Effect of Catalyst on Luminol - Hydrogen Peroxide–Water Chemiluminescence System

V.K. Jain*

Department of Chemistry, Pt. Shyamacharan Shukla College, Dharsiwa, Raipur (C.G.)

*Corresponding Author E-mail: vikaskumarjain1@rediffmail.com

ABSTRACT:

The Chemiluminescence properties of Luminol – Hydrogen peroxide reaction was studied in aqueous medium with different catalysts (CuSO₄.5H₂O, K₃Fe(CN)₆ and CrCl₃). It was observed that CL-behavior like I_max and t₁ depend on the catalyst in aqueous medium. Among the catalysts used, CuSO₄.5H₂O is the best catalyst. The study is useful for the determination of analyte by CL method.

KEYWORDS:

1. INTRODUCTION:

Chemiluminescence (CL), the production of light during a chemical reaction, has proved to be a useful phenomenon in the laboratory and is finding ever increasing applications in analytical chemistry [1]. Current researches on CL are focused in two general directions. One is the discovery of new CL reactions and investigation of their applicability for analysis of real samples and the other direction is the creation of CL detection systems for newly developed separation techniques. Researches on new CL reactions are very important since they open new horizons for the technique. However, sometimes the study of the mechanism of the reaction is bypassed and emphasis is given to the applications only. Nevertheless, a detailed study would help in studying and improving the analytical performance of the procedure.

CL based on the oxidation of Luminol (LH₂) (5-amino-2,3-dihydro-1,4-phthalazinedione) is one of the most extensively studied and best known CL system [2-4]. The oxidation is usually carried out in an alkaline solution using an oxidant, such as hydrogen peroxide [5], hypochlorite [6], permanganate [7], or iodine [8]. The Luminol-H₂O₂ system is one of the most efficient CL systems, known. Luminol-CL in water is mostly applied for analytical purposes, especially forensic medicine (to detect trace amounts of blood). This is why Luminol oxidation reaction in water has been investigated with such intension in mind. Catalyst is necessary for Luminol- H₂O₂ CL system in aqueous medium [9]. In the present study, the results of the effect of catalyst on the decomposition reaction between Luminol and hydrogen peroxide in aqueous medium, is reported.

2. EXPERIMENTAL DETAILS:

2.1 Materials:

Luminol (from Thomas backer), anhydrous sodium carbonate, sodium bicarbonate, ammonium carbonate monohydrate, copper(II) sulphate pentahydrate, potassium ferricyanide, chromium chloride, hydrogen peroxide (all from E merch, AR/GR grade) were used. Triple distilled water was used throughout during the studies.

2.2 Solutions preparation :

For the present investigation, 0.01g Luminol, 2.4g NaHCO₃, 0.4g Na₂CO₃(anhydrous), 0.05g (NH₄)₂CO₃.H₂O, 0.04g catalyst (CuSO₄.5H₂O or K₃Fe(CN)₆ or CrCl₃) were taken and dissolved in 100 ml of water. This was the stock solution of Luminol for a particular catalyst. For the preparation of 1.5% H₂O₂ stock solution, 5ml of 30% H₂O₂ solution was taken and then it was made up to 100ml by adding water (the actual H₂O₂ content was found by titration against KMnO₄ and then it was maintained 1.5% level).

2.3 Instruments and Methods:

All the experiments were performed on a chemiluminometer setup connected to an X-Y recorder (Fig.1). Stock solution of Luminol (1ml) in particular catalyst was taken in reaction cell and H₂O₂ solution (1ml) was added through

syringe.

3. RESULTS AND DISCUSSION:

Fig. 2 and 3 and Table-1 show the effect of catalyst on Luminol- H₂O₂ CL in aqueous medium. From the Table-1, it can be seen that CuSO₄.5H₂O gives the maximum intensity (I_max) and more decay time, whereas the light produced by K₃Fe(CN)₆ and CrCl₃ is less intense and having less decay time. t_max (time at maximum intensity) is not affected by the catalyst, which was used in the present investigation.

It is well known that decomposition of hydrogen peroxide and its reaction with inorganic or organic compounds are catalyzed by transition metal ions or their complexes in both heterogeneous and homogeneous systems. The radical chain mechanism for the reaction catalyzed by transition metal ions, which can exist in two oxidation states, such as Cu, Fe, Co, Cr and Mn, was suggested for this reaction. The oxidation of organic compounds by the Fenton reagent (Fe + H₂O₂) is one example [10] of this type of mechanism. In the presence of these metal ions, hydrogen peroxide decomposes to produce oxygen through the following reactions (From equation 1 to equation 3)-

Mⁿ⁺ + H₂O₂ M^(n-1)+ + HOO^. + H⁺ ...(1)

M^(n-1)+ + H₂O₂ Mⁿ⁺ + HO^. + OH^- ...(2)

2HOO^. H₂O₂ + O₂ ...(3)

This released oxygen then attack Luminol through following mechanism and emission of CL light occurs (From equation 4 to equation 8).

Fig. 1 Experiment setup of chemiluminometer

Fig. 2 Catalyst effect on the intensity of Luminol-H2O2-Water CL system

Fig. 3 Catalyst effect on decay time of Luminol-H2O2-Water CL system

From the mechanism, it can be concluded that H₂O₂ decomposition rate is more for CuSO₄.5H₂O, therefore I_max is more and H₂O₂ decomposition rate is less for K₃Fe(CN)₆ or CrCl₃, so its I_max is less. Time at maximum intensity t_max is not affected by the catalyst used which means that the reaction co-ordinate does not change by the presence of different catalyst. The above facts are evidence from Table–1.

4. CONCLUSIONS:

From the study on Luminol - H₂O₂ – water CL behavior involving the effect of catalyst (CuSO₄.5H₂O, K₃Fe(CN)₆ and CrCl₃), the important conclusions drawn are:

(i) Luminol- H₂O₂ CL in aqueous medium depends on catalyst.

(ii) Among the transition metal compounds, which were used as catalyst, CuSO₄.5H₂O is the best catalyst which produces light of maximum intensity.

(iii) Position of t_max is not affected by the catalyst used.

(iv) Decomposition reaction rate of H₂O₂ depends on the catalyst used.

(v) Decay time is also affected by the catalyst used.

5. ACKNOWLEDGEMENT:

Author is thankful to CSIR (Council of Scientific and Industrial Research) for the financial support (Award No. 9/266(63)/2003 EMR-I) and to Prof. G.L. Mundhara, Ex-Head, School of Studies in Chemistry, Pt. Ravishankar Shukla University, Raipur (C.G.) for providing the necessary facilities for the study.

Table – 1 : Effect of catalyst on the Luminol - H₂O₂ - Water CL system

Catalyst	Imax ,arb. unit	tmax ,s	M1 ,s^-1	t1,s
CuSO4.5H2O	25.0	3.0	0.2742	3.6469
K3Fe(CN)6	15.0	3.0	0.2814	3.5536
CrCl3	8.5	3.0	0.5176	1.9320

I_max = Maximum Intensity, t_max = Time at maximum intensity,

M₁ = Fast decay slope, t_1= Fast decay time.

6. REFERENCES:

1 A.M. Garcia-Campana and W.R.G. Baeyens, Chemiluminescence in Analytical Chemistry, Marcel Dekker, New York (2001).

2 K. Robards and P.J. Worsfold, Anal.Chim.Acta 266, 147(1992).

3 L.J. Kricka, Anal.Chem. 67, 499R(1995).

4 A.R. Bowie, M.G. Sanders and P.J. Worsfold, J.Biolumin.Chemilumin.11, 119(1996).

5 H.O. Albrecht, Z.Phys.Chem. 136, 321(1928).

6 D. Gonzalez-Robledo, M. Silva and D. Pervez-Bendito, Anal.Chim.Acta 228, 123 (1990).

7 A.K. Babko and N.M.Lukovskaya, Dopov.Akad.Nauk.Ukr. RSR 619 (1962).

8 A.K. Babko, L.V. Markova and N.M.Lukovskaya, Zh.Anal.Khim. 23, 401(1968).

9 D. Bersis and J. Nikokavouras, Nature 217, 451(1968).

10 R. Augusti, A.O. Dias, L.L. Rocha, R.M. Lago, J. Phys. Chem. 102, 10723 (1998).

Received on 05.07.2013 Accepted on 28.07.2013

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Asian J. Pharm. Ana. 3(4): Oct. - Dec. 2013; Page 138-140