Liquid-Liquid Extraction and Spectrophotometric Determination of Cu (II) using 5-Nitrosalicylaldehyde semicarbazone (NSS) as an Analytical Reagent

 

Lokhande R. S.¹, Khadke L., Patankar Jain K. N.^2*, Jain N. G.² 

¹Department of Chemistry, Jaipur National University, Jaipur, Rajasthan.

²Department of Chemistry, B. N. N.College, Bhiwandi, District Thane.

*Corresponding Author E-mail: knjc00@gmail.com

 

5-nitrosalicylaldehyde semicarbazone (NSS) is proposed as a new sensitive reagent for the sensitive extractive spectrophotometric determination of Cu (II). NSS reacts with Cu (II) in the pH range 8.0-8.4 to form a coloured complex, which was well extracted into Iso Amyl Alcohol. The absorption spectrum of Cu (II) NSS complex in Iso Amyl Alcohol shows maximum absorbance at 409 nm. It was observed that the colour development was instantaneous and stable for 72 hrs. The system obeyed Beer’s law up to 1-3 µg / cm3. The molar absorptivity calculated was found to be 6.232 * 104 lit mol-1 cm-1 and the sensitivity of the method as defined by sandal’s was 2.345 * 10-2 μg/cm2 . The composition of the extracted species was determined by Job’s Continuous variation method and Mole ratio method was found to be 1:4. It may be satisfactorily applied for the determination of Cu (II) with present method.

 

 

INTRODUCTION:

The cursory look at the above literature survey reveals that Copper forms chelate complexes with many organic reagents which are bonded through N, O and / S Items. Out of the reagents used for the extraction and spectrophotometric determination of Cu (II), many reagents suffer limitations as of, interference by other ions, lengthy and tedious procedure for reagent preparation, requirements of surfactants, the stability of complex with time, lack of appropriate solvent for extraction. Survey of innumerable applications of Copper leave a scope for as many reagents as can be applied for the extraction and spectrophotometric determination of Copper.

 

The present work describes a spectrophotometric method for quantitative estimation of Cu (II) with NSS.

 

MATERIALS AND METHODOLOGY:

Apparatus: Glassware used in the present investigations was all made up of Borosil. The burettes pipettes and standard flasks were calibrated in accordance with method described in vogel¹.

 

All measurements of absorption spectra² were made on one cm silica cells or 1 cm glass cells. The spectrophotometer used was Jasco (UV/VIS/NIR)Model-630.The calibration of the spectrophotometer was checked measuring absorption spectrum of 0.004% solution of potassium chromate in 0.05 M potassium hydroxide solution and also with 0.0058% solution of potassium permangnate in 1M sulphuric acid. The observed spectrum was in good agreement with the spectrum reported in the literature.

 

RESULTS AND DISCUSSION:

Absorbance Maxima

The absorption spectrum of Cu (II) NSS complex in Iso Amyl Alcohol shows maximum absorbance at 409 nm. The absorbance due to the reagent at this wavelength was negligible. Hence, 409 nm was selected for the absorbance measurement³ in spectro-photometric determination of Cu (II) against blank.

 

pH study

The extraction of Copper (II) with NSS was carried out over pH range of 1 – 12, 1 cm³ of aqueous solution of 100 ppm Copper (II) stock solution and 0.5 cm³ of 0.02% solution of the reagent⁴ were used. It reveals that 99% of metal is extracted into organic phase in the pH range between 8.0 to 8.4. It was found that complex does not form below pH 5. The analytical work for estimation of Copper (II) was carried out at pH 8.2. (Figure 1)

 

Figure 1

 

Solvent study

Various solvents were tried to determine the maximum extraction of Copper (II). Iso Amyl Alcohol was found to be most suitable solvent⁵ as it showed the highest extraction. The extraction of Copper (II) was minimum in solvents Chloform and Carbon Tetra Chloride.

 

Equilibration Time

The absorbance of Cu (II) – NSS Complex was checked by varying the time of equilibration from 30 seconds to 15 minutes. It was observed that equilibration time of 1 minute was found to be optimum for complete extraction of Copper (II).

 

Stability of complex with time

For this study, 1cm³ of 100 ppm solution was extracted with reagent in Iso Amyl Alcohol and absorbance of complex in Iso Amyl Alcohol was measured at different intervals of time. The study of stability of complex with variation in time showed that the complex was stable up to 72 hours, after which absorbance decreased slowly.

 

Effect of reagent concentration

The effect of variation in concentration of NSS in the range of 0.1 to 2.0 cm³ of 0.02% NSS on the extraction and the color development was tried. It was observed that 2.0 cm³ of 0.02% NSS was sufficient for complete extraction and color development⁶.

 

Effect of salting out agents on absorbance of Cu (II) NSS complex

Different sorting out agents such as sulphates, chlorides, carbonates and nitrates of Sodium, Potassium, Barium, Magnesium, Ammonium and Calcium were used in the extraction of Cu (II) (1cm³ of 100 ppm solution). It was observed that there was no effect on absorbance.

 

Calibration Curve

Different amounts of Copper (II) form 0.5 – 3 µg / cm³ were extracted quantitatively under optimum experimental conditions and the Iso Amyl Alcohol extract was measured at 411 nm against reagent blank. The plot of absorbance against concentration of Copper (II) gave a straight line (Figure 2) indicating that Beer’s Law is obeyed in this range. The molar absorptivity calculated was found to be 6.232 * 10⁴ dm³ mol^-1 cm^-1 and the sensitivity of the method as defined by Sandal’s was 2.345 * 10^-4 µg / cm².

 

Figure 2

 

Nature of the extracted species

The absorption spectrum of the Iso Amyl Alcohol extracts of the aqueous solution containing   Cu (II): NSS in molar concentration ration 1: 1, 1: 2, 1: 3 and 1: 4 indicated that under the experimental conditions, the nature of absorption spectrum remains identical irrespective of the reagent concentration with no change in the value of wavelength maxima. However, the absorbance increases as the molar reagent concentration increases w.r.t the metal concentration. The composition of the extracted species was determined by Job’s Continuous Variation Method and verified by Mole Ratio Method⁷.

 

Job’s Continuous Variation Method

A series of solutions were prepared by mixing 0.0 to 10.0 cm³ of 5.0 x 10^-4 M Copper (II) solution with 10.0 to 0.0 cm³ of 5.0 x 10-4 M NSS solution, such that the volume of each mixture was 10.0 cm³ each solution was treated at optimum pH as per procedure and the absorbance was then measured against blank. The absorbance values were plotted against mole ratio of Cu (II) to NSS. It shows sharp maxima at 0.2 Mole Fraction of Copper (II), indicating that the colored complex extracted into Iso Amyl Alcohol was formed by the reaction of Cu (II) and NSS in the ratio 1:4.(Figure:3)

 

Figure:3

 

Mole Ratio Method

A series of solutions containing 1 cm³ of 5.0 * 10^-4 Cu (II) increasing amounts of 5.0 * 10^-4 molar NSS were added. Each mixture was treated similarly and absorbance was measured using blank. The absorbance values were plotted against the mole ratio of NSS to Copper (II)⁸. It shows a sharp break corresponding to mole ratio 1:4 which supports the composition of Cu (II): NSS Complex.

 

Interference Study

The effect of diverse ions on the Copper (II) determination was studies in presence of a definite amount of Foreign Ion. Various cations and anions were investigated in order to find the tolerance limit of these foreign ions in the extraction of Copper (II). The tolerance limit of the foreign ion was taken as the amount required causing an error of not more than +2% in the recovery of Copper (II).

 

Effect of masking agents

The ions which interfere in the spectro-photometry determination of Copper (II) were masked by using appropriate masking agents. (Table:1)

 

Table:1

 

 

 

Applications of method

The present method was applied for the determination of amount of Copper (II) in various samples as alloys, milk samples, synthetic mixtures, beverages and industrial waste water. The results obtained were well in agreement with those of standard methods. (Table:2)

 

Table:2 Determination of Cu (II) using NSS from Different Samples

Sr No	Sample	Amount of Cu (II)
		Standard Method		Present Method
Copper Alloys
1	Devarda’s Alloy	47.9%	47.8%
2	Brass	60.0%	59.9%
3	Cupro Nickel	35.0%	34.85%
Beverages
	Wine (Bottle)	8.7ug	8.68ug
	Beer (Bottle)	6.6ug	6.57ug
	Raw Milk	4.8x10-2 mg	4.76x10-2 mg
Synthetic Mixture
1	Cu (10) + Zn (10)	9.99mg	9.98mg
2	Cu (10) + Zn (10) + Cd (10)	9.99mg	9.98mg
	Industrial Waste Water at Ulhasnagar Creek	3.6ppm	3.52ppm

 

ACKNOWLEDGEMENTS:

Authors are thankful to Prof. Irfan. R. Memon of Dept. of Chemistry, B.N.N College, Bhiwandi for his involvement and help during the tenure of this work.

 

REFERENCES:

1)       Vogel A.I.Text Book of Quantitative Inorganic Analysis . Longman Green and Co. Ltd., London.1961.

2)       Ross S.D. and Wilson D.W. Spectrovision  4,10 (1961).

3)       Lokhande R.S. and Khadke L.M. Spectrophotometric determination of Nickel(II) using 5-Bromo Salicylaldoxime as an Analytical Reagent. Asian Journal of Chemistry.17(4);2005:2343-2346.

4)       Lokhande R.S and Jain N.G. Extractive Spectrophotometric Determination of Co (II) using 5-Nitrosalicylaldehyde Thiosemicarbazone International Journal Of ChemTech Research.5(4);2013:1519-1522.

5)       Lokhande R.S and Pawar R.N.Solvent extraction and spectrophotometric determination of Cobalt(II) with Isovanillin Thiosemicarbazone. Asian Journal of Chemistry.18(4);2006:3241-3243.

6)       Lokhande R.S and Jain N.G.Liquid-Liquid Extraction and Spectrophotometric Determination of Fe (III) using 5-Nitrosalicylaldehyde thiosemicarbazone (NSTS) as an Analytical reagent. Asian Journal of Chemistry.6(10);2013:903-905.

7)       Skoog D.A et al. Fundamentals of Analytical Chemistry.Cengage Learning, Delhi.2004;8^th ed:pp.804-806.

8)       Khan S and Mahabey H. Hydroxyamidine Hydrochloride as a Spectrophotometric reagent for Iron(III) Asian Journal of Chemistry.16(1); 2004:519-521.

 

 

 

 

Received on 25.11.2013         Modified on 10.12.2013

Accepted on 15.12.2013         © AJRC All right reserved