Rhodamine B Basic Violet

Rhoda.mines, Rhodamines are commercially the most important arninoxanthenes. If phthalic anhydride is used in place of formaldehyde in the above condensation reaction with y -dialkylarninophenol, a triphenyknethane analogue, 9-phenylxanthene, is produced. Historically, these have been called rhodamines. Rhodamine B (Basic Violet 10, Cl45170) (17) is usually manufactured by the condensation of two moles of y -diethylaminophenol with phthahc anhydride (24). An alternative route is the reaction of diethylamine with fluorescein dichloride [630-88-6] (3,6-dichlorofluoran) (18) under pressure. 

The resins used to make fluorescent pigments are usually toluenesulphonamide-melamine-formaldehyde matrices. The dyes used for this purpose include Cl Disperse Yellow 11, Rhodamine 6G (Cl Basic Red 1) and Rhodamine B (Cl Basic Violet 10). More details of the fluorescent dyes used have been given in a review by Christie [31]. 

Nonchelating dyes include basic triphenylmethane dyes (e.g., Brilliant Green, Malachite Green, Crystal Violet), xanthene dyes (e.g., Rhodamine B, Rhodamine 6G), azine dyes (e.g., Methylene Blue), and acid dyes (e.g., Eosin, Erythrosin). These are intensely colored and when paired with an oppositely charged analyte ion lead to high sensitivities. 

The most important xanthenes are the imino derivatives known as rhodamines, exemplified by rhodamine B (Cl Basic Violet 10) (3.23a), A. 543 nm and 552 nm and rhodamine 6G (Cl Basic Red 1) (3.23b), /L 530 and X 557 nm (Figure 3.11). These are intensively fluorescent dyes with quantum yields close to unity. Rhodamine 6G especially has found wide apphcation in dayhght fluorescent pigments (see section 3.5.2) and this ring structure has been much modified for use in many other outlets, especially as laser dyes (see section 3.5.3) and in biomedical applications (see section 3.5.6). 

In 1887, Ceresol produced a bright reddish violet (C.I. Basic Violet 10) which is now known as Rhodamine B (2a). 

Then in 1891, Monnet esterified Rhodamine B with ethyl chloride to produce Rhodamine A (C.I. Basic Violet 11) (2b). 

High sensitivity characterizes methods based on the formation of sparingly water-soluble ion-associates of germanomolybdate (Mo-Ge) with basic dyes. The compound with Rhodamine B can be floated and then dissolved in ethanol. The molar absorptivity is -3.7-10 [40]. The Mo-Ge compounds with Methylene Blue, Crystal Violet or Malachite Green, can be centrifuged and then dissolved in acetone. The molar absorptivities are 4.5-10, 4.2-10, and 6.2-10, respectively [41 3]. The ion associate formed by the Mo-Ge anion (reduced with ascorbic acid) with Chrompyrazole II has been floated by shaking with toluene, then dissolved in acetone [44]. 

The bromide complex of indium gives extractable ion-associates with the xanthene basic dyes Rhodamine B [49] and triphenylmethane dyes. Brilliant Green [50,51], and Crystal Violet [52], extractable into non-polar solvents. The related dye. Malachite Green, has been used to form an associate with tetra-iodoindate, extractable with benzene, hexane, and CCI4 [53]. 

Iodide ions (as F or I3 ) can be extracted as ion-pairs with basic dyes such as Crystal Violet [8,9], Brilliant Green [10,11], Rhodamine B (in toluene) [12], or Butylrhodamine (in benzene) [13]. After oxidation of iodide to iodine, the iodine is extracted into CCI4 and then stripped into the aqueous phase (as F) by shaking with thiosulphate. Finally, the F ions associated with Methylene Blue, are extracted into 1,2-dichloroethane [14]. 

Some methods based on ion-association of thiocyanate anionic complexes with basic dyes are very sensitive. To name a few, they include Crystal Violet (e = 2.3-10 ) [90], Rhodamine B [91,92], and Rhodamine 6G [92,93]. The ion-associate of... 

The most sensitive spectrophotometric methods for the determination of Re involve the extraction of ion-associates formed by Re04" with basic dyes. From among the triaryl methane dyes, use has been made of Methyl Green (benzene, e = 1.2-10 at 640 nm) [37], fuchsine (formula 27.1) [1] Brilliant Green (benzene, e = 1.010 ) [38], Crystal Violet [39], Victoria Blue 4R (formula 4.28) [40], Rhodamine B [41], Safranine T [42], Nile Blue... 

Sensitive extraction-spectrophotometric methods are based on the extractable (into CHCI3, 1,2-diehloroethane, benzene, or toluene) ion-associates of basic dyes and anionic Ag complexes with cyanide [35,36], iodide [37,38], and bromide [39]. In these methods, use has been made of such dyes as Crystal Violet [35,39], Brilliant Green [38,39], Malachite Green [39], Methylene Blue [36], and Nile Blue A [37]. In some of these methods the molar absorptivities are elose to MO [36,39]. A flotation method has been proposed, based on the addition compound [R6G ][Ag(SCN )2] [R6G ][SCN ] which is formed by silver ions (at pH 2-5) in the presence of thiocyanate and Rhodamine 6G (flotation with DIPE, the precipitated compound is washed and dissolved in acetone, e = 1.5-10 ) [40]. The complex Ag(CN)2 , associated with Crystal Violet, has been utilized in another flotation-spectrophotometric method of determining silver [41]. Silver has been determined also in a system comprising thiocyanate and Rhodamine B, as an aqueous pseudo-solution, in the presence of poly(vinyl alcohol) [42]. 

The bleaching of Methylene Blue by 8203 affords a sensitive method for determination of thiosulphate [70]. It is possible to determine thiosulphate after extraction of its ion-associates with some basic dyes, e.g., Rhodamine B, Rhodamine 6G, or Crystal Violet [71]. Thiosulphate present in concentrations of the order of 10 M have been determined after the oxidation with iodine by measuring the absorbance due to I3 [72]. Thiosulphate can also be determined in an indirect reaction, in which 8203 reacts with Hg(II) thiocyanate to release SCN which gives a colour reaction with Fe(III) [73]. A method for simultaneous determination of thiosulphate, sulphite, and sulphide has been proposed [74]. 

Thallium(III), in the form of the TICU or TlBr4" complex ions, reacts in acid media (1-2 M HCl) with the basic xanthene dye, Rhodamine B (formula 4.29), to form a red-violet, slightly fluorescent ion-associate complex, which is soluble in benzene, DIPE, and isoamyl alcohol. These extracts have been used for the spectrophotometric determination of thallium [8]. A mixture of CeHe and CCI4 (2+1) is a convenient extractant since it is denser than water. 

Some sensitive methods for determining uranium are based on ion-associates consisting of anionic uranium(VI) complexes and basic dyes such as Brilliant Green and Crystal Violet [118], Rhodamine B [119], Butylrhodamine B [120], Malachite Green [ 121], Brilliant Green [122,123]. In the methods based on anthranilic acid with Rhodamine 6G [124], or thiocyanate with Rhodamine B [125] the associates formed are not extracted, but the absorbance is measured for aqueous pseudo-solutions, protected with gelatine or poly(vinyl alcohol). 

High sensitivity characterizes the methods based on ion-associates formed by anionic complexes of V(V) with basic dyes. The Brilliant Green method has been described above [33]. The vanadium complex with PAR associated with Crystal Violet is extracted into a mixture of benzene with MIBK (3-f2) (e = l.l lO ) [51]. In a proposed flotation-spectrophotometric method, the V complex with 3,5-dinitropyrocatechol, associated with Rhodamine B, is separated by shaking the solution with cyclohexane the separated compound is washed and dissolved in acetone (e = 2.1-10 at 555 nm) [52], A similar sensitivity is achieved in the method using 5,7-dichloro-oxine and Rhodamine 6G [53]. Another flotation-spectrophotometric method for determining V has been based on 3,5-dinitrosalicylic acid and Rhodamine B [54]. 

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]. 

Mauveine, the original synthetic dye, was of the azine type, its principal component being compound 6.24. This particular group of dyes is now essentially only of historic interest. Xanthene dyes, such as Rhodamine B, Cl Basic Violet 10, 6.25, Rhodamine 6G, Cl... 

Solvents 1—3 in Table 128 are suitable for separating bismarck-brown (C. I. 21000) and other basic azo dyes [61, 83]. The triphenylmethane dyes, malachite green (C. I. 42000) and methyl violet (C. I. 42535) have been separated with solvent 4 [62]. Fuchsine (C. I. 42510), rhodamine B (C. I. 45170) and rhodamine 6G (C. I. 45160) can be separated with solvent 5. Rhodamine B, malachite green, crystal dolet (C. I. 42555), methylene blue (C. I. 52015) and Victoria blue B (C. I. 44045) have been separated with solvent 7, using silica gel layers on microscope slides [49]. Many basic dyes of the xanthene class which are used for histological staining, e. g.. Acridine Red 3B (C. I. 45000), Pyronine G (C. I. 45005), rhodamine S (C. I. 45050), rhodamine G (C. I. 45150) and rhodamine B, can be separated with solvents 8—10 [78]. Numerous subsidiary conta-... 

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