Cobalt-ammonium pyrrolidine

Vanadium Co-precipitation with ferric hydroxide, cobalt ammonium pyrrolidine dithio carbarn ate or ammonium pyrrolidine dithiocarbamate Miscellaneous [920]... 

Van den Berg [620] also reported a direct determination of sub-nanomolar levels of zinc in seawater by cathodic stripping voltammetry. The ability of ammonium pyrrolidine dithiocarbamate to produce a significant reduction peak in the presence of low concentrations of zinc was used to develop a method capable of achieving levels two orders of magnitude below those achieved with anodic stripping voltammetry. Interference from nickel and cobalt ions could be overcome by using a collection potential of 1.3 V, and interference from... 

Cabezon et al. [662] simultaneously separated copper, cadmium, and cobalt from seawater by coflotation with octadecylamine and ferric hydroxide as collectors prior to analysis of these elements by flame atomic absorption spectrometry. The substrates were dissolved in an acidified mixture of ethanol, water, and methyl isobutyl ketone to increase the sensitivity of the determination of these elements by flame atomic absorption spectrophotometry. The results were compared with those of the usual ammonium pyrrolidine dithiocarbamate/methyl isobutyl ketone extraction method. While the mean recoveries were lower, they were nevertheless considered satisfactory. 

Jin [666] used ammonium pyrrolidine dithiocarbamate and electrothermal atomic absorption spectrometry to determine lead, cadmium, copper, cobalt, tin, and molybdenum in seawater. 

The metals were coprecipitated with lead-ammonium pyrrolidine dithio-carbamate and detected by X-ray spectrometry following neutron activation. Magnetic fields deflect the p rays while the X rays reach the silicon (lithium) detector undeviated. The detectors have low sensitivity to y rays. The concentration of cobalt found by this method was 1.3 xg/l, about one-fifth of that measured previously, while that of copper, 2.0 xg/l, agreed with results obtained by some previous workers. The concentration of mercury was 1.2 xg/l. 

Tseng et al. [69] determined 60cobalt in seawater by successive extractions with tris(pyrrolidine dithiocarbamate) bismuth (III) and ammonium pyrrolidine dithiocarbamate and back-extraction with bismuth (III). Filtered seawater adjusted to pH 1.0-1.5 was extracted with chloroform and 0.01 M tris(pyrrolidine dithiocarbamate) bismuth (III) to remove certain metallic contaminants. The aqueous residue was adjusted to pH 4.5 and re-extracted with chloroform and 2% ammonium pyrrolidine thiocarbamate, to remove cobalt. Back-extraction with bismuth (III) solution removed further trace elements. The organic phase was dried under infrared and counted in a ger-manium/lithium detector coupled to a 4096 channel pulse height analyser. Indicated recovery was 96%, and the analysis time excluding counting was 50-min per sample. 

Tris(pyrrolidine dithiocarbamato-)—cobalt(III) chelate, the precipitate formed by adding ammonium pyrrolidine dithiocarbamate to cobalt(II) solutions, has been found to be a good matrix for preconcentrating lead and several other metals by co-precipitation. Concentration factors of 40 to 400 are available by the method. The analyte is co-precipitated on the Co-APDC from a litre of sample. The precipitate is filtered on a fine porosity glass sinter and redissolved in a small volume of 6 M nitric acid. The solution is then used for atomic absorption analysis. 

APHA. 1985f. Determination of low concentrations of cadmium, chromium, cobalt, copper, iron, lead, manganese, nickel, silver, and zinc by chelation with ammonium pyrrolidine dithiocarbamate (APDC) and extraction into methyl isobutyl ketone (MIBK)-method 303B. In Standard methods for the examination of water and wastewater. 16th ed. Washington, DC American Public Health Association, 160-162. 

The detection limits for cobalty nickel, and lead in aqueous solution by atomic absorption are about 50 fig. per liter. Normally these elements occur at lower concentrations in fresh waters, and direct measurement by atomic absorption is not possible. A rapid, simple, accurate, and sensitive chelation-extraction method for determining lead, cobalt, and nickel is attained by chelating the metals with ammonium pyrrolidine dithiocarbamate at a pH of 2.8, extracting the metal-chelates with methyl isobutyl ketone, and aspirating the ketone layer. Results obtained by this method agreed well with results obtained by spectrographic methods. As little as 1 fig. of lead, cobalt, and nickel per liter can be detected. This is at least one order of magnitude lower than most other wet chemical procedures. 

Several methods have been reported for concentrating lead, cobalt, and nickel in blood, urine, brines, and water prior to final determination by atomic absorption. Sprague and Slavin (6) described a procedure for determining these elements plus copper, cadmium, iron, and manganese in concentrated potassium chloride solutions. The metals were chelated with ammonium pyrrolidine dithiocarbamate (APDC) and extracted with methyl isobutyl ketone (MIBK). It was reported that the optimum pH for the extraction was approximately 2.8. Berman (J) described a similar chelation-extraction procedure for determining lead in urine and blood. Burrell (2) developed a procedure for determining cobalt and nickel in natural waters by atomic absorption in which both metals are first coprecipitated with ferric chloride from ten liters of water. The separated precipitate is subsequently dissolved and made up to 100 ml. volume with hydrochloric acid and water so that the final pH of the solution is 2.5. The nickel and cobalt are then chelated with APDC and extracted with three 10 ml. volumes of MIBK. Three extractions are necessary to achieve complete recovery of the chelated cations. A detection limit of 0.3 fig. of nickel per liter and 0.15 fig. of cobalt per liter was found. 

Berndt et al. [740] have shown that traces of bismuth, cadmium, copper, cobalt, indium, nickel, lead, thallium, and zinc could be separated from samples of seawater, mineral water, and drinking water by complexation with the ammonium salt of pyrrolidine- 1-dithiocarboxylic acid, followed by filtration through a filter covered with a layer of active carbon. Sample volumes could range from 100 ml to 10 litres. The elements were dissolved in nitric acid and then determined by atomic absorption or inductively coupled plasma optical emission spectrometry. 

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