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An enzyme biosensor for the determination of 4-chlorophenol in water solutions based on potentiometric pH-sensitive field-effect transistors as semiconductor transducer and tyrosinase immobilised in saturated glutaraldehyde vapours as biorecognition element has been described for the first time. The main analytical characteristics were studied under different conditions, as well as the possibility...
A rapid and simple method has been developed for the separation of chromium (III) and Cr(VI) species in river and reservoir water. Chromium (III) can be chelated with 8-hydroxyquinoline immobilized polyacrylonitrile (PAN) fiber, whereas Cr(VI) cannot. Chelated Cr(III) can be eluted with 2 mol l -1 HCl-0.1 mol l -1 HNO 3 . Cr(VI) in the filtrate and Cr(III) in the...
Si/SiO 2 chips were used to detect the hybridization of immobilized Oligo d(T) 20 through impedance measurement. The immobilization procedure involved an aminopropyl silane grafted silicon oxide surface activated by glutaraldehyde and subsequently modified by an aminolinker supporting oligonucleotides. The immobilization procedure was optimized and, in the best conditions, the...
The effects of cetyltrimethylammonium (CTAB), sodiumdodecylsulfate (SDS) and pol(oxyethylene)(9.5)p-(1,1,3,3-tetramethyl; Triton X-100) on the dissociation constants, transition points and transition intervals of thymol blue and bromothymol blue were studied. The experimental results indicated that surfactant micelles remarkably affected dissociation constants, transition points and transition intervals...
A simple and reliable method for the selective extraction and determination of bismuth in water as well as alloy samples using octadecyl bonded silica cartridge modified with cyanex 301 and graphite furnace atomic absorption spectrometry is described. Extraction efficiency and influence of sample matrix, optimum amount of extraction ligand, type and least amount of proper eluent and flow rates were...
A method for the determination of trace amounts of germanium by hydride generation atomic fluorescence spectrometry (HG-AFS) associated on-line with flow injection (FI) coprecipitation preconcentration was described. The samples, each spiked with Ni 2+ (500 μgml -1 ), were introduced into the FI system using time-based injection, and mixed with a NaOH solution (50 gl ...
Four chelating matrices prepared by coupling Amberlite XAD-2 with chromotropic acid (AXAD-2-CA or 1), pyrocatechol (AXAD-2-PC or 2) and thiosalicylic acid (AXAD-2-TSA or 3) through azo spacer and impregnation of Amberlite XAD-7 with xylenol orange (AXAD-7-XO or 4) have been studied for enrichment of lead(II). All the four resins quantitatively sorb Pb(II) at pH 3.0-8.0 when the flow rate is maintained...
This work performed fundamental studies for the extraction of gallium(III) with 2-methyl-8-quinolinol (HMQ) and 2-methyl-5-butyloxymethyl-8-quinolinol (HMO 4 Q) into supercritical carbon dioxide (SF-CO 2 ) from a weakly acidic solution. The distribution constants of HMO 4 Q between aqueous and SF-CO 2 phases were determined at 45 o C, 8.6-20.4 MPa and I=0.1...
Mixtures of amoxycillin and clavulanic acid were determined by using kinetic data in combination with partial least-squares multivariate calibration. The reaction of oxidation of these compounds with cerium(IV) in sulfuric acid medium has been monitored fluorimetrically. To follow the kinetics of the reaction, the stopped-flow mixing technique was used. Partial least-squares calibration of the kinetic...
An ion-pair liquid chromatography method with on-line photodiode-array and electrospray mass spectrometry detection was developed to determine 10 commonly used sulphonated azo dyes (Tartrazine, Amaranth, New Coccine, Sunset Yellow FCF, Allura Red AC, Ponceau R, Ponceau 3R, Orange I, Orange II and Metanil Yellow) in food. A reversed phase C 18 column with gradient elution was utilized...
In this paper, flame atomic absorption spectrometry was used for the determination of silver in various materials. The proposed preconcentration method is based on the continuous precipitation of silver as p-dimethylaminobenzilidene-rhodanine (PDBR) complex and dissolution of the precipitate with potassium cyanide. EDTA was added to the sample solution to mask large concentrations of Fe(III), Ni(II),...
A field flow preconcentration system (FFPS) for cadmium determination in seawater is described. Seawater samples are collected and preconcentrated in situ by passing them with a peristaltic pump through a minicolumn packed with Amberlite XAD-4 impregnated with the complexing agent 1-(2-pyridylazo)-2-naphthol. Thus, cadmium is complexed, retained, and preconcentrated without the interference of the...
Two manifolds allowing the automation of the standard additions method in flame atomic absorption spectrometry by using two computer-controlled variable-speed peristaltic pumps operating in a programmed way are presented in this article. One of the pumps increases and the other decreases its turning speed linearly with time, so that the flow-rate supplied to the nebulizer is constant. In the first...
Studies of the extraction kinetics of cerium(IV) from H 2 SO 4 -HF solutions with Cyanex 923 in n-heptane have been carried out using a constant interfacial area cell with laminar flow. The experimental hydrodynamic conditions were chosen so that the contribution of diffusion to the measured rate of reaction was minimized. The data were analyzed in terms of pseudo-first order constants...
A very simple and highly specific method for the determination of cysteine and penicillamine is presented. Treatment with 1,1'-thiocarbonyldiimidazole in slightly basic solutions converts cysteine rapidly and quantitatively to a very stable derivative, 2-thioxothiazolidine-4-carboxylic acid, which is not formed by thiols or amines. The cyclic derivative has a characteristic UV spectrum with a maximum...
Two flow injection inductively coupled plasma atomic emission spectrometric methods for the preconcentration and determination of trace amounts of cadmium in sea-water and waste-water samples are described based on the adsorption of the metal ion on a micro-column placed in the injection valve of the FI manifold and packed with silica gel funtionalised with 1,5-bis(di-2-pyridyl) methylene thiocarbohydrazide...
Comprehensive studies have been carried out on the extraction behavior of uranium and plutonium matrices using cyanex-923 extractant. The near total extraction of U/Pu and quantitative separation of 22 metallic elements at trace levels has been established using inductively coupled plasma-atomic emission spectrometry (ICP-AES). The studies carried out on back extraction of U/Pu from organic phase...
A simple and sensitive kinetic-spectrofluorimetric method is described for the determination of iridium(IV) and the possible mechanism of catalytic reaction is proposed. The method is based on the fluorescent quenching reaction of salicylaldehyde p-nitro-benzoylhydrazone (SAP-NBH) with potassium periodate, inhibited by Ir(IV) in a water-ethanol (7.3+2.7, v/v) medium at pH 10.70 and 55 o C...
Four analytical methods have been applied for the determination of volatile chlorination by-products in drinking water, based on the following techniques: liquid-liquid extraction-gas chromatography-electron capture detection (LLE-GC-ECD); liquid-liquid extraction-gas chromatography-mass spectrometry (LLE-GC-MS); purge and trap-gas chromatography-mass spectrometry (purge and trap-GC-MS); and headspace-gas...
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