Biomarker responses of Cu-induced toxicity in European seabass Dicentrarchus labrax: Assessing oxidative stress and histopathological alterations.

A comprehensive approach to chemical accumulation and biological effects of short-term Cu exposure in juveniles of European seabass (Dicentrarchus labrax) has been achieved. Fish were exposed to 0.01-10mgL-1 nominal Cu concentrations for 24-96h. Metal concentrations in water and gills, liver, muscle and brain tissues were studied along with oxidative stress biomarkers (superoxide dismutase, catalase, glutathione peroxidase, lipid peroxidation). Induction of oxidative damage was observed in all the organs with differential antioxidant responses; gills appearing as the most sensitive from low environmentally water Cu concentrations as 0.01mgL-1. Histopathological alterations were also observed in liver and gills, even without a significant Cu accumulation. The results show that the combination of oxidative stress parameters, particularly lipid peroxidation and glutathione peroxidase activities, and histopathological alterations provide a good model fish and reliable early biomarkers for monitoring Cu pollution in seawater and might call for the protection agencies to revise the Cu environmental standards.

An efficient approach to designing and optimizing the analysis of Ni(II) by AdCSV in seawater.

A highly sensitive voltammetric method was developed for the determination of nickel in seawater at nanomolar concentrations. The measurement is based on the differential pulse cathodic adsorptive stripping of Ni(II) complexed with pyridoxal salicyloylhydrazone at a hanging mercury drop electrode. Optimal conditions were found following a two-step study strategy based on a Plackett Burman design and subsequently a modified simplex method. They were: deposition potential -0.8 V; deposition time 120 s; differential pulse scan mode; pulse amplitude -0.07 V; pulse time 0.04 s; voltage step 0.017 V; time interval for voltage step 0.05 s; supporting electrolyte ammonium chloride/ammonia (0.08 M, pH=8.9) and concentration of PSH 5.32 × 10(-6)M. The response of the system was found to be linear in a range of Ni concentrations from 0 to 306.7 × 10(-9)M. The detection limit was found to be 0.04 × 10(-9)M of Ni(II). The precision of the method was 1.4% for 3.4×10(-8)M of Ni(II) and 1.48% for the blank at a significance level of 95% (n=9). The method was free from interferences of inorganic salts and trace metals at usual concentrations in seawater. The application to seawater was demonstrated by analysis of CRM 505 and LGC 6016 certified reference estuarine water and real seawater samples from Tangier Bay (Morocco).

Sensitive adsorptive stripping voltammetric method for determination of lead in water using multivariate analysis for optimization.

A sensitive adsorptive cathodic stripping voltammetric (AdCSV) method is presented for direct determination of Pb(II) at nanomolar levels in water based on metal complexation with 2-acetylpyridine salicyloylhydrazone (2-APSH) and subsequent adsorptive deposition onto hanging mercury drop electrode (HMDE). The instrumental and chemical factors were optimized using exploratory (Plackett-Burman) and sequential (Simplex) designs. Under optimal conditions (pH 5.6, -0.552 V for deposition voltage, 0.0083 V for voltage step and 0.87 s for time interval for voltage step) a limit of detection of 0.17 nM was obtained and the relative standard deviation of five measurements of 17.3 nM was 1.20%. The voltammetric responses increased linearly with metal ion concentrations ranging from 2.4 to 145 nM. The method was free from interferences of inorganic salts and trace metals usually present in seawater. The proposed method was successfully validated using certified reference estuarine water (LGC 6016) with relative error of -2.15% and applied to real seawater samples (relative errors of -4.40% and +1.84%).