Arsenic silver diethyldithiocarbamate

Silver diethyldithiocarbamate [1470-61-7] is a reagent commonly used for the spectrophotometric measurement of arsenic in aqueous samples (51) and for the analysis of antimony (52). Silver iodate is used in the determination of chloride in biological samples such as blood (53). 

Arsenic. Total arsenic concentration can be determined by reduction of all forms to arsine (AsH ) and collection of the arsine in a pyridine solution of silver diethyldithiocarbamate. Organoarsenides must be digested in acidic potassium persulfate prior to reduction. The complex that forms is deep red, and this color can be measured spectrophotometricaHy. Reduction is carried out in an acidic solution of KI—SnCl2, and AsH is generated by addition of 2inc. 

Merry and Zarcinas [33] have described a silver diethyldithiocarbamate method for the determination of arsenic and antimony in soil. The method involves the addition of sodium tetrahydroborate to an acid-digested sample which has been treated with hydroxylammonium chloride to prevent the formation of insoluble antimony compounds. The generated arsine and stib-ine react with a solution of silver diethyldithiocarbamate in pyridine in a gas washtube. Absorbance is measured twice at wavelengths of 600 and 504 nm. 

In a further method the sample is heated in a sealed tube for 5 min with a mixture (3 + 1) of magnesium and magnesium oxide, which converts all the arsenic into magnesium arsenide On decomposition by dilute sulphuric acid, arsine is evolved and is absorbed in a 0.5% solution of silver diethyldithiocarbamate (AgDDC) in pyridine. The colour produced has an absorption maximum at 560 nm and is proportional to concentration up to 20 fig of arsenic in 3 ml of solution. Alternatively, the arsine is oxidized by bromine and determined iodimetrically. 

TABLE 1. Recovery of arsenic employing wet digestion with 5 ml of 30% hydrogen peroxide and 5 ml of sulphuric acid with analyses by silver diethyldithiocarbamate and atomic absorption ... 

The hydrogen peroxide-sulphuric acid digestion seemed to provide the most consistent and complete recoveries of any of the wet digestive procedures examined, and coupled with the silver diethyldithiocarbamate colorimetric analysis resulted in quantitative arsenic recoveries from waste water samples. 

A 25-mL solution containing 500 ppb of arsenic (Ag3+) was stirred with 1 g of borohydride-form A-26 anion-exchange resin. The reaction vessel was connected to an absorption tube filled with a solution to absorb the volatile hydride of arsenic (i.e., arsine, AsH3). The absorption solution is made by dissolving 1 g of silver diethyldithiocarbamate (SDDC) in 200 mL of pyridine. The volatile arsine is complexed with the SDDC solution to give a colored solution, whose absorbance is... 

Gravimetric methods and chemical methods, such as colorimetric measurements based on the arsenic-molybdenum blue complex (1,2,3) and arsine generation in combination with silver diethyldithiocarbamate (4, 5, 6,7), have been used to measure arsenic in aqueous media. Various instrumental methods such as differential pulse polarography (8), heated vaporization atomic absorption (9), arsine generation in combination with atomic absorption spectroscopy (10, 11, 12) or non-dispersive atomic fluorescence spectroscopy (13), and optical emission spectroscopy (14) can be used to determine arsenic in aqueous solutions. 

Spectrophotometric determination. The airborne aerosol is filtered and after the filter mineralization, arsenic compounds are reduced with zinc in HCl medium to arsine. Arsine with a solution of silver diethyldithiocarbamate in pyridine yields a red colour, which is suitable for spectrophotometric determination. The measurement is made at 540 nm [26]. 

Figure 2. Annual average daily intake of arsenic (as As Os) in the US. total diet as a function of the method of analysis Mo blue = molybdenum blue method AgDDC = silver diethyldithiocarbamate method A A hydride = arsine evolution, atomic absorption determination.

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. 

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