Soluble dyes rhodamine

Interfacial radical alternating copolymerization of hydrophilic vinylethers with hydrophobic maleates can be conducted in direct [181] and in inverse [182] miniemulsion, leading to encapsulation of organic liquids or water, respectively. Since the monomers do not homopolymerize, the alternating copolymerization can only take place at the interface where both monomers meet. The polymerization is initiated by an interfacially active azo initiator. The authors could show that the water soluble dye Rhodamine B can be encapsulated in the inverse miniemulsion process and released from the capsules [182]. 

Another sensitive colorimetric procedure is that of Mackenzie et al (1967), which utilizes the dye Rhodamine B to form benzene-soluble complexes with fatty acids. Nakai et al. (1970) developed a rapid, simple method for screening rancid milk based on the foregoing procedure. The test is said to detect rancid milk with an ADV above 1.2. Like the copper or cobalt soap method, the Rhodamine B reagent is also limited to the longer-chain fatty acids. Kason et al (1972) used the method employing Rhodamine 6G of Chakrabarty et al (1969) to investigate... 

Many consumers view the color of lipstick as the most important characteristic of this product. The colors and dyes of lipsticks are generally regulated within the United States and include many water-insoluble (oil-soluble) products, such as brilliant blue, erythrosine, amaranth, rhodamine, tartrazine, dibromofluorescein, and tetrabromofluorescein (bluish-red com-pound). The dyes must be water insoluble otherwise, the color would quickly fade or be removed in a short time by the consumer through the movement of the saliva-soaked tongue across the lips. Water-soluble dyes such as green or blue food dyes may be used to provide lipstick coloration, but they are usually first laked or combined with metal oxides such as aluminum hydroxide [A1(OH3)] to form an insoluble precipitate that is then suspended in the oil base of the lipstick. 

This very sensitive flotation-spectrophotometric method is based on the ion associate formed by the anionic chlorostannate(II) complex of platinum(II) with the xanthene basic dye Rhodamine 6G (formula 4.30) [41]. When the aqueous phase is shaken with DIPE, the sparingly soluble compound collects on the wall of the separating funnel. The solid associate is washed, dissolved in acetone, and its absorbance is measured. 

In hydrochloric acid medium, iridium reacts with SnCb ions to form an anionic complex which reacts with the basic dye, Rhodamine 6G (R6G), yielding a sparingly soluble ion-associate. The compound precipitates at the phase boundary when the solution is shaken (for about 1 min) with DIPE. The precipitate is readily soluble in acetone. This solution has been used as a basis for a very sensitive flotation-spectrophotometric method for determining Ir [6]. 

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. 

Karstens and Kobs have compared rhodamine B (25) and rhodamine 101 (26) as fluorescence quantum yield reference substances. For rhodamine 101 the quantum yield was 1.0 at all the temperatures investigated. This was not true for rhodamine B, and at room temperature d)p 0.5. A number of luminescence quantum counters based on organic dyes in polymer matrices have been described. " Poly(vinyl alcohol) films are suitable for water-soluble dyes, and poly(vinylpyrrolidone) is compatible with dyes soluble in organic solvents. 

As discussed earlier, the use of an indicator to determine the CMC can be applied to aqueous as well as non-aqueous systems. Rhodamine B, for example, can be added to detect reversed micelles at very low surfactant concentrations. The transition from monomers to micelles can then be followed by the depolarization of the fluorescence. Another method involving the use of a dye is dye solubilization. For non-aqueous systems, a water-soluble dye should be used, for example, Eosin Y or Merocyanin 540. As soon as the first aggregates form, the solubilized dye can be measured by its UV-Vis absorbance. This method yields satisfactory results for some surfactants. However, sometimes the solubilization of such a dye is so high that the micellar structure is affected by the dye. If the solubilization is weaker, the dye taken up by the micelles is often insufficient to produce a reasonable signal. Especially when the CMC is very low, the pseudo-phase volume fraction of the micellar phase at concentrations just above the CMC is far too low to solubilize a significant amount of dye. This makes it difficult to define a clear CMC and requires the evaluation of different water-soluble dyes. It should be mentioned that as with aqueous... 

Table 12-5 reveals a completely different behavior of the rhodamines comparing to PM dyes having low photostability when doped in PMMA. The high polarity of rhodamines can be the explanation of the low photostability in a flexible nonpolar medium. In this context, we note the low solubility of rhodamines in nonpolar solvents such as MMA, compared to the extremely high solubihty of PM dyes in the same solvent. 

Once formed phosphonium salts could have a significant effect on cellular processes, particularly on mitochondrial function. Ph3PMe has been used as a probe to measure membrane potentials, for instance in thyroid cells lymphocytes Escherichia and human granulocytes The lipid-soluble cation distributes itself across the membrane in accordance with the membrane potential Monovalent lipophilic cations which have significant membrane permeability are concentrated in mitochondria. For instance the laser dye Rhodamine 123 has been used as a specific probe for the localisation of mitochondria in living cells It has also been shown to have in vivo antitumour activity ... 

Deutsch also showed that an ionizable dye whose undissociated form is soluble in benzene, such as Rhodamine O, assumes the colour of the ionized form at the interface with water, when a benzene solution of the undissociated dye is shaken with water. Similar changes of colour may occur on glass or silica, cellulose, or on any solid surface Fajans8 has suggested that deformation of the adsorbed molecules may sometimes be responsible for the colour change. 

Uranine.—Phenolphthalein is a yellow crystalline compound, m.p. 250°. It is practically insoluble in water but is readily soluble in alcohol in which form it is used as an indicator. Fluorescein is a dark red crystalline compound, practically insoluble in water but soluble in alcohol. Its sodium salt is red in color but in dilute solution exhibits a remarkable green and yellow fluorescence, hence the name fluorescein. The salt is known as uranine. It is not used as a dye by itself because of its faint character but is used to mix with others in order to impart fluorescence. The rhodamines also possess fluorescent properties mostly blue and red. 

The base of the dye is a red powder, which is insoluble in water, but soluble in alcohol producing a red solution. The HCl salt, which is sold on the market as "Rhodamine B", is.a very fine violet black powder with yellow green fluorescence soluble in water to produce a deep red violet colour also soluble in alcohol producing a red solution melts at 2 0 C, boils at 310°C, but it begins to smoke gradually with the temperature rise from the melting point and is carbonized partly without vaporizing. The smoke particles of rhodamine B fro a smoke composition are insoluble in water. 

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]. 

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