Indirect conductometric detection of poly(oxyethylenes) after chromatographic separation

Temperature-induced phase separation of nonionic polyoxyethylated surfactant and application to extraction of metal thiocyanates

“…Although K0 was determined as 1.68 for Co(II) and 2. 19 for Cu(II) by using the solution not containing SCN", other partition coefficients cannot be determined. Since the literature values for A and ß2 are available,41•54 partition coefficients can be calculated by plotting the left side of eq 8 against L. Therefore, on the basis of the following equation, partition coefficients were evaluated.…”

Efficient evaluation of poly(oxyethylene) complex formation with alkali-metal cations

“…Refractive index detection was employed for a purely methanolic mobile phase, whereas POEs eluted with KI-containing mobile phases were conductometrically detected on the basis of a difference in mobility between K+ and K+-POE complexes. 18 The elution of POEs resulted in negative conductometric changes because of the lower mobility of a K+-POE complex than solvated K+. The retention time (ír) of each oligomer was read from chromatograms and converted into a capacity factor (k') according to the usual relation, k' = (ír -10)/to, where to is an elution time of an unretained analyte.…”

“…This suggests that only a 1:1 complex is formed in this case. The plots for PEG18 and PEG 23 appear to be linear. According…”

Pertraction of cations in a hybrid membrane system containing soluble polymeric ionophores

“…Actually, PEG and its derivatives have been used as extractants for various metal ions22–24 (i.e., starting from PEG300, which is composed of six to seven oxyethylene units, the PEG chain has adequate length for chelating metal cations). Simultaneously, as shown by Okada,25 the respective complex formation constants are dependent on the PEG degree of polymerization. The efficiency of PEG as the component of emulsion LMs26 and the corresponding comparison of PEG and its phosphoric acid derivatives were reported elsewhere 17, 27…”

“…However, due to the properties of POE units in the PPOEP macromolecule, the pertraction of ion pairs (characteristic for any neutral acyclic or macrocyclic carrier) is still possible to the degree controlled by free salt diffusion through the external ion‐exchange polymer membranes. It is also possible that POE units interact directly with counterions of sulfonic groups in the cation‐exchange membrane, as it was observed in the chromatography of PEGs on cation‐exchange resins 25. This effect can alternatively lead to enhancement of the interfacial ion‐exchange processes or to partial immobilization (retention) of POE units on the surface of the cation‐exchange membrane.…”