Spectrophotometric determination of bismuth(III) with o-hydroxyhydroquinonephthalein in the presence of Brij 58

A simple and sensitive spectrophotometric determination of bismuth(III) is based on the reaction between bismuth(III) and o-hydroxyhydroquinonephthalein in the presence of Brij 58 in acidic media. The calibration graph is linear over the range 0-3.5 mug/ml bismuth(III) in the final solution, and the apparent molar absorptivity at 520 nm is 9.03 x 10(4) l. mole(-1). cm(-1). The proposed method is 2-10 times more sensitive than other methods, and simpler. It has been applied to the assay of bismuth(III) in pharmaceutical preparations, such as dermatol and bismuth subnitrate, with good results.     

Separation of bismuth from gram amounts of thallium and silver by cation-exchange chromatography in nitric acid

Traces and small amounts of bismuth can be separated from gram amounts of thallium and silver by successively eluting these elements with 0.3M and 0.6M nitric acid from a column containing 13 ml (3 g) of AG50W-X4, a cation-exchanger (100-200 mesh particle size) with low cross-linking. Bismuth is retained and can be eluted with 0.2M hydrobromic acid containing 20% v/v acetone, leaving many other trace elements absorbed. Elution of thallium is quite sharp, but silver shows a small amount of tailing (less than 1 gmg/ml silver in the eluate) when gram amounts are present, between 20 and 80 mug of silver appearing in the bismuth fraction. Relevant elution curves and results for the analysis of synthetic mixtures containing between 50 mug and 10 mg of bismuth and up to more than 1 g of thallium and silver are presented, as well as results for bismuth in a sample of thallium metal and in Merck thallium(I) carbonate. As little as 0.01 ppm of bismuth can be determined when the separation is combined with electrothermal atomic-absorption spectrometry.     

Extractive photometric determination of gallium with 8-quinolinol in layered crystals of bismuth telluride-estimation of the determination limit

A method for determining microgram amounts of gallium in milligram samples of layered monocrystals of the type A(V)(2)B(VI)(3) is described. For the separation of 1-5 mug of gallium(III) from a large excess of bismuth in a single extraction the recommended conditions are pH 3.6-4.2 (acetate buffer, V(aq) 40 ml), an adequate excess of 8-quinolinol for complete extraction and of thiosulphate for masking bismuth. The absorbance of a chloroform extract (V(org) = 10 ml) is measured at 392.5 nm in a 50-mm cell against a blank extract concurrently obtained with a solution of pure Bi(2)Te(3). Reference polycrystalline materials are used to check the precision and accuracy of the method. In routine analysis of layered monocrystals a relative standard deviation of 4-8% is to be expected for about 1 mug of gallium in the extraction system. Estimation of the limit of determination, based on two statistical models, is discussed with respect to the error of the method and the fluctuation of the blank.     

Separation of traces and larger amounts of bismuth from gram amounts of thallium, mercury, gold and platinum by cation-exchange chromatography on a macroporous resin

Traces and larger amounts of bismuth (up to 50 mg) can be separated from gram amounts of thallium, mercury, gold and platinum (up to 5 g) by sorption from a mixture of 0.1M hydrochloric acid and 0.4M nitric acid on a column containing just 3 g (8.1 ml) of AGMP-50, a macroporous cation-exchange resin. This resin retains bismuth much more strongly than does the usual microporous resin (styrene-DVB with 8% cross-linkage). Other elements are eluted with the same acid mixture as that used for sorption, and bismuth is finally eluted with 1.0M hydrochloric acid. Separations of bismuth are sharp and recoveries quantitative. Only microgram amounts of the other elements remain in the bismuth fraction. Amounts of bismuth as little as 5 mug have been separated from 5 g of thallium, and determined (r.s.d. = 2%) by flame atomic-absorption. Only 100-mug amounts of bismuth have been separated from gram amounts of mercury, gold, and platinum, but there is no reason to believe that smaller or larger amounts of bismuth cannot be separated from these elements and recovered with the same accuracy as that for the separation from thallium. The lower limit of the method is determination of 0.4 mug of bismuth in 10 ml of solution (0.004 absorbance). An elution curve, the relevant distribution coefficients and the results of analysis of synthetic mixtures and two practical samples [thallium metal and mercury(II) nitrate] are presented.     

Determination of trace europium based on new fluorimetric system of europium(III) with thenoyltrifluoroacetone and N,N'-dinaphthyl-N,N'-diphenyl-3,6-dioxaoctanediamide

In the present paper, N,N'-dinaphthyl-N,N'-diphenyl-3,6-dioxaoctanediamide acts as a specific reagent for enhancing the fluorescence intensity of Eu(III) complex with thenoyl trifluoroacetone (TTA), the spectrofluorimetric determination of trace amounts of Eu(III) based on the above system was carried out and its luminescence mechanism was studied. The excitation and emission wavelengths are 343.6 and 613.3 nm, respectively. The fluorescence intensities vary linearly with the concentration of europium(III) in the range 3.647x10(-3)-3.039 mug ml(-1) for the original fluorescence with a detection limit down to 2.279x10(-4) mug ml(-1) and the standard deviation is 0.063 mug ml(-1) for 10 times measurements, and in the range 7.598x10(-4)-0.0243 mug ml(-1) (SD=0.035 for 15 times measurements), 0.06078-0.6100 mug ml(-1) (SD=0.52 for 10 times measurements) for the first derivative fluorescence signal with a detection limit down to 8.566x10(-5) mug ml(-1). The interferences of other rare earths and some of inorganic ions are described. This method is a direct, rapid, selective and sensitive analytical method for the determination of trivalent europium in rare earth ore samples and high purity of rare earth oxides.     

Spectrophotometric determination of bismuth with semi-xylenol orange and its application in metal analysis

Semi-Xylenol Orange forms a 2 : 1 chelate with bismuth(III), which has a logarithmic value of 3.08 for its conditional formation constant and a molar absorptivity of 4.2 x 10(4) l.mole(-1).cm(-1). Beer's law is obeyed at 540 nm over the range 10-30 mug of Bi(III), with a standard deviation of 1.1 mug (n = 18). Lactic acid is used as an auxiliary complexing agent to prevent olation and oxolation. Interference from up to 1.3 mg of copper can be eliminated by the combined use of masking Cu(II) with thiourea, ascorbic acid and thiosemicarbazide and "post-masking" Bi(III) with sodium chloride. The proposed method has been successfully applied to the direct determination of 0.002% of Bi in lead metal, with a coefficient of variation varying from 3.7 to 6.9%.     

Chemiluminescence determination of some fluoroquinolone derivatives in pharmaceutical formulations and biological fluids using [Ru(bipy)(3)(2+)]-Ce(IV) system

A new chemiluminescence (CL) method using flow injection has been described for the rapid and sensitive determination of three fluoroquinolone derivatives, namely ofloxacin, norfloxacin and ciprofloxacin hydrochloride. The method is based on the CL reaction of the studied fluoroquinolones with tris(2,2'-bipyridyl)ruthenium(II) [Ru(bipy)(3)(2+)] and Ce(IV) in sulfuric acid medium. Under the optimum conditions, the CL intensity is proportional to the concentration of the drugs in solution over the range 0.05-7.0 mug ml(-1) for norfloxacin, 0.05-6.0 mug ml(-1) for ciprofloxacin hydrochloride and 0.003-0.7 mug ml(-1) for ofloxacin. The limits of detection (s/n=3) were 3.1x10(-8) M norfloxacin, 2.6x10(-8) M ciprofloxacin hydrochloride and 5.5x10(-9) M ofloxacin. The method was applied successfully to the determination of these compounds in dosage forms and biological fluids.     

Determination of copper in the presence of a large excess of bismuth by differential-pulse anodic-stripping voltammetry without preliminary separation

Conditions have been found which make possible the determination of copper in the presence of a large excess of bismuth by differential-pulse and anodic-stripping voltammetry without preliminary separation. The electrochemical activity of the bismuth, which usually interferes in the determination of copper, is inhibited by using tetrabutylammonium chloride (TBAC) as surfactant. In 0.2M EDTA and 0.01M ascorbic acid at pH 4.5 as supporting electrolyte without the surfactant present, trace levels of copper (1.5 x 10(-8)M) can be determined accurately if the molar ratio of bismuth to copper is not higher than 3, but if the electrolyte also contains TBAC at 0.01M concentration, bismuth can be tolerated in concentrations up to 10(-4)M, and the height of the copper peak is unaffected.     

Manual and fia methods for the determination of cadmium with malachite green and iodide

A sensitive and rapid spectrophotometric method for the determination of cadmium is described, based on the formation of a blue complex at pH 4 between the anionic iodide complex of cadmium(II) and Malachite Green; the colour is stabilized with poly(vinyl alcohol). The calibration graph for measurement at 685 nm is linear over the range 1-50 mug of cadmium per 25 ml of final solution, with a relative standard deviation of +/-1.7% for 1 mug/ml cadmium. The molar absorptivity is 6.1 x 10(4) 1.mole(-1).cm(-1). The method can be successfully adapted for FIA, the peak height being proportional to the cadmium concentration over the range 0.1-3 mug/ml; a two-channel manifold is used and an improvement in selectivity is obtained. The use of a gradient tube is demonstrated to give a good calibration for Cd(II) over the range 2 x 10(-2) -2 x 10(-6)M.     

Use of a bismuth ion-selective electrode for investigation of bismuth complexes of citric and malic acids

A bismuth ion-selective electrode has been used to determine the nature and stability of the complexes formed by bismuth with citric acid and malic acid, by measurement of the response of the electrode to different total bismuth concentrations at various combinations of pH and total ligand concentration. The values found were beta(2) = 3 x 10(13) for Bi(Cit)(2)(3-) and beta(3) = 8 x 10(9) for Bi(Mal)(2)(3-).     

Investigation of concentration quenching and 1.3 microm emission in Nd(3+)-doped bismuth glasses

Nd(2)O(3)-doped 70Bi(2)O(3)-20B(2)O(3)-10SiO(2)-xNd(2)O(3) (x=0.1, 0.3, 0.5, 0.7, 1.0, 1.5 mol%) bismuth glasses were prepared by the conventional melt-quenching method, and the Nd(3+):(4)F(3/2)-->(4)I(13/2) fluorescence properties had been studied for different Nd(3+) concentrations. The Judd-Ofelt analysis for Nd(3+) ions in bismuth boron silicate glasses was also performed on the base of absorption spectrum. The transition probabilities, excited state lifetimes, the fluorescence branching ratios, quantum efficiency and the stimulated emission cross-sections of (4)F(3/2)-->(4)I(13/2) transition were calculated and discussed. Based on the electric dipole-dipole interaction theory, the interaction parameters: C(DD), for the energy migration rate (4)F(3/2), (4)I(9/2)-->(4)F(3/2), (4)I(9/2) and C(DA), for cross-relaxation rate (4)F(3/2), (4)I(9/2)-->(4)I(15/2), (4)I(15/2), and/or (4)F(3/2), (4)I(9/2)-->(4)I(13/2), (4)I(15/2) in bismuth boron silicate glasses were about 18.4 x 10(-40)cm(6)/s and 3.4 x 10(-40)cm(6)/s, respectively.     

Alkali-metal-supported bismuth polyhedra-principles and theoretical studies

We have quantum chemically investigated the structure, stability, and bonding mechanism in highly aggregated alkali-metal salts of bismuthanediide anions [RBi](2-) using relativistic density functional theory (DFT, at ZORA-BP86/TZ2P) in combination with a quantitative energy decomposition analysis (EDA). Our model systems are alkali-metal-supported bismuth polyhedra [(RBi)(n)M(2n-4)](4-) with unique interpenetrating shells of a bismuth polyhedron and an alkali-metal superpolyhedron. Furthermore, we have analyzed the trianionic inclusion complexes [M'@{(RBi)(n)M(2n-4)}](3-) involving an additional endohedral alkali-metal ion M'. The main objective is to assist the further development of synthetic approaches toward this class of compounds. Our analyses led to electron-counting rules relating, for example, the number of bonding orbitals (N(bond)) of the cage molecules [(RBi)(n)M(2n+Q)](Q) to the number of bismuth atoms (n(Bi)), alkali-metal atoms (n(M)), and net charge Q as N(bond) = n(Bi) + n(M) - Q (R = one-electron donor ligand; M = alkali metal; n = 4-12; Q = -4, -6, -8). Finally, on the basis of our findings, we predict the next members in the 5-fold symmetrical row of alkali-metallobismaspheres with a macroicosahedral arrangement.     

Kinetic determination of selenium, based on inhibition of the Pd(II)-catalysed reaction between pyronine G and hypophosphite

A new kinetic method for determination of selenium is based on its inhibitory effect on the Pd(II)-catalysed reaction between Pyronine G and hypophosphite. Under the optimum experimental conditions (6 x 10(-5)M Pyronine G, 0.4M hypophosphite, 0.4 mug/ml Pd(II), pH 2.8, temperature 22.0 +/- 0.2 degrees ), Se can be determined in the concentration range 0.033-0.50 mug/ml. The method suffers from numerous interferences and is thus limited in application. It has been applied to the determination of selenium in spring waters and pharmaceutical preparations.     

Spectrophotometric determination of Fe(III) in alkaline solutions without neutralization

Spectrometric study on the complexation of Fe(III) with an organic reagent obtained by coupling 3-methyl-1-phenyl-5-pyrazolone with diazotized 3-hydroxy-4-amino-benzene sulphonic acid was carried out in alkaline solutions. A 1:2 Fe(III): reagent water soluble complex is formed. The optimum pH is 9.0-11.8. The maximum absorbance of the complex lies at lambda = 560 nm, where the absorbance of the reagent is low. The molar absorptivity is 9000 l.mole(-1).cm(-1) at pH = 11.6. The value of the stability constant determined at 20 +/- 1 degrees C, pH = 11.6 and lambda = 560 nm is 4 x 10(5)M. The Beer-Lambert law is followed for iron concentration in the 0.2-5.0 mug/ml range. The spectrophotometric method was tested on synthetic solutions and thus applied for determination of traces of Fe(III) in several samples of alkaline hydroxides and carbonates without the neutralization of the solutions.     

Determination of bismuth in biological samples using on-line flow-injection microwave-assisted mineralization and precipitation/dissolution for electrothermal atomic absorption spectrometry

An on-line automated flow injection system with microwave-assisted sample digestion for the electrothermal atomic absorption spectrometric determination of bismuth in biological materials is described. After the exposure of the sample to microwave radiation, the analyte was subject to a precipitation/dissolution process. Bismuth was precipitated with the stannite ion in basic medium and collected on the walls of a knotted coil, while the other matrix components flowed downstream to waste. The precipitate was dissolved with nitric acid and a sub-sample was collected in a capillary of a sampling arm assembly, to introduce 20 mul volumes into the graphite tube by means of positive displacement with air through a time-based injector. The analytical figures of merit were first evaluated by filling the sampling arm with a standard solution of bismuth and thereafter injecting aliquots of this solution into the atomizer. The calibration graph was linear from the detection limit (8 pg) to 1.2 ng of bismuth. The sensitivity was of 26.8 mug l(-1) for 0.2 A-s and the characteristic mass (m(o)) was of 11.8 pg/0.0044 A-s. The precision of the method, evaluated by replicate analyses of solutions containing 20 and 200 pg of bismuth, were 5.5 and 3.0% (n=10), respectively. When solutions were introduced in the flow system here described, the calibration graph was linear in the range 0.04-6.0 mug l(-1), which means that a preconcentration factor of 10 was obtained for bismuth. The precision slightly deteriorated, e.g. the replicate analysis of solutions containing 1 and 10 pg of bismuth were 7.1 and 5.3% (n=10), respectively. However, the recoveries values obtained with urine and whole blood bismuth spiked samples were over 96.5% and the agreement between observed and certified values was good.     

Determination of thallium in bismuth by differential pulse anodic-stripping voltammetry without preliminary separation

The determination of trace levels of thallium in bismuth and bismuth salts by differential pulse anodic-stripping voltammetry has been made possible by using a surfactant as an electrochemical masking agent, in addition to a complexing agent. In 0.2M EDTA at pH 4.5 as supporting electrolyte in the absence of surfactant, bismuth at concentrations below 10(-4)M does not interfere. When the electrolyte also contains tetrabutylammonium ions at 0.01 M concentration, bismuth can be tolerated at concentrations up 0.05M, and the height of the thallium peak is unaffected. It is thus possible to determine 1 nM Tl(I) in the presence of 0.05M Bi(III), i.e., Tl at the 1 x 10(-6)% level in bismuth. The precision of the determination and the recovery are satisfactory. Neither an 800-fold ratio of Cu(II) nor a 10(7)-fold ratio of Pb(II) to Tl(I) interferes in the determination. Other cations such as Zn(2+), Cd(2+), In(3+), Hg(2+), Fe(3+), Sb(3+) and Sn(4+) in 10(4)-fold molar ratio to Tl(I) have no effect on the determination. Thallium has been determined in bismuth metal and in bismuth nitrate of various degrees of purity.     

On the spectrophotometric flow injection determination of chromium(VI) in natural waters after on-line preconcentration on activated alumina

The feasibility of chromium(VI) preconcentration on to activated alumina in a continuous flow system with spectrophotometric detection was investigated. Chemical and flow variables, and the influence of concomitant species were studied both with and without preconcentration systems. The best results were obtained by using a 2.5 cm long, 1.6 mm i.d. alumina minicolumn, and selecting 1 x 10(-4) M nitric acid as the preconcentrating medium and 0.1 M ammonium hydroxide as the eluent. The eluted chromium(VI) was mixed with diphenylcarbazide in acidic medium and the absorbance of the colored complex was measured at 540 nm. Linear calibrations for 5, 25 and 50 ml sample volumes were established over the concentration ranges 10-50 mug 1(-1), 2-10 mug 1(-1) and 1-5 mug 1(-1) with sensitivity enhancements of 44, 196 and 392 and detection limits (3sigma) of 3.0 mug 1(-1), 0.3 mug 1(-1) and 0.2 mug 1(-1), respectively. The methods is relatively fast and cheap. Natural waters were analyzed with use of the developed procedure.     

Preconcentration of iron (III), cobalt (II) and copper (II) nitroso-R complexes on tetradecyldimethylbenzylammonium iodide-naphthalene adsorbent

Iron, cobalt and copper form coloured water soluble anionic complexes with disodium 1-nitroso-2-naphthol-3-6-disulphonate (nitroso R-salt). The anionic complex is retained quantitatively as a water insoluble neutral ion associated complex (M-nitroso R-TDBA) on tetradecyldimethylbenzylammonium iodide on naphthalene (TDBA(+)I(-)-naphthalene) packed column in the pH range of: Fe(III): 3.1-6.5, Co: 3.4-8.5 and Cu 5.9-8.0 when their solutions are passed individually over this adsorbent at a flow rate of 0.5-5.0 ml/min. The solid mass consisting of an ion associated metal complex along with naphthalene is dissolved out of the column with 5 ml dimethylformamide/chloroform and metals are determined spectrophotometrically. The absorbance is measured at 710 nm for iron, 425 nm for cobalt and 480 nm for copper. Beers law is obeyed in the concentration range 9.2-82 mug of iron, 425 nm for cobalt cobalt and 3.0-62 mug of copper in 5 ml of final DMF/CHCl(3) solution. The molar absorptivities are calculated to be Fe: 7.58 x 10(3), Co: 1.33 x 10(4) and Cu: 4.92 x 10(4)M(-1)cm(-1). Ten replicate determinations containing 25 mug of iron, 9.96 mug of cobalt and 3.17 mug of copper gave mean absorbances 0.677, 0.450 and 0.490 with relative standard deviations of 0.88, 0.98 and 0.92%, respectively. The interference of large number of metals and anions on the estimations of these metals has been studied. The optimized conditions so developed have been employed for the trace determination of these metals in standard alloys, waste water and fly ash samples.     

Evaluation of luminol-H(2)O(2)-KIO(4) chemiluminescence system and its application to hydrogen peroxide, glucose and ascorbic acid assays

A novel chemiluminescence (CL) system was evaluated for the determination of hydrogen peroxide, glucose and ascorbic acid based on hydrogen peroxide, which has a catalytic-cooxidative effect on the oxidation of luminol by KIO(4). Hydrogen peroxide can be directly determined by luminol-KIO(4)-H(2)O(2) CL system. The detection limit was 3.0x10(-8) mol l(-1) and the calibration graph was linear over the range of 2.0x10(-7)-6.0x10(-4) mol l(-1). The relative standard deviation of H(2)O(2) was 1.1% for 2.0x10(-6) mol l(-1) (N=11). Glucose was indirectly determined through measuring the H(2)O(2) generated by the oxidation of glucose in the presence of glucose oxidase at pH 7.6. The present method provides a source for H(2)O(2), which, in turn, coupled with the luminol-KIO(4)-H(2)O(2) CL reaction system. The CL was linearly correlated with glucose concentration of 0.6-110 mug ml(-1). The relative standard deviation was 2.1% for 10 mug ml(-1) (N=11). Detection limit of glucose was 0.08 mug ml(-1). Ascorbic acid was also indirectly determined by the suppression of luminol-KIO(4)-H(2)O(2) CL system. The calibration curve was linear over the range of 1.0x10(-7)-1.0x10(-5) mol l(-1) of ascorbic acid. The relative standard deviation was 1.0% for 8.0x10(-7) mol l(-1) (N=11). Detection limit of ascorbic acid was 6.0x10(-8) mol l(-1). These proposed methods have been applied to determine glucose, ascorbic acid in tablets and injection.     

Spectrophotometric determination of sulfide in the presence of sulfite and thiosulfate via the precipitation of bismuth(III) sulfide.

A photometric method has been developed for the determination of sulfide at 10(-5) mol dm(-3) levels, which is based on the reaction of sulfide with a given excess amount of bismuth(III) to form a precipitate of bismuth(III) sulfide and on the spectrophotometric measurement of the residual bismuth(III) at 335 nm after extracting with bismuthiol II reagent from an aqueous solution containing acetate buffer into benzene. The presence of sulfite and thiosulfate up to 0.002 mol dm(-3) did not cause any interference in the determination of sulfide, because both sulfite and thiosulfate do not produce any precipitate with bismuth(III). A linear calibration plot with a negative slope was obtained for sulfide over the range of 5.00 x 10(-7) - 3.00 x 10(-5) mol dm(-3) (16.0 - 960 ppb). An experimental calibration plot was in accord with the theoretical plot, taking into account the known excess of bismuth(III), showing that the reaction of sulfide with bismuth(III) proceeded to completion. The relative standard deviation of results from 10 replicate determinations of standard sulfide (2.00 x 10(-5) mol dm(-3)) was 0.44%. The proposed method was successfully applied to the determination of sulfide in hotspring water samples without any pretreatment.