Copper in seawater

Copper may exist in particulate, colloidal, and dissolved forms in seawater. In the absence of organic ligands, or particulate and colloidal species, carbonate and hydroxide complexes account for more than 98% of the inorganic copper in seawater [285,286]. The Cu2+ concentration can be calculated if pH, ionic strength, and the necessary stability constants are known [215,265-267]. In most natural systems, the presence of organic materials and sorptive surfaces... 

Ruzic [278 ] considered the theoretical aspects of the direct titration of copper in seawaters and the information this technique provides regarding copper speciation. The method is based on a graph of the ratio between the free and bound metal concentration versus the free metal concentration. The application of this method, which is based on a 1 1 complex formation model, is discussed with respect to trace metal speciation in natural waters. Procedures for interpretation of experimental results are proposed for those cases in which two types of complexes with different conditional stability constants are formed, or om which the metal is adsorbed on colloidal particles. The advantages of the method in comparison with earlier methods are presented theoretically and illustrated with some experiments on copper (II) in seawater. The limitations of the method are also discussed. 

To determine down to 2.4 xmol/l of copper in seawater, Nishoika et al. [282] complexed the copper with di-ethyl-dithio carbamate, precipitated with ferric hydroxide, filtered off and dissolved the precipitate with nitric acid, and determined copper by electrothermal atomic absorption spectrometry. 

Abraham et al. [286] determined total copper in seawater spectrophotometri-cally using quinaldehyde 2-quinolyl-hydrazone as chromogenic reagent. This method is capable of determining copper at the ppb level. 

Garcia-Monco Carra et al. [296] have described a hybrid mercury film electrode for the voltammetric analysis of copper (and lead) in acidified seawater. Mercury plating conditions for preparing a consistently reproducible mercury film electrode on a glassy carbon substrate in acid media are evaluated. It is found that a hybrid electrode , i.e., one preplated with mercury and then replated with mercury in situ with the sample, gives very reproducible results in the analysis of copper in seawater. Consistently reproducible electrode performance allows for the calculation of a cell constant and prediction of the slopes of standard addition plots, useful parameters in the study of copper speciation in seawater. 

A hanging mercury drop electrodeposition technique has been used [297] for a carbon filament flameless atomic absorption spectrometric method for the determination of copper in seawater. In this method, copper is transferred to the mercury drop in a simple three-electrode cell (including a counterelectrode) by electrolysis for 30 min at -0.35 V versus the SCE. After electrolysis, the drop is rinsed and transferred directly to a prepositioned water-cooled carbon-filament atomiser, and the mercury is volatilised by heating the filament to 425 °C. Copper is then atomised and determined by atomic absorption. The detection limit is 0.2 pg copper per litre simulated seawater. 

Isotope dilution mass spectrometry has been used to determine traces of copper in seawater [298,299]. 

Marvin et al. [302] have discussed the effects of sample filtration on the determination of copper in seawater, and concluded that glass filters could seriously affect the reliability of subsequent analysis. 

Potentiometric stripping analysis has been applied by Sheffrin and Williams [320] to the measurement of copper in seawater at environmental pH. The advantage of this technique is that it can be used to specifically measure the biologically active labile copper species in seawater samples at desired pH values. The method was applied to seawater samples that had passed a 0.45 pm Millipore filter. Samples were studied both at high and at low pH values. 

Neutron activation analysis has been used [329] to determine total copper in seawater. 

Cathodic stripping voltammetry has been used to determine copper species in seawater [291,292], Van den Berg [330] determined copper in seawater by cathodic stripping voltammetry of complexes with catechol. 

Because of differing sensitivities and the natural levels of free metal or the anodic scanning voltammetric labile metal, cadmium, and copper in seawater are analysed using a 10 minute plating time, a -1.0V plating potential, and scanning in 6.67 mV/s increments. Zinc determinations can be made on a fresh aliquot of sample to eliminate any possible effects due to Cu-Zn inter-... 

Nygaard et al. [752] compared two methods for the determination of cadmium, lead, and copper in seawater. One method employs anodic stripping voltammetry at controlled pH (8.1,5.3 and 2.0) the other involves sample pretreatment with Chelex 100 resin before ASV analysis. Differences in the results are discussed in terms of the definition of available metal and differences in the analytical methods. 

Jagner et al. [802] used this technique to determine zinc, cadmium, lead, and copper in seawater. Their method includes computer control of the potentiometric stripping technique. They compared their results with those obtained by solvent extraction-AAS and showed that the computer-controlled potentiometric stripping technique is more sensitive, and has advantages over ASV. Computer control makes deoxygenation of the sample unnecessary. 

In seawater, the major chemical species of copper are Cu(OH)Cl and Cu(OH)2 and these account for about 65% of the total copper in seawater (Boyle 1979). The levels of copper hydroxide (Cu(OH)2) increase from about 18% of the total copper at pH 7.0 to 90% at pH 8.6 copper carbonate (CuC03) dropped from 30% at pH 7.0 to less than 0.1% at pH 8.6 (USEPA 1980). The dominant copper species in seawater over the entire ambient pH range are copper hydroxide, copper carbonate, and cupric ion (USEPA 1980). Bioavailability and toxicity of copper in marine ecosystems is promoted by oxine and other lipid soluble synthetic organic chelators (Bryan and Langston 1992). 

C. Mendiguchia, C. Moreno and M. Garcia-Vargas, Determination of copper in seawater based on a liquid membrane preconcentration system. Anal. Chim. Acta, 460(1), 2002, 35-40. 

Predominant species (> 10 %) of cadmium, zinc, lead and copper in seawater. 

Slowey, J.F., Jeffrey, L.M. and Hood, D.W. (1967) Evidence for organic complexed copper in seawater. Nature (London), 214, 377-378. 

Lohan, M.C., A.M. Aguilar-Islas, R.R Franks, and K.W. Bruland. 2005. Determination of iron and copper in seawater at pH 1.7 with a new commercially available chelating resin, NTA Superflow. Anal. Chim. Acta 530 121-129. 

A large discrepancy between the two concentration techniques was found for the copper results. The average difference was 72 27 ngl-1. Bruland and Frank analysed the Chelex column effluent by the solvent extraction technique, and found 63 and 135ngl-1 as the copper content for the samples at 25 m and 2500 m, respectively. These values are almost equal to the difference between the Chelex and solvent extraction results. Therefore, they concluded that about 60% of the copper in seawater (unfiltered and unacidified) is not removed by the Chelex technique. As Riley et al. suggested, copper in seawater is not liberated by the Chelex resin because of association with colloids and fine particulates [62]. In order to avoid this error, acidification and heating of seawater is necessary prior to the Chelex treatment. According to the results of Bruland and Franks, acidification and storage followed by solvent extraction appears to be superior to the Chelex resin concentration for the quantitative determination of copper in seawater [15]. Similar problems have been pointed out by Eisner and Mark, Jr. [63] and Florence and Batley [64]. 

In 1977, Mor and Beccaria investigated the roles of alkyl bromides and iodides on the corrosion of copper in seawater (89). They found that alkyl bromides enhanced the corrosion of copper, whereas alkyl iodides inhibited it, perhaps by lowering the pH of the system (59). A wide variety... 

Donat J. R. and van den Berg C. M. G. (1992) A new cathodic stripping voltammetric method for determining organic complexation of copper in seawater. Mar. Chem. 38, 69-90. 

A rapid technique has been developed for quantitatively concentrating several trace metals from aqueous solution. The metals are co-precipitated as dithiocarbamate chelates by adding an excess of another dissolved metal. This technique has been coupled with atomic absorption analysis for the precise determination of nmol/kg quantities of copper in seawater. Radiotracer experiments show that nickel, iron, and cadmium are also co-precipUated by this technique under proper experimental conditions. 

Copper in Seawater. Copper occurs in open-ocean seawater at very low levels, a few nanomoles per kilogram. Accordingly, the precipitation procedure was scaled up to use 4-1. samples. The above procedure was... 

Figure 19. Effect of salinity on the absorbance of 40 fd. of 20 ppb of copper in seawater...

Figure 21, Reproducibility of analysis of copper in seawater, 50 pi. injections of a 40-ppb spiked sample of 35%o salinity (recorder scale expansion, 2X chart speed, 5 mm/min)...

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