New extraction procedures for isolation of famotidine from aqueous samples

Liquid-liquid and solid-phase extraction procedures are proposed for famotidine isolation from aqueous samples. The isolation and spectrophotometric determination of famotidine is based on its complexation reaction with thymol blue. The composition of a complex between drug and reagent (1?:?1) was established. Dichloromethane and methanol were used as extraction solvents for LLE and SPE processes. Quantification of famotidine was done spectrophotometrically at 544?nm for dichloromethane or at 434?nm for methanolic extracts. The Beer law is obeyed in the famotidine concentration range 3?·?10^?5?mol?L^?1–2.0?·?10^?4?mol?L^?1 for LLE procedure and 2.0?·?10^?6?mol?L^?1–8.0?·?10^?5?mol?L^?1 for SPE.     

Analytical applications of 3-(2′-thiazolylazo)-2,6-diaminopyridine: Spectrophotometric determination of palladium

3-(2′-Thiazolylazo)-2,6-diaminopyridine reacts with palladium(II) in strongly perchloric acid media, to produce a blue 1:1 complex (λ_max = 665 nm, ? = 1.37 × 10⁴ liters · mol^?1 · cm^?1), which allows the spectrophotometric determination of 0.6 to 4.5 ppm of palladium. The method is applied to the determination of palladium in small samples of hydrogenation catalysts.     

Extractive-spectrophotometric determination of manganese(II) using 3-bromobenzohydroxamic acid as chelating agent

Summary A new extractive spectrophotometric method is described for determining trace amounts of Mn(II) based on its reaction at pH 10.2 with 3-bromobenzohydroxamic acid (3BrHA) and subsequent extraction into Adogen 464 in toluene. The apparent molar absorptivity of the 1:3:1 (Mn:3BrHA:Adogen 464) complex is 8.7×10³ l·mol⁻¹ cm⁻¹ at 450 nm. Beer's law is obeyed from 0.5 to 6.0 mg·1⁻¹ of Mn(II) in the aqueous phase with a C.V. of 1.2%. The detection limit is 0.18 mg·1⁻¹. The method has been successfully applied to the determination of manganese in standard steel samples, natural water samples and plant material.     

The solid state reactions of o-aminobenzoic acid with Zn(Ⅱ), Cu(Ⅱ), Ni(Ⅱ), Mn(Ⅱ) acetate hydrate at room temperature

The solid-solid state reactions of o-aminobenzoic acid with Zn(OAc)2.2H2O, Cu(OAc)2 .H2O, Ni(OAc)2.4H2O and Mn(OAc)2.4H2O result in the formation of corresponding complexes M(OAB)2 (M = Zn(Ⅱ), Cu(Ⅱ), Ni(Ⅱ), Mn(IⅡ)). XRD, IR and elemental analysis methods have been used to characterize the solid products. The activation energies of these reactions, which are calculated from the kinetic data obtained by means of the isothermal electrical conductivity measurement method, have been found to increase in the order: Cu(OAc)2.H2O(37.7 kJ.mol-1)~Mn(OAc)2.4H2O (39.7kJ.mol-1) < Zn(OAc)2.2H2O (56.3 kJ.mol-1) < Ni(OAc)2.4H2O (85.2 kJ.mol-1). The trend is related to their crystal structures.     

Extractive Spectrophotometric Determination of Fluconazole by Ion-pair Complex Formation with Bromocresol Green

An extraction-spectrophotometric method for the determination of trace amounts of fluconazole was described. Fluconazole was effectively extracted as a 1 ： 1 ion-pair complex with bromocresole green （BCG） at pH 3.0 into chloroform, followed by spectrophotometric determination at 420 nm. Beer＇s law was obeyed over the range of 4-50 μg.mL^-1 of fluconazole with a detection limit of 3.7 μg.mL^-1 . The method is simple, rapid and sensitive. The procedure was applied to the determination of fluconazole in pharmaceutical preparations as well as its recovery from a blood serum sample.     

Analytical applications of picolinealdehyde salicyloylhydrazone: II. Extraction and spectrophotometric determination of vanadium(V)

Picolinealdehyde salicyloylhydrazone reacts with vanadium(V) to produce a yellow 1:1 complex (λ_max = 400 nm, ? = 2.17 × 10⁴ liters · mol^?1 cm^?1) in aqueous ethanolic solution. The yellow complex can be extracted into chlorobenzene (λ_max = 425 nm, ? = 2.16 × 10⁴ liters · mol^?1 cm^?1) and used for the spectrophotometric determination of trace amounts of vanadium. Interferences have been investigated. The method has been applied to the determination of vanadium in steel and in lead concentrates.     

Sensitive spectrophotometric determination of La(III) with 1-(2-pyridylazo)-2-naphthol

A simple and sensitive method for spectrophotometric determination of lanthanum has been developed. At pH 9.6, in presence of 50% ethanol, lanthanum reacts with 1-(-2-pyridylazo)-2-naphthol (PAN) to form a red complex which has two absorption maxima, at 545 and 510 nm. The molar absorptivity at 545 nm is 0.55 × 10⁴ liters · mol^?1 cm^?1. On the other hand, lanthanum reacts with PAN in pure ethanol to form a red complex at 530 nm, with high molar absorptivity (8 × 10⁴ liters · mol^?1 cm^?1).     

Conductometric study of complexation reaction between 15-crown-5 and Cr3+, Mn2+ and Zn2+ metal cations in pure and binary mixed organic solvents

The stability constants (K_f) for the complexation reactions of Cr³⁺, Mn²⁺ and Zn²⁺ metal cations with macrocyclic ligand, 15-crown-5 (15C5), in acetonitrile (AN), ethanol (EtOH) and also in their binary solutions (AN–EtOH) were determined at different temperatures, using conductometric method. 15C5 forms 1:1 complexes with Cr³⁺, Mn²⁺ and Zn²⁺ cations in solutions. A non-linear behaviour was observed for changes of logK_f of the metal ion complexes versus the composition of the mixed solvent. The order of stability of the metal–ion complexes in pure AN and in a binary solution of AN–EtOH (mol% AN?=?52) at 25?°C was found to be: (15C5Zn)²⁺?>?(15C5·Mn)²⁺?>?(15C5·Cr)³⁺, but in the case of pure EtOH at the same temperature, it changes to: (15C5·Zn)²⁺?>?(15C5·Cr)³⁺?>?(15C5·Mn)²⁺. The results also show that the stability sequence of the complexes in the other binary solutions of AN–EtOH (mol% AN?=?26 and mol% AN?=?76) varies in order: (15C5·Cr)³⁺?~?(15C5·Zn)²⁺?>?(15C5·Mn)²⁺. The values of the standard thermodynamic quantities (ΔH_C°, ΔS_C°) for formation of (15C15-Cr³⁺), (15C5-Mn²⁺) and (15C5-Zn²⁺) complexes were obtained from the temperature dependence of the stability constants and the results show that the thermodynamics of complexation reactions is affected by nature and composition of the solvent systems and in most solution systems, the complexes are enthalpy stabilized but entropy destabilized.     

Spectrophotometric study of the copper(II)-2,2′-dipyridyl-2-pyridylhydrazone complex formation

The reaction of copper(II) ions with 2,2′-dipyridyl-2-pyridylhydrazone (DPPH) has been studied. Two copper complexes were found to be formed. One at pH 6.5 to 8.5 and the other at pH 11.9 to 12.6 with molecular extinction coefficients of 1.9 × 10⁴M^?1 · cm^?1 at the absorption maximum of 478 nm and 3.8 × 10⁴M^?1 · cm^?1 at 448 nm, respectively. A sensitive spectrophotometric procedure for the determination of copper at less than a 1-ppm level is proposed.     

Determination of manganese(VII) as 3,3′-Dianisole-4,4′-bis(3,5-diphenyltetrazolium chloride) complex and its application

A simple, rapid, selective and sensitive spectrophotometric method is described for the determination of trace amounts of manganese using Blue tetrazolium chloride as a chromogenic reagent. The method is based on the formation of ion-associate complex between manganese(VII) and the cation of ditetrazolium salt, having an absorption maximum at 255 nm. Beer’s law is obeyed in the range of 0.1–1.6 μg mL^?1. The molar absorptivity and Sandell’s sensitivity were found to be 4.97 × 10⁴ L mol^?1 cm^?1 and 1.11 × 10^?3 μg cm^?2, respectively. Limit of deterction is 6.86 ng mL^?1 Mn(VII) and limit of quantitation is 22.8 ng mL^?1 Mn(VII). Optimum reaction conditions were evaluated. The effect of interfering ions on the determination is described. The extraction, distribution and association constants, and the recovery factor have been calculated.     

Analytical applications of 4-(4′-methyl-2′-thiazolylazo)-2-methyl-resorcinol: Spectrophotometric determination of vanadium

4-(4′-Methyl-2′-thiazolylazo)-2-methyl-resorcinol reacts with vanadium (V) to produce a bluish-violet 1:1 complex (λ_max = 560 nm, ? = 2.50 × 10⁴M^?1 · cm^?1, 50% methanol-water medium), which allows the spectrophotometric determination of 0.1 to 1.4 ppm of vanadium. The method has been applied to the determination of vanadium in several low-alloy steels.     

Trace metal analyses in honey samples from selected countries. A potential use in bio-monitoring

Honey is a sweet product made by bees using nectar from flowers. Concentrations of Ca, K, Mg, Fe, Zn, Mn, Cu, Pb and Cd were determined in 13 honey samples from the selected regions around the world. Levels of Ca, Mg, Cu, Fe, Zn and Mn were measured using flame atomic absorption spectrometry (FAAS). Potassium concentration was determined via flame photometry. Concentrations of Cd and Pb were determined using the electrothermal technique (ETAAS). It was estimated that the examined samples of honey from Greece, Turkey, Spain, Poland, Mexico, Argentina and Italy were of good quality in terms of metal concentrations (compliant with the norms referring to food products – WHO, Fifty-third Report of the joint FAO/WHO Expert Committee on Food Additives; Technical Report Series 776, Geneva), although the analysed samples were not free of heavy metals. The concentrations of the elements in the honey samples ranged from 2.38 to 9.31 μg · g^?1 for Zn, from 3.86 to 35.10 μg · g^?1 for Fe, from 0.19 to 21.64 μg · g^?1 for Mn, from 49.53 to 1006.90 μg · g^?1 for Ca, from 388.25 to 4761.50 μg · g^?1 for K and from 0.20 to 1.53 μg · g^?1 for Cu and regarding heavy metals from 0.11 to 2.78 μg · g^?1 for Pb and from 0.02 to 0.44 μg · g^?1 for Cd. According to these results it was found that the concentrations of heavy metals in the honey samples (except for alfalfa honey and eucalyptus honey from Italy) were under the acceptable limits for foods set out by the FAO/WHO. It was confirmed that the application of chemometric tools supports the extraction of significant information from analytical data, even though the availability of samples is not fully sufficient (this problem is often encountered in environmental analyses).     

Syntheses,crystal structures,and photoluminescence of two new coordination polymers derived from dicarboxylate and N-donor ligands

Two metal-organic coordination polymers, [Co(tda)(ip)(H₂O)₂] _n (1) and [Mn(tda)(ip)(H₂O)] _n (2) [H₂tda?=?thiophene-2,5-dicarboxylic acid, ip?=?1H-imidazo[4,5-f][1,10]-phenanthroline], have been synthesized and characterized by elemental analyses, IR, PXRD, and X-ray diffraction. Single-crystal X-ray analyses reveal that 2,5-tda is a bridging ligand, exhibiting two coordination modes to link metal ions: μ₁-η¹?:?η⁰/μ₁-η¹?:?η⁰ and μ₂-η¹?:?η¹/μ₁-η¹?:?η⁰. Compound 1 demonstrates a 1-D structure in which Co²⁺ centers are connected via tda anions into 1-D chains; the chains are further connected via hydrogen-bonding and π?···?π interactions. Compound 2 displays a 2-D structure in which tda connects two Mn ions forming a dinuclear molecule. In 2 the 3-D supramolecular structure arrays through hydrogen-bonding and π?···?π interactions. In addition, photoluminescence for 1 and 2 is also investigated in the solid state at room temperature.     

A Novel Synthesis of 2-Amino-2-deoxy-D-gluconic Acid and Its Complexation with Cu（Ⅱ） in Alkaline Medium

A novel synthesis of the functional carbohydrate 2-amino-2-deoxy-D-gluconic acid was introduced and itscomplex formation with Cu(Ⅱ)was investigated to obtain the stability constant for its further applications to thefood and pharmaceutical industries.The equilibrium was investigated by spectrophotometric measurements andprocessed by dual-series linear regression method.Results:the yield of 2-amino-2-deoxy-D-gluconic acid is 70%.The complexation molar ratio is 1:2,the molar apsorptivity of the complex is 39.906 L·mol~(-1)·cm~(-1) at 630 nm,and the stability constant β_n is 6.24×10~5.     

Functionalized manganese-doped zinc sulfide core/shell quantum dots as selective fluorescent chemodosimeters for silver ion

Zinc sulfide quantum dots doped with Mn(II) ions and coated with a shell of zinc sulfide were prepared, and their surface was modified with iminodiacetic acid to form a QDs-conjugate (QDs-IDA). Such modification effectively improves the water-solubility and luminescence quantum yield of the quantum dots. The optical properties and structural features were characterized by photometry, ¹H NMR and fluorescence spectroscopy. The results displayed that QDs-IDA selectively respond to Ag (I) ion in phosphate buffer solution (pH 7.3) in quenching the fluorescence of QDs-IDA. A good linear relationship exists in the concentration range from 5.0?×?10^?7 mol·L^?1 to 4.5?×?10^?6 mol·L^?1 and the detection limit is 2.6?×?10^?7 mol·L^?1. The sensing mechanism was assumed to result from complex formation between the iminodiacetic acid of QDs-IDA and silver (I) ion which promoted photo-induced electron transfer.     

A spectrophotometric method for manganese determination in water samples based on ion pair formation and dispersive liquid–liquid microextraction

In this work, a simple, inexpensive, and environmentally friendly extractive spectrophotometric method for the determination of manganese is suggested. The method is based on the formation and dispersive liquid–liquid microextraction (DLLME) of a violet-coloured ion pair of Mn(II) with 1,3,3-trimethyl-2-[3-(3-methyl-3H-benzothiazol-2-ylidene)-propenyl]-3H-indolium (BTIC) in the presence of 1-nitroso-2-naphthol (HL) as ligand, and subsequent UV-VIS spectrophotometric detection at 560?nm of the ion pair formed. The appropriate experimental conditions for the DLLME procedure were found to be: a pH of 9.5; 0.12?mmol?L^?1 of BTIC; extraction solvent – toluene containing 1.75?mmol?L^?1 of HL; disperser solvent – methanol; auxiliary solvent – tetrachloromethane. Beer's law is obeyed in the range 0.055–0.88 µg?mL^?1 of Mn(II). The limit of detection (LOD), calculated based on three times of the standard deviation of the blank test (n?=?10), was found to be 0.004?µg?mL^?1 of Mn(II). The precision (as relative standard deviation, RSD%) and accuracy (as recovery percentage, R%) of the method were examined by performing five replicate determinations at four concentration levels over two days and varied between 1.2 and 3.8, and 97.7 and 104.5, respectively. The suggested method was successfully applied to the analysis of various water samples (mineral water, spring water and drinking water).     

Gleichgewichte der Protonenaddition an 1, 1-Bis-(4′, 4″-dimethylaminophenyl)-äthylen in Methanol und in Dimethylsulfoxid

The first and second proton addition equilibrium constants of 1,1-bis-(4′, 4″-dimethylaminophenyl)-ethylene ( 1 ) have been measured by the spectrophotometric method in methanol and in dimethylsulfoxide. Defined as acid dissociation constants of the mono- and diprotonated adduct they are: K₁ (CH₃OH) = 8.3 (± 0.9) · 10^?6M, K₂ (CH₃OH) = 1.22 (± 0.06) · 10^?4M, K₁ (DMSO) = 2.3 (± 0.9) · 10^?3M, K₂ (DMSO) ≥ 1M. The evaluation of the electronic and the NMR. spectra demonstrates that the equilibrium of the two monoprotonated tautomers 2 (methyl-carbenium ion) and 3 (ammonium ion) is, in methanol to about 96% on the side of the ammonium ion (tautomeric equilibrium constant K₂₃ = [3]/[2] ? 23). The tautomer 2 cannot be detected in dimethylsulfoxide. The possible causes of these solvent effects are discussed.     

Langmuir Aggregation of Thionin in Nucleic Acids and Its Application

Introduction　　Nucleicacidchemistryhasbeenattractingtheattentionofmanybiochemists.1 7Understandingtheinteractionofachromophorewithnucleicacidscanhelpustorealizethefunctionofsuchgeneticbiopolymersandanalyzethetransmis sionofthegeneticinformation .Thequantitativedeterminationofnucleicacidsisalsosignificantinclinicaltestsandlabora torypractice .However,theinteractionhasnotbeenelucidat edsatisfactorilyandearlierobservationshavenotbeenex plainedclearlyandreasonably ,e.g .,thePesaventoequa tion8an…     

Metal complexes of 1,4-benzodiazepines: I. Spectrophotometric study of the nickel (II)-bromazepam complex

Nickel(II) and bromazepam (LH) form a colorless complex in acid and slightly alkaline media, and another yellow one at pH values greater than 11. The influence of pH as well as the stoichiometry of both complexes was studied. Assuming Ni(LH)₃²⁺ and NiL₃^? complexes, pK values of 14.5 and 17.6 were respectively found. A spectrophotometric method is proposed for the determination of Ni as the Ni(LH)₃²⁺ complex (acid medium), a molar absorptivity of 2.02 × 10⁴ liters · mol ^?1 · cm^?1 being calculated.     

Synthesis,structure, and characterizations of a new antiferromagnetic manganese(II) dichloro-bridged 1-D polymer decorated by 5-amino-1-H-tetrazole

[Mn(5-ATZ)₂Cl₂]_n (1) (5-ATZ – 5-amino-1-H-tetrazole) was synthesized from the reaction of 5-ATZ and manganese(II) chloride and isolated by solution evaporation at room temperature. 1 was characterized by elemental analysis, X-ray crystallography, infrared, and EPR spectroscopy as well as magnetic measurements. In the crystal structure, [Mn(5-ATZ)₂Cl₂] units are linked by double μ₂-bridging chlorides to form 1-D chains parallel to the a-axis. The Mn sphere approximates to octahedral with the metal coordinated by four chlorides in the equatorial plane and two 5-ATZ molecules, bound through their ring nitrogens, in axial positions. The intramolecular N–H···Cl hydrogen bond between the 5-ATZ amino group and the adjacent coordinated Cl^? stabilizes the chain. N–H···N hydrogen bonds between adjacent chains form a 3-D supramolecular framework. No hyperfine coupling to the Mn nuclei (I = 5/2) is observed in the powdered EPR spectrum of 1 at 77 K. The frozen solution EPR spectrum provides evidence of the mononuclearity of 1 in methanol. The magnetic properties have been analyzed using the Hamiltonian H = –J∑S_i · S_i+1 with J = ?1.38(3) cm^?1 and g = 2.00(1). A small value of the exchange parameter is typical for 1-D six-coordinate bis(μ₂-chloro) Mn(II) polymers.