Phase Classification

To fully characterize and categorize the solute selectivities of GC stationary phases, Rohrschneider and McRe5molds pioneered one of the earliest characterization methods [5,6]. The Rohrschneider-McReynolds system is the oldest and widely accepted stationary phase classification systems that is based on the retention of five probe molecules namely, benzene, bufanol, 2-penfanone, nifropropane, and pyridine. Each probe molecule is used to represenf a disfincf or a combination of interactions with the stationary phase. Benzene measures dispersive interactions with weak proton acceptor properties butanol measures dipolar interactions with both proton donor and proton acceptor capabilities 2-pentanone measures dipolar interactions with proton acceptor but not proton donor capabilities nitropropane measures weak dipolar interactions and pyridine measures weak dipolar interactions with strong proton acceptor but not proton donor capabilities. 

Figure 5.6 Chiral stationary phases classification according to chiral recognition mechanisms and chemical structures. (From Reference 256.)...

FIGURE 8.4 (See color insert following page 114.) Decision tree cell cycle phase classification, (a) Cells were stained to show their levels of DNA, phospho-H3, and EdU in each nucleus, (b) Every cell was classified as G1 (2N DNA), G2 (4N DNA), M (pH3 positive) or S (EdU positive) phases using the automated four-parameter decision tree model, (c) The results of the classification were shown in two scatter plots where cells in different phases were labeled with different colors, G1 (orange), G2 (green), M (red), and S (blue), respectively. 

Phase classification of side chain nematic polymers... 

Nauman and He [1994] simulated two dimensional spinodal decomposition for ternary polymer mixtures. Variations in volume fraction and interaction parameters of the constituents yielded a multiplicity of different morphologies, some of which were verified in the film experiments. A phase classification was presented for the morphologies obtainable with ternary polymer blends. 

So far we have discussed solvation properties at a reference temperature of 120°C. The choice of reference temperature arises from historical considerations. McReynolds chose this temperature to compile his extensive database of retention measurements for volatile solutes on a large number of stationary phases. His database has been widely used for exploring new approaches to stationary phase classification and has influenced others into using the same temperature to collect additional reference data to maintain compatibility with the original database. The choice of a standard reference temperature is of less concern than whether a single reference temperature is sufficient to classify solvent properties for use at temperatures distant from the reference temperature. There is only a limited amount of data for the influence of temperature on selectivity in gas-liquid chromatography [53,81,103,121,122]. In general polar interactions are... 

It may be supposed that the particular crystal structure of an intermetallic reflects the character and strength of bonding in a sensible way, and thus the crystal structure would be a good criterion for phase classification. However, this does not mean that intermetallics with the same crystal structure are similar with respect to bonding and properties since, e.g. the B2 structure is common to the intermetallic Ni Al and to the purely ionic salt CsCl, and in the case of the transition-metal disilicides with a... 

Various scales of solvent strength (polarity) and selectivity have been used to classify stationary phases. Classification based on polarity had to be abandoned because of the lack of a working definition. There is no substance that is uniquely polar and suitable to probe the polarity of other substances. Selectivity is defined as the relative capacity of a stationary phase for specific intermolecular interactions, such as dispersion, induction, orientation, and hydrogen-bond formation. Early attempts at a systematic definition of selectivity scales were based on the system of phase constants introduced by Rohrschneider and... 

Thermal polarized light microscopy of liquid crystal systems still primarily involves the identification of phase types. Recently, however, a number of novel phases with complex structures have been discovered and detailed examinations of the configurations of their defects are required in order to provide a basis for future phase classification. Thermal microscopy is also used extensively in examination of the alignment processes of liquid crystals, and, in a related context, electric-field studies on meso-phases are carried out in aligned cells. Electric-field studies are now used as adjuncts to phase classification, e.g., antiferroelectric phases are sometimes identified in the microscope with the aid of electric-field studies. 

To choose proper test substances, McReynolds studied the behavior of a large number of substances of the following compound classes alcohols, glycols, aldehydes, ketones, esters, acetals, ethers, oxides, hydrocarbons, chloro compounds, difunctional and polyfunctional compounds, and other miscellaneous substances. " For the stationary phase classification, he eventually proposed benzene, n-butanol, 2-pentanone, 1-nitropropane, and pyridine to represent compounds of different chemical interactions. " McReynolds characteristic phase constants for these five compounds describe the selectivity of the phase. 

In spite of some critical opinions, connected mainly with incorrect determination of retention indices of standard substances, the McReynolds constants system gave logical basis for stationary phase classification and allowed for selection of the proper gas chromatographic column. Until now, it has been the most common approach employed for stationary phase selectivity ranking in GC. 

The results of the first phase classification with 8 features by using leave-one-out method were tested, and the accuracy... 

Fig. 5 Statistically effective features (second phase classification)...

Fig. 6 System diagnostic efficiency (first phase classification) --------------------------------------------------------- IFMBE Proceedings Vol. 35...

Another important phase classification that can often be found in literature has been introduced by Winsor (Winsor 1948), who found four general types of phase equilibria. A Winsor type IV phase corresponds to classical single phase microemulsions consistent with Hoar s Schulman s definition (Hoar Schulman 1943). A Winsor type I system denotes two phases in equilibrium, an o/w structure and an almost pure oil upper phase. On the contrary, in a Winsor type II system an aqueous phase containing surfactant is in equilibrium with an w/ o microemulsion in the upper phase. Finally, Winsor type III structures equal a three-phase system consisting of a surfactant poor water phase, a bicontinuous middle phase, and an upper almost pure oil phase. 

---