title stringlengths 0 1.13k | abstract stringlengths 1 15.7k | PMID int64 22 36.5M |
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A practical approach to high performance capillary electrophoresis with biosynthetic human growth hormone as a model protein. | Biosynthetic human Growth Hormone (B-hGH) is a protein comprising 191 amino acids. The molecular weight is 22,125 and the isoelectric point is close to pH 5. Due to the ready availability of closely related analogues B-hGH was used as a model protein thus allowing for the demonstration and evaluation of the high resolu... | 18,965,311 |
Adsorbing colloid flotation separation and polarographic determination of Mo(VI) in water. | A method is described for the flotation and determination of Mo(VI) in water at ng/ml levels. Mo(VI) is preconcentrated and separated by adsorbing colloid flotation employing aluminium(III) hydroxide as collector and sodium lauryl sulphate as surfactant at pH 5.3 +/- 0.1. The molybdenum content in the froth is estimate... | 18,965,320 |
Polarographic determination of atmospheric nitrogen oxides. | A new polarographic method is described for the determination of nitrite/nitrogen oxides. The nitrite is first diazotized with p-aminobenzoic acid, followed by coupling to 8-hydroxyquinoline to produce an azo dye. This azo dye is adsorbable on a mercury drop electrode and its reduction is reversible. The linear respons... | 18,965,350 |
Decomposition of Cu(PCD)(2) extracted into IBMK and DIBK phases from hydrochloric acid media. | The decomposition of the bis(1-pyrrolidinedithiocarbamato) copper(II) complex [Cu(PCD)(2)] extracted into isobutyl methyl ketone (IBMK) and di-isobutyl ketone (DIBK) from hydrochloric acid solution (0.01-8M) has been studied with UV-visible and ESR spectrometry. The mixed-ligand complex CuCl(PCD) is formed as an interm... | 18,965,358 |
A selective spectrophotometric method for determination of quercetin in the presence of other flavonoids. | A simple, rapid and highly selective method for determination of quercetin in the presence of other flavonoids was developed. The method is based on the oxidation reaction of quercetin in neutral aqueous solution with N-bromosuccinimide (NBS) in the presence of phenol to give a violet chromogen measurable at 510 nm. Be... | 18,965,372 |
Flow-injection coulometric titrations. | A flow-injection analysis technique based on stop flow coulometric titrations is described, utilizing a gradient chamber, reagent generation chamber, and detector flow cell integrated into a single unit. The use of stop flow allowed for automated sample dilution up to a factor of 100 times. The system has been used to ... | 18,965,376 |
Spectrophotometric method for determination of sulfide with iron(III) and nitrilotriacetic acid by flow injection. | A manual colorimetric method for determination of sulfide has been adapted to flow injection, systematically optimized, and more fully characterized. Its intended application is for measurement of sodium sulfide reagent strength in pulp process streams, and sulfide contamination in effluent from Kraft pulp mills. In th... | 18,965,378 |
Electrochemically-controlled generation of small amounts of carbon monoxide. | The generation of carbon monoxide is based on oxidation of carbon at a temperature of 920-950 degrees by electrolytically generated oxygen. The rate of production of CO is a linear function of the oxygen generating current over a range of 5-60 mA and corresponds to the theoretical value. By the method described it is p... | 18,965,389 |
Voltammetric determination of mercury(II) at a carbon paste electrode in aqueous solutions containing tetraphenylborate ion. | The determination of mercury(II) ions can be achieved by monitoring the decrease in the oxidation peak of the tetraphenylborate ion in the presence of this metal ion at a carbon paste electrode. The reaction between mercury(II) and the tetraphenylborate ion results in the formation of diphenylmercury, thus providing th... | 18,965,392 |
Optimization of atomic fluorescence measurements with a microcomputer-based time-multiplex multiple-slit spectrometer. | An automated multielement flame atomic fluorescence (AF) spectrometer is described. The instrument employs a multiple exit slit monochromator and a single detector. Each element is excited to fluoresce with a single-element hollow cathode lamp (HCL) and a time-multiplex mode is used for pulsing the HCLs and gated data ... | 18,965,446 |
Oscillopolarographic adsorptive wave determination of microamounts of orthophosphate. | In the system HCl-Sb(III)-ammonium molybdate-acetone-butanone, PO(3-)(4), Sb(III) and Mo(VI) form a ternary heteropoly acid, which can be adsorbed on a dropping mercury electrode and reduced to a heteropoly blue. The electrochemical reaction produces a sensitive polarographic wave with peak potential of -0.42 V vs. SCE... | 18,965,448 |
Capillary gas chromatography of hydrocarbon mixtures containing alkanes and alkenes, selective olefin stripping applied to very diluted samples. | An original subtraction method was developed to distinguish between alkanes and alkenes in a complex hydrocarbon mixture. The method described is very fast, inexpensive and requires only 100-200 mul of sample. Its steps include bromination of the olefins and adsorption on a silica gel column followed by gas chromatogra... | 18,965,449 |
Extraction mechanism of monovalent ion-pairs by polyurethane foams. | The extractability sequence of K(+) approximately Rb(+) > Cs(+) > Na(+) > Li(+) for the extraction with polyether foam suggests that the cation chelation mechanism might be operative. However, the same order was obtained for the extraction with 100% polypropylene oxide polyether foam which does not normally ad... | 18,965,459 |
Electrochemical study of solvent extraction with 8-quinolinols as complexing agent-I. Distribution behavior of 8-quinolinols. | The distribution behavior of 8-quinolinols (HQ) in organic and acidic aqueous solutions (or alkaline solutions) was electrochemically examined by current scan polarography and chronopotentiometry. It follows from the results that the half wave potential of the observed polarographic waves, corresponding to the Faradaic... | 18,965,472 |
Determination of sulfide with chloranilic acid by biamperometric and automatic potentiometric end-point detection with a lead chloranilate selective electrode. | A titrimetric method for determination of sulfide and of sulphur in steels with chloranilic acid by biamperometric and automatic potentiometric end-point detection is described. The construction of the sensor for potentiometric indication is also described. The results obtained agree with those of the iodine-thiosulfat... | 18,965,487 |
Study of the transport of silver across a supported liquid membrane containing sulphide podand. | The transport of silver through a supported liquid membrane saturated with a polydentate neutral ionophore 1,12-di-thienyl-2,5,8,11-tetrathiadodecane in m-chlorotoluene has been studied. Thiosulphate was used as the stripping solution. The influence of the feed solution composition, the type of a microporous polypropyl... | 18,965,491 |
Analytical and mechanistic aspects of the room-temperature fluorescence and phosphorescence of benzo(f)quinoline adsorbed on silica gel chromatoplates with humidified gases. | The solid-matrix room-temperature fluorescence and room-temperature phosphorescence properties of benzo(f)quinoline adsorbed on silica gel chromatoplates were investigated over a wide range of humidities in N(2), air and O(2). Both neutral and acidic conditions were used and even at the highest relative humidity used, ... | 18,965,496 |
Analysis of acrolein and acrylonitrile in aqueous solution by membrane introduction mass spectrometry. | Acrolein and acrylonitrile can be quantified directly at low levels in aqueous solution using membrane introduction mass spectrometry. Electron impact was used to generate positively charged ions and electron capture of the O-(2,3,4,5,6-pentafluorobenzyl)hydroxyl amine (PFBOA) derivative was used to generate negatively... | 18,965,502 |
Studies on complexation equilibria between water-soluble hydrazones which consist of 5-nitro-2-pyridylhydrazine and heterocyclic ketones and divalent metal ions. | Complexation equilibria between five water-soluble hydrazones which consist of 5-nitro-2-pyridylhydrazine and heterocyclic ketones and divalent metal ions have been studied spectrophotometrically. Equilibrium constants of the complexation reactions and overall formation constants of the resultant complexes have been de... | 18,965,510 |
Atomization efficiency of a Massmann-type graphite furnace. | The atomization efficiency of the Perkin-Elmer HGA-400 for the production and containment of atomic vapour has been determined for Al, Co, Au, Ni, Fe, Ag, Ga and Cu by a method developed under non-isothermal conditions. The method takes into account the residence time and the shape of the absorbance signal profile. It ... | 18,965,519 |
Simultaneous determination of Cl(-), Br(-), I(-) and F(-) with flow-injection/ion-selective electrode systems. | Flow-through ion-selective electrodes were constructed from compressed pellets (8-10 mm thick, 13 mm diameter, 10 tons/cm(2) pressure) of Ag(2)S/AgX (X = Cl(-), Br(-) or I(-)) drilled longitudinally (1.5 mm diameter hole) to be suitable for use in flow-injection analysis. A column of AgCl (5.5 cm long, 2-3 mm i.d.) was... | 18,965,525 |
Preparation and application of selenite ion selective electrode. | A new selenite ion selective electrode using 4,6-dibromopiaselenole as active material, PVC as membrane matrix and dibutyl phthalate as plasticizer has been developed. An analytically useful potential change occurs from about 10(-6)-10(-1)M Se(IV), and the slope of the linear portion is -23.6 mV/10-fold change in Se(IV... | 18,965,526 |
Rapid sequential determination of inorganic mercury and methylmercury in natural waters by flow injection-cold vapour-atomic fluorescence spectrometry. | A novel method for the rapid sequential determination of inorganic mercury and methylmercury in natural waters at the ng/l. level has been developed. Trace enrichment and separation of mercury species are achieved using a microcolumn of sulphydryl cotton which has a relatively high affinity for methylmercury. The limit... | 18,965,566 |
Phase composition analysis of hydrous aluminium oxides by thermal analysis and infrared spectrometry. | A general method for determination of the phase composition of hydrous aluminium oxides by thermal analysis and infrared spectrometry, and determination of the transformation temperature of mixtures of Al(OH)(3) and AlOOH into alpha-Al(2)O(3) are described. | 18,965,574 |
Optimal design of diffusive samplers. | Some commercially available diffusive samplers use two layers of adsorbent placed in series. After sampling is completed, the time weighted average concentration of analyte is estimated from the weighted sum of the uptake of analyte on these two layers. It is known that such a division into layers can increase the perm... | 18,965,607 |
Rapid gas analyses for the investigation of spontaneous combustion using capillary gas chromatography. | A simple and fast but sensitive and precise gas chromatographic method is described for the quantitative determination of O(2), N(2), CO, CO(2), C1 and C2-hydrocarbons for coal research. Gas analyses are necessary to obtain parameters for modelling spontaneous combustion and to predict long term coal behaviour. The met... | 18,965,618 |
Determination of chlorinated hydrocarbons introduced into air/acetylene flames by Fourier transform infrared emission spectroscopy. | A Fourier transform spectrometer is used to record the infrared emission from chlorinated hydrocarbons combusted in an air/acetylene flame. In this manner, the chlorinated hydrocarbons are determined by monitoring the infrared emission of hydrogen chloride at 2653 cm(-1). Discussion is presented of the air/acetylene fl... | 18,965,624 |
The determination of organotin compounds in edible oils by gas chromatography-atomic absorption spectrometry. | An extraction method for butyl-, cyclohexyl-, octyl- and phenyltin compounds from edible oils was developed using 0.05% tropolone in 0.04M HCl/methanol. Cooling the methanol extracts in a dry ice/methanol bath removed approximately 64% of nonvolatile coextractives without affecting recoveries. Methyl derivatives formed... | 18,965,630 |
A new method for the evaluation of the oxidizing equivalent of manganese in surface freshwaters. | The suitability of application of a number of previously used methods for the evaluation of the oxidizing equivalent (OE) of manganese in natural waters is compared with a new method, which depends upon colour development of the dye N,N'-diethyl-p-phenylenediamine (DPD) upon oxidation by oxidized forms of manganese. Th... | 18,965,662 |
Flow injection method for the assay of the anti-arrhythmic procainamide HCl in drug formulations utilizing statistical optimization techniques. | A flow injection spectrophotometric method for the determination of procainamide HCl was explored. The method was based on the oxidation of procainamide HCl with cerium(IV) in sulphuric acid media and subsequent monitoring of the absorbance of the oxidized form of the drug at 480 nm. A sample rate of 250 samples per ho... | 18,965,675 |
Direct flame atomic absorption spectrophotometric determination of Mn in rocks, nodules, soils and related materials using tartaric acidKClSrCl(2) mixture. | A mixture of tartaric acid-potassium chloride and strontium chloride has been used for accurate and precise estimation of manganese in various international reference rocks, nodules, soil and related samples by flame atomic absorption spectrophotometry (FAAS). The method is fairly rapid and involves no separation of th... | 18,965,690 |
Spectrophotometric determination of chromium with Iodonitrotetrazolium chloride and Tetrazolium Violet. | The interaction of Iodonitrotetrazolium chloride and Tetrazolium Violet with chromium(VI) has been studied and the formation of ion-associates with a 1:1 composition in hydrochloric acid medium established. Extraction photometric methods for determination of chromium in steels and soils have been developed. | 18,965,691 |
JESS, a joint expert speciation system-III. Surrogate functions. | A new, general method of coupling calculations of equilibria with those of other chemical effects and processes is described. The method, based on the use of simple empirical functions, is demonstrated by applying it to changes of ionic strength and temperature in speciation modelling. | 18,965,712 |
Assignment of standard pH values [pH*(s)] to buffers in 50 mass % methanol + water from 288.15 to 308.15 K. | The secondary dissociation constants of o-phthalic and phosphoric acids have been determined in methanol + water (50 mass %) from reversible e.m.f. measurements of the cell of the type: Pt, H(2)(1 atm)|M(2)A(m), MHA(m), MCl|AgCl; Ag at different temperatures (288.15-308.15 K) and at different ionic strengths. To minimi... | 18,965,719 |
Resin phase spectrophotometry of beryllium by an optical fiber and beryllon II. | We have developed a resin phase spectrophotometric method to determine the amount of beryllium by detecting a change in absorbance of the resin phase. 8-Hydroxynaphthalene-3,6-disulphonic acid-(1-azo-2')-1',8'-dihydroxynaphthalene-3',6'-disulphonic acid tetrasodium salt (beryllon II) immobilized by a strong base anion-... | 18,965,722 |
Difference spectrophotometric assay of benzaldehyde in benzyl alcohol. | A simple and rapid procedure is described for the selective determination of benzaldehyde in benzyl alcohol intended for use in the manufacture of parenteral dosage form. The assay is based upon the measurement of the difference absorbance between two equimolar solutions of benzaldehyde in buffer solution pH 5.75, one ... | 18,965,728 |
Responses of H(+) selective solvent polymeric membrane electrodes fabricated from modified PVC membranes. | Potentiometric responses of a novel class of pH sensitive ionophores, namely several phenoxazine derivatives, were tested in different modified PVC matrices. The ionophores were compounded into liquid membranes as usual or were covalently coupled to the polymeric matrix. The general analytical performance of the membra... | 18,965,733 |
Investigation of the composition of complexes and the stoichiometry of non-complex reactions by flow injection method. | Combining the Asmus straight-line method with the flow injection (FI) technique, a new FI-straight-line method is established to investigate the formulas of the blue, the purple and the red complexes formed by iron(III) and Tiron in different pH solutions. Using the proposed FI-straight-line method, the stoichiometries... | 18,965,734 |
Structural characterization and sequence distributions of polysiloxanes using pyrolysis MS/MS. | Novel polysiloxanes, with 4-(dialkylamino)pyridine substituents, are characterized by pyrolysis tandem mass spectrometry. These polymers form abundant cyclic oligomeric ions under both desorption electron ionization (DEI) and desorption chemical ionization (DCI) conditions. Product MS/MS spectra of the cyclic ions reve... | 18,965,774 |
Determination of gallium by square-wave voltammetry anodic stripping, based on the electrocatalytic action of 2,2'-bipyridine in dimethylsulphoxide: comparison with an aqueous NaSCN/NaClO(4) electrolyte. | Deposition potential, deposition time, square-wave frequency, 2,2'-bipyridine concentration, and gallium concentration have been studied in detail, for the determination of trace concentration levels of the metal by square-wave voltammetry anodic stripping analysis, in dimethylsulphoxide. Optimum conditions have been f... | 18,965,779 |
Flow-injection fluorimetric determination of trimeprazine and trifluoperazine in pharmaceutical preparations. | A flow-injection configuration for the fluorimetric determination of trimeprazine and trifluoperazine is proposed. The procedure is based on oxidation of the drugs by cerium(IV). The fluorescence of cerium(III) formed in the oxidation of trimeprazine or trifluoperazine is monitored. Lineal calibration graphs were obtai... | 18,965,791 |
Kinetic spectrophotometric determination of low levels of nitrite by catalytic reaction between pyrogallol red and bromate. | A kinetic spectrophotometric method for the determination of trace nitrite (0.003-1.000 microg/ml) based on its catalytic effect on the reaction between potassium bromate and pyrogallol red in acidic media is described. The reaction is monitored spectrophotometrically by measuring the decreasing colour of pyrogallol re... | 18,965,793 |
Volatilization of methyl borate in iron matrix. Determination of boron in steel by ICP atomic emission spectrometry. | A rapid and reliable method for the determination of boron by ICP-AES in steels is described. The procedure is based on a discontinuous generation of methyl borate, in concentrated sulphuric acid and phosphoric acid medium, after injecting 45 microl of methanol in 20 microl of sample. The gaseous methyl borate and exce... | 18,965,797 |
Determination of mercury in zinc ore concentrate reference materials using flow injection and cold-vapor atomic absorption spectrometry. | A flow-injection, cold-vapor atomic absorption spectrophotometric method was developed for the determination of trace amounts of mercury in a proposed zinc ore concentrate Standard Reference Material (SRM 113b). The samples were digested with nitric and hydrochloric acids in closed Teflon digestion vessels. The experim... | 18,965,808 |
Solvent extraction separation of cobalt(II) from nickel and other metals with cyanex 272. | Cobalt(II) was quantitatively extracted at pH 8.0 with 5 x 10(-3)M Cyanex 272 [Bis(2,4,4 trimethyl pentyl) phosphoric acid] in chloroform. Cobalt(II) was stripped with 0.5M nitric acid and was determined by atomic absorption spectrometry as well as by spectrophotometry of the complex with nitroso R salt. Cobalt(II) was... | 18,965,817 |
Polarographic determination of Ce(III) and Tm(III) using rare earth-DBF-chlorophosphonazo complex. | The electrochemical behaviour of the DBF-chlorophosphonazo (DBF-CPA)-rare earth (RE) complex has been investigated in this paper. A highly sensitive polarographic adsorption wave was found in the RE(III)-DBF-CPA system and a new method for determination of trace total RE(III) has been established. The limit of detectio... | 18,965,866 |
A time-based injector applied to the flow injection spectrophotometric determination of boron in plant materials and soils. | A simple and flexible time-based injector is described for the introduction of almost any desirable volume of sample and reagents in flow systems. The feasibility of application is demonstrated by improving the azomethine-H spectrophotometric method for the precise and accurate determination of boron in soil and coffee... | 18,965,877 |
Reliability of protonation constants of SNAZOXS oligomers. | Concentration protonation constants of variously protonated of oligomers of sulphoazoxine SNAZOXS were determined by regression analysis of potentiometric titration curves. The group and common parameters were estimated using different computational strategies of three regression programs, MINIQUAD, MIQUV and PSEQUAD. ... | 18,965,893 |
Flow injection colorimetric method for the assay of vitamin C in drug formulations using tris,1-10-phenanthroline-iron(III) complex as an oxidant in sulfuric acid media. | A simple, fast and accurate colorimetric flow injection (FI) method suitable for the assay of vitamin C in drug formulations was proposed. In the method, vitamin C was injected into a flowing stream of iron(III) and then mixed with 1,10-phenanthroline in 0.05M sulphuric acid media. The mixture was allowed to react in a... | 18,965,896 |
Solvent effect on the determination of sulfamethazine by room-temperature photochemically induced fluorescence. | Room-temperature photochemically-induced fluorescence (RTPF) was applied to the determination of sulfamethazine (SMT) in methanol, ethanol and 2-propanol. Optimal ultraviolet irradiation times ranged between 2 and 6 min. Linear calibration graphs were obtained over a concentration range of more than one order of magnit... | 18,965,913 |
Discontinuous-flow potentiometric determination of chloride in a large-volume wall-jet cell using an ion-selective electrode based on a silver chloride film chemically deposited on a silver iodide support. | A robust and sensitive chloride ion-selective electrode can be prepared by modifying the surface of an iodide-selective electrode using the chemical reaction with mercuric chloride in an oxidizing medium containing excess chloride. A thin film of silver chloride is thus formed ensuring a rapid and reproducible response... | 18,965,926 |
Spectrofluorimetric analysis of cefoxitin in pharmaceutical dosage. | A fluorescence method involving sample pre-treatment is investigated concerning the determination of cefoxitin. A fluorescent product is formed when samples containing cefoxitin are subjected to alkaline hydrolysis with 1.0M sodium hydroxide and heated for 60 min at 90 degrees . The fluorescence is measured in ethanol/... | 18,965,964 |
Determination of V(V), Nb(V) and Ta(V) as their 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol chelates by reversed-phase HPLC. | This paper reports the separation and determination of V(V), Nb(V) and Ta(V) by RP-HPLC using 5-Br-PADAP as a precolumn derivatizing reagent. On C(18) column, the three metal chelates can be separated on a baseline in 9 min with the mobile phase of methanol-water (59:41, v/v) containing tartaric acid (0.2%) and acetate... | 18,965,983 |
Rapid simultaneous analysis of 1-naphthol and 2-naphthol in water samples by derivative variable-offset synchronous fluorescence spectroscopy. | Derivative variable-offset synchronous fluorescence spectroscopy is developed to improve the spectral resolution and the selectivity of fluorescence measurements. 1-naphthol and 2-naphthol are employed to evaluate the proposed coupled technique and the various spectral comparisons are conducted. Second derivative varia... | 18,965,985 |
Sensing of trace copper ion by a solid phase extraction-spectrophotometry using a poly(vinyl chloride) membrane containing bathocuproine. | A new sensitive and selective spectrophotometric method for the determination of trace copper using a poly(vinyl chloride) membrane containing 4,7-diphenyl-2,9-dimethyl-1,10-phenanthroline (bathocuproine) and o-nitrophenyl-octylether as the solid phase extraction medium. Copper(I) in an aqueous sample solution is trapp... | 18,966,003 |
Influence of phospholipidic microenvironment on the performance of a polypyrrole enzyme electrode. | Enzyme loaded phosphatidylcholine vesicles have been introduced as a new component in the design of sensing layers for the direct coating of an amperometric transducer. For this purpose, choline oxidase was chosen as a model enzyme, and the resulting vesicles were mixed with an amphiphilic pyrrole derivative [12-(pyrro... | 18,966,018 |
Fiber optic chemical sensor for nitrite based on an electropolymerized cobaltporphyrin film. | Fiber optic sensors for nitrite were prepared by first electrochemically depositing a film of cobalt(II) tetrakis(o-aminophenyl)porphyrin, [Co(o-NH(2))TPP], on the surface of indium(tin) oxide glass slides. Then, the slides with the immobilized porphyrin were positioned at the tip of an optical fiber bundle. The respon... | 18,966,023 |
l- and d-Lactate assay in real milk samples with immobilized enzyme reactors and graphite electrode. | A sensitive flow system for the determination of l- and d-lactate in milk samples is described. l- and d-Lactate dehydrogenase, LDH, were immobilized on aminopropyl-controlled pore glass beads. l- and d-Lactate are oxidized to pyruvate in the presence of NAD(+) and NADH is produced. The electrochemical determination of... | 18,966,029 |
Application of pressurized sample preparation methods for the analysis of steels and copper alloys. | Pressurized sample preparation devices (High Pressure Asher, Pressurized Microwave Digestion system, compared with a PTFE decomposition vessel) were used to dissolve certified metal alloy samples (steel, copper) for ICP analysis. Based on the results of the analysis it was established that both up-to-date devices can b... | 18,966,041 |
Determination of chemical species of selected trace elements in fly ash. | Complex analytical methods have been developed for determining the chemical composition of fly ashes. Samples were collected at coal-fired power plants and municipal waste incinerators. Morphological investigations and single particle analysis were performed by SEM/EDAX method. A survey of mineralogical phases was made... | 18,966,051 |
Determination of trace metals and speciation of chromium ions in atmospheric precipitation by ICP-AES and GFAAS. | Sampling and analytical techniques used for determining trace metal concentrations in atmospheric precipitation waters collected in Hungary are presented. The results of the analyses are briefly discussed and special attention is devoted to chromium speciation. For the preconcentration of the trace metals a chelating c... | 18,966,053 |
Determination of the total dissolved sulphide in the pH range 3-11.4 with sulphide selective ISE and Ag/A92S electrodes. | An electrochemical method for the determination of the total sulphide concentration of sewage water samples has been studied using a potentiometric cell containing either a sulphide ion selective ISE-glass electrode pair or a Ag/Ag(2)S electrode-glass electrode system. The performance of the two sulphide ion sensors wa... | 18,966,059 |
Flow injection analysis with detection at mercury drop electrode in the presence of surfactants. | The surfactant presence in a sample may cause distortion of the flow injection peak obtained with amperometric detection at a mercury drop electrode. Distortion depends on detection parameters and flow system operating parameters and in some cases it may be eliminated by their careful optimization. Introduction of fume... | 18,966,073 |
Rapid spectrophotometric method (aqueous and extractive) for the determination of titanium in silicate rocks. | A sensitive and highly selective aqueous as well as extractive spectrophotometric method has been developed for the determination of titanium(IV) using 2,3-dihydroxynaphthalene (H(2)ND) as a chromogenic agent. The reagent (H(2)ND) forms a 1:3 (TiOH(3+):ligand) complex at pH 4-9. The molar absorptivity and Sandell's sen... | 18,966,077 |
The use of linear potentiometric titration curves in the determination of alkalinity and acid-base properties of diluted solutions of humic substances. | A critical study of the use of Gran and modified Gran functions for the determination of alkalinity and acid-base properties of diluted solutions containing humic substances is presented. These solutions were composed of 340 muM HCO3(-)(3) in 0, 10, 20.5 and 41 mg/1. of sodium humate in order to simulate natural waters... | 18,966,083 |
Retention and separation of some organic water pollutants with unloaded and tri-n-octylamine loaded polyester-based polyurethane foams. | The analytical utility of unloaded and polyester-based polyurethane loaded foams with tri-n-octylamine (TOA) in the removal of some phenols from water were carried out. In static mode, the TOA-loaded foams showed a good affinity of extraction towards the tested compounds as compared to the untreated foams. The various ... | 18,966,093 |
Determination of submicrogram amounts of Mercury(II) with 5-(2'-carbomethoxyphenyl)azo-8-quinolinol in presence of anionic surfactant by derivative spectrophotometry. | A new sensitive, rapid and selective method is proposed for the determination of mercury in submicrogram level. Mercury(II) forms an insoluble complex with 5-(2'-carbomethoxyphenyl)azo-8-quinolinol in aqueous medium at pH 4-4.8 which can be made soluble by the action of anionic surfactant. The dissolution of the comple... | 18,966,100 |
Determination of dissolved selenium(VI) in freshwater. | A procedure is proposed for the determination of selenate in freshwaters with a high content of dissolved organic material. After passage through an XAD-8 column, selenate is collected on a strong anion exchanger and subsequently eluted with hydrochloric acid. Following conversion into the tetravalent state, selenium i... | 18,966,120 |
Chromatographic behaviour of trace metal ions on a strong base anion exchange resin functionalized by azo ligands. | A model which allows the evaluation of the elution volume V(E) and the central point V(C) of the breakthrough curve of a metal ion at trace level on a chromatographic column containing a chelating resin is presented. V(E) and V(C) mainly depend on the complexation properties of the active groups, and on the acidity and... | 18,966,122 |
Kinetic fluorimetric determination of Cu(II) and Zn(II) by their incorporation reactions into a water-soluble porphyrin. | Kinetics of incorporation of Cu, Zn, Fe, Co, Ni and Mn divalent ions into coproporphyrin-I in imidazole buffer solution, pH 7.0, has been studied by monitoring the decrease in fluorescence intensity of the free base porphyrin. All reactions followed simple second-order rate law, the rate constants being decreased in th... | 18,966,123 |
A rapid and mercury pollution-free redoximetry determination of total iron in copper ore. | A rapid and mercury pollution-free method for the determination of total iron in the presence of copper is described. The sample was decomposed either by an acid attack of hydrochloric acid-nitric acid (1 + 2) or by fusion with sodium peroxide. The ferric ion in the sample solution was amenable to direct reduction to f... | 18,966,137 |
Tris(2-ethylhexyl)phosphate as an extractant for trivalent gallium, indium and thallium. | A systematic study of solvent extraction behaviour of gallium(III), indium(III) and thallium(III) with tris(2-ethylhexyl)phosphate from salicylate media has been undertaken and a scheme for their separation is proposed. The optimum extraction conditions are evaluated and described. The method is applicable to the analy... | 18,966,155 |
Fluorimetric determination of phenothiazine derivatives by photooxidation in a flow-injection system. | Flow-injection analysis (FIA) was combined with photochemically induced fluorescence (PF) detection for the determination of four phenothiazine derivatives, including unsubstituted phenothiazine, thionine, Azure A and Methylene Blue. The working analytical parameters (flow-rate, injected volume, photoreactor length) we... | 18,966,160 |
Sequential and rapid determination of Po-210, Bi-210 and Pb-210 in natural waters. | A sequential and rapid separation method for the determination of radon daughter nuclides, Pb-210, Bi-210 and Po-210 has been developed for application to natural waters. Rapid separation is attained by the use of the same hydrochloric acid solution. After isolation of the three radionuclides from the sample by co-prec... | 18,966,174 |
Colorimetric method for determination of chlorine with 3,3',5,5'-tetramethylbenzidine. | A new method is developed for the calorimetric determination in water of chlorine (free and combined) with 3,3',5,5'-tetramethylbenzidine. The procedure proposed achieves a detection limit of 2 ng/ml and its sensitivity is greater than that of the methods used at present. | 18,966,176 |
A PC compatible computer program for the calculation of equilibrium constants by the simultaneous processing of different sets of experimental results. | A new PC compatible computer program SIRKO for the calculation of the equilibrium constants by means of the simultaneous processing of different experimental data from various techniques is given. This program is characterized by the application of a universal response function, which allows many different physicochemi... | 18,966,178 |
Simultaneous determination of sulfite and phosphate in wine by means of immobilized enzyme reactions and amperometric detection in a flow-injection system. | A flow-injection system is proposed for the simultaneous determination of sulfite and phosphate in wine. A sulfite oxidase immobilized reactor and purine nucleoside phosphorylase-xanthine oxidase co-immobilized reactor are incorporated at fixed positions (parallel configuration) in the flow line, which is based on the ... | 18,966,179 |
A new equation for wavelength dispersive x-ray fluorescence analysis without standards. | We derive an iteration equation for calculation of the concentrations of the elements in X-ray fluorescence analysis without standards. It does not require calculation of the intensity of primary spectra, which can excite the characteristic fluorescent X-ray, so its calculation is simpler. The experiments show that the... | 18,966,180 |
Thin-layer chromatographic detection of monocrotophos in biological materials. | An organophosphorus insecticide monocrotophos is increasingly being used in agriculture to control insects on a wide range of crops. Its ready access has resulted in misuse in many instances of homicidal and suicidal poisoning cases. This paper describes a chromogenic spray reagent for the detection of monocrotophos in... | 18,966,181 |
Flow-injection fluorimetric analysis of sulfamethoxazole in pharmaceutical preparations and biological fluids. | A fluorimetric procedure for the determination of sulfamethoxazole using flow injection analysis is proposed. A two channel system is optimized for the fluorescent reaction with o-phthaldialdehyde and beta-mercaptoethanol. The detection limit is 0.007 mug/ml. No fluorescence is generated by the metabolite N-acetylated ... | 18,966,186 |
Potential characteristics of a pseudoliquid membrane electrode including coordinatively solvated UO(2)(NO(3))(2).2TBP complexes. | Mechanisms of formation of electrode potential with a pseudoliquid membrane phase including uranyl nitrate complexes coordinatively solvated by tri-n-butyl phosphate were investigated. It was stated that the electrode function of these membranes could be of cationic or anionic character depending on concentration UO(2)... | 18,966,190 |
Adsorptive stripping voltammetry of trace manganese in the presence of 2-(5'-bromo-2'-pyridylazo)-5-diethylaminophenol (5-Br-PADAP). | Trace levels of manganese can be determined by voltammetry after controlled adsorptive accumulation of the manganese-2-(5'-bromo-2'-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) complex on a hanging mercury drop electrode. Optimal conditions include an ammonia buffer solution (pH 8.8) containing 1 x 10(-5)M 5-Br-PADAP ... | 18,966,234 |
Optimal acidity of complexes by solution of polynomials and by iteration. | The methods for optimal acidity of complexes M(x)L(y)(OH)(m)H(n) based on direct iteration or solution of polynomials are described and discussed. Then, by a direct straightforward method of computation (that does not require any iteration) the complexes M(x)L(OH)(m)H(n) and ML(y)(OH)(m)H(n) are treated (where 1 x 3 an... | 18,966,247 |
Colorimetric determination of low pH with Malachite Green. | A spectrophotometric method was developed for determination of concentration-based pH values from 0 to 2 with Malachite Green indicator. A quadratic model equation was based on the ratio of the absorbances of the peak at 618 nm and the isosbestic point at 518 nm. Normalization to the isosbestic point was used to stabil... | 18,966,252 |
The trifluoroacetic anhydride-sodium iodide system as a reagent for determination and microdetermination of nitroxide radicals. | A trifluoroacetic anhydride-sodium iodide mixture (TFAA-I) reacts with nitroxide radicals with liberation of iodine. Since stoichiometric amounts of iodine are formed from nitroxides, the TFAA-I reagent can be applied to their analytical determination. Two procedures for the determination of nitroxides (titrimetric on ... | 18,966,259 |
Determination of lead in preserved egg by flame atomic absorption spectrometry after chemically modified preconcentration. | A sensitive method for the determination of lead in preserved egg by flame absorption spectrometry using ammonium pyrrolidine dithiocarbamate-polystyrene chemically modified platinum wire matrix is presented. The modified platinum wire matrix, after preconcentrating the lead, is placed in a flame burner for direct atom... | 18,966,264 |
A multi-wavelength photometer based on light-emitting diodes. | The light originating from seven light-emitting diodes of different colours is guided, one at a time, into a measuring cell by means of a fibre optic coupler. Detection is carried out with photodiodes which are connected to a log-ratio amplifier yielding direct absorbance readings. Optical filters are used to narrow th... | 18,966,270 |
Phase-inversion cellulose acetate membranes for suppression of protein interferences in anodic stripping voltammetry. | The phase-inversion (PI) method was used to cast permselective cellulose acetate membranes on glassy carbon electrodes with the aim of suppressing protein interferences in anodic stripping voltammetry (ASV). By using cadmium and lead as test analytes and differential pulse ASV as detection method, it was found that the... | 18,966,290 |
Electrocatalytic oxidation and flow detection of cysteine at an aquocobalamin adsorbed glassy carbon electrode. | A chemically modified electrode (CME) constructed by adsorption of aquocobalamin (VB12a) onto a glassy carbon electrode surface was demonstrated to catalyze the electro-oxidation of cysteine, a sulfhydryl-containing compound. The sulfhydryl oxidation occurred at 0.54-0.88 V vs. Ag AgCl depending on pH value (3.0-10.0).... | 18,966,306 |
Separation mechanism exploration on metal-MBTAE-salicylic acid mixed ligand complexes by reversed-phase high performance liquid chromatography. | The separation and determination of platinum metal and co-existing metal complexes by reversed-phase high performance liquid chromatography (HPLC) with 2-(6-methyl-2-benzothiazolylazo)-5-diethylamino phenol (MBTAE) as a precolumn derivatizing reagent is presented. The separation mechanism of these complexes was investi... | 18,966,309 |
Tensammetric determination of non-ionic surfactants combined with BiAS separation procedure (Wickbold) 2. Optimisation of the precipitation and investigation of interferences. | The precipitation step in the developed procedure (BiAS-ITM) was optimised with the aim of achieving a lower detection limit. Losses during filtration using Triton X-100 as representative non-ionic surfactant (NS), the indirect tensammetric method (ITM) and adsorptive stripping tensammetry (AdST) for the determination ... | 18,966,351 |
A beta-cyclodextrin based fiber-optic chemical sensor: a fractal analysis. | A fractal analysis is presented for the binding of pyrene in solution to beta-cyclodextrin attached to a fiber-optic chemical sensor. The specific (k(l)) and non-specific binding rate coefficients and the fractal dimension (D(f)) (specific binding case only) both tend to increase as the pyrene concentration in solution... | 18,966,390 |
Fluorimetric determination of hydrogen peroxide in water using acetaminophen. | A fluorimetric procedure for the determination of hydrogen peroxide, based on the oxidation of acetaminophen with hydrogen peroxide in acidic medium, is described. The calibration graph was linear in the range 5.0 x 10(-8) - 2.4 x 10(-5) M hydrogen peroxide at an emission wavelength of 333 nm with excitation at 298 nm.... | 18,966,391 |
Dissolved oxygen removal from aqueous media by the chromatomembrane method. | The possibilities of the new chromatomembrane method in the removal of oxygen dissolved in water are studied. The scheme of the water deoxygenation process is determined. The new reagent-free method allows production of water with oxygen content at the level of a few ppb. | 18,966,405 |
Chemiluminometric flow-injection method for determination of free l-malate in wine with co-immobilized malate dehydrogenase/NADH oxidase. | A flow-injection system with a co-immobilized malate dehydrogenase/reduced nicotineamide adenine dinucleotide (NADH) oxidase reactor and a chemiluminometer is described for the determination of free l-malate in wine. Malate dehydrogenase and NADH oxidase were co-immobilized on poly(vinyl alcohol) beads and packed into ... | 18,966,411 |
Salicylate-selective electrode based on lipophilic tin(IV)phthalocyanine. | A new PVC membrane electrode based on lipophilic (2,9,16,23-tetra-tert-butylphthalocyanine)tin(IV) dichloride which demonstrates excellent selectivity and fast response toward the salicylate ion is described. The membrane electrode displayed a linear response for salicylate in the concentration range 10(-5)-0.1 M and e... | 18,966,414 |
Lead determination at the ppb level using stopped-flow FIA. | A flow-injection-based kinetic method for the determination of lead ions was developed. In this method, resazurin was reduced to resorufin by sulfide and lead ions. The method has a detection limit of 1 ppb with a relative standard deviation of 5.2% at the 20 ppb level. Interferences can be removed by prior extraction. | 18,966,424 |
Inorganic tin(II) determination by FIA with amperometric detection of its oxinate complex. | A highly selective, rapid and direct amperometric method, based on the formation of a complex between tin(II) and 8-hydroxyquinoline (oxine), has been developed for the determination of trace levels of tin(II) using flow injection analysis. Tin(II) electro-oxidation was catalyzed by oxine; its oxidation peak occurred a... | 18,966,427 |
Spectrophotometric study of coproporphyrin-I complexes of copper(II) and cobalt(II). | The reagent 3,8,13,18-tetramethyl-21H,23H-porphine-2,7,12,17-tetrapropionic acid or coproporphyrin-I (CPI) was used for the spectrophotometric determination of copper(II) and cobalt(II) in the presence of pyridine and imidazole catalysts. Optimum conditions were investigated and the methods were applied to the determin... | 18,966,431 |
Electrochemical approach to monitoring metal exchange reaction of acetylacetonate complexes with cadmium, copper and zinc ions. | Metal exchange reactions of acetylacetonate complexes with Cd(II), Cu(II) and Zn(II) ions were investigated by using cadmium and copper ion selective electrodes. Changes in the electrode potential and pH of the solutions were monitored upon adding the pertinent metal Zn(II) of the acetylacetonate (AA) complexes. In the... | 18,966,434 |
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