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Benzeneacetaldehyde-4-hydroxy-α-oxo-aldoxime is proposed as a new sensitive and selective reagent for the spectrophotometric determination of cobalt. The reagent reacts with cobalt in the pH range 8.6–9.4 to form a yellow colored 1:3 chelate which is very well extracted in chloroform. Beer's law is obeyed in the concentration range 0.05–1.3 μg ml−1 cobalt. The molar absorptivity of the extracted species...
A highly sensitive and selective method is described for the determination of trace amounts of nitrite based on its effect on the oxidation of carminic acid with bromate. The reaction was monitored spectrophotometrically by measuring the decrease in absorbance of carminic acid at 490 nm after 3 min of mixing the reagents. The optimum reaction conditions were 1.8×10−1 mol l−1 H2SO4, 3.8×10−3 mol l−1...
A magnesium hydroxide coprecipitation technique for determination of Cd, Co, Cu, Mn, Ni in dialysis concentrate is described. The analytes are concentrated from 10 ml of dialysis concentrate into 1 ml of 1 M HNO3 and subsequently determined by graphite furnace atomic absorption spectrometry. Coprecipitation parameters and matrix effects are discussed. The precision, based on replicate analysis, is...
A system for separation of zinc traces from large amounts of cadmium is proposed in this paper. It is based on the solid-phase extraction of the zinc in the form of thiocyanate complexes by the polyurethane foam. The following parameters were studied: effect of pH and of the thiocyanate concentration on the zinc extraction, shaking time required for quantitative extraction, amount of PU foam necessary...
Simple, selective and sensitive spectrophotometric methods are described for the determination of pentoxifylline, based on the haloform reaction with a known and excess of standard iodine solution under alkaline conditions. The excess of iodine is determined at pH 3.0 with metol–isoniazid (λmax=620 nm; method A) or wool fast blue BL (λmax=540 nm, method B). All the variables have been optimised and...
A simple, rapid, sensitive and selective method for the microgram detection and spectrophotometric determination of EDTA in water, human urine and detergents, based on its reaction with Co(II) and phosphomolybdic acid at pH 0.5–2.0 is reported. Absorbance is measured against Co(II)–phosphomolybdic acid reference solution at 750 nm. The effect of time, temperature, pH and Co(II) or phosphomolybdic...
The spectrofluorimetric determination of Fe3+ using salicylic acid as an emission reagent has been investigated by measuring the decrease of fluorescence intensity of salicylic acid due to the complexation of Fe3+–salicylic acid. An emission peak of salicylic acid, which is decreased linearly by addition of Fe3+, occurs at 409 nm in aqueous solution with excitation at 299 nm. The determination of...
The modified silica gel with 1,10-phenanthroline adsorbed was obtained. The adsorption from aqueous solutions onto loaded silica gel of Fe(II), Cu(II) and Ag(I) and their complexes was studied. The loaded silica gel was applied to Fe(II), Cu(II) and Ag(I) reflectance spectroscopy determinations in water (detection limits 0.08, 0.03 and 0.01 ppm respectively). Visual test scales for Fe, Cu and Ag ion...
A new method is described for the determination of antimony based on the cathodic adsorptive stripping of Sb(III) complexed with 2′,3,4′,5,7-pentahydroxyflavone(morin) at a static mercury drop electrode (SMDE). The reduction current of the adsorbed antimony complex was measured by 1.5th-order derivative linear-sweep adsorption voltammetry. The peak potential is at −0.51 V (vs. SCE). The effects of...
An examination was made of the effect of electrode polishing on the direct pulsed amperometric detection (PAD) and indirect PAD response to penicillin G. The polishing procedure produced a temporary loss of sensitivity for both types of PAD, which over time relaxed back to higher levels. A temporary increase in the electrode kinetics can be observed as well, particularly for a PAD waveform in the...
Multi-wavelength detectors offer improved detection capabilities for liquid chromatographic methods, but require multivariate approaches to utilise all the available information. The photodiode-array detector in high-performance liquid chromatography (HPLC) generates a three-dimensional data matrix, which is conventionally presented as an isometric projection or a contour plot. In this work, a new...
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)...
The construction and electrochemical response characteristics of poly (vinyl chloride) and poly (vinyl chloride) carboxylate membrane sensors for the determination of cyclophosphamide and ifosphamide are described. Based on the formation of an ion-pair complex between the drug cation and sodium tetraphenylborate, two poly (vinyl chloride) sensors, namely a cyclophosphamide membrane sensor and ifosphamide...
The concentration of potassium was determined by a combination of flow injection analysis (FIA) with an all-solid-state potassium sensor detection. The all-solid-state potassium-selective electrode possessing long-term potential stability was fabricated by coating an electroactive polypyrrole/poly(4-styrenesulfonate) film electrode with a plasticized poly(vinyl chloride) membrane containing valinomycin...
A square-wave voltammetric method together with Nafion®-coated carbon paste electrodes were used for the selective determination of uric acid in the presence of a high concentration of ascorbic acid. Since the oxidation potential of uric acid is about 200 mV more positive than that of ascorbic acid at the Nafion®-coated carbon paste electrode, the selectivity can be greatly improved simply by applying...
The determination of a single rare earth element in a mixture with other species of this family is a very challenging problem in analytical chemistry due to the close similarity of their chemical properties. In this work, a liquid–solid extraction procedure for praseodymium, neodymium, samarium and yttrium mixtures and subsequent determination by energy dispersive X-ray fluorescence spectrometry is...
The extraction equilibrium of the ion-associate of periodate with 1-(3,5-diamino-6-chloropyrazinecarboxyl) guanidine hydrochloride (DPG+Cl−) was investigated spectrophotometrically. The optimum conditions for the extraction of the ion associate DPG+·IO4− with cyclohexanone have been established. The ion association constants, β, KD and Kex and the molar absorpativity of the formed ion associate were...
FI spectrophotometric determination of calcium using murexide has been developed. The problem of the color of the dye fading and/or its complex in an alkaline medium in the batch method can be overcome by taking advantage of FIA. A calcium solution is injected into an ethylenediamine–ethylenediamine hydrochloride buffer (1 M, pH 11) which also serves as a masking agent, and is then merged with the...
Silica gel and glass beads were modified by using acid chloride of metal–tetrakis(4-carboxyphenyl)porphine (M–TCPP) through a peptide bond, and an anion-exchange resin with M–TCPP by ion-exchange reaction and physical adsorption. The carriers modified with Co3+–TCPP proved to accelerate the redox reaction which is catalyzed by glutathione oxidase (GSHOx), while those modified with Mn3+–TCPP exhibited...
A method for the determination of total organic tin from marine water samples by electrothermal atomization absorption spectrometry (ETAAS) is described. Samples are previously preconcentrated with a chelating molecule (tropolone) impregnated on a macroporous polymer (Amberlite XAD-2). The graphite furnace programme and preconcentration parameters were optimized. Calibration and addition graphs were...
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