Spectrophotometric determination with dithizone

In acid (to almost neutral) solution silver ions react with dithizone 

Since dithizone does not react specifically with silver ions, the influence of interfering accompanying ions must be eliminated by the choice of appropriate test conditions. If extraction of the silver is carried out in acid solution, metal ions which react with the reagent only in neutral or 

Iron (II) ions form a dithizonate under alkaline reaction conditions only. Mercury and copper which are co-extracted in acid solution are separated 

Interference by halide ions is eliminated by treatment with sulphuric acid. 

It should always be noted that the photometric dithizone method is susceptible to interference and that consequently the procedure should be closely 

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Spectrophotometric determination with dithizone General remarks... 

D 2787 24 ca 10 ppm For gas turbine fuel. Digestion with cone. HC1 to PbCl2 spectrophotometric determination of dithizone (2) complex. 

The separation of copper by extraction is usually connected with spectrophotometric determination with the use of dithizone, dithiocarbamates, cuproine and related compounds, as well as other reagents. Sometimes copper is first preconcentrated by extraction as the dithizonate or dithiocarbamate before its determination by other methods [1-3]. Crown ethers [ 1 ] and porphyrin compounds [2] have also been used for extracting Cu(II). 

Spectrophotometric measurements were performed at the same time with an automatic apparatus. The air was filtered through a Whatman No. 1 filter paper and drawn through a series of scrubbers consisting of 0.1% nitric acid. The lead concentration in these solutions is determined with dithizone by means of a spectrophotometer. 

Analysis by GC of the various organolead species present in gasoline requires special detectors because of the profusion of species with retention times near those of the organometaHic compounds. An old determination method consisted of scrubbing the separated species in iodine solution, foHowed by spectrophotometric determination of the complex with dithizone (2)133,134 (see also Table 2). 

Selectivity in spectrophotometric methods for determining metals with dithizone is attained by controlling the acidity of the medium and using masking agents such as cyanide, EDTA, thiosulphate, or iodide. 

The spectrophotometric determination of cadmium in natural waters involving in-line formation of an aqueous dithizone suspension [121] illustrates another application of in-line suspension addition. Solid dithizone reagent was packed in a mini-column through which a surfactant (Triton X-100) stream was allowed to flow. The emerging suspension formed was added by confluence to the main analytical channel of a flow-injection system. With this innovation, good sensitivity was achieved without the need for an analyte separation/concentration LLE step and the entire procedure was carried out in the aqueous phase. 

Silver(I) yields a primary dithizone complex (19 in reaction 1) at low pH, Amax 460 nm, e 30500 (in CCI4)87. This complex in the presence of cetyltrimethylammonium ions has 3-max 565 nm, e 55000 (in H20)99. Instead of densitometry of Ag deposited on X-ray film images and other gel matrices, analysis can be carried out by dissolution with nitric acid, neutralization, LLE with a dithizone solution and spectrophotometric determination X 600 nm, e 32800100. 

A spectrophotometric procedure for the estimation of metallic impurities Pb, Zn and Cu in a wide range of artifical sweeteners, including cyclamate, has been reported165. The Pb and Zn were determined at 525 nm and 540 nm, respectively, by reaction with dithizone. 

Figure 4.29. FIA manifold for the determination of trace metals by solvent extraction with dithizone in carbon tetrachloride. The aqueous sample S is injected into the aqueous carrier stream AQ, to which at (a) the organic phase ORG is continuously added and after passing through the extraction coil (b), made of Teflon tubing, the organic phase is again separated at point (c) and carried on through the flow cell for spectrophotometric measurement.

It has been reported that y3-CD could improve the selectivity of the color reactions of various metal ions with triphenylmethane, xanthene acid dyes and some other coloring reagents. The effect of fi-CD on the association compound system of metal (Mo, Zn, Co)-thiocyanate basic dyes such as malachite green, crystal violet, rhodamine B, rhodamine 6G and butyhhodamine B, has been investigated and the result shows that /3-CD could contribute to a more sensitive and stable system which improve the solubility of the basic dyes and produce a favorable microenviromnent for the color reactions [63]. /3-CD could be employed to solubilize the 1,2-amino anthraquinone in water due to the formation of inclusion complex which acts as a ligand for metal ions could be used for the determination of palladium at trace levels by spectrophotometry. In the spectrophotometric determination of microamounts of Zn based on the Zn-dithizone color reaction, -CD could increase the apparent molar absorptivity at 538 nm by 8.37 times. In the presence of cr-CD, the determination sensitivity of copper in leaves based on the color reaction of Cu(II) and mesotetrakis (4-methoxy-3-sulfophenyl) porphyrin was enhanced by 50% in the spectrophotometric analysis [64,65]. 

In view of the high toxicity of cadmium it is necessary to be able to determine very small concentrations in water. AAS techniques (Sections 3.4.7.1 and 3.4.7.2) are particularly suitable for determining cadmium in water. Where no AAS facilities are available, it is still possible to use the classical spectrophotometric technique (Section 3.4.7.3) with dithizone and extraction in chloroform. 

M.S. Hosseini and H. Hashemi-Moghaddam. Sensitized extraction spectrophotometric determination of Hg(Il) with dithizone after its flotation as ion-associate using iodide and ferroin. 

Spec determination of platinum with Dithizone, by use of an iodide medium in the presence of sulfite at pH = 3 to 5, to separate palladium Extractive separation and spectrophotometric determination of platinum in the presence of stannous chloride to separate palladium... 

Graphite-furnace atomic-absorption spectrophotometric determination of silver on suspended dithizone particles from acidic sample solutions with ultrasonics to facilitate the separation... 

Kimura and Miller and coworkers [5-18] determined low levels of inorganic plus volatile mercury. The soils were digested with sulfuric acid, hydrogen peroxide and potassium permanganate and then mercury swept of this mixture with air into an absorbing solution of potassium permanganate and sulfuric acid. Mercury is then determined in this solution by a dithizone-based spectrophotometric procedure at 605 nm. 

The selectivity of spectrophotometric methods has been greatly increased by the development of derivative spectrophotometry (see Chapter 1.5). Derivative spectrophotometry enables one to single out, by means of various mathematical algorithms of data processing, a separate signal due to a selected component, from the sum of absorbances of the analysed mixture. This technique was successfully applied in determinations of a number of elements in mixtures such as Pd, Pt and Au [37], Pd and Pt in iodide solutions [38], Au, Pd and Pt in bromide solutions [39], Ru(IIl) and Rh(IIl) in the form of octadecyldithiocarbamate complexes [40], Ru and Os in chloride solutions [41], Cu, Hg and Pb as dithizonates [42], complexes of various metals with 4-(2-pyridylazo)resorcinol [43], Fe(IIl) with EDTA in the presence of Cr(III), A1 and Mn [44], Cr(III) and Cu(II) with EDTA [45], and Cu and Co in a flow system [46]. Derivative spectrophotometry was also used in the study of Sr- complexing reactions with various crown ethers [47]. 

Among the many spectrophotometric methods for determining silver, the dithizone method is particularly important. Some newer methods, such as that using thio-Michler s ketone, and methods based on ion-associates with dyes, can be recommended. 

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