Speciation,separation and enrichment of Cr(III) and Cr(VI) in environmental samples by ion-pair solvent extraction using a β-diketone ligand

A simple speciation, separation and enrichment method has been developed for the determination of Cr(III) and Cr(VI) ions in different samples by ion-pair solvent extraction with a β-diketone ligand, 2-(4-methoxybenzoyl)-N′-benzylidene-3-(4-methoxyphenyl)-3-oxo-N-phenyl-propono hydrazide (MBMP). Cr(III) was separated from Cr(VI) as Cr(III)-(MBMP)-perchlorate ternary ion-pair complex. The influences of various analytical parameters including pH, amount of reagent, shaking time, sample volume and ionic strength on the recovery of Cr(III) and/or Cr(VI) were investigated. Total chromium was obtained after reducing Cr(VI) to Cr(III) with NH₂OH?·?HCl. Recoveries were found to be higher than 95% and the relative standard deviation (RSD) was less than 2%. The method detection limit based on 3σ criterion for Cr(III) was found to be 0.32?µg?L^?1. The formed ternary ion-pair complex, Cr(III)?:?MBMP?:?2ClO₄, has a molar ratio of 1?:?1?:?2. The developed method has been applied successfully to the speciation of chromium in various natural water, soil, sediment and hair samples with satisfactory results.     

A microporous metal-organic framework for highly selective separation of acetylene, ethylene, and ethane from methane at room temperature

A novel three‐dimensional microporous metal–organic framework Zn₄L(DMA)₄ ( UTSA‐33 , H₈L=1,2,4,5‐tetra(5‐isophthalic acid)benzene, DMA=N,N′‐dimethylacetamide) with small pores of about 4.8 to 6.5 Å was synthesized and structurally characterized as a non‐interpenetrated (4,8)‐connected network with the flu topology (Schläfli symbol: (4¹²6¹²8⁴)(4⁶)₂). The activated UTSA‐33 a exhibits highly selective separation of acetylene, ethylene, and ethane from methane with the adsorption selectivities of 12 to 20 at 296 K, which has been established exclusively by the sorption isotherms and simulated breakthrough experiments, thus methane can be readily separated from their binary and even ternary mixtures at room temperature.     

Fast Determination of Clenbuterol and Salbutamol in Feed and Meat Products Based on Miniaturized Capillary Electrophoresis with Amperometric Detection

The fast separation capability of a novel miniaturized capillary electrophoresis with an amperometric detection (μCE‐AD) system was demonstrated by determining clenbuterol and salbutamol in real samples. The effects of several factors such as the acidity and concentration of the running buffer, the separation voltage, the applied potential and the injection time on CE‐AD were examined and optimized. Under the optimum conditions, the two β‐agonists could be baseline separated within 60 s at a separation voltage of 2 kV in a 90 mmol/L H₃BO₃‐Na₂B₄O₇ running buffer (pH 7.4), which was not interfered by ascorbic acid and uric acid. Highly linear response was obtained for above compounds over three orders of magnitude with detection limits ranging from 1.20×10^?7 to 6.50×10^?8 mol/L (S/N=3). This method was successfully used in the analysis of feed and meat products with relatively simple extraction procedures.     

Variations in the gross alpha and beta activity in surface waters at the Atomic Weapons Establishment Aldermaston (UK)

N,N,N′,N′-tetra-2-ethylhexyldiglycolamide (T2EHDGA) has been used for the preferential extraction of ⁹⁰Y from its mixture with ⁹⁰Sr from HNO₃ as well as HCl medium. The separation efficiencies have been found out under varying experimental conditions. The extracted species were determined from T2EHDGA concentration variation experiments carried out at 3 M nitric acid as well as HCl and were found out to be Y(X₃)₃·3(TEHDGA)_(o) for both the extraction systems, where X = NO₃ ⁻ and Cl⁻, respectively. Comparison of the T2EHDGA and TODGA based separation methods is also made. In order to avoid third phase formation, iso-decanol has been used as the modifier in all the studies. The modifier content was optimized to 30% for 4 M HCl and 20% for 6 M HNO₃ as the feed aqueous phases. Separation schemes were developed for the separation of carrier free ⁹⁰Y and the purity was checked by the half-life measurement method.     

Synthesis,crystal structure,magnetic property,and nuclease activity of a binuclear iron(III) complex

A μ-oxo-di-μ-carboxylato-bridged iron(III) complex containing two tridentate nitrogen ligands, {[Fe₂(bpma)(bpea)(μ-CH₃COO)₂ μ-O)] · (ClO₄)₂ · 0.5CH₃OH} (1) (bpma = N, N-bis(2-pyridylmethyl)methyl-amine, bpea = N,N-bis(2-pyridylmethyl)ethylamine), has been synthesized and determined by X-ray diffraction. Complex 1 crystallizes in the monoclinic space group P2₁/c with a = 10.9434(12) Å, b = 23.118(3) Å, c = 15.8721(18) Å, β = 92.736(2)° and Z = 4. In 1, each Fe(III) has a distorted octahedral geometry with a N₃O₃ donor set. The Fe(III) atoms are bridged by two carboxyl groups and one μ-oxo oxygen with Fe1–Fe2 separation of 3.064 Å. Susceptibility data of 1 indicate strong intramolecular antiferromagnetic coupling of the high-spin Fe(III) atoms with J = ?121.0 cm^?1 and g = 2.04. The interaction with calf thymus DNA was investigated by UV absorption and fluorescent spectroscopy. Results show that the complex binds to ct-DNA with a moderate intercalative mode. The interaction between 1 and pBR322 DNA has also been investigated by submarine gel electrophoresis; the complex exhibits effective DNA cleavage activity in the absence of activating agents under similar physiological conditions.     

Analysis of ecstasy with a monolithic reversed-phase column

Summary A new, rapid, and precise liquid chromatographic method has been developed for simultaneous identification and quantification of amphetamine,N-methyl-3,4-methylenedioxymetamphetamine,N-ethyl-3,4-methylenedioxymetamphetamine, andN-methyl-1-(3,4-methyl-enedioxyphenyl)-2-butanamine in the presence of other constituents. The compounds were separated on a monolithic column with a gradient prepared from acetonitrile and 20mm monobasic potassium buffer at a flow rate of 1.5 mL min⁻¹. Quantitation was performed with metoclopramide as internal standard. Use of different flow rates was investigated and enabled reduction of the separation time from 11 to 3.5 min for seven substances. The method was then applied to ten seized tablets to identify and quantify their active ingredients.     

Determination of unconjugated aromatic acids in urine by capillary electrophoresis with dual electrochemical detection – Potential application in fast diagnosis of phenylketonuria

A novel method of CE coupled with dual electrochemical detection has been developed for the determination of pathological metabolites of phenylalanine in urine samples. Factors influencing the separation and detection were examined and optimized. Five aromatic acid metabolites and a major coexisting interfering compound uric acid could be well separated within 23 min at a separation voltage of 16 kV using a 35 mmol/L SDS/60 mmol/L H₃BO₃‐Na₂B₄O₇ running buffer (pH 8.2). Highly linear response was obtained for these five biomarker compounds over three orders of magnitude with detection limits ranging from 6.6 to 0.064 μg/mL (S/N=3). The average recovery and RSD were within the range of 92.6–121.0 and 1.0–12.0%, respectively. The proposed method has been used to detect the unconjugated aromatic acids simultaneously in urine samples with the advantages of obtaining more information about target analytes and avoiding redundant measurements and high assay cost, thus could find potential applications involving assays of biomarker compounds for the purpose of fast diagnose of some metabolic diseases including phenylketonuria.     

Influence of N-hexadecyl-N,N,N-trimethylammonium nitrate on the dehydrobromination reaction of 2-phenylethyl derivatives

The basis dehydrobromination of p-substituted 2-phenylethyl bromides promoted by hydroxide ion has been studied in micelles of N-hexadecyl-N,N,N-trimethylammonium nitrate (CTANO₃). The pseudophase ion exchange model can be adapted to explain the kinetic results at low hydroxide ion concentration, i.e., less than 0.075 M of NaOH. At high hydroxide ion concentration in solution the applied model does not describe the kinetic results unless the empirical variations are applied for the mol ratio of reactive ion to micellar head group (β) and the binding constant of the organic reagent to the micelle (K_s).     

HPLC enantioseparation of α,α‐diphenyl‐2‐pyrrolidinemethanol and methylphenidate using a chiral fluorescent derivatization reagent and its application to the analysis of rat plasma

Enantioseparation of α,α‐diphenyl‐2‐pyrrolidinemethanol (D2PM) and methylphenidate (MPH; Ritalin^®) using (R)‐(?)‐4‐(N,N‐dimethylaminosulfonyl)‐7‐(3‐isothiocyanatopyrrolidin‐1‐yl)‐2,1,3‐benzoxadiazole as the chiral derivatization reagent has been achieved for the first time, and a simple, reliable detection method using HPLC with fluorescence detection has been developed. D2PM and MPH have been derivatized with (R)‐(?)‐4‐(N,N‐dimethylaminosulfonyl)‐7‐(3‐isothiocyanatopyrrolidin‐1‐yl)‐2,1,3‐benzoxadiazole at 55°C for 15 min. The derivatives of D2PM and MPH have been separated, completely and rapidly, using a reversed‐phase system within 16 min (resolution factor (R_s)=1.60 and 2.53, respectively). The detection limits of (R)‐ and (S)‐D2PM were found to be 6.8 and 13 ng/mL, respectively, and those of D ‐ and L ‐threo‐MPH were 61 and 66 ng/mL, respectively (S/N=3). The proposed method was successfully applied to the analysis of rat plasma, where the rats were separately dosed with D2PM and MPH (Ritalin).     

Determination of Active Ingredients of Hawthorn by Capillary Electrophoresis with Electrochemical Detection

A method based on capillary electrophoresis with electrochemical detection has been developed for the separa-tion and determination of epicatechin,kaempferol,chlorogenic acid,4-hydroxybenzoic acid,quercetin and proto-catechuic acid in hawthorn for the first time.The effects of working electrode potential,pH and concentration ofrunning buffer,separation voltage and injection time on CE-ED were investigated.Under the optimum conditions,the analytes could be separated in a 60 mmol·L~(-1) borate buffer(pH 8.7)within 21 min.A 300 μm diameter carbondisk electrode has a good response at 0.95 V(vs.SCE)for all analytes.The response was linear over three ordersof magnitude with detection limits(S/N=3)ranging from 3×10~(-8) to 2×10~(-7) g·mL~(-1) for the analytes.The methodhas been successfully applied to the analysis of real sample,with satisfactory results.     

Application of Tri-n-octylamine for the substoichiometric separation of chromium(VI) in activation analysis

A method has been developed for the substoichiometric separation of Cr(VI) by extraction with tri-n-octylamine solution in benzene from 0.1M H₂SO₄ solution. The method has been applied to the determination of chromium in silicon and aluminium by the neutron activation method.     

Syntheses,Crystal Structures,and Antibacterial Activities of Four Schiff Base Complexes of Copper and Zinc

Four Schiff base complexes, [Cu₂(L1)₂(μ‐NCS)₂] ( 1 ), [Cu₂(L2)₂(μ‐N₃)₂] ( 2 ), Cu[Cu(CH₃COO)(L3)]₂ ( 3 ), and [Zn{Zn(C₃H₄N₂)(L3)}₂(NO₃)](NO₃) ( 4 ) (where L1 = 2‐[(pyridin‐2‐ylmethylimino)methyl]phenol, L2 = 1‐[(pyridin‐2‐ylmethylimino)methyl]naphthalen‐2‐ol, and L3 = bis(salicylidene)‐1, 3‐propanediamine), were synthesized and characterized by elemental analyses, infrared spectroscopy, and single crystal X‐ray determinations. Both 1 and 2 are structurally similar di‐nuclear complexes, which are located at crystallographic inversion centers (with the center of the central Cu₂N₂ ring). In 1 , each copper atom has a slightly distorted square pyramidal configuration, coordinated by two nitrogen atoms and one oxygen atom from L1 and another two terminal nitrogen atoms from two bridging thiocyanate anions. The Cu···Cu separation is 3.466(3) Å. The structure of 2 is similar to that of 1 , with Cu···Cu separation of 3.368(2) Å. Both 3 and 4 are linear tri‐nuclear complexes. In 3 , the central Cu²⁺ ion is located on an inversion centre and has a distorted octahedral coordination involving four bridging O atoms from two Schiff base ligands (L3) in the equatorial plane and one O atom from each bridging acetate group in the axial positions. The coordination around the terminal Cu²⁺ ions is irregular‐square pyramidal, with two O and two N atoms of L3 in the basal plane and one O atom from an acetate group in the apical position. The acetate bridges linking the central and terminal Cu²⁺ ions are mutually trans. The Cu···Cu separation is 3.009(3) Å. In 4 , the coordination configuration of the central and the terminal zinc atoms are similar to that of the 3 , with Zn···Zn separation of 3.153(4) Å. The three Schiff bases and the corresponding three copper complexes exhibit good antibacterial properties, while the zinc complex 4 has nearly no.     

Nitropyridines,their synthesis and reactions

Reaction of pyridine and substituted pyridines with N₂O₅ in an organic solvent gives the N‐nitropyridinium ion. When this is reacted with SO₂/HSO₃‐ in water, 3‐nitropyridine is obtained (77 % yield). With substituted pyridines the method gives good yields for 4‐substituted and moderate yields for 3‐substituted pyridines. The reaction mechanism is not an electrophilic aromatic substitution but one in which the nitro group migrates from the 1‐position to the 3‐position by a [1,5] sigmatropic shift. From 3‐nitropyridine, 5‐nitropyridine‐2‐sulfonic acid is formed in a two step reaction. From this, a series of 2‐substituted‐5‐nitropyridines has been synthesized. 3‐Nitropyridine and 4‐substituted‐3‐nitropyridines have been substituted with ammonia and amines by the vicarious nucleophilic substitution (VNS) method with ammonia and amines and by the oxidative substitution method in the position para to the nitro group. High regioselectivities and yields have been obtained in both cases to afford a series of 4‐substituted‐2‐alkylamino‐5‐nitropyridines. The VNS method has also been used in alkylation reactions with 3‐nitropyridines to form dichloromethyl‐and alkoxycarbomethyl‐β‐nitropyridines. From the appropriate substituted nitropyridines imidazopyridines and azaindoles have been formed.     

Trennung von spaltprodukten durch Extraktionschromatographie

The separation of fission products which form anionic species in mineral acids and of uranium and neptunium from samples of neutron-irradiated uranium is described. The method used is extraction chromatography with tri-n-butylphosphate (TBP) and di-(2-ethylhexyl)-orthophosphoric acid (HDEHP) as extractants and polytrifluoromonochloroethylene powder as the solid support. In the first column Zr, U and Np are extracted with TBP from 8N HNO₃/NaClO₃. In the second column, HDEHP is applied as extractant and 9N HCl/NaClO₃ as the mobile phase for the isolation of Nb, Sb, and I, and in the third column (HDEHP), the rare earths and Mo are extracted from 0.1N HCl. Finally with the fourth column (TBP), Te and Tc are isolated from 6N HCl. These four groups of elements are further separated by elution from the columns. From the final effluent containing Ru, Rh, Cs, Sr, and Ba, Ru is distilled from HClO₄, and Rh is precipitated with NH₄OH. The determination of chemical yields with X-ray fluorescence techniques is described for Zr, Mo, Te, Cs, Ce and U.

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Aus einer Dissertation, Mainz 1967.     

A tetranuclear copper(II) complex: crystal structure,assembly, EPR,electrochemistry and magnetism

A tetranuclear copper(II) complex, [Cu₂L]₂(ClO₄)₂ · 4H₂O (1), where H₃L = N,N′-bis(4-(3′-formyl-5′-chlorosalicyclidene)iminoethyl)-4-chloro-2,6-bimethyliminophenol, has been synthesized and structurally characterized by ES-MS, IR and X-ray crystallography. The complex is a dimer of two dinuclear copper(II) acylic enantiomorph subunits ([Cu₂L]ClO₄ · 2H₂O), held together by π–π, coordination and hydrogen bond interactions. The Cu–Cu separation in each subunit, bridged by one phenoxide, is 3.228 Å, and the shortest distance of Cu–Cu between the two subunits is 3.252 Å. There are two crystallographically unique copper(II) environments, one (Cu1) is square-based pyramidal with O₃N₂ donor set, another (Cu2) square planar with O₂N₂ donor set. The cyclic voltammogram of the complex shows that it undergoes two stepwise reduction processes, E _pc = ?0.707 and ?0.850 V, respectively. Magnetic measurements in the 2–300 K range indicate strong antiferromagnetic interactions between Cu(II) ions in each subunit with the exchange constant J = ?211(2) cm^?1. The observation has been rationalized on the basis of the effective magnetic pathway.     

Enantiomeric bis(μ‐N,N′‐hexamethylenedisalicylaldiminato)dicopper(II) complexes

The title dimeric complex, bis{μ‐2,2′‐[hexane‐1,6‐diyl­bis(nitrilo­methyl­idyne)]­diphenolato‐1:2κ⁴O,N:N′,O′}dicopper(II),[Cu₂(C₂₀H₂₂N₂O₂)₂], has been investigated by single‐crystal X‐ray diffraction, by thermogravimetric analysis and differential scanning calorimetry, and also by FT–IR spectroscopy. Different synthetic and crystallization procedures gave crystals which were quite different in appearance, and it was initially thought that these were different polymorphic forms. Subsequent structure determination showed, in fact, serendipitous preparation of crystals in the P4₁ space group by one method and in space group P4₃ by the other. In these enantiomorphic structures, the Cu atoms have a distorted flattened tetrahedral coordination, with Cu—N and Cu—O distances in the ranges 1.954 (4)–1.983 (4) and 1.887 (4)–1.903 (4) Å, respectively.     

Determination of neurotransmitter amino acids in mouse central nervous system by CE–LIF

An MEKC method with LIF detection has been developed for the determination of seven neurotransmitter amino acids (NAAs) using 1,3,5,7‐tetramethyl‐8‐(N‐hydroxysuccinimidyl butyric ester)difluoroboradiaza‐S‐indacene as the labeling reagent. After derivatization at room temperature for 30 min, the seven target NAAs including glycine, alanine, γ‐aminobutyric acid, taurine, glutamine, glutamic acid, and aspartic acid were separated in running buffer, which consisted of 70 mM pH 4.00 H₃PO₄/Na₃PO₄ buffer, 5.5 mM cetyltrimethyl ammonium bromide and 20% v/v acetonitrile within 17 min. The LODs were 2 ～ 14 × 10^?10 M without interference from other coexisting amino acids. The proposed method has been applied to the analysis of NAAs in the central nervous systems of healthy mice and those with Alzheimer's disease with recoveries of 92–104%.     

A rapid separation of radioactive cesium by nitrobenzene extraction using the chromium complex [Cr(aniline)2(NCS)4]−

A rapid separation of radioactive cesium by the solvent extraction method was investigated. Cesium ions are quantitatively extracted with [Cr(NH₂C₆H₅)₂(NCS)₄]⁻ into nitrobenzene. EDTA is an effective masking agent for other polyvalent cations. The extracted cesium can be back-extracted into the aqueous phase by shaking with 6N HCl. The method was applied to samples of a natural mixture of fission products and a reactor coolant. The decontamination factors for other predominant isotopes in fission products were 10²∼10⁴. The separation of^137m Ba from a mixture of¹³⁷Cs and^137m Ba is also described.     

A study concerning the synthesis,basicity and hydrolysis of 4‐amino‐2‐(N,N‐diethylamino)quinazoline derivatives

A group of 2‐(N,N‐diethylamino)‐4‐aminoquinazoline derivatives have been synthesized in the reaction of N¹,N¹‐diethyl‐N²‐arylchlorocarboxyamidines with cyanamide in the presence of T1Cl₄ as a catalyst. Such quinazolines decompose into the corresponding quinazolones in dilute aqueous HC1 solutions at higher temperature. Hydrolysis rates of 2‐(N,N‐diethylamino)‐4‐aminoquinazoline and 2‐(N,N‐diethylamino)‐4‐(N,N‐dimethylamino)‐quinazoline have been determined to observe the influence of substituents at the 4‐amino group upon the hydrolysis. pK_a values have been also determined for these compounds and analyzed in conjunction with the Hammett σ constants.     

Approximate ansatz for the expansion of the spherically averaged wave function in terms of interelectronic separation r12 for the Hookean atom,atomic ions,and the H2 molecule

For the two‐electron Hookean atom, it is first emphasized that, for a specific force constant k = 1/4, the ground‐state wave function has a simple dependence on the interelectronic separation r₁₂, namely, (1 + ½r₁₂)exp(??r). For this two‐electron model, therefore, the study of Rassolov and Chipman on the electron–electron cusp conditions on the spherically averaged wave function for the N electron atomic ions can be generalized to all orders in the interelectronic separation r₁₂. This Hookean model has therefore been used to give some justification for an ansatz for the spherically averaged wave function in atomic ions with N electrons for N ≥ 2. Several approximate two‐electron wave functions satisfying the Rassolov and Chipman conditions were tested and found to give excellent results. Another ansatz has been tested numerically on the ground state of two‐electron atomic ions and the H₂ molecule. Finally, for the Hookean atom a partial differential equation that is essentially for the pair correlation density is given in the Appendix . © 2003 Wiley Periodicals, Inc. Int J Quantum Chem 95: 21–29, 2003