M.D. Galindo-Riaño

Bioavailability of heavy metals monitoring water, sediments and fish species from a polluted estuary.

Concentrations of heavy metals (Cu, Zn, Cd, Pb and As) were measured in water, sediment and two fish species, Sparus aurata and Solea senegalensis, from the estuary of Tinto and Odiel rivers in Huelva (Spain), one of the most metallic polluted estuaries in Europe. As a forward step to understand metal bioavailability and assess the potential impact on aquatic biota, a study of heavy metal speciation of sediments and water were achieved. High levels of total and dissolved Zn and Cu were found in water and high pollution of Zn, Pb, As and Cu were found in sediments. Availability of metals was established as following ranking: Cd>Zn>Cu>Pb in both water and sediment. In addition, the effect of this pollution was studied by evaluation of metal bioaccumulations and correlations obtained between metal levels in fractions of water and sediment and metal levels in fish tissues. High Cu and Zn levels were observed in liver tissue of both species, in according with higher total content and more available metals in water and sediment. Correlations among metal content in tissues and different fractions of metal in water for S. aurata and sediment for S. senegalensis were found.

Assessment of the metal pollution, potential toxicity and speciation of sediment from Algeciras Bay (South of Spain) using chemometric tools.

A study to determine total and mobile heavy metals concentrations in sediments from Algeciras Bay was performed and pollution hotspots were identified. The effects on aquatic organisms were established using sediment quality guidelines (SQGs). Ni and Cr exceeded the effect range medium and low levels, respectively, around industrial area. Potential toxicity of metals was determined by diethylenetriaminepenta-acetic acid (DTPA) extractions and low alert levels of Co, Cu, Zn, Cd, Ni and Pb were exceeded at most sampling sites. Three pollution indicators were used showing significant values for As, Ni, Cr, Pb and Cd. Sediment speciation using the sequential extraction BCR procedure was carried out, being Cd, Zn, Pb and As the most available metals. Principal component, cluster and ANOVA analyses were performed in order to assess the sources of metals and the influence of seasonality and anthropogenic activities on the sediment quality. Two principal component analysis (PCA) factors were obtained identifying the sampling sites affected by anthropogenic activities; Ni-Cr and Zn-Cu-V clusters were also obtained associated with stainless steel and petrochemical industrial activities. ANOVA showed the outstanding sites because of total metal concentration and significant differences among sampling sites by the acid extractable and reducible fractions for all metals except for Ba and V.

Biomarkers responses in muscle of Senegal sole (Solea senegalensis) from a heavy metals and PAHs polluted estuary.

The biochemical responses in muscle, such as the enzymatic activities of acetylcholinesterase, lactate dehydrogenase and isocitrate dehydrogenase, were studied in sole (Solea senegalensis) collected in Huelva estuary (SW Spain), in the vicinity of a petrochemical and mining industry. The sampling sites showed different type and degree of pollution. The results demonstrated significant differences in muscle activities of AChE and IDH in Odiel and Tinto Rivers compared to control fish. LDH activity did not show any difference between sampling sites. Significant correlations were established between some biomarkers and heavy metals: AChE was correlated with Pb, Cd and Cu concentrations in water; IDH activity was correlated with Cd and Cu concentrations in water and As, Pb and Cd concentrations in sediments; LDH activity was correlated with As and Zn concentration in water and Cd concentration in sediment. Only one correlation was established between the biomarkers analysed and the concentrations of PAHs: benzo(b)fluoranthene concentration in sediment and IDH.

Selective Chemosensor for Copper Ions Based on Fluorescence Quenching of a Schiff-Base Fluorophore

A Schiff base-based fluorescent chemosensor has been studied for divalent copper detection. The formation of 2-hydroxybenzaldehyde benzoylhydrazone-Cu2+ complex induced a fluorescence quenching of this compound in a medium of water/ethanol (53% v/v) and 0.05 M phosphate buffer (pH 7.0). The continuous variations and mole-ratio plots of absorbance suggested a complex formation with a 1:1 metal-ligand stoichiometry. The conditional stability constant for the complex was evaluated to be 6 × 106 M−1. A modified Stern–Volmer relationship was employed to obtain a linear calibration plot, obtaining a dynamic working range up to 157.4 μM. The detection limit of this system was found to be 5.6 μM and the relative standard deviation for five measurements of 78.7 μM concentration was 5.2%. This fluorescent chemosensor also showed a high selectivity for copper ions over other metal ions, such as Al3+, Ca2+, Cd2+, Fe2+, K+, Mg2+, Na+, Pb2+, or Zn2+. The results of this investigation show a simple, rapid, low-cost, and selective method that can operate in neutral solutions and is useful for biological and environmental applications.

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%).

A permeation liquid membrane system for determination of nickel in seawater

The use of a permeation liquid membrane system for the preconcentration and separation of nickel in natural and sea waters and subsequent determination by atomic absorption spectroscopy is presented. 2-Hydroxybenzaldehyde N-ethylthiosemi-carbazone (2-HBET) in toluene is used as the active component of the liquid membrane. A study strategy based on a simplex design has been followed. Several chemical and physical parameters were optimized. Maximum permeation coefficient was obtained at a feed solution pH of 9.4, 0.3mol l(-1) of HNO(3) in the stripping solution and 1.66mmol l(-1) of 2-HBTE in toluene as carrier. The precision of the method was 4.7% at 95% significance level and a detection limit of 0.012microg l(-1) of nickel was achieved. The preconcentration procedure showed a linear response within the studied concentration range from 3 to 500microg l(-1) of Ni in the feed solution. The method was validated with different spiked synthetic seawater and certified reference water samples: TMDA-62 and LGC 6016, without matrix interferences and showing good concordance with the certified values, being the relative errors -5.9% and -2.2%, respectively. Under optimal conditions, the average preconcentration yield for real seawater samples was 98+/-5%, with a nickel preconcentration factor of 20.83 and metal concentrations ranging between 2.8 and 5.4microg l(-1).

Determination of ultra-trace amounts of silver in water by differential pulse anodic stripping voltammetry using a new modified carbon paste electrode

A highly sensitive and selective new procedure for the determination of silver in aqueous media was developed using a modified carbon paste electrode (MCPE) by differential pulse anodic stripping voltammetry (DPASV). The modified electrode was based on the incorporation of 2-hydroxybenzaldehyde benzoylhydrazone (2-HBBH) in the carbon paste electrode. Silver ions were preconcentrated on the modified electrode at open-circuit by complexation with the ligand and reduced to zero valent at a potential of 0V, and followed by the reoxidation of adsorbed ions onto the electrode by scanning the potential in a positive direction. The oxidation peak of Ag(I) was observed at 0.2V (versus Ag/AgCl). The analysis of Ag(I) was carried out in a cell containing the sample solution (20mL) buffered by 0.1molL(-1) K2HPO4/NaOH at pH 5.5 in aqueous solution and nitric acid (pH 1) in real water samples. The optimum conditions for the analysis of silver include a reduction potential of 0V and a pulse amplitude of 100mV, among others. The optimum carbon paste composition was found to be 14.1% (w/w) 2-HBBH, 56.2% (w/w) graphite powder and 29.7% (w/w) paraffin oil. Differential pulse anodic stripping voltammetric response was used as the analytical signal. Under the selected conditions, the voltammetric signal was proportional to the Ag(I) concentration in the range of 0.001-100μgL(-1) with favorable limits of detection and quantification of 1.1ngL(-1) and 3.7ngL(-1) after 3min of accumulation time, respectively. By increasing the accumulation time to 10min, detection and quantification limits can be further improved up to 0.1ngL(-1) and 0.34ngL(-1), respectively. In addition, the results showed a highly reproducible procedure showing a relative standard deviation of 1.5% for 12 replicate measurements. Many coexisting metal ions were investigated and very few interferences were found on the determination of Ag(I). The proposed method was validated using certified reference estuarine waters (SLEW-3) with a relative error of -1.3% and applied to the determination of silver ions in three river water samples collected from Guadalquivir river (relative errors of +3.4%, +1.5% and -0.7%). Moreover, the method was successfully applied to the speciation analysis of total silver, free silver ions and silver nanoparticles in aqueous solutions. The results were in good agreement with those obtained by inductively coupled plasma mass spectrometry (ICP-MS).

Factorial designs applied to the development of a capillary electrophoresis method for the analysis of zinc, sodium, calcium and magnesium in water samples

The aim of this work was to study the influence of several both chemical and instrumental variables for the development of a new capillary electrophoresis (CE) method for the determination of zinc, sodium, calcium and magnesium in water samples by using 1,10-phenanthroline as complexing agent and UV photometric detection at 214 nm. Due to the number of parameters involved and their interactions, factorial experimental designs at two levels have been applied to investigate the influence of several experimental variables (concentration of complexing agent, concentration of a visualisation agent, pH, sample introduction, applied voltage and capillary length) in sets of several capillary electrophoretic responses. The method was applied to the simultaneous determination of Na(I), Ca(II), Mg(II) and Zn(II) in drinking water with satisfactory results and a detection limit of 32 ng ml(-1) for Zn(II) was obtained.

Study of the kinetics of the transport of Cu(II), Cd(II) and Ni(II) ions through a liquid membrane.

The coupled transport of Cu(II), Cd(II) and Ni(II) ions through a bulk liquid membrane (BLM) containing pyridine-2-acetaldehyde benzoylhydrazone (2-APBH) as carrier dissolved in toluene has been studied. Once the optimal conditions of extraction of each metal were established, a comparative study of the transport kinetics for these metals was performed by means of a kinetic model involving two consecutive irreversible first-order reactions. The kinetic parameters (apparent rate constants of the metal extraction and re-extraction reactions (k1, k2), the maximum reduced concentration of the metal in the liquid membrane (