Ternary solvent methods

Jandera, P, Predictive calcluation methods for optimization of gradient elution using binary and ternary solvent gradients, /. Chromatogr., 485, 113, 1989. 

The second approach is the one followed by Drouen et al. [502]. It is based on the experience that only in very few cases does the optimization of a quaternary mobile phase composition in RPLC yield an optimum that is truly quaternary, i.e. contains all four solvents. Hence, the procedure discussed before for ternary solvents usually leads to the global optimum. This argument, correct though it may be, only applies to the particular problem of mobile phase optimization in RPLC, and prohibits the application of the same method to other two-parameter optimization problems [582]. 

A number of other methods has been used to optimize ternary solvent systems, many of them69-71 similar to the window diagram used in GC. Only one more will be described briefly here. The authors, Schoenmakers et al.,72 have prepared what they call phase selection diagrams for several reverse phase LC separations. The solvents used for their mixtures are the same ones recommended by Snyder methanol, ACN, and THF. 

NPC is ideally suited for the analysis of compounds prone to hydrolysis because it employs nonaqueous solvents for the modulation of retention. An example of the use of NPC in the analysis of a hydrolysable analyte was demonstrated by Chevalier et al. [28] for quality control of the production of benorylate, an ester of aspirin. A major issue in benorylate production is the potential formation of impurities suspected of causing allergic side effects therefore monitoring of this step is critical to quality control. The presence of acetylsalicylic anhydride prohibited the use of RPLC since it can be easily hydrolyzed in the water-containing mobile phase. However, an analytical method based on the use of normal-phase chromatography with alkylnitrile-bonded silica as the stationary phase provided an ideal solution to the analysis. Optimal selectivity was achieved with a ternary solvent system hexane-dichloromethane-methanol, containing 0.2 v/v% of acetic acid to prevent the ionization of acidic function and to deactivate the residual silanols. The method was validated and determined to be reproducible based on precision, selectivity, and repeatability. 

Analysis of Phenolic Compounds. A Hewlett-Packard (Palo Alto, CA) Model 1090 HPLC System, was used to determine the levels of specific phenolic components. The HPLC system was equipped with a ternary solvent delivery system, a diode array UV-VIS detector, and HP ChemStation software for data collection and analysis. Full chromatographic traces were collected at 280, 520, 316, and 365 nm, and spectra were collected on peaks. The stationary phase was a Hewlett-Packard LiChrosphere C-18 coliram, 4mm X 250 mm, with 5 pM particle size packing. Operating conditions include an oven temperature of 40 C, injection volume of 25 pL, and flow rate of 0.5 mL/minute. The mefriod was based on a previously published method for phenolic components in wine (30) and used the modified solvent gradient shown in Table II. Solvent A was 50 mM dihydrogen ammonium phosphate, adjusted to pH 2.6 with orthophosphoric acid. Solvent... 

Barton"" " provides empirical methods based on solubility parameters for ternary solvent systems. All these methods provide only a qualitative idea on miscibility. The combination of regular solution theory and solubility parameters has been employed for predicting the partition coefficients of organic compounds between water and polystyrene and between alcohols and polyolefins. The results are useful to a first approximation. 

In Ellegaard, Abildskov, and O Connell (2010), data were analyzed from nine pharmaceutical solutes in a total of 68 binary mixtures of 10 solvents, with some of the mixtures at different temperatures. The absolute average relative deviation of using parameters from binary data was 23% while that from correlation of ternary data was 11%. Additional study of this method is described in Ellegaard (2011) with more solutes and binary solvents, as well as in some ternary solvents. Fignre 9.10 shows excess solubility results for representative systems. 

Barton provides empirical methods based on solubility parameters for ternary solvent systems. 

The above procedure cannot be used for a multisolvent system. Wang and co-workers (9,10J have extended the method to a three-solvent system. The principle of the method is the relationship between Rf and mobile phase composition in binary or ternary solvent systems the relationship between solute Rf and X is expressed by Eq. 6. 

The window diagrams approach has a distinct disadvantage compared with this method, because in window diagrams solvent optimization methods can only be generated with binary and ternary solvents (plus the base solvent). The simplex method can be used for multicomponent solvent... 

Gregory and Feldstein (94) developed an ion-paired, reversed-phase HPLC method for individual Be vitamers extracted with sulphosalicylic acid from different foods. Using a ternary solvent program, elution of nutritionally active Be vitamers from the analytical column was complete within 30 min. PLP was determined as its hydroxysulfonate derivative, following postcolumn introduction of a buffered solution of sodium bisulfite. This method was found suitable for vitamin Be analysis in foods of both plant and animal origin. Recoveries for PLP and PL from pork loin were <90% it was suggested that these vitamers were not completely released from muscle proteins, even in the presence of 5% sulfo-salicylic acid. 

In the previous edition of this book (160) I predicted that future developments in column technology would allow simple, isocratic separation of B vitamers encountered in biological material. In the past few years the ideal of simple, isocratic separation of the B vitamers has come true. HPLC methods developed in the 1980s usually relied on binary or even ternary solvent programs to separate the Be vitamers in a single run (76,136,139,141). The HPLC methods of the 1990s are usually isocratic, and some of them allow the separation of the B vitamers and 4-PA in a relatively short analysis time (77,144,146). The method developed by Kimura et al. (77) serves as an example. Kimura et al. achieved above-mentioned separation within 13 min. Furthermore, the addition of sodium bisulfite to the mobile phase allows on-column derivatization of PLP to its highly... 

Quasielashc light scattering was considered in detail in Chapter 4. The discussion here starts where Chapter 4 left off. The optical probe method refers to the special case of measurements on a ternary solvent matrix polymer rigid probe system in which the matrix polymer does not scatter significantly, while the probe species dominates scattering from the system even though it is dilute. Optical probe studies are formally similar to QELSS studies of ternary polymer polymer solvent systems containing an isorefractive polymer solvent pair. 

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