Of pyrocatechol violet

The selective determination of Cu(II) was accomplished by making use of pyrocatechol violet indicator, dissolved in plasticized PVC membrane as a... 

Figure 19. Chemical structure of pyrocatechol violet (1) and the pyrocatechol violet-tetraoctylammonium ion pair (2).

Aluminium Extraction of pyrocatechol violet complex with chloroform Spectrophotometry at 590 nm < 0.1 xg/l [26]... 

In addition to the above method, based on the use of pyrocatechol violet, Tecator also describes a flow injection analysis for determining 0.5-0.5mg/l aluminium in soil extracts based on the measurement of the chromazurol-aluminium complex at 570 nm [4,5]. 

Colour Test. Add 1 drop of sulphuric acid to a small amount of solid, then add a trace of pyrocatechol—violet-red. 

Aluminium was determined, with the use of Pyrocatechol Violet, in water and soil [103,104], minerals [33], silica [105], steel and copper alloys [34], molybdenum and tungsten [11]. The FIA technique was applied for determining Al in natural waters [106,107]. 

Fig. 27.1. Absorption spectra of Pyrocatechol Violet (PV) vs. water (1), Pb-PV complex vs. the reagent solution (2), and Pb-PV-CP complex vs. the reagent solution (3)...

Another spectrophotometric flow injection method for the determination of I- and based on the catalytic effect of this ion on the oxidation of pyrocatechol violet by potassium persulphate has been developed. The method allows the determination of 0.5-5 mg/11- at a rate of 60 samples per hour and is subject to very little interference. It was successfully applied to the determination of iodide in table salt (Cerda et al., 1993). 

An outer-sphere mechanism for the oxidation of pyrocatechol violet by C10 ion in HCl was suggested. The reaction is first order in both oxidant and substrate and follows acid-independent and acid-dependent paths via C10 and HC10 , respectively. The second-order rate constant decreases with increasing ionic strength. ... 

Anslyn has also prepared more elaborate C3 symmetric tri-podal boronic acid receptors. The binding of heparin and 190, is monitored through displacement of pyrocatechol violet. " The observed stability constant (.Kobs) for 190 was 3.8 X 10" M for unfractionated heparin (UFH) in water at pH 7.4 (HEPES buffer). 

WOl inhibit the reaction. In contrast, however, WO promotes the decomposition of H2O2 alone. The oxidation of pyrocatechol violet in the presence of amino-acid complexes of copper(n) has been suggested as a means of determining ultramicroquantities of amino-acids e.g. in the presence of glycine the 1 1 complex acts as a catalyst, the pH-dependent reaction in borate buffer obeying the rate law (PV = pyrocatechol violet)... 

Ni indirattri as ellicient as pyrocatechol violet T.A.R. cxlraclion of variadiiiin... 

Pyrocatechol Violet Indicator Solution. Dissolve 0.1 g of the solid dyestuff in 100 mL of water. 

Solvent extraction techniques are useful in the quantitative analysis of niobium. The fluoro complexes are amenable to extraction by a wide variety of ketones. Some of the water-insoluble complexes with organic precipitants are extractable by organic solvents and colorimetry is performed on the extract. An example is the extraction of the niobium—oxine complex with chloroform (41). The extraction of the niobium—pyrocatechol violet complex with tridodecylethylammonium bromide and the extraction of niobium—pyrocatechol—sparteine complex with chloroform are examples of extractions of water-soluble complexes. Colorimetry is performed on the extract (42,43). Colorimetry may also be performed directly on the water-soluble complex, eg, using ascorbic acid and 5-nitrosahcyhc acid (44,45). 

The results of the complexation study of Cu(II), Pb(II), Zn(II), Fe(III), Hg(II), Cd(II), Sn(IV), Zr(IV), Ti(IV) with arsenazo III, sulfonazo III, SPADNS, Eriochrome T, Acid Chrome Dai k Blue, Xylenol Orange, Methyl Thymol Blue, Pyrocatechol Violet, Chrome Azurol S, Eriochrome Cyanin R, Basic Blue K, Methyl Violet, Brilliant Green, Rhodamine C and Astraphoxin in solid phase. The obtained data ai e used for the working out of a new method of metal determination. 

Pyrocatechol violet forms colored complexes with a variety of metal ions, the complexes are stable in differing pH ranges. 

PVC (200 mg) was dissolved in 20 mL THF and precipitated with 50 mL EtOH. Several drops of 0.1 % pyrocatechol violet solution were added to the heated filtrate until a blue colour appeared. This solution was titrated with 0.001 M EDTA until the change via green to yellow. In the presence of Mg, Ca, and Zn, Eriochrome Black was added before titration. 

Murkovic Steinberg I., Lobnik A., Wolfbeis O.S., Characterisation of an optical sensor membrane based on the metal ion indicator Pyrocatechol Violet, Sensors Actuators B. 2003 90 (1-3) 230-235. 

Korenaga et al. [26] have described an extraction procedure for the spectrophotometric determination of trace amounts of aluminium in seawater with pyrocatechol violet. The extraction of ion-associate between the alu-minium/pyrocatechol violet complex and the quaternary ammonium salt,... 

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. 

The complex of Sn(IV) ions and pyrocatechol violet (2) in a flow system is concentrated on Sephadex QAE A-25 gel and subsequently determined by visible spectrophotometry at 576 nm. The linear range of the method is 2-40 pg/L with LOD 0.3 pg/L27a. 

The metal may he analyzed hy atomic absorption or emission spectrophotometry (at trace levels). Other techniques include X-ray diffraction, neutron activation analysis, and various colorimetric methods. Aluminum digested with nitric acid reacts with pyrocatechol violet or Eriochrome cyanide R dye to form a colored complex, the absorbance of which may be measured by a spectrophotometer at 535 nm. 

International Standard Organization. 1994. Water quality. Determination of aluminium. Spectrometric method using pyrocatechol violet. ISO 10566. International Organization for Standardization, Case Postale 56, CH-1211, Geneva 20 Switzerland. 

Fig. 14 a. Schematic arrangement for Flow Injection Analysis for a simple spectrophotometric determination, b A typical experimental output from such a system, showing lack of carry over even with large samples. (Metal ion Bismuth Reagent Pyrocatechol violet, 5 x 10 3 M pH 2-4 Sample size 200 pi Analysis rate 80 hr-1)... 

Pyrocatechol Violet (formula 4.16) is a frequently used chelating reagent, readily soluble in water and in aqueous ethanol. An aqueous solution of the reagent is yellow (pH 1-8), and the colour of the solution changes to violet with increasing pH as a result of proton dissociation from the hydroxyl groups. Pyrocatechol Violet forms coloured (most often blue) chelates with many metals (e.g., Be, Al, Bi, Co, Cu, Fe, Ga, In, Mn, Pb, V, Zn) in weakly acidic and weakly basic solutions. 

Pyrocatechol Violet (formula 4.16) is a popular reagent for determining aluminium [11,31,33-36]. The value of 8 is 6.3-10 at 580 nm (pH 6.5-7.2) [35]. A relatively small increase in sensitivity is observed in ternary systems with CTA, CP, or poly(vinylbenzyltriphenylphosphonium) chloride [37-39]. The ternary complex with Zephiramine can be extracted into CHCI3 or 1,2-dichloroethane (e 9-10 at 590 nm) [40]. The extractive (xylene) method with the use of tridodecylethylammonium bromide is of very high sensitivity (e = 1.7-10 at 613 nm [41]. Aluminium was also determined by the FIA technique using Pyrocatechol Violet [42]. 

Methods of determining aluminium with the use of Chrome Azurol S, Eriochrome Cyanine R, and Pyrocatechol Violet have been compared [60,61]. 

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