Dye partitioning

Rogers et al. [2] demonstrated the reversible pH-dependent liquid-liquid partitioning of the well-known indicator thymol blue between water and [C4CiIm][PFg]. Neutral (zwitterionic) form of the dye partitions mostly to the IL phase, while the charged forms prefer the water phase. To adjust pH, the authors used mineral acids and bases no significant difference in the... 

The membrane or interfacial potential, particularly in biological applications, is often determined from the change in fluorescence of added carbocyanine dyes (12, 13). The fluorescence intensity of the dyes depends on the solvent in which the dyes are present. When the dyes are used as potential-sensitive probes, their fluorescent intensity is a function of the interfacial potential across the membrane. We studied the behavior of dye transport on a phase boundary between water and nitrobenzene to better understand the principles of the potential dye partitioning as a function of interfacial potential (141... 

Several chelating dyes partition quantitatively to the PEG-rich phase in an ABS [52]. The majority of the early literature dealing with metal ion partitioning in ABSs concerned the extraction of f-block elements with dyes in ABSs formed between PEG-2000 and (NH4)2S04, Na2SOd, or K2CO3 [7,8,14,17-22,62,64]. The most widely studied dyes (Fig. 19) are Arsenazo... 

The pH-dependent partitioning of an ionizable, cationic dye, thymol blue, has also been investigated [6]. The dye partitions preferentially to the IL phase in the neutral, zwitterionic and monoanionic forms (from acidic solution), the partition coefficient to the IL increases with increasing IL hydrophobicity. Under basic conditions, the dye is in the dianionic form and partitions to water (Fig. 3.3-10). 

Figure 4. Comparison of Different Methods for Determination of Sulfate Endgroups of Latex A-2 0 dye partition,...

Latex surface titration Polymer solution titration X-ray fluorescence Dye partition... 

EFFECT OF POLYMER POLARITY ON THE ESTIMATION OF CHARGED GROUPS IN POLYMERS BY DYE-PARTITION TECHNIQUE... 

The amount of ionic end groups in high polymers has some bearing on the stability of "clean polymer colloids . In a recent publication Vanderhoff et al reported that the estimation of sulfate end groups by the dye partition method in polystyrene... 

From the foregoing discussion it is clear that the success of the dye partition method for the analysis of ionic end groups in polymers is controlled principally by the character of the organic solvent used in extraction and not by the polarity of the polymer. Solvents with some pennanent dipole moment capable of solvating... 

Ghosh and co-workers [42] carried out end-group analysis of persulfate-initiated PS using a dye partition and a dye interaction technique. Sulfate and hydroxyl end groups are usually found to be incorporated in the polymer to an average total of 1.5 to 2.5 end groups per polymer chain. 

Banthia and co-workers [43] determined sulfate, sulfonate and iso-thioronium salt end groups in PS by the dye-partition technique. Polymer polarity did not affect the results of end-group determination. Nitrile groups incorporated in PS by initiation or copolymerisation have been detected and estimated by dye-partition techniques after reduction to amino groups with lithium aluminium hydride in tetrahydrofuran [44]. 

Results obtained by Ghosh and co-workers [42, 64] in end-group analyses of PMMA indicate that all the polymer samples exhibit a positive response to methylene blue reagent in the dye partition test, indicating at least some sulfate (OSO ) end groups. 

Maiti and Saha [65] described a dye partition technique [66-68] utilising disulfine blue for the qualitative detection and, in some cases, the determination of amino end groups in the free radical polymerisation of PMMA. They found only 0.01-0.62 amino end groups per chain in PMMA made by amino-azo-bisbutyronitrile system, whereas in polymer made by the titanous chloride and acidic hydroxylamine systems they found 1.10-1.90 amino end groups per chain. 

Ghosh and co-workers [42, 69] also described a dye partition method for the determination of hydroxyl end groups in PMMA samples prepared in aqueous... 

Saha and co-workers [70] and Palit [66, 67] developed a dye-partition method for the determination of halogen atoms in copolymers of styrene, methylmethacrylate, methylacrylate, or vinyl acetate with a chlorine-bearing monomer such as allyl chloride and tetrachloroethylene. Copolymers were quaternised with pyridine, then precipitated with petroleum ether or alcohol, and fnrther purified by repeated precipitation from their benzene solutions with a mixture of alcohol and petroleum ether as the non-solvent. The precipitated polymers were then washed with petroleum ether and dried in air. The test for quaternary halide groups in polymers was carried out with a reagent consisting of disulfine blue dissolved in 0.01 M hydrochloric acid and the colour evaluated spectrophotometrically at 630 nm. Saha and co-workers [70] and Palit [66, 67] found that there may be some imcertainty in the quantitative aspects of this method. 

Banthia and Palit [38] applied dye partition end-gronp analysis procednres to the examination of sulfate end groups in C-labelled PS. 

A dye partition method has been decribed for the determination of low levels of nitrile groups in polystyrene [172]. 

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