Zinc detection

Formazan, l-(2-hydroxy-5-suIfophenyl)-3-phenyl-5-(2-carboxyphenyl)-zinc detection, 6, 83 Formazans cobalt complexes dyes, 6, 81 metal complexes bidentate, 6, 78 color photography, 6,111 dyes, 6, 77 tetradentate, 6, 81 tridentate, 6, 79... 

Responses in standard solutions were tested for lead, cadmium, and zinc (see Fig. 7.5). The results obtained show well-defined and single peaks for all of the metals. Sharper peaks were obtained for lead and cadmium compared to zinc. Detection limits of 23.1, 2.2, and 600 pgL-1 were estimated for lead, cadmium, and zinc, respectively, based on the signal-to-noise characteristics of these data (S/N = 3). The reproducibility of the Bi-GECE was also tested and found to be 2.99%, 1.56%, and 2.19% for lead, cadmium, and zinc, respectively. The difference in peak shapes (sharper for lead and cadmium) and in detection limits of these heavy metals can be explained by the binary and multi-component fusing alloys formation of lead and cadmium with bismuth [40]. According to these results, it was deduced that zinc competes with bismuth for the surface site rather than involving an alloy formation with this metal. 

Fig. 4 Depth and time correlated concentration range of detected heavy metals cadmium, nickel, chorme, copper, lead and zinc, detected in a undisturbed sediment core of the Lippe river (Germany).

Formazan, l-(2-hydroxy-5-sulfophenyl)-3-phenyl-5-(2-carhoxyphenyl)-zinc detection, 83 Formazans cobalt complexes dyes, 81... 

Figure 26 Schematic diagram of the excited states deactivation processes on the surfaces of the GSNPs nanoparticles for zinc detection. (Reproduced with permission from Ref. 47. 2008, American Chemical Society.)...

Cobaltic cyanide paper (Rinmnann s test for zinc detection). 

Arsenic present only in traces (in any form) can be detected by reducing it to arsine and then applying tests for the latter. In Marsh s test, dilute sulphuric acid is added dropwise through a thistle funnel to some arsenic-free zinc in a flask hydrogen is evolved and led out of the flask by a horizontal delivery tube. The arsenic-containing compound is then added to the zinc-acid solution, and the delivery tube heated in the middle. If arsenic is present, it is reduced to arsine by the zinc-acid reaction, for example ... 

For Middleton s sodium carbonate-zinc method for the detection of elements, see p. 326. 

The Sodium Carbonate-Zinc Method for Detecting Nitrogen, Halogens and Sulphur in Organic Compounds. 

THE SODIUM CARBONATE - ZINC METHOD FOR THE DETECTION OF NITROGEN, SULPHUR AND HALOGENS IN ORGANIC COMPOUNDS... 

When an organic compound is heated with a mixture of zinc powder and sodium carbonate, the nitrogen and halogens are converted into sodium cyanide and sodium hahdes respectively, and the sulphur into zinc sulphide (insoluble in water). The sodium cyanide and sodium hahdes are extracted with water and detected as in Lassaigne s method, whilst the zinc sulphide in the residue is decomposed with dilute acid and the hydrogen sulphide is identified with sodium plumbite or lead acetate paper. The test for nitrogen is thus not affected by the presence of sulphur this constitutes an advantage of the method. 

Sulphur. Moisten the centre of a filter paper with sodium plumbite solution. Add about 10 ml. of dilute hydrochloric acid to the residue in the dish and immediately cover it with the prepared filter paper. If zinc sulphide is present in the residue, a dark brown stain, visible on the upper surface of the paper, will be obtained frequently the presence of hydrogen sulphide can also be detected by its odour. 

Nitro compounds and their reduction products. Tertiary nitro compounds (these are generally aromatic) are reduced by zinc and ammonium chloride solution to the corresponding hydroxylamines, which may be detected by their reducing action upon an ammoniacal solution of silver nitrate or Tollen s reagent ... 

Mercury Telluride. Compounds of mercury with tellurium have gained importance as semiconductors with appHcations in infrared detection (9) and solar cells (10). The ratio of the components is varied, and other elements such as cadmium, zinc, and indium are added to modify the electronic characteristics. 

Analysis of zinc solutions at the purification stage before electrolysis is critical and several metals present in low concentrations are monitored carefully. Methods vary from plant to plant but are highly specific and usually capable of detecting 0.1 ppm or less. Colorimetric process-control methods are used for cobalt, antimony, and germanium, turbidimetric methods for cadmium and copper. Alternatively, cadmium, cobalt, and copper are determined polarographicaHy, arsenic and antimony by a modified Gutzeit test, and nickel with a dimethylglyoxime spot test. 

Finished zinc and zinc aHoys are usuaHy analyzed for metals other than zinc by emission spectroscopy and the zinc determined by difference. ASTM method E 27 describes a technique using a dissolved sample and photographic detection. The internal standard is the zinc line at 267.0 nm. However, procedures using soHd samples are generaHy preferred and photoelectric detection often replaces optical detection. Samples are cast and machined on the surface where the arc is stmck. Up to 15 elements can be determined in a few minutes by modem automatic spectrometers. ASTM gives wet chemical methods for metals other than zinc (79). 

Although the most sensitive line for cadmium in the arc or spark spectmm is at 228.8 nm, the line at 326.1 nm is more convenient to use for spectroscopic detection. The limit of detection at this wavelength amounts to 0.001% cadmium with ordinary techniques and 0.00001% using specialized methods. Determination in concentrations up to 10% is accompHshed by solubilization of the sample followed by atomic absorption measurement. The range can be extended to still higher cadmium levels provided that a relative error of 0.5% is acceptable. Another quantitative analysis method is by titration at pH 10 with a standard solution of ethylenediarninetetraacetic acid (EDTA) and Eriochrome Black T indicator. Zinc interferes and therefore must first be removed. 

Simultaneous detenuination of Cu and Zn in the form of coloured PAR complexes is performed at pH 10 in the presence of pyrophosphate which binds the admixtures of Al, Fe and Mn into the inactive complexes. The measurements of the change in the optical density are made at 520 and 550 nm before and after the destmction of the complexes by EDTA, or at 530 nm before and after the destruction of the copper complexes by the thioglycolic acid and the destmction of the zinc complexes by EDTA. The detection limit for Cu is 2-5, for Zn - 3 p.g/diW. The application of these methodics at pH 8 enables one to determine simultaneously Cu and Zn at high excess of the latter. 

This procedure was tested in the analysis of pharmaceutical products Poltava s bishofite (series Elite and Profi ) and a brine of bischofite with rusty precipitate. The data bear out the sufficient accuracy and reproducibility of the proposed procedure which allows to perform the determination magnesium, iron, copper and zinc ions at concentrations above 10 M. It was found that the content of Mg ion in the studied brine decreases in comparison with Poltava s bishofite . The Fe, Cu and Zn ions were not detected in the brine. 

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