Studies on the separation of osmium by flotation and spectrophotometric determination with Crystal Violet and Malachite Green

A solvent flotation technique was used for the separation of osmium from aqueous solutions in the form of the ion associates of the anionic complexes OsCl^2?₆ and OsCl₂(SnCl₃)^2?₂ with two basic dyes, Crystal Violet and Malachite Green. A sensitive spectrophotometric method for the determination of osmium based on the system osmium-tin(II) chloride—Crystal Violet—cyclohexane (?=2 × 10⁵ l mol^?1 cm^?1) was developed. Aqueous acetone solutions of the ion associate examined obey Beer's law in the range 0.04–1.0 μg Os ml^?1. The relative standard deviation is 1–6%. Ruthenium interferes with the determination of osmium.     

Kinetic-Spectrophotometric Determination of Traces of Osmium by Its Catalytic Effect on the Oxidation of Pyrogallol Red by Hydrogen Peroxide

Abstract

A Kinetic-spectrophotometric method for the determination of ultra-trace amounts of osmium(VIII) is described. It is based on the catalytic action of osmium(VIII) on the oxidation of pyrogallol red with hydrogen peroxide, yielding a colorless product in neutral medium. The reaction is followed spectrophotometrically by measuring the rate of change in absorbance at 540 nm and 30°C. Os(VIII) in the range 0.005 -100 ng.ml^?1 can be determined. The proposed method is hardly subject to interferences. The relative standard deviation is 1.5% for 1 ng.ml^?1 of Os(VIII). The kinetic parameters of the catalyzed and uncatalyzed reactions are reported. The detection limit is 1 pg.ml^?1.     

Fluorescent Complexes of Nucleic Acids/8-Hydroxyquinoline/Lanthanum(III) and the Fluorometry of Nucleic Acids

Abstract

The ternary fluorescent complexes of nucleic acids/8-hydroxyquinoline/ lanthanum (III) were studied. Nucleic acids in the study involve natured and thermally denatured calf thymus DNA, fish sperm DNA and yeast RNA. In the range of pH 8.0–8.4 (controlled by NH₃-NH₄Cl buffer) ternary fluorescent complexes are formed which emit at 485.0 nm for calf thymus DNA and at 480.0 nm for yeast RNA (when excited at 267.0 nm) and emits at 483.0 nm for fish sperm DNA when excited at 265.0 nm. Based on the fluorescence reactions sensitive fluorometric methods for nucleic acids were proposed. Using optimal conditions, the calibration curves were linear in the range of 0.4–3.6 μg˙ml^?1 for calf thymus DNA, 0.4–4.0 μg-ml^?1 for fish sperm DNA and 0.4–4.0 μg˙ml^?1 for yeast RNA, respectively. The limits of determination (3σ) were 0.076 μg˙ml^?1 for calf thymus DNA, 0.068 μg˙ml^?1 for fish sperm DNA and 0.329 μg˙ml^?1 for yeast RNA, respectively. Five synthetic samples were determined with satisfaction.

     

Rapid spectrophotometric determination of ruthenium(III) with prochlorperazine maleate

A rapid, simple spectrophotometric method for the determination of μg amounts of ruthenium, based on the formation of a pink complex between the metal and prochlorperazine maleate (PCPM) in sulphuric or hydrochloric acid solution, is described. The complex has an absorption maximum at 530 nm and its molar absorptivity is 6.733·10³ l mol^?1 cm^?1. The sensitivity is 0.0151 μg Ru cm^?2 for log I_o/I = 0.001. Beer's law is valid over the range 0.2–10 μg Ru ml^?1 ; the optimal range for spectrophotometric determination is 0.8–8.0 μg Ru ml^?1. Job's method of continuous variation, the mole ratio method and the slope ratio method indicate a 1:1 composition for the complex. The effects of acidity, time, temperature, order of addition of reagents, reagent concentration, and the interferences from various ions are reported.     

Sensitive spectrophotometric kinetic determination of osmium by catalysis of the pyrogallol red-bromate reaction

Osmium(VIII) is determined by means of its catalytic effect on the oxidation of pyrogallol red (PGR) by potassium bromate at pH 6.0, 30°C and 545 nm. The decrease in absorbance of PGR (2.5 × 10^?5 M) in the presence of KBrO₃ (0.20 M) over a period of 0–150 s is proportional to the concentration of osmium(VIII) over the range 0–1400 ng ml^?1. The limit of detection of osmium was 0.65 ng ml^?1. The precision and accuracy of the method are described. The effects of the presence of 45 cations and anions on osmium determination were studied. The effects of probable interferences were completely removed by a single extraction of osmium as osmium tetraoxide into isobutyl methyl ketone and back-extraction into sodium hydroxide solution.     

Fabrication of a Highly Sensitive Glucose Biosensor Based on Immobilization of Osmium Complex and Glucose Oxidase onto Carbon Nanotubes Modified Electrode

In this research a novel osmium complex was used as electrocatalyst for electroreduction of oxygen and H₂O₂ in physiological pH solutions. Electroless deposition at a short period of time (60 s), was used for strong and irreversible adsorption of 1,4,8,12‐tetraazacyclotetradecane osmium(III) chloride (Os(III)LCl₂) ClO₄ onto single‐walled carbon nanotubes (SWCNTs) modified GC electrode. The modified electrode shows a pair of well defined and reversible redox couple, Os(IV)/Os(III) at wide pH range (1–8). The glucose biosensor was fabricated by covering a thin film of glucose oxidase onto CNTs/Os‐complex modified electrode. The biosensor can be used successfully for selective detection of glucose based on the decreasing of cathodic peak current of oxygen. The fabricated biosensor shows high sensitivity, 826.3 nA μM^?1cm^?2, low detection limit, 56 nM, fast response time <3 s and wide calibration range 1.0 μM–1.0 mM. The biosensor has been successfully applied to determination of glucose in human plasma. Because of relative low applied potential, the interference from electroactive existing species was minimized, which improved the selectivity of the biosensor. The apparent Michaelis‐Menten constant of GOx on the nanocomposite, 0.91 mM, exhibits excellent bioelectrocatalytic activity of immobilized enzyme toward glucose oxidation. Excellent electrochemical reversibility, high stability, technically simple and possibility of preparation at short period of time are of great advantages of this glucose biosensor.     

Integrated Retention/Spectrophotometric Detection Method for the Determination of Formaldehyde

Abstract

An integrated-sensor method for the determination of formaldehyde based on retention of the reaction product of the analyte with p-rosaniline and sulfite in a flow-cell packed with Dowex 1-X-8 anion exchange resin was developed. The method has a good selectivity with a detection limit of 0.3 μg ml^?1 (1 ml sample) or 75 ng ml^?1 (2 ml sample), and a linear range between 1–30 μg ml^?1. The relative standard deviations (n = 11) were 2.8 and 1.3% for 2 and 20 μg ml^?1 formaldehyde, respectively. Depending on the working conditions, the sampling frenquency ranged between 10 and 18 h^?1. The method was applied to the determination of formaldehyde in well water.     

Spectrophotometric determination of iron(III) with EDTA tetrahydrazide

The tetrahydrazide of ethylenediamine tetraacetic acid (NH₂NH)₄-EDTA was synthesized from the EDTA ester and hydrazine hydrate in ethanolic solution, the resulting (NH₂NH)₄-EDTA being recrystallized in 60% ethanol. When the spectrophotometric study of the iron(III) (NH₂NH)₄-EDTA complex in aqueous solution was made two absorption maxima at 530 and 450 nm at pH 4.5 and 11.0, respectively, were found. Beer's law is obeyed in the range 1.0–20.0 μg Fe(III) ml^?1 at 530 nm and pH 4.5 and 0.5–12.0 μg Fe(III) ml^?1 at 450 nm and pH 11.0, the molar absorptivities being 1.95 × 10³ 1 mol^?1 cm^?1 at 530 nm and 3.35 × 10³ 1 mol^?1 cm^?1 at 450 nm, respectively. The Ringbom optimal interval falls between about 3 and 18 μg Fe(III) ml^?1 at 530 nm and about 2–14 μg Fe(III) ml^?1 at 450 nm. The reaction between the metal and the ligand was also investigated. The method has been successfully applied to the determination of iron in talcs.     

Simultaneous determination of ammonia and urea with an asymmetric merging zones/flow-injection configuration

A method is proposed for the simultaneous determination of urea and ammonia using a reagent-injection configuration that includes a dual injection valve (for insertion of Nessler's reagent and for accommodating the enzyme reactor). The resolution of the two peaks obtained on each injection allows the determination of both analytes in mixtures. The determination range is 1–5 μg ml^?1 for ammonia and 1–6 μg ml^?1 for urea, with relative standard deviations of 1.13% and 2.31% for ammonia (first and second peaks) and 1.86% for urea.     

Utility of p-chloranilic Acid and 2,3 Dichloro-5,6-dicyano p-Benzoquinone (DDQ) for the Spectrophotometric Determination of Triamterene

Abstract

Two simple and sensitive spectrophotometric procedures are suggested for analysis of triamterene. The first procedure is based on the reaction of triamterene with p-chloranilic acid (p-CA) in methylene chloride to form a highly stable coloured product, exhibiting maximum absorbance at λ 530 nm. Beer's law is obeyed in the range of 40–220 μg.ml^?1 with a mean percentage accuracy of 99.98 ± 0.446. Limit of determination is 20 μg.ml^?1. In the second procedure, the drug is determined via charge transfer complex formation with 2,3 dichloro-5,6-dicyano p-benzoquinone (DDQ) using methylene chloride as a solvent. Here the reaction product has two well defined maxima at 460 nm and 530 nm where each has been utilized for quantitative determination. Beer's law is obeyed in concentration ranges of 25–125 μg.ml^?1 and 25–150 μg.ml^?1 with mean percentage accuracies of 99.92 ± 0.449 and 100.00 ± 0.511 for both maxima. 460 and 530 nm. respectively. Limit of determination is 12.5 μg.ml^?1 at both maxima. Optimum conditions for each procedure have been studied and the stoichiometry of both reactions was ascertained using Job's method of continuous variation. The validity of the suggested procedures was assessed by applying the standard addition technique using the drug capsules. Both procedures are statistically analyzed as compared with BP method for analysis of triamterene (non aqueous titration) revealing good accuracy and precision as indicated by t and F tests.     

Square‐Wave Adsorptive‐Stripping Voltammetric Detection in the Quality Control of Fluoxetine

ABSTRACT

A simple and sensitive extraction-spectrophotometric method for the determination of barium and potassium is reported. The 18C6-Barium-Orange II (18C6-Ba-(OR II)₂) and 18C6-Potassium-Orange II (18C6-K-OR II) ternary complexes are quantitatively extracted into dichloromethane and their absorbances are measured at 483 nm. Linear calibration graphs were obtained over the barium concentration range of 0.1-5 μg ml^?1 and potassium concentration range of 1-8 μg ml^?1. The relative standard deviation for 2.0 μg ml^?1 barium and pottasium are, respectively, 4.16% and 3.60%. The interfering effect of a large number of diverse ions on the determination of barium and potassium was studied. The method was applied to a synthetic sample with natural matrix effects of tap water and the results showed high potential of the recommended method for the determination of Ba and K in water samples.     

Fluorimetric determination of mebendazole and flubendazole in pharmaceutical dosage forms after alkaline hydrolysis

The selective and very sensitive fluorimetric determination of mebendazole and flubendazole is based on alkaline hydrolysis and adsorption on Whatman 42 filter paper. Limits of detection are 0.1 μg ml^?1 and 0.5 μg ml^?1, respectively, with linear response sponse up to 10 μg ml^?1 and 50 μg ml^t?1. The fluorescence produced is very stable (λ_em = 460 nm) and the method is applicable to anthelmintic pharmaceutical preparations.     

Magnetic solid-phase extraction of rose bengal using iron oxide nanoparticles modified with cetyltrimethylammonium bromide

Magnetic solid phase extraction (MSPE) based on cetyltrimethylammonium bromide (CTAB)-coated magnetic iron oxide nanoparticles (C-MIONPs) was investigated for the separation, preconcentration and determination of Rose Bengal (RB) in aqueous solutions. The influences of different analytical parameters such as pH, temperature, ionic strength, volume of desorbent solvent, amount of adsorbent and interfering ions in the adsorption of RB on C-MIONPs were investigated. The RB adsorption on C-MIONPs follows Langmuir isotherm. The sizes of C-MIONPs were in the range of 20–80 nm. The method was capable of determining RB concentration in the range of 0.01–1.20 μg ml^?1. The limit of detection (LOD) of RB based on three times the standard deviation of the blank (3Sb) was found to be 5.91 × 10–3 μg ml^?1 (n = 8). The relative standard deviation (RSD) for 0.3 μg ml^?1 and 0.8 μg ml^?1 of RB were 4.1% and 1.1%, respectively. The proposed method was applied to the determination of RB in Brucella Antigen solution and water samples from the Karoon River.     

Rapid and selective determination of osmium(IV) by UV-visible spectrophotometry using o-methylphenyl thiourea as a chromogenic chelating ligand: sequential separation of osmium(IV), rhodium(III) and platinum(IV)

The objective of this research work was to develop a simple, highly sensitive and precise method for spectrophotometric determination of osmium(IV). O-Methylphenyl thiourea (OMPT) coordinates with osmium(IV) as a 1:1 (osmium(IV)–OMPT) complex in hydrochloric acid media (0.8 mol l^?1). The novelty of the investigated method is instant complex formation at room temperature with no need of heating or standing. The complex is stable for more than 8 days. The method is applicable over a wide linearity range (up to 110 µg ml^?1). A low reagent concentration is required (2 ml, 0.009 mol l^?1 in ethanol). The complex exhibits maximum absorption in the range of wavelength 510–522 nm and 514 nm was selected for further study. The molar absorptivity was 1.864 × 10³ l mol^?1 cm^?1, Sandell’s sensitivity was 0.102 µg of osmium(IV) cm^?2. Proposed method was successfully applied for separation and determination of osmium(IV) from binary and ternary synthetic mixtures containing associated metal ions. A scheme for mutual separation of osmium(IV), rhodium(III) and platinum(IV) is developed.     

Fluorimetric determination of danthron in pharmaceutical tablets and in urine

A simple, rapid determination is reported for danthron (1,8-dihydroxyanthraquinone) in pharmaceutical tablets. In a flow-injection system, danthron is reduced by sodium dithionite in $\text{1}\text{1}$ methanol/borate buffer to give a fluorescent complex. Linearity ranges from 30 μg ml^?1 to below 0.1 μg ml^?1. In urine samples, danthron is separated from other fluorescing species by reversed-phase high-performance liquid chromatography before its reduction by dithionite in a post-column reactor. Urine preparation requires no extraction. Spiked urine samples were studied in the working range of 0.02–2.0 μg ml^?1 danthron.     

A rapid method for the spectrophotometric determination of palladium(II) and osmium(VIII)

Propionyl promazine phosphate is proposed as a new reagent for the rapid spectrophotometric determination of microgram amounts of Pd(II) and Os(VII). PPP instantaneously forms an orange-red 1:1 complex with Pd(II) in sodium acetate-hydrochloric acid buffer of pH 0.8 to 4.0 at room temperature. The reagent also forms an orange-red radical cation with Os(VIII) in 0.5 to 2.0 M hydrochloric acid. The Pd-PPP complex exhibits an absorption maximum at 490–500 nm with molar absorptivity of 7.1 × 10³ liter mol^?1 cm^?1. The Os-PPP radical cation has an absorption maximum at 505–515 nm with molar absorptivity of 2.21 × 10⁴ liters mol^?1 cm^?1. The Sandell sensitivity is 0.022 μg/cm² (Pd) and 0.008 μg/ cm² (Os). Beer's law is valid over the concentration range 0.2 to 21 ppm (Pd) and 0.2 to 4.2 ppm (Os). The proposed method offers the advantages of simplicity, rapidity, and without the need for heating or extraction. The reagent is used for the determination of Pd in the synthetic mixtures corresponding to Pd alloys used in jewelery and Os in osmiridium alloy.     

Sensitive spectrofluorimetric determination of zinc at ultra-trace levels

An ultra-trace method based on the reaction of zinc with salicylthiocarbohydrazone (SATCH) and Triton X-100 as a non-ionic surfactant was developed for the fluorimetric determination of zinc at the picogram level. The reaction is carried out in the pH range 4.4–4.7 in an aqueous ethanolic medium [52% (v/v) ethanol]. The influence of the reaction variables is discussed. The detection limit is 10 pg ml^?1 and the range of application is 0.01–500 μg l^?1, with an optimum range of 0.04–400 μg l^?1. The relative standard deviations are 0.68% (0.01–0.1 μg l^?1 of zinc), 0.41% (0.1–1.0 μg l^?1 of zinc), 0.64% (1–10 μg l^?1 of zinc), 0.82% (10–100 μg l^?1 of zinc) and 0.15% (100–500 μg l^?1 of zinc). The method is highly sensitive and selective in the presence of Cd^II and Hg^II. The effect of interferences from other metal ions and anions was studied; the masking action is discussed. The advantages of the proposed method include its high sensitivity, simplicity and selectivity.     

Spectrofluorometric determination of zinc with 1,5-bis(2,3-dihydroxyphenylmethylene) thiocarbohydrazone

1,5-Bis(2,3-dihydroxyphenylmethylene)thiocarbohydrazone was synthesized; its ionization constants are reported. A procedure is described for the spectrofluorimetric determination of 5–540 ng ml^?1 zinc in 60/40 (v/v) ethanol/water medium, acetate-buffered to apparent pH 6.5 (λ_ex=400 nm, λ_em=508 nm). Interferences were evaluated and the procedure was applied with good results to the determination of zinc in potable waters (0.3–3 μg ml^?1) and lubricating oils.     

Spectrophotometric determination of trace amounts of beryllium using 1,8-dihydroxyanthrone as a new chromogenic reagent

A simple, rapid, and sensitive spectrophotometric method for the trace level determination of beryllium based on the formation of a 1:2 complex with anthralin (1,8-dihydroxyanthrone) as a new reagent is developed. A spectrophotometric method was used to determine the acidity constant and stepwise proton dissociation of the reagent. The experimental conditions for determining beryllium including the influences of pH, reagent concentration and time were evaluated and optimized. Under the optimum experimental conditions, the molar absorptivity of the complex is 0.47 × 10⁴ l mol^?1 cm^?1 at 545 nm. Calibration graph was linear in the range of 0.04–1.04 μg ml^?1 with a detection limit of 0.012 μg ml^?1 and a %RSD of 0.43%, for 5 replicate determinations at 0.48 μg ml^?1 of Be(II). The interferring effect of some cations and anions was also studied. The method was applied for the determination of beryllium in beryl, silicate rock and alloys. Ethylenediaminetetraacetic acid (EDTA) was used for masking interfering ions.     

Simultaneous Determination of Valsartan and Hydrochlorothiazide in Tablets by High-Performance Liquid Chromatography

ABSTRACT

A method for the simultaneous determination of valsartan and hydrochlorothiazide in tablets is described. The procedure, based on the use of reversed-phase high-performance liquid chromatography, is linear in the concentration range 5.0-10.0 μg ml^?1 for valsartan and 0.5-2.0 μg ml^?1 for hydrochlorothiazide, is simple and rapid and allows accurate and precise results. The limit of detection was 1.0 μg ml^?1 for valsartan and 0.05 μg ml^?1 for hydrochlorothiazide.