Complexes, measurement with electrodes copper

In 1932, Jannik Bjerrums) started work on ammonia complexes of copper(l) and Cu(II). Some of the results were obtained with more direct techniques, such as measurement of the ammonia vapour pressure over the solution, or solubility of weakly soluble salts in various supernatant solutions. However, most of the work involved determination of the free concentration of ammonia [NH3 ] via measurements with a glass electrode of... 

In the early 1970s, Zitko et al. (1973) noted that HAs reduced the activity of the free Cu " ion, as measured by the copper ion-selective electrode, and that this effect was quite well correlated with the observed toxicity of Cu(II) to salmon. Soon thereafter, Pagenkopf et al. (1974) also reported on the effect of complexation on the toxicity of copper to fishes. Sunda and Guillard (1976) demonstrated that the activity of the free Cu " ion in synthetic growth media containing the metal complexing agent TRIS (2-amino-2-hydroxy-methyl-1,3-propanediol) was an excellent... 

Recently, Feldmann and Melroy [131] utilized a quartz microbalance technique to simultaneously determine the net current and the partial anodic and cathodic currents in a single complete electroless copper bath. The cathodic current is calculated by converting the deposition rate measured with the microbalance into the unit of current, while the anodic current is computed by subtracting the cathodic current from the net current measured directly on the microbalance electrode. Using this technique, Feldmann and Melroy showed that the potential at which the reduction of the Cu-EDTA complex begins at 70 °C shifts by as much as 0.3 V in positive direction upon addition of formaldehyde. It was also shown that at a given potential, the rate of copper deposition increases with increasing formaldehyde concentration (Fig. 23). The observed catalytic effect of formaldehyde is attributed to an interaction between formaldehyde and the Cu-EDTA complex, possibly to the formation of Cu(EDTA)/formaldehyde complex. However, the detailed mechanism of this catalytic effect has not been clarified. 

Table 13.2 shows the concentrations of Cu2+ in tap water and lake water determined by the MPA-Gly-Gly-His modified electrode and compared with those of inductively coupled plasma mass spectrometry (ICP-MS). The measured concentration of Cu2+ in tap water when dilutions were accounted for using the MPA-Gly-Gly-His modified electrode was 0.55 +0.08 pM (95% confidence interval). This value is much lower than the copper concentration measured by ICP-MS of 1.70+0.15 pM (95% confidence interval). The peptide-modified electrode measures free Cu2+ or weakly bound copper complexes rather than the total metal-ion concentration measured by ICP-MS. Hence the use of peptides has the ability to measure metal-ion bioavailability for specific species. The results are consistent with others who have also shown that the labile fraction of copper is much less than the total copper [7]. 

Bresnahan, W.T., Grant, C.L. and Weber, 3.H., 1978. Stability constants for the complexation of copper (II) ions with water and soil fulvic acids measured by an ion selective electrode. Anal. Chem., 50 1675-1679. 

Buffle, 3., Greter, F.L. and Haerdi, W., 1977. Measurement of complexation properties of humic and fulvic acids in natural waters with lead and copper ion selective electrodes. Anal. Chem., 49 216-222. 

The fluorescence properties of two fulvic acids, one derived from the soil and the other from river water, were studied. The maximum emission intensity occurred at 445-450 nm upon excitation at 350 nm, and the intensity varied with pH, reaching a maximum at pH 5.0 and decreasing rapidly as the pH dropped below 4. Neither oxygen nor electrolyte concentration affected the fluorescence of the fulvic acid derived from the soil. Complexes of fulvic acid with copper, lead, cobalt, nickel and manganese were examined and it was found that bound copper II ions quench fulvic acid fluorescence. Ion-selective electrode potentiometry was used to demonstrate the close relationship between fluorescence quenching and fulvic acid complexation of cupric ions. It is suggested that fluorescence and ion-selective electrode analysis may not be measuring the same complexation phenomenon in the cases of nickel and cobalt complexes with fulvic acid. 

The first quantitative measurements on copper(I)-ethylene and -actylene complexes were made by Temkin etal. The reaction was followed by observing changes in potential of a copper electrode with changes in the equilibrium due to the introduction of the unsaturated hydrocarbon. 

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