Development of Extractive Spectrophotometric Method for the Determination of Osmium (IV) with Schiff base 2-[(2-Hydroxy Phenyl Imino) Methyl]-4-Nitro Phenol.

Datta Baban Mandhare, Vasant D. Barhate*

V.E. S. College of Art, Science and Commerce, Sindhi Society, Chembur, Mumbai - 400071, India.

*Corresponding Author E-mail:

ABSTRACT:

A simple spectrophotometric method has been developed for the determination of Osmium (IV) by using Schiff base 2-[(2-hydroxyphenylimino) methyl]-4-nitrophenol [HPIMNP]. HPIMNP extracts Os (IV) quantitatively (99.94%) into iso - amyl alcohol from an aqueous solution of pH range 0.0 - 2.0. The iso - amyl alcohol extracts show maximum absorption at 545 nm (λ max). Beer’s Law is obeyed over the Os (IV) concentration range of 1.5 to 24.0 µg/ ml. The Molar absorptivity and Sandell’s sensitivity for Os – HPIMNP system is 3700.00L mole^-1 cm^-1 and 0.051µg.cm^-2respectively. The composition of extracted species is found to be 1: 3 [Os - HPIMNP] by Job’s continuous variation and Mole - ratio method. Interference by various ions has been studied. The proposed method is rapid, sensitive, reproducible and accurate and it has been satisfactory applied for determination of Osmium (IV) in Synthetic mixture samples.

KEYWORDS: Solvent Extraction, Extractive Spectrophotometry, Osmium (IV), Schiff base, 2-[(2-hydroxyphenylimino) methyl]-4-nitrophenol [HPIMNP], Synthetic mixture samples.

INTRODUCTION:

Various reagents [1] are available for the spectrophotometric determination of Osmium (IV) of which Oximes, Schiff bases and it derivatives constitutes an important class [2][3]. Synthesis and Antimicrobial Activity of Schiff base 2-[(2-hydroxyphenylimino) methyl]-4-nitrophenol [HPIMNP] has been reported [4]. However Analytical application of HPIMNP was not studied. In the present communication, we describe the extractive spectrophotometric determination of Os (IV) with 2-[(2-hydroxyphenylimino) methyl]-4-nitrophenol [HPIMNP].

MATERIAL AND METHODS:

Elico- SL 159 spectrophotometer with optically matched quartz or glass cells of 1cm path length were used for absorbance measurement. An Elico– LI 127 pH meter was employed for pH measurements.

The reagent HPIMNP was synthesized by condensation of 5-Nitro salicylaldehyde with 2 - amino phenol as per reported procedure [4]. The resulting product was recrystallized by using ethanol [5] and characterized by elemental and spectral analysis. Its 1.0 % solution was prepared in dimethylformamide (DMF). A stock solution of Os (IV) was prepared by dissolving Ammonium Chloro-osmate in double distilled water containing 1 M hydrochloric acid. It was standardized by thiourea method [6]. Working solutions of Os (IV) were made by suitable dilution. All other reagents used were of AR grade and all the solutions were prepared in doubly distilled water.

Extraction and separation of Os (IV)

To an aliquot of aqueous solution containing 500 µg of Os (IV) and 2ml of 1.0 % solution of HPIMNP prepared in DMF were mixed in 25 ml beaker. The pH of solution was adjusted to desired value with dilute solution of HCl/ NaOH, Keeping the total volume to 10 ml with distilled water followed by heating on boiling water bath for 35-40 minutes. The resulting solution was then transferred into 125 ml separatory funnel. The beaker was then washed with 5 ml portion of organic solvent twice and each washing was added to the solution in separatory funnel. The two phases were equilibrated for one minute and allowed to separate. After the separation of two phases, pH of the equilibrated aqueous phase was measured and Osmium content in each phase was determined by thiourea method [6]. The extraction was carried out with different solvents to find out the best extracting solvent. On the basis of Osmium content in aqueous and organic phase, extraction coefficient and percent extraction was calculated.

Extractive Spectrophotometric Determination of Os (IV):

To an aliquot of aqueous solution containing 15-240 µg of Os (IV), 1 ml of 1 M Hydrochloric acid and 1ml of 1.0 % solution of HPIMNP prepared in DMF were added. The volume of solution was made up to 10 ml with distilled water. The solution followed by digestion on boiling water bath for 35- 40 minutes. After cooling the solution was equilibrated for one minute with 10 ml of iso- amyl alcohol and the phases were allowed to separate. The iso - amyl alcohol extract was collected in a 10 ml measuring flask and made up to mark with iso - amyl alcohol. The absorbance of iso - amyl alcohol extract was measured at 545 nm against a reagent blank prepared under identical conditions. The Os (IV) content of the sample solution was determined from calibration curve. To study the effect of other ions, the respective foreign ions were added to aqueous phase before the extraction and adjustment of pH.

Determination of Osmium in Synthetic Samples

2 ml of Synthetic sample was dissolved in boiling 10 ml aquaregia. The resulting solution was evaporated to dryness and the residue was then dissolved in 10 ml of 1 M HCl, filter if required and solution was diluted to 100 ml with doubly distilled water. The working solution was prepared by appropriate dilution of stock solution. To an aliquot of this solution (1 ml) was analyzed for Osmium by the procedure as described earlier.

RESULTS AND DISCUSSION:

Osmium (IV) could be extracted quantitatively (99.94%) by HPIMNP into iso- amyl alcohol from an aqueous solution of pH range 0.0–2.0. Further extraction of Osmium into iso- amyl alcohol from an aqueous solution containing 1 ml of 1 % HPIMNP has been studied over 1 ml of varying concentration of various acid Solution. Acid solution 1 M HCL is found to be the best for extraction. Hence it is selected for extraction work (Fig. 1). Organic solvents used for extraction of Os (IV) can be arranged on the basis of their extraction coefficient values as Iso - amyl alcohol > n- butanol > benzyl alcohol > nitro benzene > benzene > xylene > toluene > ethyl acetate > chloroform > carbon tetrachloride (Fig. 2). Iso - amyl alcohol was found to be the best extracting solvent; hence, it was selected for extraction throughout the work.

The iso - amyl alcohol extract of Os- HPIMNP complex showed an intense peak at 545 nm. The absorbance due to the reagent is negligible at this wavelength, so the absorption measurements were taken at this wavelength (Fig. 3). The result shows that the system confirmed to Beer’s law at this wavelength over a Os (IV) concentration range 1.5 to 24.0 µg/ml (Fig- 4). The molar absorptivity and sandell’s sensitivity of the extracted species on the basis of Os (IV) content were calculated to be 3700.00L mole^-1 cm^-1 and 0.051µg.cm^-2respectively. It was found that 1 ml of 1.0 % solution of HPIMNP prepared in DMF was sufficient to extract 240 µg of Os (IV). The color of the iso - amyl alcohol extract was found to be stable at least 48 hrs at room temperature.

EFFECT OF OTHER IONS:

Os (IV)(100 µg) was determined in the presence of various ions. The following ions in the amount indicated, did not interfere in the spectrophotometric determination of Os (IV) (100 µg) : 10 mg each of, Li (I), Be (II), Ba (II), Ca (II), Sr (II), Al (III), Ti(III), V (V), Mo (VI), U(VI) and 0.1mg each of Fe(II), Fe(III), Ru (III), Pt (IV) and Rh (III). And 20 mg each of chloride, bromide, iodide, fluoride, chlorate, bromate, iodate, sulphide, phosphates, tartrate, acetate, citrate and thiosulphate, thiocyanide, triethanol amine, ascorbic acid.

Interference by various ions was removed by using appropriate masking agent (Table 1).

Table – 1 Masking agents required for suppressing the interference by other ions:

Interfering ion	Amount added in mg	Masking agent added 1ml of 2M solution
Cr (III)	10	Tri ethanol Amine
Cu (II)	10	Sodium thiosulphate

COMPOSITION OF THE EXTRACTED COMPLEX:

The composition of the extracted complex was found to be 1:3 (Os: HPIMNP) by Job’s continuous variation and Mole ratio methods (Fig- 5 and Fig- 6).

Fig. 5 Composition of the extract species Os: HPIMNP by Job’s Continuous Variation Method

Fig. 6 Composition of the Extracted Species HPIMNP: Os by Mole Ratio Method

Table – 2 Determination of Osmium in Synthetic sample

Sr. No.	Synthetic Sample	Os (IV) found %
Sr. No.	Synthetic Sample	Present method	Thiourea method
1	(Osmium-0.1%) (Ruthenium-0.1%) (Rhodium -0.1%)	0.099	0.098
2	(Osmium-0.1%) (Ruthenium -0.1%) (Platinum -0.1%)	0.098	0.097
3	(Osmium- 0.1%) (Ruthenium -0.1%) (Palladium -0.1%)	0.098	0.098

Results are the average of three independent determinations.

PRECISION, ACCURACY, SENSITIVITY AND APPLICATION OF METHOD

The precision and accuracy of the method were tested by analyzing the solution containing a known amount of Os (IV) following the recommended procedure. The average of 10 determination of 10 µg of Os (IV) in 10 cm³solutions was 9.99 µg, which is varied between 9.94 and 10.04 at 95% confidence limit and standard deviation is ± 0.073. The proposed method has been applied for the determination of Osmium in Synthetic Sample. The results of the analysis of the sample were comparable with those obtained by the thiourea method[6] (Table 2).

CONCLUSIONS:

From the above discussions, it is found that Schiff base, 2-[(2-hydroxyphenylimino) methyl]-4-nitrophenol [HPIMNP] is a good sensitive reagent for development of rapid and sensitive extractive spectrophotometric method for the determination of Os (IV) and it has been satisfactory applied for determination of Osmium in Synthetic Sample.

ACKNOWLEDGEMENT:

Authors are thankful to the Principal Dr. (Mrs.) J. K. Phadnis, V.E. S. College of Arts, Science and Commerce, Sindhi Society, Chembur, Mumbai- 400071 for providing necessary research facilities.

REFERENCES:

1. Feigl F. Chemistry of specific, selective and sensitive Reactions. New York. 1949; English Ed: pp. 209-210.

2. Nath R, Nautiyal SC and Singh H. Determination of metal ions with organic reagent part1- Studies on some nitro substituted orthohydroxy ketoximes. Labdev. Journal of Science and Technology Part A- Physical Sciences. 12A(2); 1974: 53-58.

3. Scott WW. Standard Methods of Chemical Analysis. New York. 1939; 5th Ed: pp.182.

4. Fasina TM, Ejiah FN, Dueke-Eze CU and Idika N. Synthesis and Antimicrobial Activity of Schiff Bases Derived from Substituted Salicylaldehyde with 2-aminophenol and 2-aminothiophenol. Journal of Sci. Res. Dev. 14; 2013: 94-97.

5. Vogel AI. Practical Organic Chemistry. London. 1989; 5th Ed.

6. Sandell EB. Colorimetric determination of Traces of Metals. New York and London. 1961; 3rd Edition.

Received on 15.03.2016 Modified on 21.04.2016

Asian J. Research Chem. 9(6): June 2016; Page 255-259.

DOI: 10.5958/0974-4150.2016.00042.0

Masking agent added 1ml of 2M solution