Rapid Spectrophotometric Determination Of Osmium With Cyclohezane 1,3-Dione Bisthiosemicarbazone Monohydrochloride: Simultaneous Determination of Osmium and Platinum

Abstract

A simple, sensitive and rapid spectrophotometric method has been developed for the determination of osmium using cyclohexane 1,3-dione bisthiosemicarbazone mono-hydrochloride (1,3-CHDT.HCl). The method is based on the instantaneous colour reaction between 1,3-CHDT. HCl and osmium(VIII) in sodium acetate—acetic acid buffer medium (pH range 3–6). The osmium complex shows maximum absorbance at 375 nm and considerable absorbance at 510 nm. Although the complex formed between platinum(IV) and reagent (1,3-CHDT.HCl) shows maximum absorbance at 375 nm, it does not show any absorbance at 510 nm. Simultaneous determination of osmium and platinum is carried out when present alone and in presence of other foreign (associated) ions. Some physico-chemical and analytical characteristics of osmium and platinum complex are described. Interference of various foreign ions have studied and osmium is estimated selectively in the presence of constituents of platinum ores.     

Prochlorperazine bismethanesulfonate: Sensitive and selective reagent for the spectrophotometric determination of microgram amounts of osmium

Prochlorperazine bismethanesulfonate (PCPMS) is proposed as a new sensitive and selective reagent for the spectrophotometric determination of microgram amounts of osmium. PCPMS forms a red-colored species with osmium(VIII) or osmium(VI) instantaneously at room temperature in 5 M phosphoric acid medium. The red species exhibits maximum absorbance at 529 nm. Beer's law is valid over the concentration range 0.05–3.6 ppm for osmium(VIII) and 0.15–6.4 ppm for osmium(VI). Sandell's sensitivity of the reaction is 2.89 nm cm^?2 for osmium(VIII) and 4.24 ng cm^?2 for osmium(VI). The effects of time, temperature, acidity, order of addition of reagents, reagent concentration, and diverse ions are investigated. The application of the proposed method in the determination of osmium content in synthetic ores has been explored.     

Spectrophotometric determination of osmium with p-(morpholino)-n-(4'-hydroxy-3'-methoxy)benzylidineaniline

A sensitive spectrophotometric determination of osmium is based on the blue color (absorption maximum at 615 mμ formed by reaction of osmium with p-(morpholino)-N-(4'-hydroxy-3'-methoxy)benzylidineaniline (“anil”) in acetate-buffered solution containing ethanol to prevent formation of a precipitate, Full color development is attained in I h at room temperature, and the color is stable for several hours. The absorbance is reproducible. The optimum concentration range for I-cm optical path is about I to 4 p.p.m. of osmium. Several transition elements interfere ; osmium can be separated as its tetroxide by the usual distillation method. The blue product is a cationic complex formed by reaction of anil with osmium in a 2 : I mole ratio. When osmium is in excess a red cationic complex (absorption maximum at 466 mμ) is formed by a I : I reaction between osmium and the reagent. The I : I complex is slowly converted to the 2 : I complex by excess reagent.     

Spectrophotometric determination of osmium: Sulphanilic acid as a reagent

Sulphanilic acid has been found to be a very effective reagent for the spectrophotometric determination (if hexavalent and octavalent osmium in the pH range between 1.8 – 3.5. In these two valence states, the element forms a dark-violet complex with the reagent, the absorption maximum of the complex being at 490 mμ. As most of the other ions interfere in the determination, the element must be separated as osmic acid by nitric acid distillation. Beer's law is obeyed in the case of 0.5 to 9 p.p.m. of osmium (VIII) and l to 18 p.p.m. of osmium (VI); tin-optimum concentration ranges are from 2 to 8 p.p.m. for osmium(VIII) and from 4 to 16 p.p.m. for osmium(Vl). In these ranges, the % relative errors per 1% absolute photometric error are 3.02 for osmium (VIII) and 3.1 for osmium(VI). Application of the method of continuous variations and the molar ratio method indicates that in solution hexavalent osmium and the reagent form a 1:2. complex, with an average dissociation constant of 1.2 ? 10^-7.     

Improved spectrophotometric determination of osmium(VIII) with 4-(2-pyridylazo) resorcinol in mixed surfactants

The colour development between 4-(2-pyridylazo)-resorcinol(PAR) and osmium(VIII) in the presence of cationic and nonionic surfactants in a weakly acidic medium was more stable and reproducible than in the absence of surfactant (PAR-alone method). An improved spectrophotometric determination of osmium(VIII) with PAR was investigated in the presence of mixed surfactants of N-hexadecyltrimethylammonium chloride (HTAC) and Brij 58 [poly(oxyethylene)lauryl ether] as cationic and nonionic surfactants at pH 6.0-7.2. The calibration graph was linear in the range 0-110 microg/10 ml osmium(VIII), and the apparent molar absorptivity was 2.4 x 10(4) l.mole(-1).cm(-1) with a Sandell sensitivity of 0.0079 microg/cm(2) osmium(VIII).     

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.     

Spectrophotometric methods for the determination of the antidepressant drug paroxetine hydrochloride in tablets

Simple, sensitive, and accurate visible spectrophotometric methods are described for the determination of paroxetine hydrochloride (PA) in tablets. Among them, the first 3 methods are based on the ion-pair complexes of PA formed with bromothymol blue (BTB), bromophenol blue (BPB), and bromocresol green (BCG) in aqueous acidic buffers. The complex species extracted into chloroform were quantitatively measured at 414 nm with BTB and BCG and at 412 nm with BPB. Beer's law was obeyed over the concentration ranges of 2-20, 2-16, and 2-16 microg/mL, respectively. The fourth method described is based on a coupling reaction between PA and 7-chloro-4-nitrobenzofurazon (NBD-Cl) in borate buffer, pH 8.5, in which a yellow reaction product that was measured at 478 nm was formed. The Beer's law range for this method was 2-10 microg/mL. The last method developed describes the interaction of PA base, as an n-electron donor, with 7,7,8,8-tetracyanoquinodimethane (TCNQ), as a pi-acceptor, in acetonitrile to give blue-colored TCNQ- radical anion with absorption maxima at 750 and 845 nm. Measured at 845 nm, the absorbance-concentration plot was rectilinear over the range of 1.5-15 microg/mL. The new methods developed were successfully applied to the determination of PA in tablets without any interference from common tablet excipients. The results of the methods were in good agreement with those obtained with an official liquid chromatographic method. This report describes first colorimetric methods for the determination of PA.     

Spectrophotometric determination of chromium in waste water and soil

The reaction of Cr(VI) with o-nitrophenylfluorone (NPF) in presence of cetyltrimethyl-ammonium bromide (CTMAB) to form a purplish red complex at pH 4.7-6.6 by heating at 50 degrees for 10 min has been investigated. The composition of the complex is 1:2:2 [Cr(VI):NPF:CTMAB], the wavelength of maximum absorbance is 582 nm. The molar absorptivity is 1.11 x 10(5)1.mole(-1).cm(-1). Beer's law is obeyed up to 0.2 microg ml Cr(VI) concentration. The interference of several ions, including Cu(2+), Fe(3+) and Al(3+), is eliminated by addition of a masking mixture containing KF, DCTA and tartrate. A new sensitive method for determination of chromium in waste water and soil is presented.     

Spectrophotometric reaction rate method for the determination of osmium by its catalytic effect on the oxidation of gallocyanine by bromate

A simple kinetic spectrophotometric method was developed for the determination of osmium. The method is based on the catalytic effect of osmium as osmium tetroxide on the oxidation of gallocyanine by bromate at pH 7. The reaction is monitored spectrophotometrically by measuring the decreasing absorbance of gallocyanine at 620 nm by the fixed-time method. A detection limit of 0.01 ng/ml and linear calibration curve from 0.1 to 100 and from 100 to 1200 ng/ml Os(VIII) is reported. The relative standard deviation for 0.0100 microg/ml Os(VIII) is 0.8% (N = 10). The method is free from most interferences. Osmium in synthetic samples is determined by this method, with satisfactory results.     

Colorimetric determination of osmium (VI) with 1-naphthylamine-3,5,7-trisulfonic acid

An investigation has been made of the organic compound, 1-naphthylamine-3,5,7-trisulfonic acid, for use as a colorimetric reagent for the determination of trace quantities of osniiun(Vl). When this compound is added to an osmium (OsO₄^-2) solution, a violet colored organo-osmium complex is formed which has highest sensitivity at wavelength 560 mμ. The complex reaches maximum color intensity after four hours. The solution should be brought to pH 1.5 and maintained at tins pH with a buffer, after maximum color development. The colored complex conforms to Beer's law over an osmium concentration range of 0 to 6 p.p.m. Its absorbance is not affected by either excess reagent (up to a 7 : 1 ratio) or by temperature variation over the range 15° to 35° C. Many metallic ions interfere with the color reaction and hence require a separation, of osmium from these ions.The nature of the complex in solution was studied by the following three methods: (1) mole ratio, (2) continuous variations and (3) slope ratio. All three methods indicate a ratio of reagent to osmium of 2 to 1.A procedure for the colorimetric determination of osmium(VI) has been developed; it has a sensitivity of 1 part osmium in 15,000,000 parts of solution, with good precision.     

2-Amino-3-hydroxypyridine as a chromogenic reagent for the spectrophotometric determination of osmium

2-Amino-3-hydroxypyridine forms two coloured complexes, green and violet, with osmium, depending on the pH of the solutions. Based on this reaction, a selective and sensitive spectrophotometric method for the determination of osmium (3-13 ppm in the final solution) alone and in the presence of other metal ions has been developed.     

1,3-双(二苯基膦氧)丙烷锰(Ⅱ)配合物磷光蒸气变色研究

本文以1,3-双(二苯基膦氧)丙烷(DPPPO2)为配体,合成了两种不同结构的锰(Ⅱ)配合物,其化学式分别为[Mn(DPPPO2)Br2]n(1G)和[Mn2(DPPPO2)4Br2]Br2·4CH3OH(1R).通过X射线单晶衍射确定了这两个化合物的结构.1G呈现一维链状结构,1R则为笼状结构的双核配合物.四面体构型的Mn(Ⅱ)化合物1G在紫外灯照射下呈现绿光发射(λem=514 nm),而扭曲四方锥构型的Mn(Ⅱ)化合物1R呈现红光发射(λem=634 nm).无论是晶体、粉末还是PMMA掺杂薄膜,1G暴露在甲醇蒸气中可发生结构重排,转化为1R,伴随磷光发射光谱显著红移,最大发射峰从514 nm红移到634 nm,同时绿光转变为红光发射.另一方面,若150℃加热1R,则转化为1G,伴随着红光转换为绿光发射.X射线衍射实验表明,化合物1G吸收甲醇蒸气后转变为1R,但加热到150℃时1R又可以恢复到1G,由此实现1G与1R可逆转化.     

Spectrophotometric determination of nickel in vegetable oil with ammonium 2-amino-1-cyclohexene-1-dithiocarboate

The reaction between nickel and ammonium 2-amino-1-cyclohexene-1-dithiocarboate in aqueous acetone medium at pH 3.0-8.0 results in a stable dark red complex. The ratio of reagent to nickel in the complex is 2:1 and the formation constant is 7.38 +/- 0.12 x 10(10). Beer's law is obeyed up to 4 microg/ml nickel at the absorption maximum at 535 nm. The apparent molar absorptivity is 2.8 x 10(4) l.mole(-1). cm(-1), and the detection limit is 10 ng/ml nickel. The method is applied to the determination of nickel in vegetable oil.     

Nature of the cherry-red transient formed during the interaction of osmium tetroxide with hydrogen peroxide

Summary A cherry-red transitory coloration is formed when OsO₄ or osmium(VI) is added to alkaline hydrogen peroxide solution in the pH range 9–13. The transient has an absorption maximum at 530 nm and its concentration depends on the pH of reaction mixture reaching a maximum at pH 10.5–11. The transient is designated as a peroxo-derivative of osmium(VIII) [or an osmium(VII) — Superoxide radical pair if the peroxoderivative undergoes a fast intramolecular one-electron transfer].Many decades ago it was observed¹ that a cherry-red coloration appears transiently when osmium tetroxide solution is added to alkaline hydrogen peroxide solution. However, to our knowledge, there are no literature data about the nature of this transient. Further, we observed recently that there is a close connection between the rate of decomposition of hydrogen peroxide catalysed by osmium tetroxide and the intensity of the coloration, and therefore an attempt was made to investigate the transient by using a fast spectrophotometer technique.     

Spectrophotometric determination of osmium with 1-naphthylamine-4,6,8-trisulfonic acid

This investigation was undertaken to determine if the naphthylamine sulfonic acid-osmate (OsVI) reaction is suitable for a spectrophotometric determination of osmium. The 1-naphthylamine- 4, 6,8-trisulfonic acid osmate complex is water-soluble and forms a stable violet-colored system at PH 1 to 1.5 that is independent of reagent concentration. At 555 mμ the colored complex obeys Beer's law over a concentration range of 0.1 to 6.5 p.p.m. osmium and remains stable with respect to time and temperature. The effects of pH, temperature, reagent concentration, and diverse ions were studied. The nature of the organo-osmate complex in solution was studied by three techniques and the effect of temperature and pH on the rate of complex formation was determined. A procedure for the removal of osmium from all interfering ions was developed based on well known distillation techniques.A convenient, sensitive, reproducible and accurate method for the spectrophotometric determination of osmium has been developed.     

Solvent extraction and photometric determination of molybdenum (VI) with 2-aminobenzenethiol

A new extractive photometric method is described for estimation of molybdenum with 2-aminobenzenethiol. The green complex in chloroform has its absorbance maximum at 700 nm and is stable for 2 hr when extracted from a solution of optimum pH range 1.4-2.8. The extraction is quantitative. The sensitivity is 0.0075 microg cm (2). Beer's law is obeyed over the range 0.25-10 ppm with optimum range 0.5-4.5 ppm. The molar absorptivity is 7.08 x 10(4) 1.mole(-1). cm(-1). The overall stability constant is 2.0 x 10(8) at 25 +/- 0.1 degrees.     

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.     

A study on photochemical behavior of lysozyme-bromophenol blue complex and its analytical application

It was found that macromolecular complexes were formed between lysozyme and bromophenol blue (BPB) with the electrostatic attraction in acetate medium (pH 6.5). The binding constant and the number of binding site for lysozyme-BPB complex were obtained, and the thermodynamic parameters were given. In addition, a remarkable enhancement of resonance light scattering (RLS) intensity for the macromolecular complex was observed with a scattering peak at 336 nm. And the increment of RLS intensity was proportional to the concentration of lysozyme in the range of 5 ng ml(-1) to 10.0 microg ml(-1). The influence of experimental conditions including pH, BPB concentration, and ionic strength on RLS system were tested, especially the effect of temperature was examined in detail. The proposed method was successfully applied to determine lysozyme in human saliva and tear samples without any special pretreatment. Compared with other methods the proposed method is of higher sensitivity and wider linear range.     

Flotation-spectrophotometric determination of osmium (ruthenium) with thiocyanate and Capri blue

A sensitive flotation-spectrophotometric method for the determination of osmium, based on the ion associate formed by the anionic thiocyanate osmium complex with oxazine basic dye, Capri blue (CB), has been developed. The ion associate is separated by shaking the aqueous solution (pH 2–3) with diisopropyl ether, washing the precipitate with water, and dissolving it in methanol. Molar absorptivity in this method amounts to 2.7 × 10⁵ liters mol⁻¹ cm⁻¹ at 630 nm. The molar ratio Os:SCN:CB in the separated associate is 1:8:5. Under the conditions of the determination of osmium, ruthenium can be determined as well. Metals that form anionic thiocyanate complexes, including other platinum metals, interfere. The method becomes highly selective for osmium and ruthenium after their separation by distillation as tetroxides. Osmium and ruthenium were determined with Capri blue after their extractive separation as thiocyanate complexes.     

Spectrophotometric determination of osmium using acenaphthenequinonemonoxime (AQM)

A water-soluble dark-brown complex formed by osmium with acenaphthenequinonemonoxime exhibits an absorption maximum at 430 nm. The composition of the complex comes out to 1:2 (metal:ligand) as revealed by Job's method of continuous variations, logarithmic method, and Gerade method of Asmus. The pH range for complete formation of the complex is 6.5–8.5. Its sensitvitiy has been found to be 0.0323 μg/cm². The effect of diverse ions has also been investigated.