Ionics (2015) 21:1445–1452 DOI 10.1007/s11581-014-1295-9
ORIGINAL PAPER
Electrocatalytic quantification of thrombin inhibitor dabigatran etexilate in solubilized system Rajeev Jain & Ankita Sinha
Received: 28 September 2014 / Revised: 20 October 2014 / Accepted: 21 October 2014 / Published online: 11 February 2015 # Springer-Verlag Berlin Heidelberg 2015
Abstract A new graphene-cerium dioxide nanocompositemodified glassy carbon electrode (GR/CeO2/GCE)-based sensor has been developed for sensitive voltammetric quantification of thrombin inhibitor anticoagulant drug dabigatran etexilate (DAB) in solubilized system of Triton X-100. The voltammetric studies of DAB at GR/CeO2/GCE sensor exhibits a well defined cathodic peak for its reduction in Britton Robinson (BR) buffer at pH 3.8 in 0.001 % Triton X-100. The morphological characteristics of the developed GR/CeO2/ GCE sensor were studied by scanning electron microscopy (SEM). The influence of optimization parameters such as pH, effect of different solvents, critical micelle concentration, and effect of loading of composite mixture of GR and CeO2 at GCE on electrocatalytic performance of the developed sensor was evaluated. Under optimized experimental conditions, the squarewave reduction peak current was linear over the concentration range of 5 (ng mL−1) to 5 (μg mL−1) with a correlation coefficient (r2) of 0.9968 with detection limit (LOD) and quantification limit (LOQ) of 12.480 ng mL−1 and 41.602 ng mL−1 respectively with good stability and an acceptable reproducibility of 3.62 % relative standard deviation. The electrochemical quantification of DAB at GR/CeO2/ GCE sensor holds great promise for its highly selective, sensitive screening and use of less hazardous Triton X-100 as solubilizing media. Keywords Dabigatran (DAB) . Graphene-cerium dioxide nanocomposite-modified glassy carbon electrode (GR/CeO2/GCE) . Triton X-100 . Voltammetry R. Jain (*) : A. Sinha School of Studies in Chemistry, Jiwaji University, Gwalior 474011, India e-mail:
[email protected] A. Sinha e-mail:
[email protected]
Introduction In recent years, atrial fibrillation (AF) has become the most common cardiac arrhythmia. Atrial fibrillation can lead to congestive heart failure, systematic embolism and a major risk factor for stroke [1, 2]. Dabigatran etexilate is basically Ethyl 3-{[(2{[(4-{N′-(hexyloxy)carbonyl]carbamimidoyl}phenyl)amino] methyl}-1-methyl-1H-benzimidazol-5-yl)carbonyl](pyridin-2yl-amino)propanoate (Scheme 1), a direct thrombin inhibitor and an anticoagulant drug that is used in antithrombotic treatments. It is also employed for the prevention of stroke and systematic embolism in patients with atrial fibrillation [3–6]. Fabrication of voltammetric sensors holds great promise in electrochemistry with a number of possible applications in the pharmaceutical analysis. Use of various chemically modified electrodes for electrocatalytic studies of various pharmaceuticals has gained much attention in recent years [7–29]. Applications of graphene (GR) decorated with nanoparticles (NPs) for electrochemical sensing and detection of compounds have been widely reported. GR in combination with Pt/Ru NPs has been used for electrooxidation of methanol [30]. Zhou et al. [31] used gold NP (AuNP)-modified graphene for enzymatic detection of graphene. A composite of GR/AuNP/GR oxide-modified GCE was fabricated for glucose sensing [32]. Shana et al. [33] constructed GR/ AuNP/chitosan nanocomposite electrodes and studied the electrocatalytic activity of H2O2 and O2. GR/Nafion/GCE-modified electrode was used for the sensitive determination of cadmium [34]. Again GR/Chitosan/GCE and GR/Fe3O4/GCE composite electrodes were used to study guanosine electrochemically [35]. Cerium dioxide NP has also been reported for electroanalysis of many compounds. Ispas et al. [36] studied the unique catalytic and electrochemical properties of CeO2 as an electrode material to develop CeO2-based sensor to determine hydrogen peroxide. A nanoceria-modified platinum-gold composite electrode for the electrochemical oxidation of methanol and ethanol in acidic media has been fabricated by Anderson et al. [37]. Also,
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Ionics (2015) 21:1445–1452 H3C
Scheme 1 Structure of dabigatran etexilate
Mumbai, India, and was used as received. Capsules of dabigatran etexilate labeled 150 mg manufactured by Sun Pharmaceuticals Pvt. Ltd., India, were obtained from commercial sources. All chemicals used were of analytical reagent grade and were employed as received. All chemicals were procured at Jiwaji University, Gwalior (MP), India.
O O N N O
Apparatus
H3C
N
N
NH
H2N H3C
N O
O
Pt/CeO2 composite electrode was constructed by Saha et al. [38] and used to study glucose oxidase. A ceria/titania composite electrochemical enzyme biosensor has been fabricated to study phenol and dopamine [39]. CeO2/indium tin oxide electrode was applied for the study of cholesterol electrochemically [40]. Cu/CeO2 electrode was constructed by Gammara et al. [41] and used as catalyst for carbon monoxide oxidation. The study of an analyte in solubilized media is of great importance and proved to be very effective in electroanalysis [42, 43]. Various surfactants tend to adsorb at the interface between electrode surface and analyte solution and show a significant enhancement in the voltammetric peak response [44–49]. In the present study, GR/CeO2 nanocomposite-modified GCE sensor has been developed and applied for the first time for the electrocatalytic study of an anticoagulant drug dabigatran etexilate (DAB) in solubilized system. The fabricated GR/CeO2/GCE sensor has been successfully applied to the DAB determination in pharmaceutical formulation and in waste water. The developed GR/CeO2/GCE sensor is much sensitive toward DAB reduction and show a great promise for its determination with high accuracy and precision.
Electrochemical measurements were carried out at using μ-AUTOLAB TYPE III (Eco-chemie B.V., Utreht, The Netherlands) potentiostat-galvanostat with 757 VA computrace software. GR/CeO2 nanocomposite-modified glassy carbon electrode was used as working electrode, Ag/AgCl as reference electrode (3.0 M KCl), and graphite rod was employed as an auxiliary electrode. Electrochemical impedance spectroscopic measurements were carried out using AUTOLAB (Eco-chemie B.V., Utreht, the Netherlands) potentiostat-galvanostat with NOVA 1.10 software. All the solutions examined by electrochemical techniques were purged for 10 min with purified nitrogen gas. The morphological characteristics of GR/CeO2/GCE electrode were studied by scanning electron microscope using ZEISS EVO 50 instrument. All the pH metric measurements were carried on Decible DB-1011 digital pH meter fitted with a glass electrode and saturated calomel electrode as reference electrode. Fabrication of working electrode The surface of glassy carbon electrode was modified with GR/ CeO2 nanocomposite. Before each measurement, the GCE surface was polished with alumina powder of particle size ranging from 0.05 to 0.1 μm on microcloth pads and rinsed thoroughly with distilled water, followed by constant washing with distilled water till a clean mirror-like finish was obtained. It was then again washed with 0.2 M H3PO4 to remove adhered powder on the electrode surface followed by rinsing with distilled water and dried at room temperature for around 15 min. Then GR and CeO2 in the ratio of 3:1 were dispersed in N,N-dimethylformamide (DMF) to give a solution of 1 mg mL−1 with ultrasonication for 2 h. A known volume of this suspension (7 μL) was adsorbed onto the surface of GCE using a microsyringe and kept at room temperature till the fabricated surface was completely dried.
Experimental
Results and discussion
Reagents and chemicals
Optimization of experimental conditions
Graphene (97 % purity) was obtained from Graphene Laboratories, USA. CeO2 nanoparticles (99.5 % purity,
