Lipophilicity index

Retention Factors Used as RPLC Lipophilicity Indices... 

Martel, S., Carrupt, P. A. Retention factors in RP-HPLC as lipophilicity indices comparison between extrapolated and non-extrapolated logfc . Unpublished results. 

Block polymers that are able to form core-shell particles in aqueous media are also very promising. For example, lipophilic indicators can be embedded into the core of a block polymer of styrene and vinylpyrrolidone. The neutral lipophilic shell is responsible for the unique stability of the beads in water which do not aggregate even at very high ionic strength. 

The purpose of this review is to summarize the conditions used to derive chromatographic lipophilicity indices, to appraise associated difficulties, and to provide an overview of their relation with octanol-water partition coefficients. In this aspect, both techniques will be discussed in parallel. 

The lipophilicity indices measured by RP-TLC and HPLC are derived from the retardation factor Rf and the retention time h, respectively. R( and h are converted to the logarithm of the capacity factor ( M/log Id) via Eqs. 1 and 2 ... 

However, extrapolated capacity factors may be affected by the nature of the organic modifier. In a study concerning the measurement of lipophilicity indices for monosubstituted benzenes by HPLC, the log values of the more polar derivatives appeared to be lower when methanol was used as an organic modifier, compared to the log values obtained with acetonitrile. In contrast, for nonpolar derivatives, acetonitrile led to lower log fcw values. An analogous decrease in the log fcw values for a series of lipophilic 9//-xanthene and 9//-thioxan-thene derivatives was observed when tetrahydrofuran was... 

RP-TLC and HPLC provide a variety of descriptors that can be used as lipophilicity indices. Among them, extrapolated capacity factors often lead to 1 1 correlation with octanol-water log P. On the other hand, isocratic capacity factors need fewer experiments to be determined however, they depend strongly on chromatographic conditions. The CHI combines easy and rapid measurements with a uniform lipophilicity scale. However, both h-pophilicity and reversed-phase chromatographic retention are composite phenomena and, consequently, their resemblance cannot always be anticipated. Because standard reference sets cannot be available for all strucmrally diverse compounds, a comparison between chromatographic indices and octanol-water log P within the series of the investigated compounds is still indispensable. 

Testa, B. Measurement of lipophilicity indices hy reversed-phase high-performance hquid chromatography 21. 

The lipophilic indices for insulin and its acyl derivatives were calculated from the HPLC retention times of these compounds. The lipophilicity (log K ) of the novel analogs was larger than that of native insulin, suggesting that chemical modification with fatty acids improved lipophilicity of insulin with increasing carbon numbers of fatty acids attached to the native insulin [57]. 

Medina-Castillo et al. [187] fabricated a new multifunctional nonwoven mat made of tri-functional core-shell fibers prepared by coaxial electrospinning. A fluorescent pH-sensitive copolymer was used for the shell while the core contained magnetic NPs and a lipophilic indicator dye. Therefore, the fibers were magnetic, sensitive to O2, and able to change their optical properties upon pH change, thus enabling the optical monitoring of pH and O2 in sim and in real time. 

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