Potential of ethylenediaminedi(o-hydroxyphenylacetic acid) and N,N'-bis(hydroxybenzyl)ethylenediamine-N,N'-diacetic acid for the determination of metal ions by capillary electrophoresis

Two aromatic polyaminocarboxylate ligands, ethylenediaminedi(o-hydroxyphenylacetic acid) (EDDHA) and N,N′-bis(hydroxybenzyl)ethylenediamine-N,N′-diacetic acid (HBED), were applied for the separation of transition and heavy metal ions by the ion-exchange variant of electrokinetic chromatography. EDDHA structure contains two chiral carbon centers. It makes it impossible to use the commercially available ligand. All the studied metal ions showed two peaks, which correspond to meso and rac forms of the ligand. The separation of metal–HBED chelates was performed using poly(diallyldimethylammonium) polycations in mixed acetate–hydroxide form. Simultaneous separation of nine single- and nine double-charged HBED chelates, including In(III), Ga(III), Co(II)–(III) and Mn(II)–(III) pairs demonstrated the efficiency of 40 000–400 000 theoretical plates. The separation of Co(III), Fe(III) complexes with different arrangements of donor groups and oxidation of Co(II), Mn(II), Fe(II) ions in reaction with HBED have been discussed.     

Separation selectivity of some ethylenediaminetetraacetic acid and cyclohexane-1,2-diaminetetraacetic acid complexes in column and ion electrokinetic chromatography

The complexes of Mn²⁺, Cd²⁺, Fe³⁺, Pb²⁺, Ni²⁺, Co²⁺, Zn²⁺ and Cu²⁺ with EDTA and cyclohexane-1,2-diaminetetraacetic acid (CDTA) were separated and detected in column and ion electrokinetic chromatography with suppressed conductivity and direct UV detection, respectively. In column ion chromatography (IC) these complexes were separated on an IonPac AS4A anion-exchange column (Dionex, USA). Parameters of carrier electrolyte, which were examined in the ion electrokinetic chromatography (IEKC) mode, include polymer and sulfate concentrations. In IEKC separation selectivity of complexes with poly(diallyldimethylammonium) cation as modifier is similar as for an IonPac AS4A column both for EDTA and CDTA chelates. It was shown that the ion-exchange capacity of the electrokinetic system is more than 100-times lower than the capacity of the IC column for the same peak resolution. In comparison with column main advantages of electrokinetic version are high separation efficiency (220 000–390 000 theoretical plates) and the absence of the analyte interaction with the sorbent matrix.     

Copper(II), lead and zinc complexes of ethylenediamine-N,N'-diacetic acid

From potentiometric measurements with glass and ion-specific electrodes, the formation constants of the complexes of ethylenediamine-N,N'-diacetic acid (EDDA, H(2)X) and Cu(2+), Pb(2+) and Zn(2+) have been determined at 25.0 degrees and ionic strength of 0.1 (NaNo(3)). The formation constants of the protonated species of EDDA were determined from separate measurements. The following species and log beta values were found (standard deviations in parentheses): HX(-) 9.17 (0.03); H(2)X 6.36 (0.02), H(3)X(+) 1.54 (0.16); CuX 17.47 (0.02); CuHX 20.87 (0.05); Cu(OH)X 6.34 (0.05); Cu(2)X 20.85 (0.14); PbX 11.71 (0.01); PbHX 15.60 (0.02); PbOHX 12.27 (0.02); Pb(2)X 15.02 (0.01); ZnX 11.71 (0.01); ZnHX 15.48 (0.03); Zn(OH)X 11.98 (0.03); Zn(2)X 14.91 (0.01). (Stepwise constants are given for HX(-), H(2)X and H(3)X(+).).     

Spectral studies on the interaction of yttrium ion with the ligands of phenolic groups: N,N'-Ethylenebis[2-(o-hydroxyphenolic)glycine] and N,N'-di(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid

The interactions of yttrium with N,N'-ethylenebis[2-(o-hydroxyphenolic)glycine] (EHPG) and N,N'-di(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid (HBED) are investigated by using UV difference and fluorescence spectra methods in 0.1M N-2-hydroxyethylpiperazine-N-2-ethanesulfonic acid (Hepes) at pH 7.4. Yttrium binding produces two UV difference peaks near 240 and 294 nm, respectively, that both are the characteristic of phenolic groups binding to yttrium. The molar extinction coefficient of Y-EHPG and Y-HBED are (15.7 +/- 0.40) x 10(3), (15.8 +/- 0.80) x 10(3)cm(-1)M(-1) at 240 nm, respectively. Using EDTA as a competitor the obtained conditional equilibrium constants of the complexes are logK(Y-EHPG) = 15.07 +/- 0.32 and logK(Y-HBED) = 15.18 +/- 0.26, respectively. However, the effects of yttrium binding on the fluorescence intensity of EHPG and HBED are quite different, the former showing a decrease but the latter an increase.     

Liquid chromatography of lanthanide chelates of 1-(p-nitrophenyl)ethylenediamine-N,N,N',N' -tetra-acetic acid

Preparation of the chelating agent, 1-(p-nitrophenyl)ethylenediamine-N,N,N',N'-tetra-acetic acid (p-nitrophenylEDTA), is described in detail. Separation of p-nitrophenylEDTA chelates of ytterbium(III), erbium(III), dysprosium(III) and europium(III) has been achieved by reversed-phase ion-pair liquid chromatography. With spectrophotometric detection at 254 nm, linear responses over about four orders of magnitude were achieved with detection limits (S/N = 2) of about 0.5 pmole.     

Anionic N-heterocyclic carbenes with N,N'-bis(fluoroaryl) and N,N'-bis(perfluoroaryl) substituents

A series of rhodium complexes, [Rh(cod)(NHC-F(x))(OH(2))] (cod = 1,5-cyclooctadiene; NHC = N-heterocyclic carbene), incorporating anionic N-heterocyclic carbenes with 2-tert-butylmalonyl backbones and 2,6-dimethylphenyl (x = 0), 2,6-difluorophenyl (x = 4), 2,4,6-trifluorophenyl (x = 6), and pentafluorophenyl (x = 10) N,N'-substituents, respectively, has been prepared by deprotonation of the corresponding zwitterionic precursors with potassium hexamethyldisilazide, followed by immediate reaction of the resulting potassium salts with [{RhCl(cod)}(2)]. These complexes could be converted to the related carbonyl derivatives [Rh(CO)(2)(NHC-F(x))(OH(2))] by displacement of the COD ligand with CO. IR and NMR spectroscopy demonstrated that the degree of fluorination of the N-aryl substituents has a considerable influence on the σ-donating and π-accepting properties of the carbene ligands and could be effectively used to tune the electronic properties of the metal center. The carbonyl groups on the carbene ligand backbone provided a particularly sensitive probe for the assessment of the metal-to-ligand π donation. The ortho-fluorine substituents on the N-aryl groups in the carbene ligands interacted with the other ligands on rhodium, determining the conformation of the complexes and creating a pocket suitable for the coordination of water to the metal center. Computational studies were used to explain the influence of the fluorinated N-substituents on the electronic properties of the ligand and evaluate the relative contribution of the σ- and π-interactions to the ligand-metal interaction.     

Cobalt(III) complexes of ethylenediamine-N,N′-di-S-isobutylacetic acid

A new optically active ONNO-type tetradentate ligand, ethylenediamine-N,N′- di-S-isobutylacetate (SS-eniba), has been synthesized. During the preparation of diaqua cobalt(III) complexes of SS-eniba, [Co(SS-eniba)(H₂O)₂]⁺, the title ligand has coordinated stereospecifically to the cobalt(III) ion to give three isomers, Δ-s-cis, Δ-uns-cis and Λ-uns-cis, which have been isolated and characterized via electronic absorption, circular dichroism (CD), and ¹H NMR spectroscopy, along with elemental analysis data. The preparation of Δ-s-cis-[Co(SS-eniba)Cl₂]⁺ and Δ-s-cis-[Co(SS-eniba)CO₃]⁺ are also reported.     

Determination of hydrogen ion by ion chromatography (IC) with sulfonated cation-exchange resin as the stationary phase and aqueous EDTA (ethylenediamine-N,N,N',N'-tetraacetic acid) solution as the mobile phase

An ion chromatographic (IC) method has been developed for determination of hydrogen ion (H+). It is based on the use of sulfonated cation-exchange resin as stationary phase, aqueous ethylenediamine-N,N,N',N'-tetraacetic acid (dipotassium salt, EDTA-2K, written as K2H2Y) solution as mobile phase, and conductivity for detection. H+ was separated mainly by cation-exchange, but its elution was accelerated by the presence of EDTA. The order of elution for the model cations was H+ > Li+ > Na+ > NH4+ > Ca2+ > > Mg2+. A sharp and highly symmetrical peak was obtained for H+ and this was attributed to the capacity of H2Y2(2-) to receive and bind H+. H+ was detected conductiometrically and detector response (reduction in conductivity as a result of H+ +H2Y2- --> H3Y-) was linearly proportional to the concentration of H+ in the sample. The detection limit for H+ with this IC system was better than 4.7 micromol L(-1). A significant advantage of this method was the ability to separate and determine, in one step, H+ and other cations. The successful determination of H+ and other cation species in real acid-rain samples demonstrated the usefulness of this method.     

2-羟基-1-萘醛缩乙二胺Schiff碱及其过渡金属配合物的合成和表征

Schiff 碱配体包含着酚氧桥氧原子和亚胺氮原子这类强电子给体,他们与过渡金属原子有较强的配位能力,在催化、抗癌、抗菌、抗病毒等方面都有广泛的应用[1-4],受到人们的高度关注.     

Separation and sweeping of flavonoids by microemulsion electrokinetic chromatography using mixed anionic and cationic surfactants

In this report, a novel means for the separation and sweeping of flavonoids (quercetin, rutin, calycosin, ononin and calycosin-7-O-β-d-glucoside) by microemulsion electrokinetic chromatography using mixed anionic and cationic surfactants as modified pseudostationary phase was presented. The optimized background electrolyte consisted of 0.5% (w/v) ethyl acetate, 2.0% (w/v) SDS, 9 mM DTAC, 4.0% (w/v) 1-butanol and 10 mM sodium borate or 25 mM phosphoric acid. We systematically investigated the separation and preconcentration conditions, including the concentrations of surfactant, types of sweeping, sample matrix, the effect of high salt or acetonitrile, and sample injection volume. It was found that the use of mixed surfactants significantly enhanced the separation efficiency through the change of the efficient electrophoretic mobility of analytes. Compared with normal sample injection, 185-508-fold sensitivity enhancement in terms of limit of detection was achieved through effective sweeping of large sample volume at 50 mbar pressure (up to 45% capillary length). At last, the proposed method was suitable for the determination of Radix Astragali sample.     

Synthesis and structural characterisation of heavy alkaline earth N,N'-bis(aryl)formamidinate complexes

Treatment of calcium or strontium with 2.0 equivalents of N,N-bis(o-methylphenyl)formamidine (o-TolFormH), N,N-bis(2,6-dimethylphenyl)formamidine (XylFormH) or N,N-bis(o-phenylphenyl)formamidine (o-PhPhFormH) in the presence of 1.0 equivalent of Hg(C6F5)2 in tetrahydrofuran (thf) affords the bis(formamidinate) complexes [Ca(o-TolForm)2(thf)2] (1), [Ca(XylForm)2(thf)2] (2), [Ca(o-PhPhForm)2(thf)2].thf (3), [Sr(o-TolForm)2(thf)3] (4), [Sr(XylForm)2(thf)3].3thf (5) and [Sr(o-PhPhForm)2(thf)3].2thf (6). Analogous reactions with barium were generally unsatisfactory but [Ba(o-PhPhForm)2(thf)3].2thf (7) was successfully prepared. Compounds 1-7 have been characterised by various spectroscopic methods (1H, 13C{1H} NMR and IR), elemental analyses and, for 1, 2 and 4-6, X-ray crystallography. The calcium complexes are monomeric and six-coordinate with either transoid octahedral or trigonal prismatic geometry, whilst the larger radius of strontium accommodates an additional thf solvent donor to give seven-coordinate structures with two types of coordination polyhedra.     

Retention model for the separation of anionic metal-EDTA complexes in ion chromatography

A retention model is derived for complex anions eluted from an anion-exchange column with multiple ionic eluents containing hydrogencarbonate, carbonate, and hydroxyl species and the sample solution, containing transition metals, anions and complexing ligand. The theory is based on the generalized ion-exchange equilibrium, protonation and complex-formation equilibria. The unknown parameters of chromatographic ion-exchange equilibrium constants for sample and eluent species are determined from the experimental retention data by iterative minimization, using a non-linear regression algorithm. The model was utilized to predict the retention behaviour of CdEDTA²⁻, CoEDTA²⁻, MnEDTA²⁻ and NiEDTA²⁻ ions. The capacity factors of complex ions were determined for wide ranges of pH values and eluent concentrations. Good agreement was obtained between the observed and predicted retentions.     

N,N′-Bis(2-hydroxybenzyl)ethylenediamine-N,N′-dipropionic acid. A new chelating ligand for iron(III)

A new potentially chelating ligandN,N′-bis(2-hydroxybenzyl)ethylenediamine-N,N′-dipropionic acid, (HBEP) has been prepared in high yield and its ionization constants have been determined by potentiometric and spectrophotometric methods. The stability constant for the Fe^III-HBEP chelate has been determined spectrophotometrically, and the ligational behaviour of HBEP with iron(III) compared with that of its homologue, HBED (N,N′-bis(2-hydroxybenzyl)ethylenediamine-N,N′-diacetic acid). IPCL Communication No. 169.     

在线扫集-胶束毛细管电动色谱法测定扛板归中的阿魏酸、咖啡酸和原儿茶酸

采用在线扫集-胶束毛细管电动色谱法(sweeping-MEKC)分离测定扛板归中的阿魏酸、咖啡酸和原儿茶酸。采用未涂层熔融石英毛细管(50 cm×50μm,有效柱长36 cm);环境温度25℃;缓冲体系为20 mmol/L NaH2PO4-80mmol/L十二烷基磺酸钠(SDS)-12.5%乙腈(V/V)(pH 2.20),紫外检测波长为216 nm,运行分离电压-20 kV,进样时间100 s。在优化条件下,3种有机酸均在20 min内出峰,峰面积RSD均小于5%。检出限分别达到98.52,118.73和27.27μg/L。     

Separation and on-line concentration of bisphenol A and alkylphenols by micellar electrokinetic chromatography with anionic surfactant

Separation and on-line concentration of bisphenol A and three alkylphenols were investigated by micellar electrokinetic chromatography with the anionic surfactant, sodium dodecyl sulfate. The separation conditions were optimized by the simultaneous addition of the organic solvent and cyclodextrin to the running solution. The separation of hydrophobic analytes and 4-nonylphenol isomers was improved by the addition of 10% methanol and 5 mM beta-cyclodextrin to the running solution. When the sweeping with the running solution was used as the on-line concentration procedure, 69-, 48-, 55- and 41-fold increases in detection sensitivity were obtained for bisphenol A, 4-tert.-butylphenol and 4-(1,1,3,3-tetramethylbutyl)phenol, and the second peak of 4-nonylphenol isomers, respectively. The detection limits were 0.0071, 0.0065, 0.021 and 0.055 mg/l, respectively. These results were better than those with the cationic surfactant, tetradecyltrimethylammonium bromide.     

Synthesis, spectroscopy, and electrochemistry of copper(II) complexes with N,N'-bis(3,5-di-t-butylsalicylideneimine)polymethylenediamine ligands

Bulky salen CuL(x) derived from aliphatic polymethylene diamines, H(2)N-(CH(2))(x)-NH(2), where n = 2-6, and 3,5-di-t-butylsalicylaldehyde (H(2)L(x)) and some corresponding tetrahydrosalan complexes (CuL(x)') have been synthesized and characterized by their IR, UV-vis absorption and EPR spectra, by magnetic moments and by cyclic voltammetry in acetonitrile (for H(2)L(x)) and DMF (for CuL(x)). Complexes CuL(x) and CuL(x)' are magnetically normal (mu(exp) = 1.83-1.91 mu(B)). EPR spectra CuL(x) characterized by the axial g and A(Cu) tensors with g parallel > g perpendicular and without (14)N-shf resolution in CHCl(3)/toluene at 300 and 150K. The CV studies on acetonitrile solutions of H(2)L(x) revealed a well-defined quasi-reversible redox wave at E(1/2) = 0.95-1.15 V versus Ag/AgCl but CV of the CuL(x) complexes in DMF exhibit weak pronounced irreversible oxidation waves at E(pa)(1) = 0.51 - 098 V and E(pa)(2) = 1.16 - 1.33 V attributable to metal centered Cu(II/III) and ligand centered CuL(x)/CuL(x)*+ couples, respectively. A poorly defined wave was observed for the quasi-reversible reduction Cu(II)/Cu(I) at potentials less than -1.0 V.