Ion-pairing HPLC methods to determine EDTA and DTPA in small molecule and biological pharmaceutical formulations

Ion-pairing high-performance liquid chromatography-ultraviolet （HPLC-UV） methods were developed to determine two commonly used chelating agents, ethylenediaminetetraacetic acid （EDTA） in Abilify （a small molecule drug with aripiprazole as the active pharmaceutical ingredient） oral solution and die- thylenetriaminepentaacetic acid （DTPA） in Yervoy （a monoclonal antibody drug with ipilimumab as the active pharmaceutical ingredient） intravenous formulation. Since the analytes, EDTA and DTPA, do not contain chromophores, transition metal ions （Cu2＋, Fe3＋） which generate highly stable metallocom- plexes with the chelating agents were added into the sample preparation to enhance UV detection. The use of metallocomplexes with ion-pairing chromatography provides the ability to achieve the desired sensitivity and selectivity in the development of the method. Specifically, the sample preparation in- volving metallocomplex formation allowed sensitive UV detection. Copper was utilized for the de- termination of EDTA and iron was utilized for the determination of DTPA. In the case of EDTA, a gradient mobile phase separated the components of the formulation from the analyte. In the method for DTPA, the active drug substance, ipilimumab, was eluted in the void. In addition, the optimization of the concentration of the ion-pairing reagent was discussed as a means of enhancing the retention of the aminopolycarboxylic acids （APCAs） including EDTA and DTPA and the specificity of the method. The analytical method development was designed based on the chromatographic properties of the analytes, the nature of the sample matrix and the intended purpose of the method. Validation data were presented for the two methods. Finally, both methods were successfully utilized in determining the fate of the chelates.

A Method for Detection of Trace Concentrations of Underivatized Amino Acid in Hydrothermal Fluids by Ion-Pairing Reversed-Phase UPLC-ESI-QTOF-MS

Investigation of amino acids in hydrothermal systems is of prime importance for the understanding of geochemistry and microbiology of hydrothermal vents and plumes, for carbon and metals global cycles, for metabolism of some hydrothermal microorganisms and for the origin of life issue. Extensive theoretical and experimental work on amino acids behaviour in hydrothermal fluids has been done, conversely only few data exist on natural samples. Because each hydrothermal vent is unique, the more data we collect the better we will be able to address each of these questions. Usually amino acids in hydrothermal fluids have been measured by HPLC-FLD. The chromatographic separation was at least 26 min and up to 135 min and the required derivatization step may be time consuming, may use harmful chemicals and may be source of contamination. Alternatively, we describe here a method combining quickness (4.5 min), high resolution (10,000), very low LOD (sub-ppb) and without derivatization. Characterisation and separation of 10 relevant proteinogenic underivatized amino acids was achieved by ion-pairing reversed-phase Ultra-high Performance Liquid Chromatography-Electrospray Ionisation-Quadrupole Time of Flight-Mass Spectrometry (UPLC-ESI-QTOF-MS). Excellent linearity in the response was obtained for all amino acids with correlation coefficients > 0.9921. This method was successfully applied to natural hydrothermal fluid samples from ultramafic-hosted vents of the Mid-Atlantic Ridge region. Results are consistent with the only 2 other studies published on ultramafic-hosted vents and complete the few available data.

Investigation of multilevel ion-pairing effect of triferrocenylmethane in organic phase

The intramolecular electronic communication and multilevel ion-pairing effect of triferrocenylmethane（TriFcM） in organic phase was studied with the ＂thin-layer electrochemistry＂ approach.Three pairs of symmetric peaks in cyclic voltammetry of TriFcM correspond to three one-electron electrochemical reaction processes and indicate strong intramolecular electronic communication,which could be used to study the multilevel ion-pairing effect.Three different formation constants of ion-pairs between the three ferroceniums of TriFcM and perchlorate in thin organic film were obtained and compared.

Ion-Pairing Chirality Transfer in Atropisomeric Biaryl-Centered Gold Clusters

The stereocontrol of chiral metal clusters and nanoclusters has become a focus of interest in metal cluster chemistry due to their promising applications in asymmetric catalysis.Despite being a general chirality transfer strategy,the ion-pairing process is still ambiguous in the course of bestowing chirality to metal clusters.Here we construct a biaryl-centered axially chiral gold-cluster system to study an outside-in ion-pairing chirality transfer process.Four hexanuclear gold(I)clusters,centered by two types of biaryl ligands[(2-indolyl)aniline(L^(1))and biindole(L^(2))],were synthesized via in situ cyclization reactions.In the crystalline state,the biaryl centers showed axial chirality in which the gold atoms were in an asymmetric arrangement.In solution,the chiral phosphates induced an outside-in chirality transfer by significant interactions with the periphery of the biaryl-centered gold clusters.Finally,the chiral resolution of hexa-aurated biindoliums was accomplished via an efficient outside-in chirality transfer process relying on strong aurophilic interaction and extra peripheral coordination.This study not only deepens the understanding of the outside-in ion-pairing chirality transfer process but also provides a new approach for fabricating desired chiral metal clusters by a combination of organometallic transformation and chirality transfer.

The Quantum Scattering Study for Ion-pair Formation Reaction Na+I_2→Na^+I_2^- with the LCAC-SW method

The selected-state probabilities of collinear ion-pair formation process Na+I2→Na++I2-on Aten-Laming-Los two-State potential energy surface have been calculated by using LCAC-SW method. The results show that reaction probabilities are oscillatory with collision energy; the threshold energy of this ioniZation reaction is 2.8 ev, which is in modest agreement with experimental result.

Novel additives for the separation of organic acids by ion-pair chromatography

This paper proposes the use of novel surfactant additives for the separation of organic acids by ion-pair chromatography and studies the influences of surfactants on the chromatographic separation behaviors.Researches have been carried out on both silica gel matrix and polymer supporters in order to compare the two ordinary kinds of stationary phases,and the phenomenon is similar. Separation is based on differences in the stabilities of analyte-additive complexes in solution.Retention times of analytes can ...

Enantiomeric Separation of Amino Alcohols by Ion-pair Chromatography

Enantiomers of four amino alcohols were resolved by ion-pair chromatography with (+)-10-camphorsulphonic acid as chiral counter ion. Studies of the influence of the mobile phase composition, the solute structure and the mobile phase flow-rate on separation are presented. Under the optimized conditions enantiomeric propanolol, norephedrine, metropolol and salbutamol were separated using dichloromethane-1-pentanol (97:3 v/v) as mobile phase on Lichrospher-100-DIOL column.

Ion-pair induced solvent extraction of lithium(Ⅰ)from acidic chloride solutions with tributyl phosphate

Lithium(Li)is an important energy metal in the 21st century.However,the selective recovery of Li is still a big challenge,especially from acidic solutions with multiple metal ions existence.Herein we report a new ion pair induced mechanism for selectively extracting Li^(+)from acidic chloride solutions by tributyl phosphate(TBP).It is shown that the acidity and the chloride ions in the aqueous phase have great effects on the extraction of Li^(+).The FT-IR,UV-Vis and ESI-MS experiments provide solid evidence for the formation of ion-pair complex[Li(TBP)_n(H_(2)O)_(m)]^(+)[FeCl_(4)]^(-)(n-1,2,3;m-0,1)in the organic phase,which brings about the effective and efficient extraction of Li^(+).This mechanism can overcome the Hofmeister bias and allow for the selective extraction of Li^(+) from the extremely hydrophilic chlorides.It has also been proved that the loaded Li in TBP can be effectively stripped by concentrated HCl solution with a Li/Fe separation factor>500.The understanding of the ion-pair transport mechanism is helpful for optimizing the recovery process or further advancing more efficient recovery techniques for Li from acidic liquor.

Preparation,Crystal Structure and Density Functional Theory Calculations of the Ion-pair Compound [Cl2Bz(3-MeQl)](TCNQ)

A novel compound [Cl2Bz（3-MeQl） ]（TCNQ） （[Cl2Bz（3-MeQl） ]^＋ = 1-（3,4-dichlo-robenzyl） 3-methlquinoline cation,TCNQ-= 7,7,8,8-tetracyanoquinodimethanide anion） has been synthesized by the reaction of [Cl2Bz（3-MeQl） ]Br and LiTCNQ,and its structure was determined by single-crystal X-ray diffraction. The crystal belongs to monoclinic,space group P21/c. The structure analysis shows that the anions are stacked into a column with isolated π-dimers,and there is one type of TCNQ entries（TCNQ^-） ,in agreement with the IR spectra analysis and density functional theory calculations of the compound. The most prominent structural features are the completely segregated stacking columns of the TCNQ- anions and [Cl2Bz（3-MeQl）]＋ cations.

Synthesis and Crystal Structure of an Ion-pair Compound: [H_2(teta)]^(2+)·[Ni(CN)_4]^(2-)·2H_2O (teta = Meso-5,7,7,12,14,14-hexamethyl- 1,4,8,11-tetraazacyclotetradecane)

The ion-pair compound [H2（teta）]^2＋·[Ni（CN）4]^2-·2H2O （C20H42N8NiO2, teta = meso- 5,7,7,12,14,14-hexamethyl- 1,4,8,11-tetraazacyclotetradecane） was synthesized and characterized by single-crystal X-ray diffraction. The crystal belongs to monoclinic, space group P211n with a = 10.0784（10）, b = 9.5411（7）, c = 14.1010（14）А, β= 106.752（2）°, V= 1298.4（2）A^3, Mr = 485.33, Z= 2, De= 1.241 g/cm^3,μ（MoKα） = 0.778 mm^-1 and F（000） = 524. The structure was refined to R = 0.0391 and wR = 0.0870 for 2614 observed reflections with I 〉 2σ（I）. The title compound contains one [Ni（CN）4]^2- anion, one protonated macrocyclic tetraamine cation [H2（teta）]^2＋ and two water molecules. There are multiform hydrogen bonds in the compound to link the different components and stabilize the crystal structure.

Synthesis and Crystal Structure of a Novel Ion-pair Compound Consisting of 1-(4-Bromobenzyl)pyridinium Cation and 7,7,8,8-Tetracyanoquinodimethanide Anion

The title compound [BrBzPy][TCNQ] （BrBzPy^＋=1-（4-bromobenzyl）pyridinium cation, TCNQ = 7,7,8,8-tetracyanoquinodimethanide anion） was synthesized by the reaction of [BrBzPy]Br and LiTCNQ in ethanol solution and its structure was determined by single-crystal X-ray diffraction. The crystal belongs to monoclinic, space group P21/c with a = 14.067（3）, b = 7.3089（14）, c = 23.796（4）A, β = 122.011（9）°, V= 2074.6（7）A^3, Z = 4, C24H15BrN5, Mr = 453.32, Dc = 1.451 g/cm^3,μ = 2.002 mm^-1, S = 1.047, F（000） = 916, R = 0.0398 and wR = 0.0921. The most prominent structural features are the completely segregated stacking columns of the TCNQ- anions and [BrBzPy]^＋ cations. In a TCNQ column, the centroid-to-centroid distances of the neighboring anions of TCNQ are 3.2693 and 4.9464 A, respectively.

Synthesis and Crystal Structure of a Novel Ion-pair Compound Consisting of 1,3-Bis(4-cynobenzyl) Imidazole Cation and 7,7,8,8-Tetracyanoquinodimethanide Anion

A novel compound [（CNBz）2Im]2（TCNQ）3（CH3CN）（（CNBz）2Im = 1,3-bis（4-cyano-benzyl） imidazole cation,TCNQ-1 = 7,7,8,8-tetracyanoquinodimethanide anion） was synthesized by the reaction of [（CNBz）2Im]Br and LiTCNQ in water and its structure was determined by single-crystal X-ray diffraction.The crystal belongs to monoclinic,space group P21/c with a = 10.1823（17）,b = 20.292（3）,c = 16.952（3） ,β = 104.73（0）°,V = 3387.6（10）3,Z = 4,C39H24N11,Mr = 646.69,Dc = 1.268 g/cm3,μ = 0.080 mm-1 and F（000） = 1340.The structure was solved by direct methods and refined to R = 0.0596 and wR = 0.0911 for 2690 observed reflections（Ⅰ 〉 2σ（Ⅰ））.The most prominent structural feature is that there are two types of TCNQ entries（TCNQ-1 and TCNQ0） in agreement with the IR spectra analysis of the compound.

Theoretical Study on the Ion-pair Formation Mechanism for the Li+I_2 →Li^+ + I_2^- System

For the Li + I2 →Li+ + I2- system, theoretical study has been performed on the QCISD(T) level by using the ab initio method. The collision complex in ion-pair formation process was found and optimized. These results show that the crossed molecule beam (CMB) experimental phenomenon is verified and the detailed geometry is given for the first time. A mechanism for ion-pair formation was proposed in detail. The position where the collision complex occurs affects the reaction path. Specifically, the process has threshold when the collision complex appeared before the crossing point between the covalent and ionic state potential energy surfaces. On the contrary, the process has no threshold after the crossing point. Theoretically, the title system belongs to the former case.

Synthesis and Structure of a Novel Ion-pair Palladium(Ⅱ) Compound Containing 2-Thioxo-1,3-dithiole-4,5-bis(thiolate)

A novel ion-pair palladium（Ⅱ） compound, （NOzBzPy）2[Pd（dmit）2] （NO2BzPy^＋ = 1-（4-nitrobenzyl）pyridinium, dmit^2- = 2-thioxo-1,3-dithiole-4,5-bis（thiolate））, was synthesized and characterized by single-crystal X-ray structure determination. This compound crystallizes in the monoclinic system, space group P21/n with a = 10.4463（11）, b = 8.5627（9）, e = 20.017（2）A, β = 97.7730（10）°, V = 1774.1（3）A^3, Z = 2, C30H22N4O4S10Pd, Mr = 929.52, Dc = 1.740 g/cm^3,μ = 1.155 mm^-1, S = 1.006, F（000） = 936, R = 0.0354 and wR = 0.0675. The most intriguing general structural feature of the compound is the completely segregated columnar stacks of anions and cations. There exist hydrogen-bonding interactions within the cation column.

An Ion-Pair HPLC Method for Simultaneous Determination of Exogenous Phosphocreatine and Its Metabolite Creatine and Related ATP in Rabbit Plasma and RBC: Application to a Pharmacokinetic Study

A specific, precise and accurate ion-pair HPLC-UV method has been developed and validated for simultaneous determination of phosphocreatine (PCr), and its metabolite creatine (Cr) as well as related ATP in plasma and red blood cell (RBC) of rabbits. After addition of TMP as IS, the samples were deproteinized with 6% PCA. The analytes were separated on a Kromasil C18 column using a tertiary gradient mobile phase composed of buffer A (0.2% KH2PO4 + 0.08% tetrabutyl ammonium hydrogen sulphate, pH 3.0), buffer B (buffer A adjusted to pH 7.5 with 1 mol/L NaOH) and MeOH. Detection wavelengths were set at 210 nm for PCr and Cr and 260 nm for ATP and TMP. Some blank samples were initially run for baseline subtraction. The linear detection responses were obtained for PCr concentration over a range of 10 - 7500 mg/ml (plasma) and 5 - 2500 mg/ml (RBC) and for both Cr and ATP concentrations of 10 - 1500 mg/ml (plasma) and 5 - 750 mg/ml (RBC) (r > 0.99). The QC samples of 3 analytes showed intra-day and inter-day precisions (RSD) of - 107%. The method was successfully used to simultaneously determine plasma and RBC concentrations of the 3 analytes and to study pharmacokinetics after iv administration of PCr to rabbits.

液相色谱-质谱法对奶粉中唾液酸含量的测定

A simple and sensitive ion-paring HPLC-MS/MS method with negative ion mode has been developed and validated for the quantification of SA in milk.The separation was performed on C18 column with a mobile phase consisting of 4 mmol/L tetrabutylammonium hydroxide-methanol at a flow rate of 0.2 mL/min under the gradient elution.The retention time of SA was 6.1 min.Triple-quadrupole MS/MS detection was operated in negative mode by monitoring the transition of m/z 308.1>87.1 for SA.Validation results indicated that the lower limit of quantification was 0.060 mg/L and the assay showed a linear range of 0.1-100 mg/L and gave a correlation coefficient(r) of 0.998.The relative standard deviations were less than 10% at all tested concentration levels.The method has been successfully applied to the analysis of SA in milk,milk powder and breast milk.

Distribution of Ag(I), Li(I)-Cs(I) Picrates, and Na(I) Tetraphenylborate with Differences in Phase Volume between Water and Diluents

Ionic strength conditions in distribution experiments with single ions are very important for evaluating their distribution properties. Distribution experiments of picrates (MPic) with M = Ag(I) and Li(I)-Cs(I) into o-dichlorobenzene (oDCBz) were performed at 298 K by changing volume ratios (Vorg/V) between water and oDCBz phases, where “org” shows an organic phase. Simultaneously, an analytic equation with the Vorg/V variation was derived in order to analyze such distribution systems. Additionally, the AgPic distribution into nitrobenzene (NB), dichloromethane, and 1,2-dichloroethene (DCE) and the NaB(C6H5) 4 (=NaBPh4) one into NB and DCE were studied at 298 K under the conditions of various Vorg/V values. So, extraction constants (Kex) for MPic into the org phases, their ion-pair formation constants (KMA,org) for MA = MPic in the org ones, and standard distribution constants () for the M(I) transfers between the water and org bulk phases with M = Ag and Li-Cs were determined at the distribution equilibrium potential (dep) of zero V between the bulk phases and also the Kex (NaA), KNaA,org, and values were done at A-=BPh-4. Here, the symbols Kex, KMA,org, and or were defined as [MA] org/[M+][A-], [MA] org/[M+]org [A-]org, and [M+]org/[M+] or [A-]org/[A-] at dep = 0, respectively. Especially, the ionic strength dependences of Kex and KMPic,org were examined at M = Li(I)-K(I) and org = oDCBz. From above, the conditional distribution constants, KD,BPh4 and KD,Cs, were classified by checking the experimental conditions of the I, Iorg, and dep values.

POLYMERIZATION MECHANISM OF N-VINYLCARBAZOLE WITH CHIRALLY ORGANIC SALT AS CATALYST

The polymerization mechanism is described by the conductance change with the time during the polymerization. The mechanism can be explained by the equilibrium feature (i.e. main ion-pairs) between the free ions and the ion-pairs dissociated by the organic salt (-) Sp*(+)(+) CSA*(-) (An asterisk represents the chirality) and the scheme of the polymerization process is described mainly by the charge transfer complexes having chiral induction power.

Theoretical Study on the Long-lived Complexes for the Na +I_2Collision System

For the Na + I2 collision system, theoretical study is performed on the QCISD(T) level by using ab initio method. The ab initio potential energy surfaces are got and on them the long-lived complexes are found and optimized. These results verify the crossed molecule beam experimental phenomenon and the detailed geometry structures are given for the first time. The role of the complexes in the reaction path is also described in detail.

Studies on Non-potentiometric Piezoelectric Sensor System for Determination of Vitamin B_1

A piezoelectric sensor responsive to vitamin B 1 was fabricated based on the vitamin B 1 tetraphenylborate ion pair. The general performance characteristics of the sensor are presented here. The proposed sensor showed a wide working pH range, a good sensitivity and selectivity. The response range is between 1 0×10 -7 -4 9×10 -5 mol/L with a detection limit of 8×10 -8 mol/L at pH 4 0. The selectivity should be attributed to the preferential adsorption of the component ion on the membrane/solution interface. The adsorption behavior of vitamin B 1 on the crystal surface was investigated with a quartz crystal impedance(QCI) system.