No abstract

In this study, four electrodes based on unmodified graphite (G) and graphite modified with iron (II) phthalocyanine (Fe(II)Pc), nickel (II) phthalolocyanine (Ni(II)Pc) and Chitosan from crab shells (Ch) were compared and evaluated for determination of nitrites in different types of water samples using differential pulse anodic voltammetry. For the Ni(II)Pc modified graphite sensor, a high sensitivity (6.62 × 10 −8 A mg L −1 ) and a lower quantification limit (0.0014 mg L −1 ) were obtained in comparison with G (sensitivity of 3.23 × 10 −8 A mg L −1 ; LOD of 0.0040 mg L −1 and LOQ of 0.0046 mg L −1 ) and Fe(II)Pc/G (sensitivity of 3.13 × 10 −8 A mg L −1 ; LOD of 0.0032 mg L −1 and LOQ of 0.0460 mg L −1 ). For the modified graphite microsensor based on Chitosan from crab shells a lower limit of detection (0.0002 mg L −1 ) and a lower limit of quantification (0.0005 mg L −1 ) were obtained. The unmodified graphite microsensor has a detection limit of 0.0040 mg L −1 for nitrite. These microsensors are indeed all suitable and reliable to employ for the assay of nitrite in different types of water samples from aquatic ecosystems in Romania with an RSD less that 0.11%.

In this study, dot microsensors based on graphite/graphene paste modified with iron (II) phthalocyanine, nickel (II) phthalocyanine and 5,10,15,20-tetra(4pyridyl)21H, 23H porphine chloride tetrakis(methochloride) manganese(III) were used for the determination of trace amounts of lead and cadmium from various water catchments areas using differential pulse anodic stripping voltammetry. The response of the proposed dot microsensors were sensitive enough to detect very low levels of both metals ions in drinking water resources to take corrective action for the supply of safe and suitable drinking water. The lowest limits of quantification for lead is 0.00207 µg L −1 and for cadmium 5.6 µg L −1 , with a correlation coefficient (R 2 ) between 0.9951 and 0.9981 for lead, and between 0.9951 and 0.9984 for cadmium. The recovery of Pb(II) and Cd(II) in water samples were higher than 93.06 % with RSD(%) values lower than 0.29%. These results of the proposed dot microsensors compared favorably with the results from a standard ISO certified method.

Three (Z)-5-(azulen-1-ylmethylene)-2-thioxo-thiazolidin-4-ones are electrochemically characterized by cyclic voltammetry, differential pulse voltammetry, and rotating disk electrode voltammetry. The electrochemical investigations revealed that the redox potential is influenced by the number and position of the alkyl groups, and the possible oxidation mechanism is proposed. These compounds, after their immobilization on glassy carbon electrodes during oxidative electropolymerization, were examined as complexing ligands for heavy metal ions from aqueous solutions through adsorptive stripping voltammetry.