Analysis of organomercury compounds in sediments by capillary GC with atomic fluorescence detection

Analysis of methyl- and ethylmercury (MM and EM) halides in biological and environmental samples is generally performed by gas chromatography with electron capture detection. Tedious sample work-up protocols and poor chromatographic response (using packed columns) have, however, shown the need for the development of new methods in this field. This paper reports a sensitive method, free from these deficiencies, for the determination of methyl- and ethylmercury. The organomercury compounds (MM and EM) are first released from the sample matrix, by the combined action of acidic potassium bromide and cupric ions, and then extracted into dichloromethane. The initial extracts are subjected to thiosulfate clean-up and the organomercury species are isolated as their chloride derivatives by addition of cupric chloride, and subsequent extraction into a small volume of organic solvent. Capillary GC coupled with atomic fluorescence detection provided excellent separation efficiencies for methyl- and ethylmercury and proved to be a very selective and sensitive technique. The absolute detection limit for both MM and EM was found to be 0.2 pg.     

Determination of methyl- and ethylmercury in rat blood and tissue samples by capillary gas chromatography with electron-capture detection

A precise and accurate method has been developed for the determination of either methyl- or ethylmercury in the blood and tissue of rats using capillary gas chromatography with electron-capture detection. The biological sample was spiked with an internal standard (methyl- or ethylmercury chloride) and after treatment with sodium thiosulphate and cupric bromide the alkylmercurials were extracted into benzene as their bromide derivatives and analysed on an OV-275 glass capillary column. The sensitivity and selectivity of the method enabled determinations to be made on small volumes of blood and tissue homogenates. The method has been applied to a pharmacokinetic study in rats dosed orally with 8 mercury as methylmercury chloride or ethylmercury chloride.     

Nickel(II) and cobalt(II) complexes of 2,4-diaminothieno[2,3-d]-pyrimidines

Summary The reactions of methyl-2-amino-4-diethylamino thieno-[2,3-d]pyrimidine 6-carboxylate, methyl-2-amino-4-ethyl-phenylamine thieno-[2,3-d]pyrimidine-6-carboxylate) and methyl-2-amino, 4-morpholino-thieno-[2,3-d]pyrimidine-6-carboxylate with Ni^II and Co^II halides produced complexes of the general formula ML₂X₂ (where L is thieno pyrimidine and X is Cl or Br). The complexes were characterized by elemental analyses, conductivity and magnetic susceptibility measurements and spectroscopy. All of the complexes were found to have pseudotetrahedral structures with the metal coordinated through the N(1) site of the thieno-[2,3-d]-pyrimidine.     

Paper chromatography in the separation of ions : Separation of silver,copper and arsenic group elements

A paper Chromatographic study ot the separability of ions of elements of the silver, copper and arsenic groups, using different solvents and a number of complexing agents, reveals that the solvents consisting of (1) acetone, hydrochloric or acetic acid (with or without ammonium iodide) and (2) tert. -butyl alcohol, hydrochloric or acetic acid, promote the complete separation of at ; least five elements present in microgram amounts in a mixture. Other complexing agents, such as thiourea, bismuthiol I, bismuthiol II and 2-mercaptobenzothiazole are not very useful in the separation of the ions. The R_I., R_T values and the sequences of separation are tabulated to show their behaviour.     

Unperturbed dimensions of poly-p-chlorostyrene

Viscosity measurements on poly-p-chlorostyrene (PPCS) in benzene-methanol mixtures have been carried out at their corresponding theta temperatures determined by the phase separation method. Viscosity measurements were also run in benzene at the same temperatures. The Stockmayer-Fixman extrapolation method was applied to the data to obtain the chain unperturbed dimensions. K_θ. It was found that these, for PPCS in benzene, decrease with increasing temperature and that, both in benzene and in binary mixtures, they decrease with increasing values of the parameter a from the relationship [η] = KM^α. PPCS theta temperature in benzene was 8.     

Estimation of Perospirone in Human Plasma by LC–MS–MS and Its Application to Pharmacokinetics Study

A sensitive liquid chromatography-tandem-mass spectrometry method was developed and validated for the determination of perospirone in human plasma, using quetiapine as internal standard. Plasma samples were extracted from 1 mL of plasma using n-hexane. Chromatographic separation was performed on an Agilent Zorbax SB C₁₈ column with a mobile phase of 5 mM ammonium acetate solution-methanol (12:88, v/v, adjusted to pH 3.8 with glacial acetic acid) at a flow rate of 0.2 mL min^?1. The chromatographic separation was achieved in less than 4.6 min. The linearity was established over the concentration range of 0.05–20 ng mL^?1. Both of the intra- and inter-batch standard deviation was less than 9.8%. The method was successfully applied to study the pharmacokinetic parameters of perospirone hydrochloride tablets in healthy Chinese volunteers.     

Adsorption of organics on MSC5A in supercritical CO2, chromatographic measurements & stop & go simulation

Chromatographic measurements were made for the adsorption of benzene, toluene and m-xylene on molecular sieving carbon (MSC) in supercritical fluid CO₂ mixed with organics. Supercritical chromatograph packed with MSC was used to detect pulse responses of organics. Adsorption equilibria and adsorption dynamics parameters for organics were obtained by moment analysis of the response peaks. Dependences of adsorption equilibrium constants, K ^?, and micropore diffusivity,?D, on the amount adsorbed were examined. The dependencies of adsorption equilibrium constants, K ^?, and micropore diffusivity, D, of benzene, toluene and m-xylene, on molarity of benzene with each parameters of temperature or pressure were obtained. It was found that the values of K ^? and D for an organic substance depended on the amount adsorbed of other organics strongly. And stop & go method was used as simulation method of perturbation chromatography for investigating adsorption equilibrium and rate. Numerical solution for multicomponent chromatogram in time domain could be obtained by appropriate model equations with experimental conditions. This simulated chromatogram can be compared with experimental chromatogram to determine the adsorption equilibrium and rate parameters. In addition, molecular simulation of multicomponent adsorption equilibria was performed, and potential parameters were determined by comparing the simulation with experimental results. Simulation soft ware is Cerius2 (Version?4.2) made by MSI. The purpose of performing simulation is to elucidate an adsorption mechanism on the molecule level.     

The study of iron(III) and gold(III) separation by paper chromatography using diisopropyl ether

The influence of experimental conditions on the Chromatographic behavior and separation efficiency of iron(III) and gold(III) in partition paper chromatography was investigated, when solvents containing diisopropyl ether (IPE) were used. The influence of temperature (range investigated from 15 to 50 °C), initial acid concentration (1–11 M HCl), and concentration of active solvent component (0.7–7.1 M IPE, benzene as diluent) on the R_f values were particularly studied. Ascending technique using Whatman No. 1 paper was employed. Considerable influence of temperature was found. The best separation (ΔR_f = 0.26) was achieved with 9 M concentration of hydrochloric acid and 3.6 M (50% volume) concentration of IPE.     

Solvent extraction of zinc by 2-hexylpyridine in benzene from aqueous mineral acid — Thiocyanate media

Solvent extraction of Zn(II) by 2-hexylpyridine (HPy) in benzene has been studied from aqueous mineral acid—thiocyanate media. The extraction, though dependent on the acidity of the aqueous phase, is poor from mineral acids (HCl, HNO₃ or H₂SO₄). Addition of 0.02M KSCN to the aqueous phase enhances the distribution ratio by a factor of almost one thousand. The stoichiometry of the extracted complex established by the usual slope analysis method indicates that an ionic type complex, e.g. Zn(SCN)₄·(HPyH)₂, is responsible for extraction. Complexing anions like acetate, oxalate or citrate at 1 M concentration mask the extraction of Zn(II) almost completely. Separation factors determined at optimal conditions (0.1M HPy in benzene −0.05M H₂SO₄+0.2M SCN⁻) indicate that Zn(II), along with Hg(II), can be separated in a single extraction from a number of metals, e.g. Cs(I), Sr(II), Ln(III), Y(III), Cr(III) and (VI). Other metals of interest like Cu(II), Co(II), Fe(III), Mo(VI), U(VI) and Tc(VII) are coextracted but the separation factors are large enough to allow separation in a multistage extraction process.     

Evaluation of some Isolation Methods for Organomercury Determination in Soil and Fish Samples by Capillary Gas Chromatography—Atomic Fluorescence Spectrometry

Abstract

Three extraction methods, acidic KBr/CuSO₄ isolation-methylene chloride extraction. acidic KBr/CuSo₄ isolation-methylene chloride extraction with an alkaline digestion pretreatment, and an extration method at a milder condition with citrate buffer and dithizone in chloroform, were studied for methylmercury and ethylmercury determination in soils, sediments and fish samples by the recently developed capillary gas chromatography—atomic fluorescence spectrometry system (GC-AFS). The acidic KBr/CuSO₄-methylene chloride extraction and the acidic KBr/CuSO₄-methylene chloride extraction with an alkaline digestion pretreatment were shown to be the effective methods for soils/sediments and fish samples analysis, respectively. The presence of ethylmercury species in soils of the Florida Everglades, observed with the acidic KBr/CuSO₄ isolation and methylene chloride extraction procedure, was further confirmed with the dithizone complexation/extraction procedure. The GC-AFS analytical method offers high senstivity and selectivity for the determination of organomercury halides. The GC column maintenance, a critical step for organomercury halides analysis using GC, is also discussed.     

Novel vic-dioxime ligand containing calix[4]pyrrole moiety: synthesis,characterization, anion binding studies and complexation with Ni(II)

A new vic-dioxime functionalized calix[4]pyrrole was synthesized from anti-chloroglyoxime and 4-aminophenyl-calix[4]pyrrole at room temperature. The Ni(II) complex has been prepared by reacting the ligand with NiCl₂·6H₂O in ethanol. These receptors were characterized by elemental analyses, ¹H and ¹³C NMR spectra, IR and mass spectra. Electrochemical properties of the ligand, and its Ni(II) complex were investigated in CH₂Cl₂ solution by cyclic voltammetry at 100 mV s^?1 scan rate. Anion-binding studies were carried out using UV–Vis, and ¹H NMR titrations, revealed that the Ni(II) complex exhibits selective recognition toward F^? over other anions. The selectivity for F^– among the halides is attributed mainly to the hydrogen-bond interaction of the receptor with F^–. Receptor showed colour change from red to brown in the presence of tetrabutylammonium fluoride (TBAF) with 1:2 stoichiometry.     

Growth of a faujasite-type zeolite membrane and its application in the separation of saturated/unsaturated hydrocarbon mixtures

Faujasite type zeolite membranes were synthesized on porous ceramic alumina supports by using direct (in situ) and secondary (seeded) growth methods. In the secondary growth method a seed layer of ZSM-2 nanocrystals (prepared according to a report by Schoeman et al. J. Colloid Interface Sci. 1995, 170, 449–456) was deposited on the surface of the support before the hydrothermal growth. For both in situ and secondary growth, the mixture composition was 4.17 Na₂O:1.0 Al₂O₃:10 TEA (triethanol ammonium):1.87 SiO₂:460 H₂O. X-ray diffraction (XRD), scanning electron microscopy (SEM), and electron microprobe analysis (EPMA), indicate well intergrown 5–30 μm thick FAU films with Si/Al ∼1–1.5. The separation of saturated/unsaturated hydrocarbon mixtures is demonstrated over a range of temperatures (40–160°C). The mixtures examined (and the corresponding equimolar mixture separation factors) are benzene/cyclohexane (160), benzene/n-hexane (144), toluene/n-heptane (45), propylene/propane (6.2), and ethylene/methane (8.4). In all cases, the membranes are unsaturated hydrocarbon permselective. With equimolar feed mixtures (5 kPa/5 kPa benzene/cyclohexane) and in the temperature range 65–160°C, the membranes exhibit separation factor of 20–160 with the benzene flux in the range 10⁻⁴–10⁻³ mol m⁻² s⁻¹. Decreasing the total feed partial pressure (0.31/0.31 kPa benzene/cyclohexane) reduces both separation factor (12) and benzene flux. Similar trend is observed when the benzene/cyclohexane ratio in the feed mixture (0.5/9.5 kPa benzene/cyclohexane) is reduced. A sorption diffusion model based on the Stefan–Maxwell formulation has also been employed to show that the benzene/cyclohexane separation can mainly be attributed to differences of their adsorption properties.     

Syntheses, characterizations and crystal structures of two new lead(II) amino and carboxylate-sulfonates with a layered and a pillared layered structure

Reactions of lead(II) acetate with m-aminobenzenesulfonic acid (HL¹) and 5-sulfoisophthalic acid (H₃L²) afforded two new lead(II) sulfonates, Pb(L¹)₂1 and Pb₂(L²)(μ₃-OH)(H₂O) 2. In compound 1, the lead(II) ion is eight-coordinated by two sulfonate groups bidentately, two sulfonate groups unidentately and two amino groups from six ligands. Each L¹ ligand is tetradentate and bridges with three Pb(II) ions. The interconnection of the Pb(II) ions via bridging sulfonate ligands resulted in 〈100〉 and 〈200〉 layers. In compound 2, one Pb(II) ion is six-coordinated by a carboxylate group bidentately, by two carboxylate groups unidentately, by a sulfonate oxygen atom and by an OH anion, whereas the other one is six-coordinated by a bidentate chelating carboxylate group, two μ₃-OH anions, a sulfonate oxygen atom and an aqua ligand. The interconnection of irregular PbO₆ polyhedra via carboxylate-sulfonate ligands resulted in the formation of a pillared layered structure with the 2D layer being formed; the lead(II) ions, hydroxyl groups, carboxylate and sulfonate groups and the benzene ring as the pillar agent.     

Extraction with benzene and its derivatives

The extractability of selenium halides with benzene and some of its derivatives has been investigated using a radioactive tracer technique in order to establish the optimum conditions for its extraction. It has been found that Se(IV) is poorly extracted from HCl, HBr or H₂SO₄ solutions but high distribution ratios are observed with binary mixtures of 9M H₂SO₄ and acid halides. The extraction of some other elements is also studied under the conditions selected for Se(IV) extraction and it has been found that only antimony follows Se(IV) in the organic phase. In view of the data obtained, analytical advantages are mentioned and separation procedures are recommended. The extraction mechanism is also discussed and the role of sulfuric acid in the extraction system is explained.     

Cloud-Point Extraction Combined with LC–MS for Analysis of Memantine in Rat Plasma

The feasibility of using cloud-point extraction as a simple and effective means of recovery of memantine from rat plasma before LC–MS analysis has been demonstrated. A non-ionic surfactant Triton X-114 was used for extraction of the memantine. On increasing the temperature to the cloud point, phase separation occurred, resulting in an aqueous phase, and a surfactant-rich phase containing most of the analytes. The extraction conditions, for example amount of surfactant, temperature, NaOH concentration, and time of incubation, were optimized. Chromatographic separation was accomplished on a C₁₈ analytical column with 56:44 (v/v) methanol–0.2% aqueous formic acid as isocratic mobile phase at a flow rate of 0.8 mL min^?1. Under the optimum experimental conditions recovery was satisfactory (91–101%) without interference from the surfactant. The method was shown to be reproducible and reliable with intraday precision below 6.6%, interday precision below 14.3%, and linear range from 1 to 400 ng mL^?1. The method was successfully applied to a pharmacokinetic study of memantine in rats after oral and intravenous administration.     

Thermosensitivity of poly(<Emphasis Type="Italic">N</Emphasis>-vinylpyrrolidone): Effect of transition-metal halides

The effect of the halides of a series of transition metals on the properties of aqueous solutions of poly(N-vinylpyrrolidone) is studied. It is shown that the introduction of ZnCl₂ into solutions of poly(N-vinylpyrrolidone) causes phase separation with an increase in temperature. In the presence of halides of other transition metals (CdCl₂, CuCl₂), this phenomenon is not observed. However, the addition of HCl and/or alkali-metal halides to these systems likewise gives rise to phase separation, and in the ZnCl₂-based systems, the cloud point of solution substantially decreases with the introduction of alkali-metal salts. The same situation is observed in the case of polyvinylcaprolactam. Thus, it is concluded that the observed phenomena are associated with the formation of MtCl₄²⁻ complex anions in solutions that promote the globulization of polymer chains with participation of water molecules surrounding polymer chains and cations of transition-metal salts bound to complexes with C=O groups of lactam rings of the polymers.     

Validated UPLC method for the determination of guaiphenesin,oxeladin citrate,diphenhydramine, and sodium benzoate in their quaternary mixture used in treatment of cough,in the presence of guaiphenesin-related substance (guaiacol)

Accurate, precise, and sensitive UPLC method was developed and validated for the simultaneous determination of a quaternary mixture containing guaiphenesin (GUP), oxeladin citrate (OXC), diphenhydramine (DPH), and sodium benzoate (SOB) in the presence of GUP-related substance, guaiacol (GUA). Chromatographic separation was achieved using NUCLEOSHELL^® column—C₁₈ (4.0?×?50.0 mm, 2.7 μm). Isocratic elution at a flow rate 1.0 mL/min was performed using a mobile phase consisting of acetonitrile:phosphate buffer pH 3.5?±?0.1 (25.0:75.0, v/v). The specificity of the developed method was investigated by analyzing of laboratory-prepared mixtures containing different ratios of the four drugs, in the presence of GUA as well as their combined pharmaceutical formulation. The obtained results were statistically compared with those obtained by the official or reported methods, showing no significant difference with respect to accuracy and precision at p?=?0.05.     

Phase Separation in the Systems Constituted by Tetradecane (Hexane,Decane), Tri-n-Butyl Phosphate,and Cerium(III) Nitrate Solvate with Tri-n-Butyl Phosphate

Phase diagrams of ternary liquid systems constituted by tetadecane (hexane, decane), tri-n-butyl phophate, and cerium(III) nitrate solvate with tri-n-butyl phosphate Ce(NO₃)₃(TBP)₃ with phase separation into liquid phases I and II were studied at 298.15 K. Phase I is enriched in the hydrocarbon diluent, and phase II, in Ce(NO₃)₃(TBP)₃. The distribution of components between phases I and II was considered.     

LC Determination and Pharmacokinetic Study of Sinomenine in Dog Plasma

A simple HPLC method has been developed for determination of sinomenine in dog plasma and has been used to evaluate the pharmacokinetics of sinomenine tablets in dogs. Chromatographic separation was performed on a reversed-phase column with 0.78% (w/v) NaH₂PO₄-acetonitrile, 88:12 (v/v), as mobile phase, delivered at a flow rate of 1.5 mL min^?1. Detection was performed at 265 nm. The limit of quantification was 5.0 ng mL^?1. The calibration range was from 5.0 to 1000 ng mL^?1. The developed method was applied to pharmacokinetic studies of sinomenine sustained-release tablets (test preparation) and sinomenine conventional tablets (reference preparation) in six dogs. Pharmacokinetic data t _max, C _max, AUC _0-t , AUC _0-∞, and t _1/2 for both preparations were determined from plasma concentration-time profiles. The method was sufficiently sensitive, simple, and repeatable for use in pharmacokinetic studies.