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Novel reagents and the rapid technique were developed for the simultaneous determination of water and ene-diols or thiols in chemical products, drugs and other materials which are inaccessible for direct K. Fischer titration. The reagents consist of iodine, tetramethylammonium iodide or potassium iodide, base (diethanolamine, triethanolamine, sodium acetate and/or urea) in methanol mixed with N,N-dimethylformamide,...
A highly sensitive detection system using a semiconductor laser (SCL) and a thin long flow-through cell (TLFCT) to match flow-based analysis, such as flow injection analysis (FIA), has been developed. The SCL was a GaAlAs semiconductor laser emitting at 780 nm (5 mW), and the TLFTC, which has a 100 mm thin long light path, was made of a poly(tetrafluoroethylene) (PTFE) rod. The sensitivity was essentially...
A highly sensitive method is proposed for the determination of thiosulfate based on the oxidation of aqueous thiosulfate (100 or 200 ml) by iodide in 4 ml of carbon tetrachloride. The excess of iodine was extracted into 8 ml of aqueous iodide solution as triiodide to be measured spectrophotometrically; the thiosulfate could therefore be indirectly highly concentrated and determined selectively. ...
A sequential injection analysis (SIA) assembly for the atomic absorption determination of Fe(III) in natural waters is proposed. Iron is preconcentrated on a microcolumn packed with a chelating resin (Chelex 100) that is inserted in the manifold. The sample is passed through the column and the iron retained by the resin is subsequently eluted with 2 M HNO 3 . The proposed SIA system affords...
The ionic product of water, pK w = - log[H + ][OH - ] has been determined in aqueous solutions of tetramethylammonium chloride over the concentration range of 0.1-5.5 M at 25°C using high-precision glass electrode potentiometric titrations. pK w data relating to aqueous potassium and sodium chlorides at ionic strengths up to 5 M are markedly lower than the tetramethylammonium...
Measurement of iron and manganese is very important in evaluating the quality of natural waters. We have constructed an automated Fe(II), total dissolved iron(TDI), Mn(II), and total dissolved manganese(TDM) analysis system for the quality control of underground drinking water by reverse flow injection analysis and chemiluminescence detection(rFIA-CL). The method is based on the measurement of the...
A procedure is developed for determination of As, Co, Se, Cr, Pb, Zn, Cu, Mn, Cd, Sb, and Sn in water by ICP-AES analysis of alcohol eluates after pre-concentration of the samples. The pre-concentration is performed on a sodium diethyldithiocarbamate supported soft polyurethane foam. The sorbed elements are subsequently eluted with 1-propanol and the alcohol eluates are analysed by ICP-AES. A eight-fold...
A new concentration method of rhodium using Mg-W cell-electrodeposition has been developed. The method was combined with electrothermal atomic absorption spectrometry (ETAAS) with a tungsten tube atomizer. The optimal immersing time was 120 s. The most suitable pH for rhodium electrodeposition was 1.0. Under optimal conditions, the detection limit of rhodium by the ETAAS with the preconcentration...
A sensitive analytical method for the simultaneous assay of nitrate and nitrite in water and some fruit samples is presented. The method is based on nitrite determination using the diazotization-coupling reaction by column preconcentration and on the reduction of nitrate to nitrite using the Cd-Cu reductor column. Nitrite is diazotized with sulfanilamide (SAM) in the pH range 2.0-5.0, sulfamethizole...
Tl(I) and Tl(III) are preconcentrated simultaneously from aqueous solutions by colloid precipitate flotation using two collectors: hydrated iron(III) oxide (Fe2O3·xH2O) and iron(III) tetramethylenedithiocarbamate (Fe(TMDTC)3). After the coprecipitation step and the addition of foaming agents, Tl(I) and Tl(III) were separated from the water by a stream of air bubbles. Various factors affecting Tl(I)...
A flow injection catalytic spectrophotometric method is proposed for the determination of nitrite based on its catalytic effect on the redox reaction between naphthol green B and potassium bromate in phosphoric acid medium. The reaction is monitored spectrophotometrically by measuring the decrease in absorbance of naphthol green B at the maximum absorption wavelength of 722 nm. The detection limit...
Sodium diethyldithiocarbamate in the presence of a weak oxidizing agent is used as a co-precipitative agent for the pre-concentration of Se, Cu, Pb, Zn, Fe, Co, Ni, Mn, Cr and Cd. A procedure was developed for ICP-AES determination of these elements after pre-concentration in river and waste water (an enrichment factor of 40). The recovery of all the elements tested for was more than 98%. The limits...
Microwave-assisted extraction (MAE) for the separation of atrazine, simazine and prometryne from synthetic soil samples, using water and some organic solvents as the extractants, was studied in detail. The effects of the soil matrix, the soil moisture and the pH of the aqueous extraction system on the MAE efficiency were also studied. It was found that the three triazines could be efficiently extracted...
A solid-phase microextraction method coupled with a flame photometric detector was developed for the analysis of organophosphorus pesticides in water. Two kinds of fiber (100 μm polydimethyl siloxane (PDMS) and 85 μm polyacrylate (PA) fibers) were used and compared. Parameters that may affect the extraction, such as the duration of absorption and desorption, temperature of absorption, ionic strength,...
The voltammetric method of Cr(VI) determinations in the flow system, based on the combination of selective accumulation of the product of Cr(VI) reduction on HMDE and a very sensitive method of chromium determination in the presence of bipyridine [Z. Gao K.S. Siow, Electroanalysis 8 (1996) 602] is proposed. The calibration graphs were linear from 3x10 -9 to 3x10 -8 and from...
A method for the preconcentration and speciation of chromium was developed. After formation of an anionic compound with ethylenediaminetetraacetic acid (CrY - ), Cr (VI) and Cr (III) are retained on a strong anionic phase (SAX) and controlled elution with 0.5 M NaCl permits their speciation. The retention and elution conditions were optimised, and interferences due to the presence of other...
A flow injection (FI) on-line precipitation-dissolution was developed for electrothermal atomic absorption spectrometry (ETAAS) determination of (ultra)trace amounts of beryllium in water samples. Beryllium was precipitated quantitatively with NH 4 OH+NH 4 Cl and collected in a knotted tube of Tygon without using a filter, while the other matrix components flowed downstream to waste...
The rubidium content of some well and mineral waters has been determined by flame atomic emission spectrometry using the methane-air flame. Effects of the flame and of instrumental parameters (flame composition, the observation height, spectral bandpass of the monochromator) on the emission of rubidium in methane-air flame was studied and optimized. The best results were obtained using the 780.0 nm...
A simple, sensitive, rapid and reliable method has been developed for spectrophotometric determinations of As(III) in the presence of As(V) based on its inhibition effect on the redox reaction between bromate and hydrochloric acid. The decolorization of methyl orange by the reaction products was used to monitor the reaction spectrophotometrically at 525 nm. The method allows the determination of arsenic...
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...
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