AASCIT Communications

Volume 3, Issue 3

ISSN: 2375-3803

Cyclic Voltammetry Study of Copper Chloride Salt

with Ceftazidime Antibiotic

E. A. Gomaa Chemistry Department, Faculty of Science, Mansoura University, Mansoura, Egypt

S. E. Salem Chemistry Department, Faculty of Science, Mansoura University, Mansoura, Egypt

Received: March 16, 2016; Accepted: April 11, 2016; Published: May 13, 2016

Keywords

Ceftazidime Antibiotic (CFZ), Copper Chloride Salt (CuCl2.2H2O), Cyclic Voltammetry (CV), Anodic Peak Potential (∆Ep)

he interaction of copper chloride salt with Ceftazidime antibiotic has been studied using cyclic voltammetric technique in

the potential range (+1.5 to -1.0) V at a scan rate 50 (mV/s) with mixed (MeOH+H2O) using NaClO4 (0.3M) as

supporting medium and platinum as a working electrode at 298.15K. The voltammetry pattern of the blank medium didn't

show any significant peak during the anodic and cathodic scans in the selected potential range while the peaks of the free metal

ions clearly indicates a stripping anodic peak at ≈ 0.1V vs SCE (0.342 V vs NHE). This peak is due to the dissolution of

metallic copper deposited during the cathodic scan between -0.1 to -0.5 V. The results of interactions of CuCl2.2H2O with CFZ

in the ratio (1:1) and (1:2) are displayed and show regular decrease of the anodic peaks as a result of complexation of Cu ions

with CFZ. In conclusion, both CFZ and alcohol had affected Cu ions deposition. The redox mechanism was explained also.

The aim of the work is to estimate the stability constant and free energy of interaction between copper and the drug.

Introduction

Nowadays the rheumatoid arthritis is one of the most common conditions, manifested by muscle and articulations

inflammation [1-3]. The treatment includes intake of non steroidal anti-inflammatory drugs (NSAIDs) of the oxicam family.

Ceftazidime (CFZ)[4-13] is a broad-spectrum antibiotic that kills a wide variety of bacterial infections known as a

cephalosporin antibiotic. It used for urinary tract infections, bone, blood infections respiratory tract infections, bacterial

meningitis, chronic bacterial infections of the middle ear, management of people who have a low white blood cell count

(neutropenia) and a fever that is suspected to be due to a bacterial infection.

Cyclic voltammetry (CV) has become a popular tool in the last fifteen years for studying electrochemical reactions. Organic

chemists have applied the technique to the study of biosynthetic reaction pathways [14] and to studies of electrochemically

generated free radicals [15]. An increasing number of inorganic chemists have been using cyclic voltammetry to evaluate the

effects of ligands on the oxidation/reduction potential of the central metal ion in complexes and multinuclear clusters [16-19].

It can be used to study qualitative information about electrochemical processes under various conditions such as the

presence of intermediates in oxidation-reduction reactions or the reversibility of a reaction. CV can also be used to determine

the electron stoichiometry of a system, the diffusion coefficient of an analyte and the formal reduction potential which can be

used as an identification tool [17-19].

Experimental

Chemicals and Reagents

Copper chloride salt (CuCl2.2H2O) was Merck pure while Ceftazidime antibiotic (CFZ) was from "GlaxoSmithKline" and

used as purchased.

T

ISSN: 2375-3803 170

Ceftazidime antibiotic (CFZ) structure

Synonyms [6R [6α, 7β (Z)]]-1-[[(6R, 7R)-7-[2-(2-Amino-4-thiazolyl) glyoxylamido]-2-carboxy-8-oxo-5-thia-1-azabicyclo [4.2.0] oct-2-en--3-yl] methyl] pyridinium hydroxide, inner salt, 72-(Z)-[O (1-carboxy-1-methylethyl) oxime], pentahydrate.

Formula C22H22N6O7S2·5H2O

Mol. Wt. 636.65 g/mol Trade name Fortum

Methanol solvent (MeOH) was provided from El- Nasr pharmaceutical chemicals co and used directly without purification.

Experimental Method

Cyclic voltammetry measurements (CV)

The PCI4-G750 physical electrochemistry software is used with a Gamry Potentiostat to perform in-depth studies of the

structure of the electrode interface and the mechanisms of electrochemical reactions. Cyclic voltammetry is the most common

techniques used to study the electrochemical systems which obtained in undivided glass cell of 25ml capacity with three

electrodes system consisting of a platinum wire (0.05cm2), platinum foil (1 cm

2) and a saturated calomel as working, counter

and reference electrodes, respectively. Cyclic voltammetry experiments were carried out using definite concentration of CFZ

(5×10-3

M) and (CuCl2.2H2O) (5×10-3

M) in MeOH-H2O mixture with NaClO4 (0.3M) as supporting electrolyte at a scan rate of

50mV/s. After each run, the working electrode was rinsed with dist water and electrically pretreated to obtain reproducible

results. The solutions were purged with purified nitrogen gas for (10-15) min before each experiment. All experiments were

repeated to ensure reproducibility. Fresh solution was used for each experiment and performed at 298.15 K (room

temperature).

The supporting electrolyte NaClO4 (1M) was obtained by standardization of (0.1M) of HClO4 with Na2CO3 using phenol

phethaline (Ph. Ph) as indicator. Then, standardization of (0.1M) NaOH with HCl using Ph. Ph. Finally, add equivalent amount

of HClO4 step by step on 100ml NaOH until formation of neutral solution of NaClO4 (1M) with pH (6-8).

Results and Discussion

Cyclic voltammetry analysis

The interaction of CuCl2.2H2O with Ceftazidime (CFZ) had been studied using cyclic voltammetry technique in the

potential range (+1.5 to -1.0) V at a scan rate 50 (mV/s) with mixed (MeOH+H2O) at 298.15K using NaClO4 (0.3M) as

supporting medium and platinum as a working electrode.

Mechanism of redox reaction:

The copper ions used show one oxidation peak at 60 mV and reduction peak at -520 mV. These two peaks corresponding to

the oxidation of copper zero valent to copper divalent. The vice verse for the reduction peaks is the reduction of cupric to

copper metal involving two electrons in this media versus saturated calomel electrode as follows:

Cu+2 (aq.) + 2e- = Cu

The other reduction and oxidation processes for copper (1) is not seen here in this medium because of the disportionation of

monovalent copper to divalent and zero valent ones [19] due to its unstable character in this medium.

2 Cu+ (aq.) = Cu +2 + Cuo

Adding ligand, Ceftazidime antibiotic to the copper salt both peak height were decreased indicating the reaction between

them forming complex [20-35]. It was proved that two complexes 1:1 and 1:2 metal/ligand were formed in case of using nano

CuSO4 with Ceftazidime [20] which are the same on using CuCl2 salt.

171 2016; 3(3): 169-176

The blank medium (MeOH/ NaClO4) didn't show any significant peak during the anodic and cathodic scans in the selected

potential range as shown in Fig. 1. Fig. 2 clearly indicates a stripping anodic peak at ≈ 0.1V vs SCE (0.342 V vs NHE). This

peak is due to the dissolution of metallic copper deposited during the cathodic scan between -0.1 to -0.5 V.

Using the values of cathodic peak potentials, the stability constants (Kc) for each complex at 1:1 and 1:2 molar ratio (M-

CFZ) is evaluated from the cyclic voltammetry data [20] using the equation (1),

log Kc = 0.434 ZF / RT ∆Ep (1)

where, (Z) is the charge of the metal ions, (F) is the faraday, (R) is the gas constant, (T) is the temperature and (∆Ep) is the

difference in the peak potentials without and with CFZ. For each complex, the values of ∆Gº is calculated from the equation

(2),

∆Gº = -2.303 R T log Kc (2)

The values of stability constant and ∆Gº of complexes at 1:1 and 1:2 molar ratio were given in Table 1 and Table 2 as

explains in various literature [21-51].

It is well known that Cu in aqueous solution within pH range 3-7 can be oxidized as Cu2O at the vicinity of the observed

anodic peak potential, Fig. 2. The recorded positive shift in the anodic peak potential Tables (1, 2) is due to the increase in

alcohol percentage in the solution. The results of interactions of CuCl2.2H2O with CFZ in the ratio (1:1) and (1:2) are displayed

in Fig. 3 and Fig. 4 and show regular decrease of the anodic peaks as a result of complexation of Cu ions with CFZ.

Fig. 1. Cyclic voltamogram of ((0.3M) NaClO4 as supporting medium) at platinum electrode in the potential range (+1.5 to -1.0 V) at the scan rate 50 (mV/S)

at 298.15K.

(a)

ISSN: 2375-3803 172

(b)

(c)

Fig. 2. Cyclic voltamogram of (CuCl2.2H2O + (0.3M) NaClO4) in the potential range (+1.5 to -1.0 V) at the scan rate 50 (mV/S) in (a) (20%

MeOH+80%H2O) (b) (40% MeOH+60% H2O) (c) (60% MeOH+40%H2O) at 298.15K.

(a)

173 2016; 3(3): 169-176

(b)

(c)

Fig. 3. Cyclic voltammogram of (CuCl2-CFZ in the ratio (1:1) + (0.3M) NaClO4) using platinum electrode in the potential range (+1.5 to -1.0 V) at the scan

rate 50 (mV/S) in (a) (20% MeOH+80%H2O) (b) (40% MeOH+60% H2O) (c) (60% MeOH+40%H2O) at 298.15K.

(a)

ISSN: 2375-3803 174

(b)

(c)

Fig. 4. Cyclic voltamogram of (CuCl2-CFZ in the ratio (1:2) + (0.3M) NaClO4) using platinum electrode in the potential range (+1.5 to -1.0 V) at the scan

rate 50 (mV/S) in (a) (20% MeOH+80%H2O) (b) (40% MeOH+60% H2O) (c) (60% MeOH+40%H2O) at 298.15K.

Table 1. Anodic peak potentials, anodic peak current of [free (CuCl2.2H2O)] and [CuCl2-CFZ complexes], values of log Kc and free energies change for (1:1)

metal complexes at 298.15K.

Solvent EFree (mv) Ip (A) EComplex (mv) Ip (A) ∆Ep (EFree-EComplex)

log Kc ∆G◦(104) J/mol mv Volt

(20% MeOH + 80% H2O) 91.8 426.7 79.9 72.6 11.9 0.0119 3.45 -1.97

(40% MeOH + 60% H2O) 133.8 495.2 77.8 81.33 56 0.0560 2.78 -1.59

(60% MeOH + 40% H2O) 161.6 370.4 75.6 53.02 86 0.0860 2.59 -1.48

Table 2. Anodic peak potentials, anodic peak current of [free (CuCl2.2H2O)] and [CuCl2-CFZ complexes], values of log Kc and free energies change for (1:2)

metal complexes at 298.15K.

Solvent EFree (mv) Ip (A) EComplex (mv) Ip (A) ∆Ep (EFree-EComplex)

log Kc ∆G◦(104) J/mol mv Volt

(20% MeOH + 80% H2O) 91.8 426.7 9.8 28.78 82 0.082 2.61 -1.49

(40% MeOH + 60% H2O) 133.8 495.2 34 43.2 99.8 0.0998 2.53 -1.44

(60% MeOH + 40% H2O) 161.6 370.4 23.6 35.53 118.4 0.1184 2.46 -1.4

175 2016; 3(3): 169-176

Conclusion

From cyclic voltammetry measurements it is worth noticing that addition of CFZ to Cu ions not only decreased the amount

of deposited Cu during the cathodic scan as evident by the decreasing of the cathodic peaks but also inhibited the dissolution of

Cu during the anodic scan as evident by the drop of anodic peak current in presence of CFZ. In conclusion, both CFZ and

alcohol had affected Cu ions deposition. The redox mechanism was presented. The stability constant and Gibbs free energy of

interaction between Cu and CEZ was estimated. ■

Prof. Dr. Esam A. Gomaa

Prof. of Physical Chemistry, Faculty of Science, Mansoura University.

Special area, Chemical Thermodynamics and Solution Chemistry. Dr. Rer. Nat. from Munich Technical

University, Germany on 1982. Got Prof. degree on 1994. Has many published paper in international

journals in Chemistry, Physical Chemistry and Environment.

eahgomaa65@yahoo.com

Dr. S. E. Salem

Dr. of Chemistry in Atomic Absorption Unit, Chemistry Department, Faculty of Science, Mansoura

University. Got degree of Ph.D. on Dec. 2015 entitled "The thermodynamics of the effect of some

solvents on the interactions of divalent cations and some pharmaceutical drugs" and the master degree

on Feb. 2013 entitled "Study of Solvation of Some Transition Metal Salts and Their Metal Complexes

in Different Organic Solvents" in Chemistry (Physical Chemistry, Thermodynamics) from Faculty of

Science, Mansoura University. She published papers in Journal of Environments, Southern Brazilian

Journal, American Association for Science and Technology (AASICT Communications) and American

Journal of Chemistry and Application.

Sara_salem669@yahoo.com

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