# Introduction he gilded staphylococcus(staphylococcus aureus) is the stock of staphylococcus most frequently met in pathology human and veterinary. It shares with the bacterium Escherichia coli the unhappy privilege to be in the forefront of the germs responsible for infection nosocomial (infection contracted at the hospital) [1]. The staphylococcus aureus is pathogenic opportunist which can cause various diseases at the human ones, energy of the affections which evolve spontaneously to the cure with pathologies mortals [2].The food poisoning by the staphylococcus is characterized by a brutal appearance of nauseas, vomiting, abdominal pains, cramps and of diarrhea [2,3]. The food which facilitates the growth of the staphylococcus is mainly pastry makings with the cream, dairy ice creams, the food treated such as hams, the pies and rillette, and tuna and poultry, the potato salads. Cooked products contaminated after cookings (chopped meats, fish, sections of pork-butchery). Products with water content reduced (saltings, fish dried and smoked, dried milk). Cheeses, following an insufficient acidification of curd. Ovoproduits, mayonnaise, dairy products (e.g. condensed milk), creams, ices. The contaminated food has the same aspect (appearance, odor, taste) that the healthy food [4].The placement of detector of this bacterium is essential in order to prevent the risks of contamination. A preliminary work was published on the AMX-NP characteristics as for the detection of the staphylococcus aureus [5].The objective of this work is to make an analytical application of this electrode in potato juice by using the method of the square waves voltammetry. # II. # Experimental a) Reagent Provisions were made for oxygen removal by bubbling the solution with azotes gas for about 5 min then the solution was blanketed with azotes gas while the experiment was in progress. For reproducible results, a fresh solution was made for each experiment. # b) Instrument Voltammetric experiments were performed using a voltalabpotentiostat (modelPGSTAT100, EcoChemie B.V., Utrecht, The Netherlands) driven by the general purpose electrochemical systems data processing software (voltalab master 4 software) run under windows 2007. The three electrode system consisted of a chemically modified carbon paste electrode as the working electrode a saturated calomel electrode (SCE) serving as reference electrode, and platinum as an auxiliary electrode # c) Electrodes The working natural phosphate paste electrode was prepared by mixing appropriate weight of natural phosphate powder with paraffin oil. The whole cell modified natural phosphate paste was subsequently packed firmly into the electrode cavity (0.1256 cm 2 ) and polished to a smooth shiny finish by gently rubbing over an ordinary weighing paper. Electrical contact was established with a bar of carbon. Amoxil-modified natural phosphatepaste electrodes (AMX-NP) were prepared by immobilizing the Amoxil system by soaking the preformed natural phosphate paste electrode in a solution containing the Amoxil solution. The modified natural phosphate paste electrode was immersed in a cell containing bacteria sample to get a chemical accumulation. Meanwhile, the solution was rotated about 600 rpm at open circuit. After a desired contact time, the electrode was removed from the preconcentration cell, rinsed with DW and placed in the measurement cell containing the supporting electrolyte (1.0 mol L ?1 NaCl). The solution was deaerated with nitrogen for 10 min. The voltammetric curve was recorded. The same procedure was carried out in sample analysis and all electrochemical experiments were carried out at room temperature. The square wave voltammograms were recorded in different bacteria concentrations using 5 mV of the pulse amplitude, step potential 50 mV and the duration time is 2 s at scan rate 1 mVs ?1 . # III. # Result and Discussion In order to study the effect of the optical density of the bacterium on the electrode, we made the electrochemical characterization of this one by using the methods of voltammetry square waves. The electrode with natural phosphate paste modified by the amoxicillin with a concentration of 30g/L was characterized in the presence of bacteria with different density optical. In the presence of the bacteria, the electrode displays a significant increase in the density of current. This electrochemical behavior of the electrode is confirmed by the voltammetry square waves. The capacity of detection of the electrode thus increases with the increase in the bacterial load. (figure 1). A study of the influence of the pH on the electrochemical sensor in the presence of the bacteria was made. The electrode showed a good electroactivity in the presence of the bacteria in the acid media, neutral and basic. We thus compared the aforementioned voltammogrammes in order to identify the medium which is most favorable for him. The results are illustrated by (figure 3). Taking into consideration these result, we can say that our electrode presents a better electro activity in acid medium, pH = 4, 22. Under the optimized conditions, the sensor (AMX-Np) was used for the detection of staphylococcus aureus in sample of potato juices which were the subject of no preliminary treatment. The analytical application consisted in adding various quantities of physiological water containing the bacterium in the potato juice in order to vary the optical density and we have each time made an electrochemical characterization by using the voltammetry with square waves. The seresults are presented in table 1. The density of current increases with the evolution of the optical density of the bacteria, measured using a spectrophotometer. Figure 4 shows a typical linear answer, which can be expressed according to the following equation: di = 14,039DO + 1,9863. Taking into consideration these result, it arises that the electrochemical sensor being studied, shows a better SD, LD and LQ in the potato juice. This result comes to confirm the effectiveness of this sensor, considering the potato juice is a hostile environment with the bacteria. Indeed the potato juice contains certain active molecules anti-bacterial in the fight against the bacteria (the helicobacter pylori) responsible for the ulcer of the stomach [ 5 ]. IV. # Conclusion The electrochemical sensor (AMX-Np) is extremely sensitive to the bacterium. The pH has an influence on the electroactivity of this electrode and the acid medium seems more favorable. Also, its duration of detection is satisfactory. The analytical study in a potato juice sample showed good results. # Table 2: Sensibilities of detection (SD), Limitate detection (LD) and limits of quantification (LQ) of the bacterium according to analytical mediums' 1![Figure 1: Superposition of the voltammogrammes with square waves of EPN/AMX ads. to white and EPN/AMX ads. (30g/l) in the presence of the bacteria with various optical densities in NaCl to 0,1 M; v = 100mV/s, of -2V with 2V; pH = 7,42 This sensor was the subject of an electrochemical characterization by the cyclic voltammetry for identifying the duration of detection of the bacterium. Within sight of the results, it arises that](image-2.png "Figure 1 :") 2![Figure 2: Comparison of the voltammogrammes cyclic of AMX-NP ads. with white and the bacteria after 50 cycles in NaCl to 0,1 M; v = 100mV/s, of -2V with 2V; pH = 7,42](image-3.png "Figure 2 :") 3![Figure 3: Superposition of the cyclic voltammogrammes of EPN/AMX ads. to different pH in the presence of the bacteria in NaCl to 0,1 M; v = 100mV/s, of -2V with 2V](image-4.png "Figure 3 :") 14![Figure4shows the variation of the density of current according to the optical density.](image-5.png "Table 1 :Figure 4") d) Analytical procedureYear 20171MotsClés: modified electrodes; SWV; CV; bacteria; electrochemical sensor.( ) Volume XVII Issue IV Version I JJournal of Researches in EngineeringGlobalT © 2017 Global Journals Inc. (US) © 2017 Global Journals Inc. (US) * PRMurray EJBaron JHJorgensen MLLandry MA PFaller RHYolken Manual of Clinical Microbiology Herdon, VA, United States of America American Society for Microbiology 2003 8th ed.) » * YLeLoir FBaron MGautier Staphylococcus aureus and food poisoning 2003 2 * A Natural Phosphate Electrode Modified with Antibiotic for the Detection of Bacteria OfakBertrand BBea NBelkhouya AChtaini J Biosens Bioelectron 7 202 2016