Retention in Normal-Phase Liquid Chromatography

Both the solvent-interaction model (Scott and Kucera, 1979) and the solvent-competition model (Snyder, 1968, 1983) have been used to describe the effects of mobile-phase composition on retention in normal-phase liquid chromatography. The solvent interaction model on the one hand provides a convenient mathematical model for describing the relationship between retention and mobile phase composition. The solvent competition model on the other hand provides a more complete, quantitative description of the relative strengths of adsorbents and organic solvents used in normal-phase chromatography. 

T. Hanai, Quantitative in silico analysis of retention in normal-phase liquid chromatography, / Liq. Chramatagr., Relat. Technol, 2010, 33, 297-304. 

The correlation coefficient for silica was significantly improved compared to the MI values calculated using the graphitized (Hypercarb ) carbon model. The coefficients for MIPS and MIHB were 0.807 and 0.856, compared to 0.558 and 0.706 obtained with the model carbon phase. No reasonable correlation was obtained for MIES and MIVW because these interactions are not the main contributors to retention in normal-phase liquid chromatography. In terms of chromatographic behavior, phenol and p-cresol were not outliers. Their strong retention on the graphitized carbon is partly supported by the silica gel model phase. 

Retention in Normal-Phase Liquid Chromatography Table 5.8... 

Due to the absence of hydrogen donor capabilities [31], cyanopropyl silica phases are less retentive in normal-phase liquid chromatography than under-ivatized silica or other NP packing materials. Therefore, very few applications have been reported that utilize cyanopropyl-bonded silica in the HILIC mode [32,33]. The limited number of applications may also be attributed to the mechanical instabiUty of cyanopropyl-bonded silica when operated with solvents of intermediate polarity. This instabihty is caused by a decrease in the adhesion of particles to each other that maintain the integrity of the column bed in either nonpolar or highly polar solvents [25]. Dinh et al. [34] performed a multivariate modeling of column selectivity by principal component analysis of chromatographic data from polar compounds of various structures on 20 commercially available HILIC columns and verified the low potential of cyanopropyl-bonded silica columns due to insufficient hydrophilicity. 

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