Solvent systems, ternary

Figure 28 Diagram of the Ternary Solvent System for Methanol/Water Mixtures...

Frequently, ternary solvent systems are resorted to. Examples are water-propylene glycol-benzyl alcohol and water-propylene glycol-ethanol. In such cases the solubility profile is usually presentable by a ternary diagram [12]. This type of diagram usually demands a fair amount of work that is, solubility of the drug substance in many solvent compositions must... 

Fig. 16. Cross-relaxation or Z-spectra derived from the solvent proton spectra of cross-linked bovine serum albumin gel supported in a ternary solvent system consisting of 8.8% H2O, 8.7% acetone, and 8.8% methanol and 63% D20.The offset axis represents the frequency offset of the off-resonance preparation pulse which partly saturates the immobilized spin. In this case the 3 s preparation had an amplitude of 880 Hz at a Larmor frequency of 500 MHz (87).

Metabolism and pharmacokinetics of piprozolin were studied by RPC without prior clean-up of the urine sample (565). Misonidazole, metronidazole, and their metabolites have been analyzed using a ternary solvent system containing methanol-acetonitrile-5 mAf KH1PO4, pH 4, at volume ratios 4 3 93. The results facilitated the determination of the respective serum levels in a particular regimen of chemotherapy (364). The sig-... 

Recently, a study on the effect of cosolvents on a degradation of zileuton has been reported [104], Under aqueous conditions, zileuton follows Lrst order kinetics. In this study, authors have used a ternary solvent system consisting of water, ethanol, and propylene glycol to examine both the solubility and stability of zileuton. 

It would be impossible to handle ternary solvent systems such as acetonitrile/ water/methanol or mixtures which contain further additives such as triethyla-mine. Therefore most techniques nowadays use modulated shaped pulses for multiple presaturation or pulse frequency generation (PFG) techniques. With basic hardware, it is then possible to suppress an arbitrary number of solvents. 

Polar group selectivity also occurs in ternary solvent systems (5.10). For example, the addition of 5% to 25% of a third solvent to a water-acetonitrile mixture can alter the relative retention of peaks, and often resolve overlapping peaks. Dolan et al (11) have employed ternary mobile phases of water, methanol and tetrahydrofuran to analyze vitamin tablets where interfering peaks could not be resolved with binary mixtures. See Figure 4. 

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. 

Improved Resolution in High Performance Liquid Chromatography Analysis of Polynuclear Aromatic Hydrocarbons Using Ternary Solvent Systems... 

Figure 4. Orthogonal representation of ternary solvent systems ABC and BC D ...

Figure 5. Ternary solvent system design check points for determination of lack-of-fit indicated by open circles.

Figure 12. Comparison of binary and ternary solvent systems for soft coal tar pitch (A) acetonitrile/water, 55 45 to acetonitrile/water, 72 28 linear, 30 min (B) acetonitrile/methanol/water, 48 8 44 to acetonitrile/methanol/water, 43 37 20 ...

Figure 13. Comparison of binary and ternary solvent systems for "hard coal tar pitch same solvent ratios as Figure 13 40-min linear gradient.

Michaels et al.50 53) reported the chemical and physical properties of the polyelectrolyte complex of NaSS-PVBMA. This complex is used as a membrane in various fields. Polyelectrolyte complexes prepared by casting homogeneous solutions of ternary-solvent systems mentioned above are transparent and amorphous. Dried polyelectrolyte complexes are hard materials whereas wetted ones are rubber-like or skin-like. The polyelectrolyte complex with an equimolar composition is neutral whereas that with a non-equimolar composition can display ion-exchange properties. The range of the water content depends on the excess of polycation or polyanion in the complex. 

Fig. 17 a, b. Solubility of polyelectrolyte complexes in ternary solvent systems at 30 °C. 

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. 

In ternary organic mobile phases with a constant concentration ratio of two solvents with great elution strengths, (px/tpi, the sum of the two concentrations, tpx =

retention behaviour in normal-phase ternary solvent systems often can be described by the equation formally identical with Eq. (1.15) [27,80], as is illustrated by Fig. 1.20 ... 

Development is carried out in tanks without liners, for experience has shown that the shape of the spot is more symmetrical if there is no liner present, especially when binary or ternary solvent systems are used. 

Experimental design methodology was applied for the optimization of the elution program for the RP-HPLC resolution of a mixture of nine phenols, with a ternary solvent system (water-AcOH-MeCN). Important factors were the initial isocratic elution, the gradient running time and the gradient curvature . ... 

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. 

FlO. 40. Kinetics of formation of colored species from DPE in a ternary solvent system viz., 2.90 M ClCH,COOH in CHsCOOH plus 15% H,S04. Hydrocarbon concentration was 1.02 X 10 4 M in the combined solvent. 

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