ZnO nanoparticles as an oxidase mimic-mediated flow-injection chemiluminescence system for sensitive determination of carvedilol Pourya Biparva n , Seyed Mohammad Abedirad n , Sayed Yahya Kazemi Department of Basic Sciences, Sari Agricultural Sciences and Natural Resources University, P.O. Box 578, Sari, Iran article info Article history: Received 13 January 2014 Received in revised form 16 June 2014 Accepted 18 June 2014 Available online 3 July 2014 Keywords: Carvedilol Flow-injection chemiluminescence ZnO nanoparticles Nanocatalyst Mechanochemical Luminol abstract A simple, rapid and sensitive method was developed using ZnO nanoparticle (ZnO-NP) amplified flow- injection chemiluminescence to detect carvedilol, a non-cardioselective β-blocker. It has been found that carvedilol strongly inhibits the chemiluminescence of luminol–H 2 O 2 catalyzed by ZnO-NPs. Under optimum conditions, a linear working range for carvedilol concentrations from 5  10 8 to 1.0  10 6 mol L 1 (r 40.9894, n ¼8) was obtained with a detection limit of 3.25  10 9 mol L 1 . The relative standard deviation for 8 repetitive determinations was less than 2.9% and recoveries of 99% and 102% were obtained. ZnO-NPs were synthesized using a green mechanochemical route. Transmission electron microscopy and x-ray diffraction were used to characterize ZnO-NPs. The method was successfully applied to detect carvedilol in pharmaceutical formulations. & 2014 Elsevier B.V. All rights reserved. 1. Introduction Carvedilol, 1-(9H-carbazol-4-yloxy)-3-[2-(2-methoxyphenoxy) ethylamino]propan-2-ol, is a nonselective adrenergic blocking agent with 1-blocking activity indicated for the treatment of hypertension and mild or moderate heart failure of ischemic or cardiomyopathic origin. Its molecular structure is shown in Fig. 1. Carvedilol shows minimal inverse agonist activity when compared with other beta blockers and its use has been shown to decrease morbidity from congestive heart failure [1]. Methods have been introduced to assay the presence of carvedilol in plasma, urine and pharmaceuticals in recent years. These include luminescence [2] HPLC–MS/MS [3], HPLC–fluorime- try [4], differential pulse voltammetry [5], fluorimetry [6,7], and chemiluminescence [8,9]. New attempts to introduce efficient methods are under study. Chemiluminescence (CL) is a phenomenon in which chemically-generated molecules emit light in excited states. The superior emission of CL has recently been tested for use in biotechnology, industry, medicine, and water treatment plants [10].The attractiveness of CL techniques lies in their simplicity, rapidity, high sensitivity, low cost of instrumentation and maintenance, and requiring no background light. Since CL is directly related to the concentration of the reactants, it has been exploited as an ultrasensitive method for quantification and localization of chemical analytes that generate luminescence by participating in the CL reaction. These include CL precursors, catalysts, oxidants, cofactors, sensitizers, enhancers and inhibitors [11–17]. Nanotechnology is rapidly expanding in industry for catalysts, separation, luminescence, synthesis, and sensing [18–22]. Because of their unique chemical and physical characteristics, such as high surface area, activity, and sensitivity, nano-materials are in demand for CL reactions as catalysts, enhancers, energy acceptors and CL resonance energy transfer platforms [23,24]. Zinc oxide nanoparticles (ZnO-NPs) are interesting multifunc- tional metal oxides that have a variety of applications. ZnO-NPs are polar inorganic crystalline materials with a unique combination of properties, including lack of toxicity, good electrical, optical and piezoelectric behaviors, stability in a hydrogen plasma atmo- sphere, and low cost. ZnO is a well-known semiconductor with a wide direct band gap (3.37 eV) and a large exciton binding energy of 60 meV at room temperature [25]. ZnO-NPs are widely-used in solar cells, as a luminescent, in drug delivery, as an anti-bacterial in the food industry, in electrical and acoustical devices, gas and chemical sensors, coatings, catalysts, micro-lasers, memory arrays and for biomedical applications [25–29]. The present study developed a novel flow-based CL method to detect carvedilol. This method is based on the inhibition effect of carvedilol on CL of luminol catalyzed by ZnO-NPs. It is introduced Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/talanta Talanta http://dx.doi.org/10.1016/j.talanta.2014.06.036 0039-9140/& 2014 Elsevier B.V. All rights reserved. n Corresponding authors. Tel.: þ98 1513822655; fax: þ98 151 3822567. E-mail addresses: pb.biparva@sanru.ac.ir (P. Biparva), abediradm@yahoo.com (S.M. Abedirad). Talanta 130 (2014) 116–121