Shashikant R. Kuchekar

Selective determination of selenium(IV) from environmental samples by UV-visible spectrophotometry using O-methoxyphenyl thiourea as a chelating ligand

A selective extraction–spectrophotometric method has been developed for determination of selenium(IV) using O-methoxyphenyl thiourea (OMePT) as a chelating agent. The basis of the proposed method is the spectrophotometric determination of selenium(IV)–OMePT complex obtained after extraction of selenium(IV) from 3.5 M hydrochloric acid media using OMePT in chloroform solvent. The complex shows maximum absorbance at 350 nm against the reagent blank. The Beer’s law was obeyed over the concentration range 5–60 µg mL−1 of selenium(IV). The optimum concentration range was 20–50 µg mL−1 as evaluated from Ringbom’s plot. The molar absorptivity and Sandell’s sensitivity of the selenium(IV)–OMePT complex in chloroform were 3.312 × 102 L mol−1cm−1 and 0.2384 µg cm−2, respectively. The composition of selenium(IV)–OMePT complex was 1:2 established from slope ratio method, mole ratio method and Job’s continuous variation method. The complex was stable for more than 72 h. The interfering effect of various foreign ions was studied and suitable masking agents were used wherever necessary to enhance the selectivity of the developed method. The proposed method was successfully applied for the determination of selenium(IV) from real samples, viz. pharmaceutical formulations, shampoo, vegetable sample, synthetic mixtures and environmental samples. Repetition of the method was checked by finding the relative standard deviation (RSD) for 10 determinations which was 0.35%.

Development of a reliable analytical method for extraction spectrophotometric determination of ruthenium(III) from catalyst and fissium alloy using o-methylphenyl thiourea as a chromogenic chelating ligand

A simple and selective method is developed for the extraction spectrophotometric determination of ruthenium(III) using o-methylphenyl thiourea (OMPT) as a chromogenic chelating ligand. The basis of the proposed method is ruthenium(III)-OMPT complex formation in aqueous hydrochloric acid media (3.0molL(-1)) after 5.0min heating on a boiling water bath and the complex formed is extracted into chloroform. The absorbance of green colored ruthenium(III)-OMPT complex is measured at 590nm against the reagent blank. Beers law was obeyed up to 42.5μgmL(-1) of ruthenium(III) and the optimum concentration range is 7.56-39.81μgmL(-1) of ruthenium(III) as evaluated by Ringboms plot. Molar absorptivity and Sandells sensitivity of ruthenium(III)-OMPT complex in chloroform are 2.34×10(3)Lmol(-1) cm(-1) and 0.043μgcm(-2) respectively. The composition of ruthenium(III):OMPT complex (1:2) was established from slope ratio method, mole ratio method and Jobs continuous variation method. Complex was stable for more than 48h. The interfering effect of various foreign ions was studied and suitable masking agents are used wherever necessary to enhance the selectivity of the method. Proposed method is successfully applied for determination of ruthenium(III) from binary and ternary synthetic mixtures, synthetic mixtures corresponding to fissium alloy and ruthenium catalyst. Repetition of the method was checked by finding relative standard deviation (R.S.D) for 10 determinations which was 0.23%. A scheme for sequential separation of palladium(II), ruthenium(III), rhodium(III) and platinum(IV) has been developed.

Separation and Spectrophotometric Determination of Osmium(IV) and Ruthenium(III) with O-methoxyphenyl Thiourea as Chromogenic Legand: Sequential Separation of Osmium(IV), Ruthenium(III), and Platinum(IV)

A precise and selective method has been developed for extraction spectrophotometric determination of osmium(IV) and ruthenium(III) using o-methoxyphenyl thiourea (OMePT) as a chromogenic ligand. The basis of the proposed methods are osmium(IV)-OMePT complex was formed in 0.8 mol L−1 at room temperature while ruthenium(III)-OMePT complex was formed in 3.4 mol L−1 aqueous hydrochloric acid media after 5.0 min heating in boiling water bath. The osmium(IV)-OMePT and ruthenium(III)-OMePT complex were measured at 518 and 640 nm against the reagent blank, respectively. Complexes were also extracted in 10 mL chloroform and showed comparable absorbance values. Beer’s law was obeyed up to 110.0 μg mL−1 for osmium(IV)-OMePT complex and up to 50.0 μg mL−1 for ruthenium(III)-OMePT complex. Molar absorptivity and Sandell’s sensitivity of osmium(IV)-OMePT and ruthenium(III)-OMePT complexes were 2.12 × 103 L mol−1 cm−1, 0.089 μg cm−2 and 2.34 × 103 L mol−1 cm−1, 0.043 μg cm−2, respectively. The stoichiometry of osmium(IV)-OMePT and ruthenium(III)-OMePT complex was 1:1 and 1:2, respectively. Stability of osmium(IV)-OMePT complex was > 8 days and that of ruthenium(III)-OMePT complex was > 48 h. The proposed method was successfully applied for determination of osmium(IV) and ruthenium(III) from synthetic mixtures corresponding to platinum-osmium alloy and fissium alloy, respectively. The method was successfully applied for sequential separation of osmium(IV), ruthenium(III), and platinum(IV).

Reverse Phase Extraction Chromatographic Separation of Trivalent Bismuth Using Liquid Anion Exchanger

The extraction behavior of bismuth(III) was studied with N-n-octylaniline as a function of parameters viz. concentration of mineral acid, reagent, eluents and elution time. A selective, sensitive, less expensive and more precise method has been developed for the extraction chromatographic separation of bismuth(III) and its separation from several metal ions with N-n-octylaniline (liquid anion exchanger) as a stationary phase on silica as solid support. The quantitative extraction of bismuth(III) was found at 0.087 mol/L N-n-octylaniline and 0.7 mol/L hydrochloric acid media. The extracted bismuth(III) was eluted from the column with acetate buffer and analyzed spectrophotometrically with potassium iodide method. The proposed method is free from interferences from a large number of cations and anions. The method was applied for separation of bismuth(III) from binary mixtures with lead(II), copper(II) and manganese(II). The method was also extended for separation of bismuth(III) from synthetic alloy mixtures. The log-log plot of N-n-octylaniline concentration versus the distribution coefficient indicates that the probable extracted species is [(RR′NH 2 + )2BiCl 5 2− ](org).

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.