Ion-pair Complex Research Articles

Determination of Lomefloxacin Hydrochloride by Ion-pair Complex Formation with Ammonium Reineckate Using Atomic Absorption Spectrometry

Determination of Lomefloxacin Hydrochloride by Ion-pair Complex Formation with Ammonium Reineckate Using Atomic Absorption Spectrometry

Anion Coordination Characteristics of Ion-pair Complexes in Highly Concentrated Aqueous Lithium Bis(trifluoromethanesulfonyl)amide Electrolytes.

We report on the structures of Li-ion complexes in salt-concentrated aqueous electrolytes based on lithium bis(trifluoromethanesulfonyl)amide (LiTFSA), particularly focusing on the anion coordination behavior of the ion-pair complexes in the high concentration region cLi > 3.0 mol dm-3. Quantitative data analysis of the Raman spectra revealed the following. (1) Li ions do not coordinate with TFSA anions at lower cLi (<3.0 mol dm-3) to exist as ion pair-free ions. (2) In the concentrated region (cLi = 3.0 - 4.0 mol dm-3), the TFSA anions coordinate as monodentate ligands (mono-TFSA) with Li ions to form ion-pair complexes and coexist with free TFSA in the bulk. (3) Further increasing the cLi (4.0 - 5.2 mol dm-3) results in both monodentate and bidentate coordination (bi-TFSA) modes of TFSA anions to Li ions, yielding complicated ion-pair complexes in the first coordination sphere. The Walden plots, based on ionic conductivity and viscosity data, implied that the ion-conducting mechanism in the highly salt-concentrated region was considerably different from that in the dilute region (i.e., vehicle mechanism).

Validated spectroscopic methods for the estimation of triamterene in bulk powder and capsule form via derivatization reactions.

Sensitive, simple and specific spectrophotometric and spectrofluorimetric methods were developed for the determination of triamterene in bulk powder and pharmaceutical dosage form. The spectrophotometric method (Method A) is based on the formation of an ion-pair complex with eosin Y in acetate buffered solution of pH3.7 followed by measuring the absorbance at 545nm. The absorbance-concentration plot is rectilinear over the range 3.0-15.0μg/mL with a limit of detection (LOD) of 0.429 μg/mL and a limit of quantitation (LOQ) of 1.031μg/mL. The spectrofluorimetric method (Method B) is based on the reaction of triamterene with 7- chloro-4-nitrobenzo-2-oxa-1,3-diazole (NBD-Cl) in basic solution (pH10) to form a product with high fluorescence measured at 546 nm after being excited at 438 nm. The plot of fluorescence versus concentration is linear within the range 2.0-10.0μg/mL. The suggested methods were applied for the analysis of commercial capsules containing the studied drug with successful results. The results obtained from the proposed method were statistically compared with those of a reported one and revealed good agreement. The presented methods are useful in routine analysis of triamterene in laboratories of quality control.

Controlling Structure Beyond the Initial Coordination Sphere: Complexation-Induced Reversed Micelle Formation in Calix[4]pyrrole-Containing Diblock Copolymers.

A diblock copolymer containing a strapped calix[4]pyrrole-based ion pair recognition subunit has been synthesized via RAFT polymerization. As prepared, the polymer is hydrophobic and devoid of any particular morphological form. However, upon ion pair complexation, the copolymer self-assembles to generate reverse micelles in organic media. The reverse micelles formed in this way may be used to extract alkali cation and cesium halide anion salts from an aqueous source into an organic receiving phase. The polymer proved more effective as an extractant than the corresponding free ion pair receptor.

Determination of Fluoroquinolones in Pharmaceutical Formulations by Extractive Spectrophotometric Methods Using Ion-Pair Complex Formation with Bromothymol Blue.

In this paper, we reported a new, simple, accurate, and precise extractive spectrophotometric method for the determination of fluoroquinolones (FQs) including ciprofloxacin (CFX), levofloxacin (LFX), and ofloxacin (OFX) in pharmaceutical formulations. The proposed method is based on the ion-pair formation complexes between FQs and an anionic dye, bromothymol blue (BTB), in acidic medium. The yellow-colored complexes which were extracted into chloroform were measured at the wavelengths of 420, 415, and 418 nm for CFX, LFX, and OFX, respectively. Some effective conditions such as pH, dye concentration, shaking time, and organic solvents were also systematically studied. Very good limit of detection (LOD) of 0.084 µg/mL, 0.101 µg/mL, and 0.105 µg/mL were found for CFX, LFX, and OFX, respectively. The stoichiometry of the complexes formed between FQs and BTB determined by Job's method of continuous variation was 1 : 1. No interference was observed from common excipients occurred in pharmaceutical formulations. The proposed method has been successfully applied to determine the FQs in some pharmaceutical products. A good agreement between extractive spectrophotometric method with high-performance liquid chromatography mass spectrometry (HPLC-MS) for the determination of FQs in some real samples demonstrates that the proposed method is suitable to quantify FQs in pharmaceutical formulations.

Preparation, Characterization, and In Vivo Evaluation of an Oral Multiple Nanoemulsive System for Co-Delivery of Pemetrexed and Quercetin.

Co-administration of conventional and natural chemotherapeutics offers synergistic anticancer efficacy while minimizing adverse effects. In this study, an oral co-delivery system for pemetrexed (PMX) and quercetin (QCN) was designed based on water-in-oil-in-water nanoemulsion (NE), which is highly absorbable because it enhances the intestinal membrane permeability of PMX and aqueous solubility of QCN. To create this system, an ion-pairing complex of PMX with Nα-deoxycholyl-l-lysyl-methylester (DCK) was formed and further incorporated with QCN into the NE, yielding PMX/DCK-QCN-NE. The results revealed synergistic inhibitory effects on human lung carcinoma (A549) cell proliferation and migration after combined treatment with PMX/DCK and QCN. The intestinal membrane permeability and cellular uptake of PMX/DCK and QCN from the NE were significantly improved via facilitated transport of PMX by the interaction of DCK with bile acid transporters, as well as NE formulation-mediated alterations in the membrane structure and fluidity, which resulted in 4.51- and 23.9-fold greater oral bioavailability of PMX and QCN, respectively, than each free drug. Tumor growth in A549 cell-bearing mice was also maximally suppressed by 62.7% after daily oral administration of PMX/DCK-QCN-NE compared with controls. Thus, PMX/DCK-QCN-NE is a promising oral nanocarrier of PMX and QCN for synergistic anticancer efficacy and long-term chemotherapy.

Validated Analytical Spectrofluorimetric Method for Quantitation of Diphenhydramine HCl in Commercial Dosage Forms

Diphenhydramine HClis a weakly fluorescent drug having tertiary amine group forming ion pair complex with eosin Y in dichloromethane at pH 5 in disodium hydrogen phosphate-citric acid buffer solution. The complex formation was the basis for the development of new analytical method for determination of active diphenhydramine in pharmaceutical formulations. The stoichiometric ratio between diphenhydramine and eosin Y was studied by mole ratio method and found to be 2:1. The ion-pair complex showed maximum fluorescence emission intensity at 554 nm with excitation at 259 nm. The linear dynamic range was obtained in the concentration range of 2-22 µg mL-1 with a linear equation of FI = 0.361 + 13.675 C. The apparent Gibb’s free energy (ΔGº) was calculated and found to be -80.783 KJ mol-1, confirmed the feasibility of the reaction. The proposed method was successfully applied to the determination of diphenhydramine HCl in pharmaceutical formulations and in good agreement with the reference method.

Syntheses, Structures, and Catalytic Activities of the Anionic Heterobimetallic Rare-Earth Metal Complexes Supported by Pyrrolyl-Substituted 1,2-Diimino Ligands.

A series of the anionic heterobimetallic rare-earth metal complexes supported by trans- or chiral pyrrolyl-substituted 1,2-diimino ligands were synthesized in good yields via reactions of [(Me3Si)2N]3RE(μ-Cl)Li(THF)3 with the corresponding 1,2-diimino proligands. Reactions of [(Me3Si)2N]3RE(μ-Cl)Li(THF)3 with 2 equiv of trans-1,2-bis(pyrrol-2-ylmethylene)-1,2-diphenylethanediamine (H2L1) afforded the discrete ion-pair rare-earth metal complexes [Li(THF)4]+[(L1)2RE]- (RE = Sm(5), Dy(6), Er(7)). Reactions of [(Me3Si)2N]3RE(μ-Cl)Li(THF)3 with 2 equiv of ( R, R)-1,2-bis(pyrrol-2-ylmethylene)-1,2-diphenylethanediamine (H2L2) gave the heterobimetallic rare-earth metal complexes (L2)2RELi(THF)2 (RE = Sm(8), Y(9)). When the rare-earth metal is Er, the chiral linear rare-earth coordination polymer {(L2)2ErLi} n (10) was obtained. Reactions of [(Me3Si)2N]3RE(μ-Cl)Li(THF)3 with 2 equiv of trans-1,2-bis(pyrrol-2-ylmethyleneamino)cyclohexane (H2L3) gave the heterobimetallic rare-earth metal complexes (L3)2RELi(THF)2 (RE = Pr (11), Sm(12), Eu(13)). Reactions of [(Me3Si)2N]3RE(μ-Cl)Li(THF)3 with 2 equiv of ( R, R)-1,2-bis(pyrrol-2-ylmethyleneamino)cyclohexane (H2L4) also gave the heterobimetallic rare-earth metal complexes (L4)2RELi(THF)2 (Ln = Pr(14), Sm(15)). All complexes were characterized by spectroscopic methods and elemental analyses, and complexes 5-11, 13, and 14 were further determined by single-crystal X-ray diffraction. The catalytic properties of racemic rare-earth metal complexes on cyanosilylation of ketones were examined, and results showed that the above complexes could effectively catalyze the cyanosilylation of ketones. Chiral rare-earth metal complexes as catalysts for the enantioselective epoxidation of α,β-unsaturated ketones were also examined to afford the chiral epoxides in high yields with moderate enantioselectivities.

Polysulfide Speciation and Electrolyte Interactions in Lithium–Sulfur Batteries with in Situ Infrared Spectroelectrochemistry

Understanding redox mechanisms as well as interactions between redox species and electrolyte is critical for rational design of electrolyte/cathode systems for Li–S batteries. Here, we demonstrate in situ FT-IR with attenuated total reflection (ATR) to monitor both polysulfide (PS) speciation (Sx2–, 2 ≤ x ≤ 8) and triflate anion (electrolyte) coordination state while simultaneously discharging/charging a full battery coin cell. We report the concentration of various PS species as a function of voltage during cell discharge. In addition, we found that molecular-level changes occurred in the electrolyte salt anion in response to PS speciation. During discharge, PS dissolution increases total solute concentration, inducing anion interactions between low coordination state complexes—ion pairs and free ions—to form aggregate complexes. Under fast cyclic voltammetry sweep, less progressive formation of all PSs, due to diffusion limitations, resulted in a higher concentration of aggregates and PSs even upon comp...

Ion-pairbased liquid–liquid extraction of gold(III) from malonate media using 2-octylaminopyridine as an extractant: analysis of alloys, minerals, and drug samples

Liquid-liquid extraction of Au(III) from aqueous sodium malonate medium using 2-octylaminopyridine (2-OAP) as an extractant in xylene was achieved. The current work explored the influence of several experimental parameters such as pH, weak acid concentration, extractant concentration, equilibrium time, stripping agents, and aqueous:organic volume ratio on the extraction of Au(III). The experimental results showed that the Au(III) was quantitatively extracted to about 99.5% by 0.05 M 2-OAP in 0.05 M malonate at 5.0 pH. Ammonia solution was used to strip the gold-loaded organic phase and about 99.5% of Au(III) was reversibly extracted into the aqueous phase. Gold(III) was extracted into the organic phase via formation of ion-pair complex [2-OAPH$^{+}$.Au (C$_{3}$H$_{2}$O$_{4})_{2}^{-}$]. The stoichiometry of the extracted species was 1:2:1 (metal: acid: extractant) determined by slope analysis. The method affords the binary, ternary mixture separation as well as separation of Au(III) from synthetic mixtures and alloys. The method is applicable for the determination and separation of gold from ayurvedic samples and recovery of gold from e-wastes. A reproduction of the method was checked by finding relative standard deviation for n = 5, which was 0.29%, and the limit of detection was 1.08 $\mu $g/mL.

Novel skin penetrating berberine oleate complex capitalizing on hydrophobic ion pairing approach

Berberine hydrochloride (Brb) is a well-known herbal drug that holds a great promise in the recent years thanks to its various pharmacological actions. Currently, Brb is extensively researched as a natural surrogate with evidenced potentiality against numerous types of skin diseases including skin cancer. However, Brb’s high aqueous solubility and limited permeability hinder its clinical topical application. In the current work, to enhance Brb’s dermal availability, hydrophobic ion pairing approach was implemented combining the privileges of altering the solubility characteristics of Brb and the nanometric size that is usually gained during the ion pairing precipitation process. Sodium oleate (SO) was selected as the complexing agent due to its low toxicity and skin penetrating characteristics. Ion paired berberine oleate complex (Brb-OL) was prepared by simple precipitation technique. Brb-OL complex formation was confirmed by differential scanning calorimetry (DSC), infrared spectroscopy (IR), X-ray powder diffraction (XRD) and saturation solubility studies. It was found that Brb-OL complex formed at stoichiometric binding between oleate and Brb had an average particle size of 195.9 nm and zeta potential of −53.6 mV. The proposed Brb-OL showed 251-fold increase in saturation solubility in n-octanol which confirmed the augmented lipid solubility of the complex compared with free drug. Comparative in-vitro release study showed that Brb-OL complex had much slow and sustained release profile compared to that of free Brb. Furthermore, ex-vivo permeation study using rat skin revealed the enhanced skin permeation of ion-paired Brb-OL complex compared with free Brb. In-vivo study on healthy rats confirmed that topical application of hydrogels enriched with Brb-OL had superior skin penetration and deposition than free Brb as revealed by confocal microscope. Conclusively, ion pair formation between Brb and oleate lead to the formation of more lipophilic Brb-OL complex with nanometric particle size which is expected to be a major progressive step towards the development of a topical berberine formulation.

Direct Spectrophotometric Determination of Glimepiride in Pure Form And Pharmaceutical Formulations Using Bromocresol Purple

A simple, direct and accurate spectrophotometric method has been developed for the determination of Glimepiride (GLM) in pure and pharmaceutical formulations by complex formation with bromocresol purple (BCP). The method involves the formation of a yellow ion-pair complex between BCP with glimepiride at pH&lt;3,8; after reacting GLM with Na2CO3 to give C24H33N4H+O5NaS which is extracted by chloroform. The formed complex [GLM]:[ BCP] was measured at lmax 418 nm against the reagent blank prepared in the same manner. Variables were studied in order to optimize the reaction conditions. Molar absorptivity (e) for complex was 20600 L.mol-1.cm-1. Beer’s law was obeyed in the concentration range of 1.226 – 46.608 mg.mL-1 in present of 5.0x10-4 mol/l of BCP with good correlation coefficient (R2= 0.9997). The relative standard deviation did not exceed 3.6%. The limit of detection (LOD) and the limit of quantification (LOQ) were 0.15 and 0.46 mg.mL-1, respectively. The proposed method was validated for specificity, linearity, precision and accuracy, repeatability, sensitivity (LOD and LOQ) and robustness. The developed method is applicable for the determination of GLM in pure and different dosage forms with average assay of 98.8 to 102.0% and the results are in good agreement with those obtained by the RP-HPLC reference method.

Assay of Orphenadrine Citrate in Pharmaceuticals via Extraction-Spectrophotometric Method

An extraction-spectrophotometric technique has been applied and approved for the estimation of orphenadrine citrate in the presence of paracetamol in a binary synthetic mixture and in combined drugs. The procedure is built on the formation of a soluble red colour orphenadrine citrate – eriochrom black T (EBT) ion pair complex at pH 1.40, while the paractamol not paired. The produced red colour ion-pair complex was extracted with chloroform and showed maximum absorption at 509 nm. For quantitative evaluation Beer’s law applied to plot the absorbance against concentration, the relation was a linear in the concentration range of 0.10-6.00 µg/ mL with the molar absorptivity 4.4025 x104 L / mol. cm. The limit of detection and limit quantification were 0.024 µg/ mL, and 0.100 µg/ mL respectively. The intra-assay precision evaluated in terms of % relative standard deviation (RSD) (< 2%). And accuracy was validated with % recovery (98.8-102.5%). The results showed that orphenadrine citrate could be determined successfully in the combined tablet without interference by paracetamol and other common co-formulated substance.

Comparative study of photodynamic activity of methylene blue in the presence of salicylic acid and curcumin phenolic compounds on human breast cancer.

Curcumin and salicylic acid are both phenolic compounds and they can both affect cancer treatment efficacy. In this study, the effects of methylene blue-curcumin (CU-MB) and methylene blue-salicylic acid (SA-MB) ion pair complexes on MDA-MB-231 human breast cancer cells are studied. According to the thermodynamic parameters, the stability of curcumin and salicylic acid complexes ion pair complexes was compared. The free energy of ion pair interactions was calculated based on binding constants. A comparison of the free energies of the complexes (CU-MB: ∆G°b1 = - 21.11kJ/mol and ∆G°b2 = - 8.37kJ/mol, SA-MB: ∆G°b1 = - 12.92kJ/mol and ∆G°b2 = - 9.02kJ/mol) indicates that the interaction of methylene blue in first binding interaction with curcumin is greater than that of methylene blue with salicylic acid. Electrostatic interactions are the main forces in the binding of both compounds to methylene blue. All forces are inter-molecular physical interactions. The results of cellular experiments show that ion pairing has enhanced the reduction of cell viability. By increasing molecular stability and prevention of dimerization of methylene blue, the cell killing potential of methylene blue increases and it subsequently causes enhancement of photodynamic efficacy.

Indirect ultra-trace determination of nitrate and nitrite in food samples by in-syringe liquid microextraction and electrothermal atomic absorption spectrometry

A simple and rapid method for simultaneous separation and preconcentration of ultra-trace amounts of nitrate and nitrite using in-syringe liquid microextraction is developed. The extraction procedure is based on the selective ion-pairing complex formation of nitrate and nitrite with Cu(I)-neocuproine in 100 μL of 1-butyl-3-methylimidazolium hexafluorophosphate as an extracting phase within a syringe. The atomic-absorption signal of copper in the ionic liquid layer is proportional to the nitrate and nitrite concentrations. When barbituric acid is used, nitrite is converted into violuric acid and thus it is removed from the environment. In this case, the selectivity of the modified-ligand is limited to nitrate. Under optimum experimental conditions, the calibration graph was in the range from 0.1 to 25 μg L−1 for nitrate and 0.05 to 10 μg L−1 for nitrite, respectively. The detection limits for these two anions were around 0.013 μg L−1. The resultant repeatability expressed as relative standard deviations (RSDs, n = 6) was <5.1%. The accuracy of the proposed method was confirmed using addition/recovery test and analyzing with the reference method. At two different addition levels for each analyte, recoveries were determined to be within the range from 94.2 to 103.3% for nitrate and 93.4 to 98.2% for nitrite, respectively. There was also no significant difference between the results when t-test is used with 95% confidence (n = 6). The applicability of the method was extended to the extraction and preconcentration of nitrate and nitrite from tuna fish, tomato paste and infant food sample.

Ion-Pair Complex Method for the Spectrophotometric Determination of Tamsulosin In the Presence of Dutasteride by using Bromo Thymol Blue

Ion-Pair Complex Method for the Spectrophotometric Determination of Tamsulosin In the Presence of Dutasteride by using Bromo Thymol Blue

Synthesis of high surface area nanostructured La2 Zr2 O7 by thermal decomposition of new ion pair complex precursor

The paper presents an investigation on the influence of the production method upon crystallite and particle size, surface area and morphology of La2Zr2O7 pyrochlore. Mesoporous La2Zr2O7 nanopowders were synthesized by thermal decomposition of [Zr(sal)3(H2O)2][La(dipic)2(H2O)3]⋅3(H2O), (dipic = 2,6-pyridinedicarboxylate, sal = salicylate), ion-pair complex precursor as a new method. For comparative purposes, two other samples were fabricated by co-precipitation and citrate sol-gel methods. The ion-pair complex precursor technique displays the low degree agglomeration, the smallest crystallite size (8.6 nm) and the highest surface area (119.20 m2/g) and total pore value (0.13 cc/g), in comparison with two other conventional methods which are related to the influence of the fabrication method. The high structural stability of the complex precursor prevents the rapid growth of particles during the calcination process and thus improves the textural properties.

The ion pair mechanism in the thermal deamination of primary amines catalyzed by HBr in the gas phase: DFT and AIM analysis

The possible reaction mechanisms for the gas-phase thermal deamination of isopropylamine, tert-butylamine, and dextroamphetamine in the presence of hydrogen bromide are investigated by DFT calculations with several functionals. In each case, QTAIM analysis supports the formation of an ion-pair complex, which subsequently decays through a six-membered cyclic transition state (TS). NBO charges and interatomic lengths suggest the polarization of the N1δ−···δ+C2 bond in the TS is rate determining.

A novel potentiometric microsensor for real-time detection of Irgarol using the ion-pair complex [Irgarol-H]+[Co(C2B9H11)2

The detection of the algaecide Irgarol using in-situ and fast potentiometric measurements is reported in this work. For this purpose, three all-solid-state Irgarol-selective microelectrodes based on PVC-type sensitive membrane were prepared using three different plasticizers and the novel ion-pair complex [Irgarol-H]+[Co(C2B9H11)2]− as the active site for selective irgarol recognition. This strategy enables the sensor’s selectivity to be improved by incorporating the target molecule to the sensitive membrane. The chemical sensors developed have provided excellent and quick response within the range 10−6 mol/dm3 to 10−3 mol/dm3 of irgarol concentration, a limit of detection between 2 and 4 μmol/dm3 and a slope between 48 and 57 mV/decade depending on the membrane composition. The potentiometric coefficient of selectivity, KA,Bpot, shown that the Irgarol-selective microsensors were highly selective towards irgarol when compared to some possible interfering phytotoxins. In addition, from the Reilley diagram it can be observed that the sensor signal is stable for a working pH interval between 6.00 and 12.0 making possible its application in sea water monitoring.

Investigating the role of ion-pair strategy in regulating nicotine release from patch: Mechanistic insights based on intermolecular interaction and mobility of pressure sensitive adhesive

The aim of this study was to prepare a drug-in-adhesive patch of nicotine (NIC) and use ion-pair strategy to regulate drug delivery rate. Moreover, the mechanism of how ion-pair strategy regulated drug release was elucidated at molecular level. Formulation factors including pressure sensitive adhesives (PSAs), drug loading and counter ions (C4, C6, C8, C10, and C12) were screened. In vitro release experiment and in vitro transdermal experiment were conducted to determine the rate-limiting step in drug delivery process. FT-IR and molecular modeling were used to characterize the interaction between drug and PSA. Thermal analysis and rheology study were conducted to investigate the mobility variation of PSA. The optimized patch prepared with NIC-C8 had the transdermal profile fairly close to that of the commercial product (p > 0.05). The release rate constants (k) of NIC, NIC-C4 and NIC-C10 were 21.1, 14.4 and 32.4, respectively. Different release rates of NIC ion-pair complexes were attributed to the dual effect of ion-pair strategy on drug release. On one hand, ion-pair strategy enhanced the interaction between drug and PSA, which inhibited drug release. On the other hand, using ion-pair strategy improved the mobility of PSA, which facilitated drug release. Drug release behavior was determined by combined effect of two aspects above. These conclusions provided a new idea for us to regulate drug release behavior from patch.