide by intravenous injection of pancuronium

This report details a suicide by pancuronium bromide injection by a 31-year old female anesthesiologist. Pancuronium bromide was identified in the blood and brain by means of ion-pair extraction followed by thin-layer chromatography, spectrophotometry and electrospray ionization/tandem mass spectrometry. After this positive identification, the levels of pancuronium were carefully quantified by spectrophotometry: 1.05 mg/ml in the blood and 0.51 mg/g in the brain. The cause of death was judged to be asphyxia due to respiratory muscle paralysis caused by pancuronium.

Determination of histamine in port wines and grape juices by ion-pair extraction and stable isotope dilution GC-MS

An isotope dilution, GC-MS method for the quantitation of histamine in wines and grape juices was assayed. This method includes isolation of histamine and its, deuterated analogue [α,α,β,β-2H4]histamine, used as the labelled internal standard, by ion-pair extraction with bis-2-ethylhexylphosphate, conversion to the volatile derivative: tris-pentafluorobenzyl-histamine, capillary GC separation and measurement of the abundance ratio of the (M-181)+ ions from labelled and unlabelled derivatives.

REACTIVE EXTRACTION OF BETA-LACTAM ANTIBIOTICS: IR SPECTROSCOPIC STUDIES

Infrared spectroscope study on reactive extraction of Cephalosporin-C (CPC) and 6-Aminopenicillanic acid (6-APA) with secondary and tertiary amines and a quaternary amine salt as the extractants in butyl acetate as the diluent has been reported. The study aims at analysing the chemical interaction involved in the complexation of the molecules with the extract-ant and the reaction stoichiometry. Amberlite LA-2, Trioctylamine and Aliquat-336 (Tricaprylyl methyl ammonium chloride) were used as the extractants. The results of experimental extraction equilibrium study and spectroscopic analysis indicate the formation of (1:1) complex vie ion-exchange reaction of CPC and 6-APA with Aliquat-336. The ion-pair extraction with Amberlite LA-2 and Trioctylamine exhibited non-stoichiometric complexation in accordance with experimental observation on equilibrium relationship

Combined ion-pair extraction and gas chromatography–mass spectrometry for the simultaneous determination of diamines, polyamines and aromatic amines in Port wine and grape juice

An accurate and very sensitive method which allows for the simultaneous determination of the diamines (1,3-diaminopropane, putrescine and cadaverine), of the polyamines (spermidine and spermine), and of the aromatic amines (β-phenylethylamine and tyramine) found in Port wines and corresponding grape juices is presented. Sample clean-up consisted of the extraction of the amines with the ion-pairing reagent bis-2-ethylhexylphosphate dissolved in chloroform followed by a back-extraction with 0.1 M HCl. The hydrochloric extract obtained was dried and the amines were further derivatized with heptafluorobutyric anhydride and analyzed by GC–MS in the selected ion-monitoring mode, with a total run time of 18 min. Under the adopted conditions, the extraction of all the studied compounds was almost complete and the obtained extracts were free of potential interferents present in the samples, namely sugars, and most of the aminoacids and polyphenols. Via the use of a set of five selected internal standards (amphetamine, [ 2H 8]putrescine, 1,7-diaminoheptane, norspermidine and norspermine), the data obtained from the linearity, repeatability and recovery experiments were very good for all the compounds assayed. The corresponding limits of detection were invariably below 10 μg l −1. The method was successfully applied to measure the content of biogenic amines in twelve young and five aged Port wine samples, eleven grape juice samples as well as in ten Portuguese red and white table wines. Results are presented and briefly discussed.

Secondary structure composition of reconstituted subunit b of the Escherichia coli ATP synthase.

Subunit b of the Escherichia coli ATP synthase was isolated by preparative gel electrophoresis, acetone precipitated and after ion-pair extraction redissolved in a buffer either containing n-dodecyl-beta-D-maltoside or sodium cholate. The secondary structure of isolated subunit b was shown to be the same as within the FO complex, but was strongly dependent on the detergent used for replacement of the phospholipid environment. This was shown by an identical tryptic digestion pattern, which was strongly influenced by the detergent used for solubilization. An influence of the detergent n-dodecyl-beta-D-maltoside on the secondary structure of the hydrophilic part of subunit b was also shown for the soluble part of the polypeptide comprising residues Val25 to Leu156 (bsol) using CD spectroscopy. In order to determine the secondary structure of subunit b in its native conformation, isolated subunit b was reconstituted into E. coli lipid vesicles and analyzed with CD spectroscopy. The resulting spectrum revealed a secondary structure composition of 80% alpha helix together with 14% beta turn conformation. These results suggest that subunit b is not a rigid rod-like alpha helix simply linking F1 to FO, but rather provides an inherent flexibility for the storage of elastic energy within the second stalk generated by rotational movements within the F1FO complex.

Equilibrium studies on complexation in water and solvent extraction of zinc(II) and cadmium(II) with benzo-18-crown-6

The formation constants ( K ML) in water of 1:1 complexes of benzo-18-crown-6 (B18C6) and 18-crown-6 (18C6) with Zn 2+ and Cd 2+, the sizes of which are much smaller than the ligand cavities, were determined at 25°C by conductometry. Compared with Cd 2+, the crown ethers form more stable complexes with Zn 2+ although the size of Zn 2+ is less suited for the cavities. B18C6 forms a more stable complex with each metal ion than 18C6. Moreover, the extraction equilibria of these metal ions (M 2+) with B18C6 (L) for the benzene/water system in the presence of picric acid (HA) were investigated at 25°C. The association between L and HA in benzene was examined for evaluating the intrinsic extraction equilibria of M 2+ with B18C6. The extracted species were found to be MLA 2 and ML 2A 2, and the overall extraction constants ( K ex,1 and K ex,2, respectively) were obtained. The values of K ex,1 for these metal ions are almost the same, but the K ex,2 is larger for Zn 2+ than for Cd 2+. The extraction selectivity was interpreted quantitatively by the constituent equilibrium constants, i.e. K ML, the ion-pair extraction constant of ML 2+ with A −, and the adduct formation constant of MLA 2 with L in benzene.

Effect of the Hydrophobic Anion of Picrate on the Extraction of Europium(III) with Diamide

Abstract The effect of the picrate (pic-) ion on Eu(III) extraction with a diamide (da) from aqueous nitric acid (0.001—0.1 mol dm-3) solutions into benzene was clarified on the basis of the stoichiometry of ion-pair extractions by analyzing the distribution data of Eu(III) and picric acid (Hpic). The extraction of Eu(III) with da was extremely enhanced by adding a hydrophobic anion of pic- to the liquid-liquid system. From analyses of the distribution data of Eu(III) and Hpic, it was concluded that the effect of the hydrophobic anion was caused by the extraction of a single ion-pair of [Eu(da)2](pic)3. The nitrate ion had no relation with the cooperative effect of da and pic-, i.e., the extraction of [Eu(da)2](NO3)3, [Eu(da)2](pic)(NO3)2, and [Eu(da)2](pic)2(NO3) was practically negligible as against the [Eu(da)2](pic)3 extraction. The cooperative effect was reduced by an increase in the aqueous HNO3 concentration, which was induced by a decrease in the pic- concentration in the aqueous phase; the dissociation of Hpic into pic- ion was suppressed by an increase in the H+ concentration, and a part of molecular Hpic was extracted into the organic phase. Furthermore, the extraction of Hpic was also enhanced by an increase in the da concentration in the organic phase, which also induced a decrease in the aqueous pic- concentration. This was found to be due to the formation of a 1 : 1 complex between da and Hpic. However, the extraction of the complexes between da and HNO3 was negligible in the acid concentration range in the present study.

Measurement of albuterol in guinea pig serum by high performance liquid chromatography with fluorescence detection

A sensitive, simple and reproducible high performance liquid chromatographic method for detecting and quantifying albuterol in guinea pig serum is described. A structurally related compound, bamethan, was used as an internal standard. The method employs ion-pair extraction with di(2-ethylhexyl)phosphate followed by chromatography on a Zorbax SB C18 reversed-phase column. Fluorescence detection was used to identify the compounds of interest. The calibration curve was linear between 1 and 50 ng/mL albuterol hemisulfate salt (0.83 and 41.50 ng/mL albuterol base), and the limit of detection for a 1 mL sample was 1 ng/mL albuterol hemisulfate salt (0.83 ng/mL albuterol base). Serum levels of albuterol were quantified from guinea pigs that had received the drug by continuous subcutaneous infusion at a dose of 0.2 mg/kg/day for 1, 5 or 10 days, or 10 days followed by a 24 h washout period. Copyright © 2000 John Wiley & Sons, Ltd.

Measurement of albuterol in guinea pig serum by high performance liquid chromatography with fluorescence detection.

A sensitive, simple and reproducible high performance liquid chromatographic method for detecting and quantifying albuterol in guinea pig serum is described. A structurally related compound, bamethan, was used as an internal standard. The method employs ion-pair extraction with di(2-ethylhexyl)phosphate followed by chromatography on a Zorbax SB C18 reversed-phase column. Fluorescence detection was used to identify the compounds of interest. The calibration curve was linear between 1 and 50 ng/mL albuterol hemisulfate salt (0.83 and 41.50 ng/mL albuterol base), and the limit of detection for a 1 mL sample was 1 ng/mL albuterol hemisulfate salt (0.83 ng/mL albuterol base). Serum levels of albuterol were quantified from guinea pigs that had received the drug by continuous subcutaneous infusion at a dose of 0.2 mg/kg/day for 1, 5 or 10 days, or 10 days followed by a 24 h washout period.

Novel dual-host approach in ion pair extraction: a simple tripodal nitrate host facilitates CsNO3 transfer to 1,2-dichloroethane by a large crown ether

The readily available benzene-1,3,5-tricarboxamide 1 enhances CsNO3 extraction by tetrabenzo-24-crown-8 via hydrogen bonding to the nitrate anion, as demonstrated by NMR and electrospray ionization mass spectrometry.

Prediction of the carrier-mediated cation flux through polymer inclusion membranes via fundamental thermodynamic quantities: complexation study of bis(dodecyloxy)calix[4]arene-crown-6 with alkali metal cations

In a systematic study of alkali metal cation transport through a polymer inclusion membrane (PIM) with calixcrown carriers, a model that postulates diffusion-limited flux successfully describes PIM transport behavior. The model developed herein is based on an ion-pair extraction equilibrium at the PIM interface and provides a convenient tool for the quantitative understanding and interpretation of the transport data. Cation permeability coefficients can be easily determined and used for the quantitative correlation of fluxes employing a range of aqueous and PIM compositions. The described approach can be readily extended to competitive-transport experiments. Transport of a single cation as well as several cations in a competitive experiment was related to the stability constants of the carrier-metal complexes and the Gibbs energies of ion partitioning between source and membrane phases. The expected dependence of Cs+ ion transport on the Gibbs energy of anion partitioning was validated in a series of 8 univalent anions. Accordingly, the permeability coefficient once determined for a given metal salt, carrier, and PIM provides the basis for the prediction of the transport fluxes under different initial conditions if the thermochemical quantities which govern the complexation and distribution of the metal species into the membrane phase are known or can be estimated. In support of these efforts, a calorimetric study was carried out to obtain thermodynamic parameters for the complexation of bis(dodecyloxy)calix[4]arene-crown-6 with alkali metal ions in acetonitrile.

Determination of perchlorate at trace levels in drinking water by ion-pair extraction with electrospray ionization mass spectrometry.

Perchlorate has been added to the U.S. Environmental Protection Agency's Drinking Water Contaminant Candidate List (CCL). The present work describes the analysis of perchlorate in water by liquid-liquid extraction followed by flow injection electrospray mass spectrometry (ESI/MS). Cationic surfactants, mostly alkyltrimethyl-ammonium salts, are used to ion-pair aqueous perchlorate, forming extractable ion pairs. The cationic surfactant associates with the perchlorate ion to form a complex detectable by ESI/MS. The selectivity of the extraction and the mass spectrometric detection increases confidence in the identification of perchlorate. The method detection limit for perchlorate based on 3.14 sigma n-1 of seven replicate injections was 100 ng L-1 (parts per trillion). Standard addition was used to quantitate perchlorate in a drinking water sample from a contaminated source, and the concentration determined agreed within experimental error with the concentration determined by ion chromatography.