Analyses for copper

Duplicate samples were processed onshore after a variety of storage procedures. All samples were analysed for copper and iron by GFA-AS. Only samples filtered (< 1 pm), acidified, and stored frozen gave extractable copper and iron results comparable with those for samples extracted immediately after collection. Cold storage with sample acidification in polyethylene containers appeared less satisfactory. Organic extracts from samples processed onboard are best retained in all-Teflon containers pending complete digestion and analysis onshore. Unless clean (ultra-filtered air) conditions can be ensured onboard, the estuarine water samples are best returned in a filtered, acidified, and frozen condition for onshore processing. 

The concentration of copper in the solution should be followed by a rapid, approximate colorimetric procedure until it reaches approximately 17 g. copper per liter. At this point the solution is decanted into a tightly stoppered bottle and stored in the refrigerator pending accurate analyses for copper and ammonia. It will usually be necessary to build up the ammonia content by the introduction of ammonia gas at this point, and a second analysis is often required before final adjustment to the desired concentrations can be made. 

The automated system is controlled by a specially designed programmer which controls the potentiostat, the recorder, two peristaltic pumps, and five solenoid-operated valves which alternately circulate a mercuric nitrate solution, a seawater sample, or a standard solution through the electrode assemblage. Automated analyses for copper, zinc, cadmium, and lead were made on the pier of the Scripps Institution of Oceanography, San Diego, Calif., and aboard ship in Puget Sound, Wash. This report describes the automated system, discusses the performance of the electrode imder continued use, and presents the results obtained in the field. 

Analyses for "copper, cadmium, and lead were carried out continually by DPASV. Zinc determinations were excluded to permit use of a lower electrolysis potential. The samples were analyzed at pH 4.9 by sparging with carbon dioxide. An 8-min. electrolysis at —1.0 V vs. silver/ silver chloride and a 25-mV pulse were used during the Seattle-Saanich portion of the trip (Leg 1) while a 10-min. electrolysis and a 50-mV pulse were used from Saanich to Seattle (Leg 2). Application of the DPASV technique resulted in greater sensitivity and thus shorter plating times for the low levels encountered. It also afforded better resolution for "copper than linear-sweep ASV. It should be pointed out, however, that DPASV does not result in shorter analyses times because the stripping portion of the analysis is very slow. Nevertheless, it is worthwhile to limit the time of electrolysis because this also reduces the concentrations of interfering metals accumulated in the mercury fllm. Under the... 

Starting Materials. Polyethylene, low density (0.92), was obtained from Union Carbide as additive-free pellets. Copper propionate, used only for liquid-phase solubilities, was obtained commercially and used without further purification. All other copper salts were synthesized as follows equal equivalents of Cu(OH)2 CuC03 ( 99+%, ROC/RIC Chemical Corp.) and the appropriate carboxylic acid were stirred in a minimum amount of xylene and heated to 120°C under N2 overnight. After reacting the xylene solution was diluted with additional xylene, reheated, and filtered hot to remove any copper oxides and/or carbonates. The xylene solution was cooled and the resultant precipitate collected by suction filtration and washed with additional xylene and then hexane. Additional recrystallization was done from hexane, isooctane, and/or xylene. In the case of the copper octanoate the solubility in xylene was quite high, so minimum amounts were used and recrystallization was done from hexane. Analyses for copper Cu(C7Hi5C02)2,... 

Bruland et al. [122] have shown that seawater samples collected by a variety of clean sampling techniques yielded consistent results for copper, cadmium, zinc, and nickel, which implies that representative uncontaminated samples were obtained. A dithiocarbamate extraction method coupled with atomic absorption spectrometry and flameless graphite furnace electrothermal atomisation is described which is essentially 100% quantitative for each of the four metals studied, has lower blanks and detection Emits, and yields better precision than previously published techniques. A more precise and accurate determination of these metals in seawater at their natural ng/1 concentration levels is therefore possible. Samples analysed by this procedure and by concentration on Chelex 100 showed similar results for cadmium and zinc. Both copper and nickel appeared to be inefficiently removed from seawater by Chelex 100. Comparison of the organic extraction results with other pertinent investigations showed excellent agreement. 

Elemental composition Cu 64.18%, Cl 35.82%. Copper(I) chloride is dissolved in nitric acid, diluted appropriately and analyzed for copper by AA or ICP techniques or determined nondestructively by X-ray techniques (see Copper). For chloride analysis, a small amount of powdered material is dissolved in water and the aqueous solution titrated against a standard solution of silver nitrate using potassium chromate indicator. Alternatively, chloride ion in aqueous solution may be analyzed by ion chromatography or chloride ion-selective electrode. Although the compound is only sparingly soluble in water, detection limits in these analyses are in low ppm levels, and, therefore, dissolving 100 mg in a liter of water should be adequate to carry out aU analyses. 

Conditioning of the manganese oxide suspension with each cation was conducted in a thermostatted cell (25° 0.05°C.) described previously (13). Analyses of residual lithium, potassium, sodium, calcium, and barium were obtained by standard flame photometry techniques on a Beckman DU-2 spectrophotometer with flame attachment. Analyses of copper, nickel, and cobalt were conducted on a Sargent Model XR recording polarograph. Samples for analysis were removed upon equilibration of the system, the solid centrifuged off and analytical concentrations determined from calibration curves. In contrast to Morgan and Stumm (10) who report fairly rapid equilibration, final attainment of equilibrium at constant pH, for example, upon addition of metal ions was often very slow, in some cases of the order of several hours. 

To three four-gram subsamples of nine different plant materials were added copper, manganese and zinc at concentrations of 10, 100 and 50 mg/kg, respectively. All samples were subsequently ashed and analysed for these three elements by the method described below. The mean recoveries varied from 96 to 100% for copper, 95 to 101% for manganese and 96 to 99% for zinc (Table 7.8). 

Aliquots of the digest are analysed for aluminium, chromium, iron copper and zinc by direct flame AAS. Together with the samples, blanks and standards covering the range from 0.1 to 30 pg/ml of each of the above metals in 10% sulfuric acid were also run. 

Water is decomposed into hydrogen and oxygen as the net result of the Cu-CI thermochemical cycle. The cycle involves five steps, as listed in Table 1 1) HCl(g) production using equipment such as a fluidised bed 2) oxygen production 3) copper (Cu) production 4) drying 5) hydrogen production. Recent studies by Chukwu, et al. (2008) and Orhan, et al. (2008) have analysed the overall thermal efficiency of the five-step Cu-CI cycle. The efficiency of the cycle versus temperature was analysed for three cases x = 0.2, 0.3 and 0.4, where x refers to the fraction of heat loss to heat input to the cycle. The calculated efficiencies varied from 42 to 55% at 550°C. 

The results of the analyses for the reactions of oxygenates on silica-supported copper suggest that reaction schemes based on reactions occurring... 

The present assumptions are that the coins are reasonably homogeneous, that the melt was reasonably homogeneous, that probably two batches of copper were made each day, and that dies were stored over night in a container of some sort (a strong-box). Table VIII contains the analyses for pairs of coins having double die links. Both obverse and reverse dies are the same in some cases this cannot be determined with certainty since some coins are worn or corroded, and on rare occasion two different dies are nearly the same. In all cases the die orientations of the doubly-die linked pair are the same within experimental error, 30 min. The... 

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