Determination of Chloramphenicol by Voltammetric Method

A new voltammetric method for the determination of chloramphenicol (CAP) is developed. The method is based on the reaction of chloramphenicol and zinc in HCl solution to form a new substance [I] which produced a sensitive oxidation peak at 0.825 V (vs. Ag/AgCl) in pH 7.0 phosphate buffer solutions using differential pulse voltammetry (DPV). There is a linear relationship between the intensity of the peak current and the concentration of CAP. Effects of different chemical and variables such as pH, heating time on the determination of CAP have been optimized. It had been discussed that the electrochemistry characteristic and the reaction mechanism. Calibration graphs were linear in the 0.8 to 30.0 μg mL −1 concentration range with a correlation coefficient of 0.9983. The relative standard deviation for 9 repetitive determinations of 10.0 μg mL −1 CAP was 2.7%. The method has been successfully applied to pharmaceutical formulations and spiked milk samples. © 2014 The Electrochemical Society. [DOI: 10.1149/2.058403jes] All rights reserved. Manuscript submitted October 23, 2013; revised manuscript received December 20, 2013. Published January 4, 2014 Chloramphenicol is a broad-spectrum antibiotic, exhibiting activity against both Gram-positive and Gram-negative bacteria. Owing to its low cost and ready availability, it is extensively used to treat animals, including food-producing animals. However, in certain susceptible individuals, chloramphenicol is associated with serious toxic effects in humans in the form of bone marrow depression, and can be particularly severe in the form of fatal aplastic anemia. 1,2 Hence, its applications in both human and veterinary medicine are restricted. Therefore, specific, economic, and sensitive methods are required in order to effectively monitor the occurrence of residues of CAP. The present methods for the determination of chloramphenicol are thin-layer chromatography, 3 gaschromatography (GC), This paper reports a voltammetric method for estimating the concentration of chloramphenicol, which is based on the reaction of chloramphenicol and zinc in HCl solution to form a new substance [I]. It can produced a sensitive oxidation peak at 0.825 V (vs. Ag/AgCl) in pH 7.0 phosphate buffer solutions using differential pulse voltammetry (DPV). This method is able to detect the quantitative of chloramphenicol. The principal advantages of the method are that it is rapid, sensitive, and possesses good reproducibility. Experimental Reagents.-Chloramphenicol was obtained from the National Institute for the Control of Pharmaceutical and Biological Products (Beijing, China). A 5.0 mg mL −1 stock solution was prepared by dissolving chloramphenicol in 1.0 mL anhydrous ethanol and diluted with water. Working solutions of chloramphenicol were prepared by dilution of the stock solution with water and phosphate buffer solution. Zinc was obtained from Shanghai sulfuric acid plant Shuangliu Industry and Trade Company (Shanghai, China). Five kinds of buffers, HAc-NH 4 Ac buffer, Na 2 HPO 4 -C 6 H 5 O 7 buffer, H 3 BO 3 -Na 3 BO 3 buffer, Tris-HCl buffer and phosphate buffer solution (PBS), were used in the experiments. All other reagents were of analytical grade, and twice-distilled water was used throughout. Apparatus.-Cyclic voltammetric (CV) and differential pulse voltammetric (DPV) experiments were performed with a CHI 760 electrochemical workstation (CH Instrument Company, Shanghai, China). A conventional three-electrode system was adopted. The working electrode was a platinum electrode (3.0 mm in diameter), the auxiliary and reference electrodes were platinum wire and Ag/AgCl electrode, respectively. Absorption spectra were acquired at a 1102 UV spectrofluorimeter (Shanghai Tian Mei Scientific instrument Co,. Ltd, Shanghai). Procedures.-A certain portion of 5.0 mg mL −1 of CAP solution was transferred into a 20.0 mL standard flask, 0.30 g zinc and 5.0 mL of 1.0 mol l −1 HCl solution were added, and diluted to approximately 15.0 mL with water. The mixture was shaken and heated for 60 min in a 90 • C water bath and then cooled in ice water at once, diluted to the mark with water and mixed well. Then the mixture was centrifuged for 5 min at 3000 rpm, so the supernatant was fetched. The prepared [I] used for voltammetric determination of CAP. The chloramphenicolHCl system used for comparison was prepared in the same way by omitting the zinc addition step. Ten microliters 0.10 M phosphate buffer solution (pH 7.0) with certain amount of [I] was transferred into a cell, and then the three-electrode system was immersed in it. The differential pulse voltammetric measurement the voltammogram was recorded from 0.5 to 1.1 V (experiment parameters: Init EV: ) unless CC License in place (see abstrac