Eriochrome cyanine

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. 

Reagents. Eriochrome cyanine R solution. Dissolve 0.1 g of the solid reagent in water, dilute to 100 mL, and filter through a Whatman No. 541 filter paper if necessary. This solution should be prepared daily. 

Solder analysis of by EDTA, (ti) 337 Solochrome black 317, 692 Solochrome (Eriochrome) cyanine R 678 Solochrome dark blue 318 Solubility product 24 calculations involving, 25 importance of, 26 principal limitations of, 24 Solution of sample 110 Solvents amphiprotic, 282 aprotic, 282 ionising, 18 non-protonic, 18 protogenic, 18, 282 protophilic, 282... 

Erbium, tris(2,2,6,6-tetrametbyl-3,5-hep tanedione) structure, 1, 65, 66 Erbium complexes acetylacetone, 2, 374 Erhium(ill) complexes glycolic acid, 2, 472 Eriochalcite, 6, 855 Eriochrome black T metallochromic indicators, 1, 555 Eriochrome blue black R metallochromic indicators, I, 556 Eriochrome cyanine R metallochromic indicator, 1, 556 Erythrocruorin, 6, 689 dioxygen transport, 6,683 stability... 

Analysis. Be can be quantitatively determined by colorimetry down to 40 ppb using eriochrome cyanine R or acetylacetone. The sensitivity may be improved by electrothermal absorption spectroscopy (ETAS) to 1 ppb and to 0.1 ppb by inductively-coupled plasma emission spectroscopy (ICPES) or inductively-coupled plasma mass spectroscopy (ICPMS). A simple spot test for qualitative detection of Be is one with quinalizarin in alcoholic NaOH which can detect 3 ppm. The color is produced by both Be and Mg. If the color persists after the addition of Br2 water. Be is present. If the color is bleached. Mg is indicated. 

C23H18O9S, 4 -hydroxy-3,3 -dimethyl-2"-sulphofuchsone-5,5 -dicarboxylic acid (eriochrome cyanine R), H4L ... 

GroBere Bedeutung hat dagegen das chlorfreie Produkt, Eriochrom-cyanin , oft auch als Eriocliromcyanin R ... 

Eriochrome Cyanine R (ECR) (formula 4.17) and Chrome Azurol S (CAS) (formula 4.18) have carboxylate groups besides hydroxyl and sulphonate groups [41,42]. These reagents can be purified by various methods [43,44]. ECR and CAS react with many metals in weakly acidic or neutral solutions [45-47]. The yellow-orange colour of the reagents changes to blue or violet solutions of the metal chelates. 

The extraction method using 8-hydroxyquinoline is not very sensitive, but it is highly selective. The really sensitive methods for spectrophotometric determination of aluminium are based on ternary systems, including triphenylmethane reagents (mainly Chrome Azurol S and Eriochrome Cyanine R) and some surfactants. 

Eriochrome Cyanine R (ECR) (formula 4.17), triphenylmethane reagent, is often used for determining aluminium, like the CAS presented above [29,30]. The optimum pH for the colour reaction lies within the rather narrow limits of 6.0-6.2. The absorptivity of the complex drops rapidly at higher or lower pH values [29]. The molar absorptivity of the complex is -6.5-10" at 535 nm. Interfering Fe(III) can be reduced with ascorbic or thioglycolic acid. Also many other elements interfere [30]. 

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

Triphenylmethane and azo reagents are used in most methods for determining beryllium. Methods using Chrome Azurol S or Eriochrome Cyanine R and some cationic surfactants are very sensitive. The selectivity of methods for beryllium determination is improved by the use of EDTA as masking agent. 

Eriochrome Cyanine R (ECR) (formula 4.17) reacts with beryllium ions [4,9,10,16,30] similarly to Chrome Azurol S (see Section 9.2.1). At pH 9.7, A-max of ECR is 435 nm and that of its water-soluble beryllium complex is 525 nm. The molar absorptivity of the complex is 1.5 10 . EDTA, tartrate and cyanide are used as the main masking agents for interfering metals. In the presence of cationic surfactants, the sensitivity is increased several times, and significant bathochromic shifts are observed. In the case of CTA, e = 8.7-1 O at 590 nm (pH 7) [31,32]. Beryllium was also sorbed on anion exchange resins impregnated with ECR [33]. 

Eriochrome Cyanine R was applied in determination of beryllium in water [33] and in silicates [4]. 

Methods for chromium with use of triphenylmethane reagents are less sensitive examples are Chrome Azurol S (e = 5.9-10 ) [43,44], Xylenol Orange (e = 1.0-10" ) [45], and Malachite Green [46]. A much higher sensitivity is obtained when Cr(III) is determined with the use of Eriochrome Cyanine R in the presence of surfactant CTA (e = 6.8-10" ) [47]. Cr(lll) was determined with Eriochrome Cyanine by means of the derivative spectrophotometry [48]. 

The direct method for determining traces of fluoride is based on the coloured ternary complex formed by fluoride with Alizarin Complexone and lanthanum or cerium(III). Fluoride ions form stable complexes with some multivalent metals, namely Zr, Th, Ti, Fe(III), and Al. The colour changes resulting from the reactions of fluoride with coloured complexes of these metals provide indirect methods for the determination of fluoride. Examples of these methods are the Eriochrome Cyanine R-zirconium method, and the (less sensitive) Fe(III)-sulphosalicylate method. 

Zirconium ions (in dilute HCl) react with Eriochrome Cyanine R (ECR) (formula 4.17) to form red complexes. The complex formed at a deficiency of ECR ( max = 515 nm) is favoured by a more acidic medium (pH 0-1). Conversely, the complex formed in the presence of excess of ECR ( max = 540 nm) is formed at lower acidities (pH 1-2). The absorption maximum of Eriochrome Cyanine R in dilute HCl is at 475 nm. 

The most suitable molar ratio of Zr-ECR in the zirconium-Eriochrome Cyanine R reagent is 1 4. The highest sensitivity of the reaction is obtained at pH 1 0.1 [39]. 

Zirconium-Eriochrome Cyanine R reagent (Zr ECR molar ratio = 1 4), freshly prepared. 

As well as the zirconium-Eriochrome Cyanine R complex, the coloured complexes of zirconium with other organic reagents are used for indirect spectrophotometric determination of fluoride. These include Alizarin S [44-46], SPADNS [6,16,47,48], Xylenol Orange [49-52] Chrome Azurol S [53], and rutin [54]. 

In indirect methods for determination of fluoride, aluminium complexes with Eriochrome Cyanine R (ECR) [58] and Xylenol Orange [59] have been applied. The sensitivity of the ECR method increases considerably in the presence of CP [60]. The complexes of scandium with Methylthymol Blue (e = 1.07-10 at 590 nm) and Pyrocateehol Violet [61] have also been recommended. 

The sensitive and selective spectrophotometric methods involve extraction of ion-associates of the GaCU" ion with basic dyes (e.g., Rhodamine B). Methods based on ternary complexes of gallium with chelating triphenylmethane reagents (e.g., Eriochrome Cyanine R) and some surfactants are very sensitive but less selective. 

Fig. 21.1. Absorption spectra of Eriochrome Cyanine (ECR) (vs. water) (1), Ga-ECR complex (2), and Ga-ECR-CTA complex (3) (vs. reagent blank) (pH 5.4)...

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