Dithiocarbamates ammonium pyrrolidine

Liquid-liquid extractions using ammonium pyrrolidine dithiocarbamate (APDC) as a metal chelating agent are commonly encountered in the analysis of metal ions in aqueous samples. The sample and APDC are mixed together, and the resulting metal-ligand complexes are extracted into methyl isobutyl ketone before analysis. 

Ammonium pyrrolidine dithiocarbamate (APDC). The reagent is a white to pale yellow crystalline substance and is commonly supplied in bottles which contain a piece of ammonium carbonate in a muslin bag. In this form it is stable for at least one year at temperatures below 30 °C, but the finely divided material exposed to the ordinary atmosphere is much less stable. 

Mullins [37] has described a procedure for determining the concentrations of dissolved chromium species in seawater. Chromium (III) and chromium (VI) separated by co-precipitation with hydrated iron (III) oxide and total chromium are determined separately by conversion to chromium (VI), extraction with ammonium pyrrolidine diethyl dithiocarbamate into methyl isobutyl ketone, and determination by AAS. The detection limit is 40 ng/1 chromium. The dissolved chromium not amenable to separation and direct extraction is calculated by difference. In waters investigated, total concentrations were relatively high (1-5 xg/l), with chromium (VI) the predominant species in all areas sampled with one exception, where organically bound chromium was the major species. 

The concentration of copper in the column eluent was determined by flame atomic absorption spectroscopy of samples which were preconcentrated with ammonium pyrrolidine dithiocarbamate (APDC) and methyl isobutyl ketone. The pH of the acidified sample was adjusted to pH 2.5-3.5 using 400 pi 8 M ammonium acetate (Chelex cleaned). 

Moore [355] used the solvent extraction procedure of Danielson et al. [119] to determine iron in frozen seawater. To a 200 ml aliquot of sample was added lml of a solution containing sodium diethyldithiocarbamate (1% w/v) and ammonium pyrrolidine dithiocarbamate (1 % w/v) at pH to 4. The solution was extracted three times with 5 ml volumes of 1,1,2 trichloro-1,2,2 trifluoroethane, and the organic phase evaporated to dryness in a silica vial and treated with 0.1 ml Ultrex hydrogen peroxide (30%) to initiate the decomposition of organic matter present. After an hour or more, 0.5 ml 0.1 M hydrochloric acid was added and the solution irradiated with a 1000 W Hanovia medium pressure mercury vapour discharge tube at a distance of 4 cm for 18 minutes. The iron in the concentrate was then compared with standards in 0.1 M hydrochloric acid using a Perkin-Elmer Model 403 Spectrophotometer fitted with a Perkin-Elmer graphite furnace (HGA 2200). 

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. 

Cadmium, copper, and silver have been determined by an ammonium pyrrolidine dithiocarbamate chelation, followed by a methyl isobutyl ketone extraction of the metal chelate from the aqueous phase [677], and finally followed by graphite furnace atomic absorption spectrometry. The detection limits of this technique for 1% absorption were 0.03 pmol/1 (copper), 2 nmol/1 (cadmium), and 2 nmol/1 (silver). 

Ammonium pyrrolidine dithiocarbamate (APDC) chelate coprecipitation coupled with flameless atomic absorption provides a simple and precise method for the determination of nanomol kg 1 levels of copper, nickel, and cadmium in seawater. With practice, the method is not overly time-consuming. It is reasonable to expect to complete sample concentration in less than 20 min, digestion in about 4 h, and sample preparation in another hour. Atomic absorption time should average about 5 min per element. Excellent results have been obtained on the distribution of nickel and cadmium in the ocean by this technique. 

Antimony Sb(III) and Sb(VI) adsorbed as ammonium pyrrolidine dithiocarbamate complexes onto Cis bonded silica Graphite furnace AAS 0.05 [xg/1 [860]... 

Bismuth Liquid-liquid extraction into xylene as the ammonium pyrrolidine dithiocarbamate complex Electrothermal AAS 0.3 ppt or 0.0005 xg/l [95]... 

Cadmium Extraction of ammonium pyrrolidine dithiocarbamate complex with chloroform AAS 0.0006 xg/l [134,863]... 

Nickel Nickel adsorbed onto poly (triaminophenyl)glyoxal, desorbed with ammonium pyrrolidine dithiocarbamate in MIKB AAS [897]... 

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

Zinc Formation of zinc ammonium pyrrolidine dithiocarbamate complex Cathodic stripping voltammetry [619]... 

Apte and Gunn [23] used liquid-liquid extraction, involving 1 1 1 trichlor-ethane extraction of the ammonium pyrrolidine dithiocarbamates to concentrate copper, nickel, lead, and cadmium from estuary water. (Detection limits... 

Tsunogai and Nozaki [6] analysed Pacific Oceans surface water by consecutive coprecipitations of polonium with calcium carbonate and bismuth oxychloride after addition of lead and bismuth carriers to acidified seawater samples. After concentration, polonium was spontaneously deposited onto silver planchets. Quantitative recoveries of polonium were assumed at the extraction steps and plating step. Shannon et al. [7], who analysed surface water from the Atlantic Ocean near the tip of South Africa, extracted polonium from acidified samples as the ammonium pyrrolidine dithiocarbamate complex into methyl isobutyl ketone. They also autoplated polonium onto silver counting disks. An average efficiency of 92% was assigned to their procedure after calibration with 210Po-210Pb tracer experiments. 

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. 

Graphite furnace atomic absorption spectrophotometry has been used for the determination down to 5 ng/1 inorganic and organic mercury in seawater [61]. The method used a preliminary preconcentration of mercury using the ammonium pyrrolidine dithiocarbamate-chloroform system. A recovery of 85 - 86% of mercury was reproducibly obtained in the first chloroform extract and consequently it was possible to calibrate the method on this basis. A standard deviation of 2.6% was obtained on a seawater sample containing 529 ng/1 mercury. 

Simultaneous speciation of inorganic selenium and tellurium in water samples by ICP-MS was performed after selective solid phase extraction (SPE), as discussed by Yu et al 9 Under acidic conditions Se (IV) and (TV) complexes with ammonium pyrrolidine dithiocarbamate were formed. The detection limits for Se and species in water samples were found to be 7ngl 1 and 3 ng 1 1, respectively. 

Official methods have been published for the determination of nitric-perchloric acid-soluble lead [111] and ammonium pyrrolidine dithiocarbamate-extractable lead [ 112] in soil. Atomic absorption spectrometric evaluations of the digest or extract is conducted at the 217 nm emission line from a lead hollow cathode lamp. Rigin and Rigina [122] determined lead in soil by flameless atomic fluorescence using electrolytic preconcentration. The limit of detection is 15 pg lead and the standard deviation is not greater than 0.04. 

Standard official methods have been described for the determination of nitric-perchloric acid-soluble nickel [174] and acetic acid-extractable nickel [175] in soil. To determine nitric acid-perchloric acid-soluble nickel [174], the acid digest is dissolved in hydrochloric acid and the nickel is determined by atomic absorption spectrometry. To determine extractable nickel, the nickel is first extracted from the soil with 0.5 M acetic acid and the nickel is then converted to the ammonium pyrrolidine dithiocarbamate complex. Extraction of the complex with chloroform provides an extract for the determination of nickel by atomic absorption spectrometry. 

FAAS Metals are determined by FAAS Pb and Cd at low concentrations are chelated (ammonium pyrrolidine dithiocarbamate at pH = 2.5), preconcentrated, and then extracted with methyl isobutyl ketone prior to quantification Applicable to surface and saline waters Ionization interferences are generally removed by the addition of LaCl3 51... 

FAAS Metals are directly determined by FAAS metals are determined after chelation with ammonium pyrrolidine dithiocarbamate and extraction in methyl isobutyl ketone and metals are determined after chelation with hexamethyleneammonium-hexamethylenedithiocarbamate and extraction in di-isopropyl ketone-xylene Applicable to natural waters 103... 

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