INTRODUCTION:

Ruthenium is one of the rare transition metals. Naturally occurring Ru is comprised of seven isotopes. One kilo of fission products of U²³⁵will contain 63.44 grams of Ru isotopes with half-lives longer than a day. One ton of used fuel will contain more than 1.9 kilogram of Ru. Ruthenium can be used in the alloys of Pt, Pd to make severe wear-resistant electrical contacts due to its high hardening ability. Ru can be alloyed with titanium to improve its resistance to corrosion by a hundredfold. Ru is also a versatile catalyst. This may be useful in the removal of H₂S from oil refineries and other industrial processes. Ruthenium-centered complexes are being researched for possible anti cancer properties.

NAMI-A and KP1019 are the two drugs undergoing clinical evolution against Metastatic tumors and colon cancers. Ruthenium can also be used in some advanced high temperature single-crystal super alloys with applications including the turbine blades in jet engines. Organo metallic Ruthenium carbene and allenylidene complexes have been found as highly efficient catalysts for olefin metathesis with important applications in organic and pharmaceutical chemistry.

Since Ruthenium complexes absorb light throughout the visible spectrum and are being actively researched in various solar energy technologies. Ruthenium red, [(NH₃)₅ Ru-O-Ru (NH₃)₄-O- Ru (NH₃)₅]⁺⁶is a biological stain used to visualise poly anionic areas of membranes.

The oximes and hydrazones are the most important spectrophotometric reagents for the determination of metal ions. Complex formation reactions are of great use in determining metal ions at the micro level or even nano gram level. In this context organic reagents occupy a better place over inorganic reagents because of their complexing ability with metal ions giving highly coloured stable compounds. Among the large number of available organic reagents, the oximes and hydrazones became important spectrophotometric reagents for the determination of metal ions. The potential application of hydrazone derivatives for the spectrophotometric determination of metal ions was reviewed by singh ¹ and others. Some hydrazone reagents^{2- 4} were used for the spectrophotometric determination of Ruthenium (III).

In view of good analytical characteristics of hydrazones, the author has investigated the colour reaction between Ru (III) and DMIH spectrophotometrically. Subsequently the author has developed a sensitive method for the spectrophotometric determination of Ruthenium (III) using an organic reagent namely Diacetyl Monoxime Isonicotinoyl hydrazone(DMIH). The author has incorporated the results of the zero and first order derivative spectrophotometric method in the determination of Ruthenium (III) in aqueous medium here in this paper.

EXPERIMENTAL:

Spectrophotometric measurements were made in an shimadzu 160A microcomputer based UV –Visible spectrophotometer equipped with 1.0 cm quartz cells, an ELICO LI- 120 digital P^Hmeter. All the reagents used were of AR grade unless otherwise stated. All solutions were prepared with distilled water. The standard Ru (III) solution (0.01M) was prepared by dissolving 0.2076 gm of Ruthenium chloride (RuCl₃) AR Loba in minimum Quantity of dilute hydrochloric acid and diluted up to the mark with distilled water in a 100 mL standard flask.

The reagent Diacetyl Monoxime Isonicotinoylhydrazone (DMIH) was prepared by simple condensation of Diacetyl Monoxime and Isonicotinic hydrazide in 1:1 mole ratio and its structure is given in fig- 1.

Fig 1. Structure of Diacetyl Monoxime Isonicotinoylhydrazone (DMIH)

The reagent solution (0.01 M) was prepared by dissolving 0.22 grams of DMIH in 100 mL of dimethyl Formamide. The reagent is stable for 48 hours. Buffer solutions were prepared by mixing 1 M hydrochloric acid – 0.2 M sodium dihydrogen phosphate.

Reaction with metal ions: The reactions of some important metal ions were tested at different P^H values. The samples were prepared in 10 mL volumetric flasks by adding 3 mL of buffer ( P^H 1.0 – 11.0), 0.5 mL of metal ion ( 1X 10 ^-3 M) and 0.5 mL of DMIH ( 1 X 10 ^-2 M ) solutions .The solution mixture was diluted up to the mark with distilled water. The absorbance was measured in 300–600 nm range against reagent blank. The results are summarised in Table -1

Recommended Procedure:

Determination of Ru (III) (Zero order spectrophotometry):

An aliquot of the solution containing 0.505 - 6.06 µg /mL of Ru (III), 3 mL of buffer solution of P^H 4.5 and 0.5 mL of 0.01M DMIH reagent were taken in a10 mL volumetric flask and the solution was diluted up to the mark with distilled water. The absorbance of the solution was recorded at 346 nm in a 1.0 cm cell against the reagent blank prepared in the same way but without Ru (III ) metal solution .The measured absorbance was used to compute the amount of Ru(III) from the calibration plot.

Determination of Ru (III) by first order derivative spectrophotometry: The first order derivative spectrum was recorded for the above solution of Ru (III)–DMIH with a scan speed having degrees of freedom 9 in a wavelength range 300-600 nm. The derivative spectrum was measured by peak height (h) method at 424 nm. The peak height (h) at 424 nm is proportional to the concentration of Ru (III). Therefore the peak heights were measured at this wavelength for the construction of calibration plots.

RESULTS AND DISCUSSION:

Diacetyl Monoxime Isonicotinoylhydrazone (DMIH) reagent can be easily prepared like any other Schiff base reagent. This new chromogenic reagent DMIH was not used for spectrophotometic determination of Ru (III) so far.

The reactions of some important metal ions with DMIH are summarised in table-1. The colour reactions are mainly due to the complex formation of DMIH with divalent, trivalent, and tetravalent and hexavalent metal ions like Hg (II), Ru (III), Au (III), Th (IV), Mo (VI) and U (VI) in acidic buffer medium to give intense coloured complexes.

Table –1: Analytical Characteristics of Diacetyl Monoxime Isonicotinoyl Hydra zone (DMIH)

Sl No	Metal Ion	P^H	λ _max (nm)	Molor absorptivity (L.mol ^-1 cm ^-1) X10 ⁴
1	Ru (III)	4.5	346	1.4
2	Hg (II)	5.5	351	2.23
3	U (VI)	3.25	364	1.63
4	Th (IV)	5.0	352	2.265
5	Au (III)	4.5	361	1.5
6	Mo (VI)	5	346	1.93

Table-2: Some of Physico- Chemical and analytical characteristics of Ru (III) –DMIH Complex

Characteristics	Results
λ _max (nm)	346
P^H Range (Optimum)	4.0-5.0
Mole of reagent required per mole of metal ion for full colour development	5 folds
Molar absorptivity (L.mol ^-1 cm ^-1)	1.4 X10⁴
Sandell’s sensitivity (µg/ Cm²)	0.0048
Beer’s law validity range (µg / mL)	0.505-6.06
Optimum concentration range (µg / mL)	1.01-5.05
Composition of complex (M: L) obtained in job’s and mole ratio method	1:1
Stability Constant of the complex	2. 694 X 10 ⁶
Standard deviation in the determination of 3.03 µg/mLof Ru (III) for 10 determinations	0.0005
Relative standard deviation	0.11494

Table –3: Tolerance limit of Foreign Ions in the determination of 2.525 µg / mL Ru (III)

Ion Added	Tolerance Limit (µg / mL)		Ion Added	Tolerance Limit (µg / mL)
	Zero Order	First Derivative		Zero Order	First Derivative
Urea	600.6	300.3	Sn⁺²	178	118.7
Sulphate	480	480	Bi⁺³	313	208.98
Phosphate	475	475	Ba⁺²	206	137.3
Nitrate	310	310	Zn⁺²	98	98.1
Acetate	295	295	Zr⁺⁴	136.8	91.2
Oxalate	670	670	U⁺⁶	357	238
Thio Urea	38	76	W⁺⁶	275.7	183.8
Tartarate	42.3	42.3	Al⁺³	40.47	26.98
Ascorbic Acid	264	176	Ag +	161.85	107.9
Fluoride	95	95	Ca⁺²	20	40
Iodide	634.5	634.5	Ni⁺²	80	80
Bromide	399.5	399.5	Pd⁺²	159.6	106.4
Chloride	532.5	532.5	V⁺⁵	76.35	50.9
Mo ⁺⁶	144	95.9	Sr⁺²	87.6	87.6
Mn ⁺²	82	54.9	Sb⁺³	182.7	182.7

Determination of Ru (III) using DMIH:

Ru (III) reacts with DMIH in acidic medium to give purple coloured water-soluble complex. The colour reaction between Ru (III) and DMIH is instantaneous even at room temperature in the P^H range1.0-7.0. The absorbance of the purple coloured complex remains constant for more than 2 hours. The maximum colour intensity is observed at P^H 4.5.

It is observed that a 5 fold molar excess of reagent is adequate for full colour development. The order of addition of buffer solution, metal ion and reagent has no adverse effect on the absorbance. The complex formation reaction between Ru (III) and DMIH has been studied in detail based on the composition of the complex as determined by using Job’s and molar ratio methods. Some of the important physico-Chemical and analytic characteristics of Ru (III) and DMIH are summarised in table-2.

Derivative spectrophotometry is an important useful technique as it decreases the interference i.e., increase the tolerance limit value of the foreign ions. Therefore it may be useful for the determination of metal ions having overlapped spectra. The recommended procedure has been used for the determination of Ru (III). The zero order and first order derivative spectra of Ru (III) complex of DMIH are given in Fig 2 and 3 respectively.

Effect of diverse ions: The effect of various diverse ions in the determination of Ru (III) was studied to find out the tolerance limit of foreign ions in the present method. The tolerance limit of foreign ions was taken as the amount of foreign ion required to cause an error of ± 2% in the absorbance or amplitude The results are given in table - 3. The data obtained in the derivative method is also incorporated.

Applications

The proposed method was applied for determination of Ru (III) in various synthetic samples of alloy and river water samples.

Fig 2. Zero order absorption spectra of (a) reagent DMIH 1X10 ^-2 M vs water blank at P^H4.5 (b) Ru (III) - DMIH complex vs reagent blank at P^H =4.5, Ru (III) =1X10 ^-3 M; DMIH=1X10^-2 M

Fig.3. First order Derivative Spectrum of Ru (III) –DMIH Complex Vs Reagent Blank at P^H 4.5, Ru (III) =1X10^-3 M, DMIH = 1X 10^-2 M

Table- 4: Estimation of Ruthenium (III) (µg / mL) in synthetic alloy samples

Sample (µg / mL)	Amount of Ru (III) (µg / mL)
Sample (µg / mL)	Amount Added	Amount found *	Error (%) Found
Pb (II) (0.9) + Co(II) (21.0)	0.860	0.836	+2.80
Os (VIII)(9.0) + Rh (III) (100)	3.0	2.98	+0.67

* Average of best three determinations among five determinations

Table 5: Estimation of Ru (III) (µg / mL) in River water samples

Sample (µg / mL)	Amount of Ru (III) (µg / mL )
Sample (µg / mL)	Amount Added	Amount found *	Error (%) Found
River Water	0.550	0.539	+2.0
River Water	0.710	0.698	+1.7

· Average of best three determinations among five determinations

Table 6: COMPARISSION OF SPECTROPHOTOMETRIC METHODS FOR THE DETERMINATION OF Ru (III)

Reagent	λ _max (nm)	P^H	Molor absorptivity (L.mol ^-1 cm ^-1)	Extraction /Heating	Beers Law Range	Ref.
Tropolone	415	4.5-6.0	1.87 X 10 ⁴	Extraction	0-5.7 ppm	5
4,5-Diamino-6-hydroxy pyrimidine sulphate	530	Acidic medium	6.5 X 10 ⁴	Heating	-------	6
3-Nitraso-4-hydroxy-5,6-benzocoumarin	520	5.5-8.0	1.04 X 10 ⁴	Extraction	1-7.4 ppm	7
2,2’,2’’ – Terpyridine	690	3.0-4.5	8.3 X 10 ⁴	Heating	2-10 ppm	8
3-( 2-Pyridyle )-5,6-diphenyl 1,2,4- triazine	485	5.0	2.1 X 10 ⁴	Extraction	0.5-3.4 ppm	9
3-hydroxy -2-methyl -1,4-napthaquinone-4-oxime	450	5.7	2.7 X 10 ⁴	-----------	0-10.1 ppm	10
Cinnamaldehyde isonicotinoyl hydrazone ( CINH )	402	3.0	1.25 X 10 ⁴	--------------	0.4-4.04 µg / mL	11
Diacetyl Monoxime Isonicotinoyl Hydrazone (DMIH )	346	4.5	1.4 X 10 ⁴	-----------	0.505-6.06 µg / mL	Present Method

Analysis of synthetic alloy sample:

0.5 grams of sample of the synthetic alloy was digested in 15 mL of 2:1 ratio mixture of concentrated Hcl and concentrated HNO_3.It was heated until it is dissolved and final volume is reduced to 5 mL. To this, 5 mL of 5M HCl was added and filtered. Then the filtrate was collected in a 25 mL volumetric flask and made up to the mark. Ru (III) present in this solution was determined by the recommended procedure from a predetermined calibration plot and the obtained results are presented in table-4.

Analysis of river water Sample:

A known aliquot river water sample was added to 3 mL buffer (P^H 4.5) solution in a 10 mL volumetric flask and 0.5 mL of (1x10 ^-2 M) of the reagent is added and made up to the mark with distilled water. The absorption at 346 nm is recorded against the reagent blank. The amount of Ru (III) present was determined from a predetermined Calibration plot and results are presented in table -5.

CONCLUSIONS:

The present method using DMIH as a spectrophotometric reagent for the determination of Rhuthenium (III) in aqueous medium is sensitive and simple. The determination of Ru (III) using DMIH is not laborious and there is no need of heating the components or extraction. Further the reagent is easy to synthesis using available chemicals. Moreover the present method is simple, rapid, reasonably sensitive and selective for the determination of Ruthenium (III). A list of previously reported works in the spectrophotometric determination of Ruthenium (III) is incorporated in the table-6. for the sake of comparison purpose.

ACKNOWLEDGEMENT

The authors are thankful to the Jawaharlal Nehru Technological University, Anantapur for providing research facilities to carry out the present work.

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Received on 05.02.2011 Modified on 17.03.2011

Asian J. Research Chem. 4(6): June, 2011; Page 997-1000