On the role of the ground state Tb(III)/acetylacetone complex in sensitized emission of Tb(III) in ethanol solution

Summary The Tb(III)-acetylacetone system in ethanol solution has been studied by spectroscopic methods. The formation of a Tb(III)/acetylacetone (1:1) complex in the ground state has been proved and its stability constant determined,K=(0.97±0.06)·10⁴dm³mol^–1. The role of this complex in the spectrofluorimetric determination ofLn(III) ions in the presence of acetylacetone has been discussed.

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Über die Rolle eines Tb(III)-Acetylaceton-Komplexes im Grundzustand in der sensibilisierten Emission von Tb(III) in Ethanol-Lösung

Zusammenfassung Das Tb(III)-Acetylaceton-System in Ethanol-Lösung wurde mit spektroskopischen Methoden untersuchung. Die Bildung eines Tb(III)-Acetylaceton(1:1)-Komplexes im Grundzustand wurde bestätigt und seine Stabilitätskonstante bestimmt,K=(0.97±0.06)·10⁴dm³mol^–1. Die Rolle dieses Komplexes in der spektrofluorimetrischen Bestimmung vonLn(III)-Ionen in Gegenwart von Acetylaceton wurde erörtert.

     

Spectrofluorimetric determination of trace amounts of thorium

A spectrofluorimetric method, based on the formation of a fluorescent complex with salicyladehyde carbohydrazone, is optimized for the determination of thorium (20–800 μg l^?1) at “pH” 1.3–1.7. The relative standard deviation is 2.7% for 100 μg Th l^?1. The method is applied to synthetic mixtures containing various amounts of thorium and to the determination of thorium in monazite samples.     

Spectrofluorimetric trace determination of terbium(III) with potassium oxalate

Potassium oxalate acts as a specific reagent in enhancing the fluorescence intensity of terbium in aqueous solutions. Maximum fluorescence intensity is obtained by irradiating (at 255 mμ) terbium(III) dissolved in 0.01 M potassium oxalate solution at pH 7.8. The enhancement and quenching phenomena caused by other lanthanides, errors in the determination, and various examples of spectrofluorimetric analysis of traces of terbium in mixtures with other lanthanides are described. The sensitivity of the method is 5·10^-2μg/ml of terbium.     

Spectrophotometric determination of trace amounts of acetylacetone in aqueous solutions

A sensitive spectrophotometric method for the determination of trace amounts of acetylacetone in aqueous solution is carried out. In the presence of bicarbonate solution, diazotized anthranilic acid reagent reacts rapidly with acetylacetone to form a yellow-colored compound with maximum absorption at 330 nm, which is water-soluble and reasonably stable. Adherence to Beer's law is observed in the range 20–200 μg of acetylacetone/25 ml, with a molar absorptivity of 19.5 × 10³ liters mol⁻¹ cm⁻¹, a sensitivity index of 0.0051 μg cm⁻², relative to + 0.3 to −0.9%, and a relative standard deviation of 0.5–1.4%, depending on the concentration level.     

Spectrofluorimetric determination of trace amounts of europium(III) ion with lutetium(III)-sparfloxacin-sodium dodecyl sulfate luminescence enhancement system.

A new luminescence-enhancement system based on complex formation between europium and sparfloxacin in the presence of lutetium in a sodium dodecyl sulfate solution has been discovered. By adding a suitable amount of Lu3+ to the Eu-sparfloxacin-sodium dodecyl sulfate system, the luminescence can be enhanced by approximately 5-fold compared with that of the system without Lu3+. Under the optimum conditions, the luminescence intensity of the system is a linear function of the concentration of europium in the range of 1.0 x 10(-10) - 5.0 x 10(-7) mol L(-1). The detection limit of europium is 2.0 x 10(-13) mol L(-1) (S/N = 3). The system was used for the determination of trace amounts of europium in rare earth samples with satisfactory results.     

Spectrofluorimetric flow injection determination of trace amounts of periodate

A sensitive, rapid and selective procedure is proposed for the flow injection determinations of periodate by spectrofluorometric detection. The method is based on the reaction of periodate with Alizarin Navy Blue in basic solution. The reagents and manifold variables influence on the sensitivity have been investigated and the optimum conditions are established. Periodate can be determined for the range of 0.250-5.00 microg ml(-1) with a limit of detection of 0.08 microg ml(-1), and with a sample rate of 15 +/- 2 samples h(-1). The relative standard deviations for eight replicate determination of 0.500 and 5.00 microg ml(-1) was 1.3 and 1.1%, respectively. Periodate can be determined in the presence of iodate and bromate. The proposed method was used to determination of periodate in water samples.     

Spectrofluorimetric determination of trace amounts of aluminium with 5-bromo-salicylaldehyde salicyloylhydrazone

The fluorescent reagent 5-bromo-salicylaldehyde salicyloylhydrazone (5-Br-SASH) was synthesized and its ionization constants were established spectrophotometrically. The fluorescent reaction of this reagent with aluminium was studied. Based on this chelation reaction, a spectrofluorimetric method was developed for the determination of aluminium in acetic acid-ammonium acetate buffer solution of pH 5.4. Under these conditions, the A1-5-Br-SASH complex has excitation and emission maxima at 370 and 460 nm, respectively. The linear range of the method is from 0 to 120 ppb and the detection limit is 1.1 ppb of aluminium. The molar ratio of aluminium to the reagent is 1:3. Interferences of other ions were studied. The method was successfully applied to the determination of aluminium in glucose injection and common beverages.     

Spectrofluorimetric determination of submicrogram amounts of aluminium using salicylidene-o-aminophenol

Salicylidene-o-aminophenol provides a sensitive spectrofluorimetric reagent for the determination of aluminium down to 27 ng (or 2.7 x 10(-4) ppm in the final solution). The most suitable conditions of pH (5.6), reagent concentration and development time (>20 min) have been established. Extraction with sodium diethyldithiocarbamate into ethyl acetate at the pH of the determination renders the method highly selective; out of 46 foreign cations examined only chromium(III), scandium and thorium interfere. Anions which form complexes with aluminium, such as citrate, tartrate and fluoride, also cause interference, but none of the common anions interferes. A 1:1 stoichiometry of the complex has been established and some conclusions have been drawn concerning its nature.     

Spectrofluorimetric determination of trace heparin using lomefloxacin-terbium probe

A new spectrofluorimetric method was developed for determination of trace amount of heparin (Hep). Using lomefloxacin (LOM)-terbium ion (Tb3+) as a fluorescent probe, in the buffer solution of pH 8.70, Hep can remarkably enhance the fluorescence intensity of the LOM-Tb3+ complex at lambda = 545 nm and the enhanced fluorescence intensity of Tb3+ ion is in proportion to the concentration of Hep. Optimum conditions for the determination of Hep were also investigated. The linear range for the determination of Hep was 0.6-2.0 microg/ml and the detection limit was 45.22 ng/ml. This method is simple, practical and relatively free of interference from coexisting substances and can be successfully applied to assess Hep in biological samples. By the Rosenthanl graphic method, the association constant of Hep with the probe is 4.56 x 10(4) l/mol and binding numbers is 18.2. Moreover, the enhancement mechanism of the fluorescence intensity in the LOM-Tb3+ system and the LOM-Tb3+-Hep system have also been discussed.     

Spectrofluorimetric determination of trace amounts of beryllium in mineral water and human's hair

A new fluorescent reagent, 2-hydroxy-1-naphthaldehydene-8-aminoquinoline (HNAAQ), was synthesized. The fluorescent reaction of this reagent with beryllium was also studied. Based on this chelation, a highly sensitive spectrofluorimetric method was developed for determination of trace amounts of beryllium at pH 9.2. Under these conditions, the Be-HNAAQ complex has excitation and emission maxima at 410 and 450 nm, respectively. The linear range of the method is from 0 to 35 microg l(-1) and detection limit is 0.099 microg l(-1) of beryllium. Interference of other ions was studied. It is necessary to remove the interfering cations through concealing by EDTA and extraction separation techniques. The selectivity of the method can be increased remarkably. The procedure can be easily performed and affords good precision and accuracy. This method has been successfully applied to the determination of beryllium in mineral water and human's hair.     

Rapid and sensitive spectrophotometric determination of trace amounts of iron(III) using leuco Xylene cyanol FF

A new, simple, sensitive, and reliable method is presented for the rapid spectrophotometric determination of trace amounts of iron(III) using leuco Xylene cyanol FF. The method is based on the oxidation of leuco Xylene cyanol FF (LXCFF) to its blue form of xylene cyanol FF by iron(III) in sulfuric acid medium (pH 2.0–3.0), the absorbance of the formed dye is measured in an acetate buffer medium (pH 2.8–4.4) at 615 nm. The method obeys Beer's law over a concentration range of 0.15–0.9 g mL^-1 iron, having a molar absorptivity of 5.6×10⁴ L mol^-1 cm^-1 and a Sandell's sensitivity of 0.0001 g cm^-2. The optimum reaction conditions and other analytical parameters have been evaluated. The developed method has been successfully applied to the determination of iron in water, soil, industrial effluent, plant material, pharmaceutical preparations, synthetic mixtures, and aluminum alloys.     

Extractive spectrophotometric determination of trace amounts of iron(III) with benzyltriethylammonium chloride

The ion-association complex formed between a thiocyanato-iron(III) ion and a benzyltriethylammonium ion is extracted into 1,2-dichloroethane, and its absorbance at 476 nm is used for determination of the iron. Beer's law is obeyed up to about 4 mug/ml iron concentration in the final solution. The molar absorptivity is 2.79 x 10(4) l.mole(-1).cm(-1).     

Spectrofluorimetric determination of Er (III) with diantipyrylmethane

The optimum fluorescence conditions for erbium (III) are obtained by irradiating this lanthanide at 435 nm in 0.04 microg ml(-1) diantipyrylmethane solution at pH = 8 (lambdaem = 510 nm). The method proposed is satisfactory for the determination of erbium (III) in the range of 0.001 to 1 microg ml(-1). The relative standard deviation 0.02 microg ml(-1) Er (III) in 0.04 microg ml(-1) diantipyrylmethane solution is 1.1%. The effect of other rare earths upon the intensity of the fluorescence emitted by erbium (III) is discussed.     

Spectrophotometric determination of trace amounts of iron(III) with norfloxacin as complexing reagent

The complexation of iron(III) with norfloxacin in acidic solution at 25 degrees C, at an ionic strength of about 0.3 M and a pH of 3.0 has been studied. The water-soluble complex formed, which exhibits an absorption maximum at 377 nm, was used for the spectrophotometric determination of trace amounts of iron(III). The molar absorptivity was 9.05 x 10(3) I mol-1 cm-1 and the Sandell sensitivity 6.2 ng cm-2 of iron(III) per 0.001 A. The formation constant (Kf) was determined spectrophotometrically and was found to be 4.0 x 10(8) at 25 degrees C. The calibration graph was rectilinear over the range 0.25-12.0 p.p.m. of iron(III) and the regression line equation was A = 0.163c - 0.00042 with a correlation coefficient of 0.9998 (n = 9). Common cations, except cerium (IV), did not interfere with the determination. The results obtained for the determination of iron(III) using the described procedure and the thiocyanate method were compared statistically by means of the Student t-test and no significant difference was found.     

Spectrofluorimetric determination of microgram amounts of lead

The violet fluorescence at 480 mmu of lead in concentrated hydrochloric acid-potassium chloride solution (excitation maximum 270 mmu) provides a method for the spectrofluorimetric determination of 10-60mug of lead. The optimum conditions for the determination have been established, and the effect of 31 foreign ions examined at the 50-fold molar excess level. The interference from iron(III) and vanadium(V) is eliminated by addition of tin(II) chloride, and that of chromium(VI) by treatment with sodium sulphite.     

Spectrofluorimetric determination of trace amounts of Ga(III) in aluminium and biological samples with 1-(2-pyridylazo)-2-naphthol in sodium dodecyl sulphate micellar medium

Summary A spectrofluorimetric method is proposed for the determination of gallium with 1-(2-pyridylazo)-2-naphthol as derivative reagent in sodium dodecyl sulphate micellar medium. Sensitivity is increased by a factor of 20 with respect to that obtained in 20% ethanol medium. The stoichiometry of the complex is 11. Optimum working conditions are about pH 4, 0.3% sodium dodecyl sulphate and absence of ethanol. The calibration graph is linear in the range 5–400 ppb of Ga(III) with a variation coefficient of 1.5% at 210 ppb of Ga for 10 replicates, and detection limit is 0.8 ppb. Main interferences are from copper and cobalt. Results obtained in the determination of Ga(III) in urine and aluminium samples show the validity of the method proposed.

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Spektrofluorimetrische Bestimmung von Spuren Ga(III) in Aluminium und biologischen Proben mit 1-(2-Pyridylazo)-2-naphthol in micellarem Natriumdodecyl-sulfatmedium

     

Spectrophotometric determination of trace amounts of iron(III) by extraction of the mixed-ligand iron-fluoride-purpurin complex

The characteristics of the mixed-ligand iron(III)-fluoride-purpurin complex, including optimum conditions of formation and extraction into methyl isobutyl ketone are described. A procedure for determination of trace amounts of iron in fluoride medium (0.5M) with purpurin (1,2,4,-trihydroxy-anthraquinone) in methyl isobutyl ketone is given. The method is suitable for determining iron in the presence of large amounts of aluminium, cyanide, phosphate and nickel.     

Novel potentiometric membrane sensor for the determination of trace amounts of chromium(III) ions.

A plasticized Cr3+ ion sensor by incorporating 2,3,8,9-tetraphenyl-1,4,7,10-tetraazacyclododeca-1,3,7,9-tetraene (TTCT) ionophore exhibits a good potentiometric response for Cr3+ over a wide concentration range (1.0 x 10(-6)-1.0 x 10(-1) M) with a slope of 19.5 mV per decade. The sensor response is stable for at least three months. Good selectivity for Cr3+ in comparison with alkali, alkaline earth, transition and heavy metal ions, and minimal interference are caused by Li+, Na+, K+, Co2+, Hg2+, Ca2+, Pb2+ and Zn2+ ions, which are known to interfere with other chromium membrane sensors. The TTCT-based electrode shows a fast response time (15 s), and can be used in aqueous solutions of pH 3-5.5. The proposed sensor was used for the potentiometric titration of Cr3+ with EDTA and for a direct potentiometric determination of Cr3+ content in environmental samples.