In this work a new, simple, fast, and efficient electrochemical approach for the determination of inorganic mercury (Hg2+) using the differential pulse anodic stripping voltammetry (DPASV) technique was presented. This is achieved by modifying the surface of a carbon paste electrode by electropolymerization of Eriochrome blue black R. First, the behavior of Hg2+ on the modified electrode is studied by cyclic voltammetry and electrochemical impedance spectroscopy, to evaluate performance and understand the phenomena that take place on its surface. DPASV is then used to optimize the sensor in HClO4 medium. After optimization, a linear calibration graph was obtained in the concentration range of 1x10-9 to 9x10-9 mol.L-1 with correlation coefficient R2= 0.9975%, the limit of detection (LOD) and the limit of quantification (LOQ) obtained are respectively 3.23x10-10 mol.L-1 and 1.07x10-9 mol.L-1. The relative standard deviation (RSD) for 7 measurements is 3.07%, which proves that this sensor is reproducible. Finally, this method has been successfully applied in real samples of water and the results obtained are satisfactory because the recovery rates of Hg2+ vary from 99.2 to 100.1%.

In recent years, sachet water known as "pure water" has gained the confidence of the Nigerien public because of its low price, availability, convenience, and quality perception by consumers. This study highlights the impact of storage on the quality of pure water sold in Niamey. Thus, eleven of the twelve analyzed physicochemical parameters have been monitored during six weeks of "pure water" storage in the sun and at laboratory ambient temperature. From the results obtained, the physicochemical parameters are in norms except the turbidity and the residual chlorine. On the Bacteriological plan, the total germs, the salmonellae, the fecal streptococci and the Escherichia coli have been identified. In addition, the monitoring of the evolution of the parameters analyzed during six weeks of storage revealed a change of the organoleptic quality that appears in the fourth week and a development of Escherichia Coli for the "pure water" exposed in the sun. This study showed, on the one hand, that these "pure water" would be unfit to the human consumption and on the other hand, their storage for a prolonged period and a high temperature affects their qualities. Les eaux conditionnées en sachet plastique, communément appelées "pure water", ont depuis quelques années, gagné la confiance du public nigérien en raison de leur faible prix, leur disponibilité, la commodité, et de la perception de qualité par les consommateurs. Ce travail étudie l’impact du stockage sur la qualité des "pure water" vendues à Niamey. Ainsi, onze parmi les douze paramètres physico-chimiques analysés ont été suivis pendant six semaines de stockage des "pure water" au soleil et à la température ambiante de laboratoire. A l’issue des résultats obtenus, les paramètres physico-chimiques sont dans les normes hormis la turbidité et le chlore résiduel. Sur le plan bactériologique, les germes totaux, les salmonelles, les streptocoques fécaux et les Escherichia colis ont été identifiés. Par ailleurs, le suivi de l’évolution des paramètres analysés pendant six semaines de stockage a révélé une altération de la qualité organoleptique qui se manifeste à la quatrième semaine et un développement des Escherichia colis pour les "pure water" exposées au soleil. Cette étude a montré, d’une part, que ces "pure water" seraient impropres à la consommation humaine et d’autre part, leur stockage pendant une période prolongée et une température élevée affecte leurs qualités.