Diethyldithiocarbamate extraction

Water (alkyl lead) Complexation of sample with diethyldithiocarbamate extraction with pentane removal of water butylation extraction with nonane GC/AAS 1.25 ng/L 90-108 Chakra borti et al. 1984... 

Human whole blood Treatment of sample with dilute hydrochloric acid addition of a pH buffer and a complexing agent (diethyldithiocarbamate) extraction of mercury species into toluene ETAAS 2 g/dm3 >94% Emteborg et al. 1992... 

Approximately 75 ml solution was used for the analysis. Buffering was performed with ammonium citrate at pH 9, followed by addition of 0.5 ml of 0.25 mol 1 diethyldithiocarbamate. Extraction was carried out with 5 ml pentane. The extract was dried with Na2S04, evaporated to 0.5 ml and redissolved into hexane. Derivatization involved the addition of 0.5 ml of 2mol BuMgCl in THE, followed by addition of H2SO4.Separation was by CGC (fused-silica column of 60 m length. 

Colorimetric procedures are often used to determine copper in trace amounts. Extraction of copper using diethyldithiocarbamate can be quite selective (60,62), but the method using dithhone is preferred because of its greater sensitivity and selectivity (50—52). Atomic absorption spectroscopy, atomic emission spectroscopy, x-ray fluorescence, and polargraphy are specific and sensitive methods for the deterrnination of trace level copper. 

Sodium diethyldithiocarbamate, (C2H5)2N CS S Na+. This reagent is generally used as a 2 per cent aqueous solution it decomposes rapidly in solutions of low pH. It is an effective extraction reagent for over 20 metals into various organic solvents, such as chloroform, carbon tetrachloride, and ethanol. The selectivity is enhanced by the control of pH and the addition of masking agents. 

Multi-element analyses involving solvent extraction and high performance liquid chromatography (HPLC) have also been described. The extracts, containing metal-chelate complexes with sulphur-containing reagents, such as dithizone and diethyldithiocarbamate, were used directly for determination of the metals by HPLC.14... 

Discussion. Sodium diethyldithiocarbamate (B) reacts with a weakly acidic or ammoniacal solution of copper(II) in low concentration to produce a brown colloidal suspension of the copper(II) diethyldithiocarbamate. The suspension may be extracted with an organic solvent (chloroform, carbon tetrachloride or butyl acetate) and the coloured extract analysed spectrophotometrically at 560 nm (butyl acetate) or 435 nm (chloroform or carbon tetrachloride). 

The following procedure has been recommended by the Analytical Methods Committee of the Society for Analytical Chemistry for the determination of small amounts of arsenic in organic matter.20 Organic matter is destroyed by wet oxidation, and the arsenic, after extraction with diethylammonium diethyldithiocarbamate in chloroform, is converted into the arsenomolybdate complex the latter is reduced by means of hydrazinium sulphate to a molybdenum blue complex and determined spectrophotometrically at 840 nm and referred to a calibration graph in the usual manner. 

If copper is known to be absent or present only in negligible proportions, dilute the solution with water to 50 mL in a graduated flask, and continue as detailed below. Otherwise, transfer the solution to a small separatory funnel and add 5 mL of the diethylammonium diethyldithiocarbamate in chloroform reagent (diluted 1 20 with chloroform when required). Shake and run off the chloroform layer, extract the aqueous layer with successive 1 mL portions of the reagent until the chloroform layer is colourless finally, wash the aqueous layer with a few mL of chloroform. Dilute the aqueous solution with water to 50 mL in a graduated flask. 

Roberts et al. (198 7) and Muller and Campbell (1990) used slightly different methods to extract and purify pholasin. They used lOmM ascorbate, instead of diethyldithiocarbamate, to inhibit luciferase in the process of extraction and purification, which enabled them to obtain the purified preparations of both pholasin and the luciferase. 

Alternatively, an aqueous solution of sodium diethyldithiocarbamate (3.5%, 2 ml) or freshly prepared solution of dithizone in chloroform (0.1%, 10 ml) was added to sample A. The metal diethyldithiocarbamates (termed sample B) or metal dithizon-ates (termed sample C) thus formed were extracted in chloroform. The volume of chloroform extract was reduced to 1.0 ml. Aliquots (10 pi) each of sample B and sample C were chromatographed on plates coated with 0.25-mm layer of silica gel G using benzene -t methyl isopropylketone (50 1) and toluene -r chloroform (50 1), respectively, as mobile phases. Metal dithizonates were self-detected. The namral colored metal diethyldithiocarbamates were converted into brown spots by spraying... 

Selenium is extracted as diethyldithiocarbamate complex from the solution containing citrate and EDTA [5]. Ohta and Suzuki [6] found that only a few elements, such as copper, bismuth, arsenic, antimony, and tellurium, are also extracted together with selenium. They examined this for effects of hundredfold amounts of elements co-extracted with the selenium diethyldithiocarbamate complex. An appreciable improvement of interferences from diverse elements was observed in the presence of copper. Silver depressed the selenium absorption in the case of atomisation of diethyldithiocarbamate complex, but the interference of silver was suppressed in the presence of copper. The atomisation profile from diethyldithiocarbamate complex was identical with that from selenide. 

Several ions (e.g., manganese, iron (II), iron (III), cobalt, nickel, copper, zinc, cadmium, lead, and uranyl) react with pyrocatechol violet, and to some extent are extracted together with aluminium. The interferences from these ions and other metal ions generally present in seawater could be eliminated by extraction with diethyldithiocarbamate as masking agent. With this agent most of the metal ions except aluminium were extracted into chloroform, and other metal ions did not react in the amounts commonly found in seawater. Levels of aluminium between 6 and 6.3 pg/1 were found in Pacific Ocean and Japan Sea samples by this method. 

A Cis column loaded with sodium diethyldithiocarbamate has been used to extract copper and cadmium from seawater. Detection limits for analysis by graphite furnace atomic absorption spectrometry were 0.024 pg/1 and 0.004 xg/l, respectively [283]. 

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). 

Statham [448] has optimised a procedure based on chelation with ammonium dithiocarbamate and diethylammonium diethyldithiocarbamate for the preconcentration and separation of dissolved manganese from seawater prior to determination by graphite furnace atomic absorption spectrometry. Freon TF was chosen as solvent because it appears to be much less toxic than other commonly used chlorinated solvents, it is virtually odourless, has a very low solubility in seawater, gives a rapid and complete phase separation, and is readily purified. The concentrations of analyte in the back-extracts are determined by graphite furnace atomic absorption spectrometry. This procedure concentrates the trace metals in the seawater by a factor of 67.3. 

In many applications, such as the analysis of mercury in open ocean seawater, where the mercury concentrations can be as small as 10 ng/1 [468,472-476], a preconcentration stage is generally necessary. A preliminary concentration step may separate mercury from interfering substances, and the lowered detection limits attained are most desirable when sample quantity is limited. Concentration of mercury prior to measurement has been commonly achieved either by amalgamation on a noble-metal metal [460,467, 469,472], or by dithizone extraction [462,472,475] or extraction with sodium diethyldithiocarbamate [475]. Preconcentration and separation of mercury has also been accomplished using a cold trap at the temperature of liquid nitrogen. 

To determine 63 Ni in seawater the nickel was adsorbed on to hydrous manganese dioxide and the precipitate dissolved in hydrochloric acid. The nickel was then extracted with diethyldithiocarbamate in chloroform and determined by liquid scintillation counting [527]. 

Chakraborti et al. [665] determined cadmium, cobalt, copper, iron, nickel, and lead in seawater by chelation with diethyldithiocarbamate from a 500 ml sample, extraction into carbon tetrachloride, evaporation to dryness, and redissolution in nitric acid prior to determination by electrothermal atomic absorption spectrometry in amounts ranging from 10 pg (cadmium) to 250 pg (nickel). 

Sugimae [447] developed a method for heavy metals in which they are chelated with diethyldithiocarbamic acid, the chelates are extracted with chloroform, and each chelate decomposed prior to determination. When 1 litre water samples are used, the lowest determinable concentrations are Mn (0.063 pg/1), Zn (0.13 pg/1), Cd (0.25 pg/1), Fe (0.25 pg/1), V (0.38 pg/1), Ni (0.5 pg/1), Cu (0.5 pg/1), and Pb (2.5 pg/1). Above these levels the relative standard deviations are better than 12% for the complete procedure. 

Thallium has been determined in 10 ml of ashed serum or in urine by extracting with sodium diethyldithiocarbamate into MIBK n°). More recently, Savory and co-workers 1131 described a wet digestion procedure for 50 ml of urine or 5 ml of serum in which the thallium is separated by extracting the bromide into ether, evaporating the ether and then taking up in dilute acid for aspiration. As little as 0.1 ppm is determined in urine. Curry et al.114) determined less than 1 ng of thallium in 200 /d of urine by using the tantalum sample boat technique. The sample in the boat is dried by holding the boat 1 cm from the flame and then it is inserted into the flame where it is vaporized. A similar procedure is used for >3 ng of thallium in 50-100/al of blood, except that the blood is preashed with 3 drops of nitric acid. Since the tantalum boat method is susceptible to interelement interferences, the method of standard additions is used for calibration. 

Berman u°) could determine as little as 0.005 ppm cadmium in serum and 0.002 ppm in urine by extracting the cadmium from the digest with lead in sodium diethyldithiocarbamate into MIBK. Torres 112) isolated cadmium from urine by ion exchange chromatography. 

Lobinski et al. [72] optimized conditions for the comprehensive speciation of organotin compounds in soils and sediments. They used capillary gas chromatography coupled to helium microwave induced plasma emission spectrometry to determine mono-, di-, tri- and some tetraalkylated tin compounds. Ionic organotin compounds were extracted with pentane from the sample as the organotin-diethyldithiocarbamate complexes then converted to their pentabromo derivatives prior to gas chromatography. The absolute detection limit was 0.5pg as tin equivalent to 10-30pg kg-1. 

Ion exchange and solvent extraction data indicate that the compound contains one diethyldithiocarbamate ion attached to each polonium atom. It sublimes at about 110°C (81). 

The most versatile reagent of this group is diethyldithiocarbamic acid (40), which forms coloured and extractable complexes with very many metals, selectivity being assured by control of the pH and the presence of masking agents.52 Here again the practical disadvantages stem from the ease of oxidation and many alternate carbamic acids derived from pyrrolidine and other dialkylamines have been studied. 

Smith and Lloyd [82] determined chromium(VI) in soil by a method based on complexation with sodium diethyldithiocarbamate in pH 4 buffered medium followed by extraction of the complex with methylisobutylketone and analysis of the extract by atomic absorption spectrometry (Evans R, City Analyst, Dundee, UK, private communication) [86]. Using this method, levels of chromium(V) of between 90 and 176 mg/1 were found in pastureland on which numerous cattle fatalities had occurred. 

A standard official method [6] has been used for the determination of cadmium in plant material. In this method the sample is digested with 1 4 v/v perchloric acidmitric acid at 200 °C and the residue dissolved in hydrochloric acid. Cadmium is then converted to the diethyldithiocarbamate. A chloroform extract of this solution is used for the determination of cadmium at the 228.8 nm emission line. See also Sects. 7.34.1 and 7.34.4. 

The techniques used were based on solvent extraction (e.g. with pentane), complexation (e.g. with diethyldithiocarbamate, EDTA), derivatisation (e.g. hydride generation, propylation or ethylation), and capillary GC separation followed by a range of detection techniques (e.g. QFAAS, ICPMS, MIP-AES, MS) DPASV has also been successfully used. In the frame of this project, two new techniques were also developed and successfully applied, namely supercritical fluid extraction followed by CGC/MS and isotope dilution ICPMS after ethylation and CGC separation. A full description of the techniques is given elsewhere (Quevauviller, 1998b). 

The filtered sample is neutralized with ammonia, and then buffered sodium diethyldithiocarbamate (SDDC) is added. The pH is adjusted to approximately 6, and the sample, in a separatory funnel, is shaken thoroughly. The analyte is then extracted twice with organic solvent. Nitric acid is added to the solvent, and it is evaporated to dryness on a hotplate. The residue is taken up in nitric and hydrochloric acids, and the dissolved residue is analyzed by AAS. It should be noted that the soluble metals are those that pass through the 0.45-pm filter, while total metals do not include those that are so tightly bound into the particles filtered out that they were not solubilized in the slow, mild acid leaching process to which the sample was exposed. For a true total metal analysis, an acid digestion would be required. 

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