Non-aqueous capillary zone electrophoresis method for the analysis of paroxetine, tamoxifen, and their main metabolites in urine

The potential of non-aqueous capillary electrophoresis (NACE) was investigated for the simultaneous separation of paroxetine, tamoxifen, and their main metabolites. Baseline separation of the studied solutes was obtained on a  μm capillary using a non-aqueous buffer composed of 18 mM ammonium acetate and 1.1% acetic acid in 80:20 (v/v) methanol-acetonitrile, with a temperature and voltage of 22 °C and 15 kV, respectively. Clomipramine was used as internal standard. Aspects such as stability of the solutions, linearity, accuracy, precision and ruggedness were examined in order to validate the proposed method. Detection limits obtained for all the studied compounds ranged between 3.0 and 7.1 μg l⁻¹. The developed method is sensitive and robust and was used to determine paroxetine, tamoxifen, and their metabolites at clinically relevant levels in human urine. Before NACE determination, the samples were purified and enriched by means of an extraction-pre-concentration step with a pre-conditioned C₁₈ cartridge. Determination of these analytes in the urine of four females urines was demonstrated.     

Determination of sulfur-containing amino acids by capillary electrophoresis dynamic reaction cell inductively coupled plasma mass spectrometry

Capillary electrophoresis dynamic reaction cell™ inductively coupled plasma mass spectrometry (CE-DRC-ICP-MS) for the determination of sulfur-containing amino acids is described. The sulfur-containing amino acids studied include l-cysteine, l-cystine, dl-homocystine and l-methionine. The species studied were well separated using a 70 cm length×75 μm i.d. fused silica capillary while the applied voltage was set at +22 kV and a 10 mmol l⁻¹ disodium tetraborate buffer (pH 9.8) containing 0.1 mmol l⁻¹ EDTA and 0.5 mmol l⁻¹ Triton X-100 was used as the electrophoretic buffer. The sulfur-selective electropherogram was determined at m/z 48 as by using its reaction with O₂ in the reaction cell. The method avoided the effect of polyatomic isobaric interferences at m/z 32 caused by and on by detecting as the oxide ion at m/z 48, which is less interfered. The detection limit of various species studied was in the range of 0.047-0.058 μg S ml⁻¹, which corresponded to the absolute detection limit of 1.3-1.6 pg S based on the injection volume of 27 nl. We determined the concentrations of selected sulfur-containing amino acids in urine and nutritive complement samples. The recovery was in the range of 92-128% for various species.     

A validated liquid chromatographic tandem mass spectrometric method for the determination of mirtazapine and demethylmirtazapine in human plasma: application to a pharmacokinetic study

A new liquid chromatographic tandem mass spectrometric method for the determination of mirtazapine and demethylmirtazapine in human plasma has been developed and fully validated. The article describes in detail the bioanalytical procedure and summarizes the validation results obtained. The samples were extracted using liquid-liquid extraction with a mixture of 1-chlorobutane/isopropanol/ethyl acetate (88:2:10, (v/v/v)). The chromatographic separation was performed on a reversed-phase XTerrra MS C₈ column ( i.d.; 3.5 μm particle size) using a mobile phase consisting of 0.010 M ammonium formate (pH 7.8) and acetonitrile (35:65, (v/v)), pumped at a flow rate of 0.80 ml min⁻¹. The analytes were detected using a Finnigan LCQ advantage ion-trap mass spectrometer with positive electrospray ionization in selected reaction monitoring (SRM) mode. Tandem mass spectrometric detection enabled the quantitation of both compounds down to 0.10 ng ml⁻¹. Calibration graphs were linear (r better than 0.990, n=11), in concentration ranges 0.10 to 200 ng ml⁻¹ for mirtazapine demethylmirtazapine. The intra- and inter-day R.S.D. values were less than 14.8 and 16.6% for mirtazapine and demethylmirtazapine, respectively. The method was successfully applied to a kinetic study in order to assess the main pharmacokinetic parameters of mirtazapine and demethylmirtazapine.     

Reactions of pyridyl donors with halogens and interhalogens: an X-ray diffraction and FT-Raman investigation

Three different N-donors L, namely N-ethyl-N′-3-pyridyl-imidazolidine-4,5-dione-2-thione (1), N,N′-bis(3-pyridylmethyl)-imidazolidine-4,5-dione-2-thione (2), and tetra-2-pyridyl-pyrazine (3), bearing one, two and four pyridyl substituents, respectively, have been reacted with halogens X₂ (X = Br, I) or interhalogens XY (X = I; Y = Cl, Br). CT σ-adducts L · nXY, bearing linear N?XY moieties (L = 3; X = I; Y = Br, I; n = 2), and salts containing the protonated cationic donors H_nLⁿ⁺ (L = 1 − 3; n = 1, 2, 4), counterbalanced by Cl⁻, Br⁻, , , , , I₂Br⁻, , or anions, have been isolated. Among the reactions products, (H1⁺)Cl⁻, (H1⁺)Br⁻, , , and 3 · 2IBr have been characterised by single-crystal X-ray diffraction. The nature of the products has been elucidated based on elemental analysis and FT-Raman spectroscopy supported by MP2 and DFT calculations.     

A one-dimensional zirconium hydroxyfluoride, [Zr(OH)2F3][enH]

The first example of a unidimensional zirconium hydroxide fluoride was synthesized under mild solvothermal treatment and characterized by X-ray diffraction and thermal techniques. Monoprotonated ethylenediamine cations reside between the anionic chains. Crystal data for this material are as follows: [C₂N₂H₉][Zr(OH)₂F₃], M=243.35, orthorhombic, space group Pca2₁, a=6.8016(13), b=6.1393(12), , , , Z=4, , μ(Mo-Kα)=1.777 mm⁻¹, . The material transforms to an unknown layered material at ∼175 °C, a common occurrence for 1D structures where the chains are arranged in hydrogen-bonded layers and separated by interlayer organoammoniums. Collapse to the known condensed mineral phase Zr(FO)_2.7 occurs at ca. 275 °C before finally transforming to the baddeleyite form of ZrO₂ at ca. 460 °C.     

Hetero dimer from tetrakisammonium cavitand and tetratopic crown ether cavitand

Hetero dimer between tetrakis(m-ammonium)cavitand and tetrakis(dibenzo-25-crown-8)cavitand 5 was formed in CDCl₃ at room temperature. The effects of solvent polarity and temperature on the stability of were studied and the thermodynamic parameters for the formation of are , ΔH⁰ = −67.4 kcal mol⁻¹ and ΔS⁰ = −201.6 cal mol⁻¹ K⁻¹.     

Synthesis and application of novel ionic phosphine ligands with a cobaltocenium backbone

Six novel ionic phosphine ligands with a cobaltocenium backbone, 1,1′-bis(dicyclohexylphosphino) cobaltocenium hexafluorophosphate () (1a), 1,1′-bis(di-iso-propylphosphino) cobaltocenium hexafluorophosphate () (2a), 1,1′-bis(di-tert-butylphosphino) cobaltocenium hexafluorophosphate () (3a), and the monophosphine ligand (Cc⁺ = cobaltocenium; R = Cy, 1b; R = i-Pr, 2b; R = t-Bu, 3b) were synthesized and characterized by elemental analysis, spectroscopy, and X-ray diffraction techniques. These ligands are air-stable and useful for Suzuki coupling reactions in the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (), enabling high catalytic activity.     

Syntheses, structures, and magnetic properties of the europium(II) selenido pnictogenates(III), EuPnSe3 (Pn=Sb, Bi)

EuPnSe₃ (Pn=Sb, Bi) have been synthesized through the reaction of Eu with Pn₂Se₃ (Pn=Sb, Bi) and Se at 850-900 °C. These compounds are isotypic with SrPnSe₃ (Pn=Sb, Bi) and consist of square pyramidal PnSe₅ units and distorted PnSe₆ octahedra that form hollow columns that extend along the c-axis. These columns are separated by Eu²⁺ cations that occur as nine-coordinate tricapped trigonal prisms. There are also additional V-shaped triselenide Se₃²⁻ anions between the columns that bind the Eu²⁺ cations. The Se?Se contacts (in EuSbSe₃) in these units are 2.4584(11) and 2.4359(11) Å, which are consistent with Se-Se single bonds. The overall structure is chiral. Bond-valence sum calculations indicate that these compounds contain Eu²⁺. Magnetic susceptibility measurements provide values of 7.66 μ_B/Eu for EuSbSe₃ and 7.64 μ_B/Eu for EuBiSe₃, which are close to the expected free-ion moment for Eu²⁺. These compounds follow essentially Curie behavior from 300 to 5 K, and undergo an apparently antiferromagnetic transition below 5 K. Crystallographic data: EuSbSe₃, orthorhombic, space group P2₁2₁2₁, , , , , Z=16, R(F)=2.63% for 183 parameters and 5095 reflections with I>2σ(I); EuBiSe₃, orthorhombic, space group P2₁2₁2₁, , , , , Z=16, R(F)=2.68% for 183 parameters and 4895 reflections with I>2σ(I).     

Synthesis and crystal structures of the layered uranyl tellurites A2[(UO2)3(TeO3)2O2] (A=K, Rb, Cs)

The reactions of UO₃ and TeO₃ with KCl, RbCl, or CsCl at 800 °C for 5 d yield single crystals of A₂[(UO₂)₃(TeO₃)₂O₂] (A=K (1), Rb (2), and Cs (3)). These compounds are isostructural with one another, and their structures consist of two-dimensional sheets arranged in a stair-like topology separated by alkali metal cations. These sheets are comprised of zigzagging uranium(VI) oxide chains bridged by corner-sharing trigonal pyramidal TeO₃²⁻ anions. The chains are composed of dimeric, edge-sharing, pentagonal bipyramidal UO₇ moieties joined by edge-sharing tetragonal bipyramidal UO₆ units. The lone-pair of electrons from the TeO₃ groups are oriented in opposite directions with respect to one another on each side of the sheets rendering each individual sheet non-polar. The alkali metal cations form contacts with nearby tellurite oxygen atoms as well as with oxygen atoms from the uranyl moieties. Crystallographic data (193 K, MoKα, ): 1, triclinic, space group , , , , α=101.852(1)°, β=102.974(1)°, γ=100.081(1)°, , Z=2, R(F)=2.70% for 98 parameters and 1697 reflections with I>2σ(I); 2, triclinic, space group , , , , α=105.590(2)°, β=101.760(2)°, γ=99.456(2)°, , Z=2, R(F)=2.36% for 98 parameters and 1817 reflections with I>2σ(I); 3, triclinic, space group , , , , α=109.301(1)°, β=100.573(1)°, γ=99.504(1)°, , Z=2, R(F)=2.61% for 98 parameters and 1965 reflections with I>2σ(I).     

Determination of arsenic, iron and selenium in moss samples using hexapole collision cell, inductively coupled plasma-mass spectrometry

Different collision gases (H₂, He and premixed 7% H₂ in He) used in the hexapole collision cell of an inductively coupled plasma-mass spectrometer (ICP-MS) were compared, and the gas-flow rates were optimized for the determination of arsenic (), iron () and selenium (). The study showed that the argon-based interferences at mass-to-charge ratios (m/z) of 56, 75 and 80 can be overcome by the optimized gas flows (7.5 ml min⁻¹ premixed 7% H₂ in He and 2 ml min⁻¹ H₂) in the hexapole collision cell. Detection limits of 15.5 ng l⁻¹ for iron () and 29 ng l⁻¹ for selenium () in 2% (v/v) HNO₃ were obtained under optimized collision cell conditions. The detection limit for arsenic () obtained in difficult hydrochloride acid matrix (5% HCl (v/v)) was 153 ng l⁻¹. The accuracy of the optimized method was confirmed by analyzing two moss reference materials. The results obtained by ICP-MS for arsenic, selenium and iron from both moss reference samples were, in most cases, in good agreement with the certified values.     

Syntheses, crystal and electronic structure, and some optical and transport properties of LnCuOTe (Ln=La, Ce, Nd)

Three new compounds, LaCuOTe, CeCuOTe, and NdCuOTe, have been synthesized from the respective rare-earth elements, CuO, and a KI flux at 1023 K. The compounds, which have the ZrSiCuAs structure type, are isostructural to LaCuOS, and crystallize in space group P4/nmm of the tetragonal system with two formula units in cells of dimensions at 153 K of , , for LaCuOTe; , , for CeCuOTe; and , , for NdCuOTe. The structure of LnCuOTe (Ln=La, Ce, Nd) is composed of alternating PbO-like [Ln₂O₂] and anti-PbO-like [Cu₂Te₂] layers stacked perpendicular to [0 0 1]. The experimental optical band gaps of LaCuOTe and NdCuOTe are 2.31 and 2.26 eV, respectively. At 298 K the electrical conductivity of LaCuOTe is 1.65 S/cm and the Hall mobility is +80.6 cm² V⁻¹ s⁻¹. The positive values of the Seebeck and Hall coefficients indicate p-type electrical conduction. First-principles theoretical calculations were performed on LaCuOQ (Q=S, Se, Te). In LaCuOTe, Cu 3d and Te 5p orbitals dominate the states near the valence band maximum; the states near the conduction band minimum are composed of Cu 4s, Te 5p, and La 5d orbitals. The larger dispersion of Cu 3d orbitals and the presence of Te 5p orbitals near the valence band maximum are responsible for the larger hole mobility of LaCuOTe compared to LaCuOS and LaCuOSe.     

Synthesis of poly(ethylene adipate) and poly(ethylene adipate-co-terephthalate) via ring-opening polymerization

Syntheses of poly(ethylene adipate) (ROP-PEA) and poly(ethylene adipate-co-terephthalate) (ROP-PEA-co-PET) were achieved via ring-opening polymerization of corresponding cyclic oligoesters. In case of ROP-PEA, cyclic oligo(ethylene adipate) (C-OEA) was equilibrated in the presence of di-n-butyltin oxide as a catalyst under high-concentration conditions at 180 and 200 °C for 1-24 h. The polymer products were obtained in yields up to 100% with the and in the ranges of 3000-23 000 g/mol and 5000-60 000 g/mol, respectively. The ROP-PEA-co-PET was prepared by equilibrating an equimolar amount of C-OEA and cyclic oligo(ethylene terephthalate) (C-OET) using di-n-butyltin oxide catalyst under high-concentration conditions at 250 °C for 24 h. The copolyester produced was obtained in yield of 97% with the and of 18 000 and 46 000 g/mol, respectively. ¹H NMR spectrum of ROP-PEA-co-PET showed two new proton signals of ethylene unit representing the existence of heterolinkage with different chemical environment in the copolymer. This indicated the random transesterification of C-OEA and C-OET resulting in random structure in copolyester. In addition, the result of ROP-PEA-co-PET from DSC showed the glass transition temperature in the values of −8 °C with no melting temperature indicating thermoplastic elastomeric behavior.     

Crystal growth, characterization and physical properties of PrNiSb3, NdNiSb3 and SmNiSb3

The crystal structures of three new intermetallic ternary compounds in the LnNiSb₃ (Ln=Pr, Nd and Sm) family have been characterized by single crystal X-ray diffraction. PrNiSb₃, NdNiSb₃ and SmNiSb₃ all crystallize in an orthorhombic space group, Pbcm (No. 57), Z=12, with , , , and ; , , , and ; and , , , and , for Ln=Pr, Nd and Sm, respectively. These compounds consist of rare-earth atoms located above and below layers of nearly square, buckled Sb nets, along with layers of highly distorted edge- and face-sharing NiSb₆ octahedra. Resistivity data indicate metallic behavior for all three compounds. Magnetization measurements show antiferromagnetic behavior with (PrNiSb₃), 4.6 K (NdNiSb₃), and 2.9 K (SmNiSb₃). Effective moments of 3.62 μ_B, 3.90 μ_B and 0.80 μ_B are found for PrNiSb₃, NdNiSb₃ and SmNiSb₃, respectively, and are consistent with Pr³⁺ (f ²), Nd³⁺ (f ³), and Sm³⁺ (f ⁴).     

Enthalpies of solution of 1,1,3,3-tetramethylurea in normal and branched alkanols (C2-C4) at 298.15 K

The enthalpies of solution were determined for 1,1,3,3-tetramethylurea in ethanol, 1-propanol, 2-propanol, 1-butanol, and t-butanol (2-methyl-2-propanol). Measurements were made at 298.15 K and molalities m ≅ (0.007 to 0.036) mol · kg⁻¹ with a precise isoperibol ampoule-type calorimeter. Standard enthalpies of solution and transfer from one alkanol to the other (including methanol) were calculated. The obvious relationship between the enthalpic and volumetric effects of solution of tetramethylurea in the n-alkanols (C₁-C₄) was discovered. The enthalpic effects of transfer caused by branching of the alkanol molecules, 1-propanol → 2-propanol, and 1-butanol → t-butanol, are opposite in sign and dominated by the configurational changes in the solvation environment of tetramethylurea.     

Phase polymorphism of [Zn(DMSO)6](ClO4)2 studied by differential scanning calorimetry

Four solid phases of [Zn(DMSO)₆](ClO₄)₂ have been detected by differential scanning calorimetry (DSC). Specifically, the phase transitions were detected between: metastable phase KII ↔ supercooled phase K0 at , stable phase KIb ↔ stable phase KIa at , stable phase KIa ↔ stable phase K0 at . At T_m2 = 389 K crystals partially and at T_m1 = 465 K completely melts. From the entropy change values it was concluded that the phases: K0 and K0′ are the orientationally dynamically disordered phases, so called ODDIC crystals, and phases KIa, KIb and metastable KII are dynamically ordered but with some degree of positional disorder.     

Quaternary ammonium salt-based chromogenic and fluorescent chemosensors for fluoride ions

Chemosensors 5-7 possessing a quaternary ammonium cation (for electrostatic interactions) and an N-H group(s) (for H-bonding) as recognition sites and an anthracene-9,10-dione as both a chromogenic and fluorescent moiety exhibit absorption and emission changes with fluoride ions only. No significant response to other anions such as Cl⁻, Br⁻, I⁻, , CH₃COO⁻, , and is observed. The dual emission at λ_max 580 nm (free 5/6) and λ_max 510 and 540 nm (5/6 + F⁻) in chemosensors 5 and 6 enables ratiometric analysis of fluoride ions.