PARABENS LIPOPHILICITY DETERMINATION WITH MOBILE PHASES CONTAINING LOW AND MEDIUM HYDROPHOBIC ALCOHOLS

Abstract

The efficiency of low and medium hydrophobic alcohols as mobile phase additives for lipophilicity determination of parabens was investigated using reversed-phase liquid chromatography and C18 chromatographic column as stationary phase. The eluting strength was evaluated by methylene selectivity determination for different mobile phases, containing water (0.1% H₃PO₄)-hydrophobic alcohols mixtures, starting with methanol and continued with methanol with 1% upper alcohols (differing through one methylene group, from ethanol to octanol) as organic additive. A good linear dependence (R ² > 0.99) was observed between the retention factors (log k) and the organic content of the mobile phase in all cases. Several methodologies such as arithmetic mean computation of experimental retention values, extrapolation to zero methanol concentration procedure, and principal component analysis were applied to retention data values in order to determine relevant parameters [mlog k - mean of experimental retention values log k, log k_w – extrapolated capacity factor to 100% water, and respectively PC1/log k (scores corresponding to the first principal component)]. The evaluation of the experimental lipophilicity parameters revealed a significant correlation with the reference octanol–water partition coefficients (log K_ow) and also with various computed lipophilicity parameters (log P).

Keywords:

• elution strength
• hydrophobic alcohols
• lipophilicity
• mobile phase additives
• parabens
• reversed-phase liquid chromatography

Notes

^a experimental log K_ow determined by Hansch and taken from the KowWin database (http://esc.syrres.com/interkow/interkow.exe).

^b experimental log K_ow from the literature.^{[ 20 ]}

^c values calculated using Chem3D Ultra 8.0 software(http://www.cambridgesoft.com).

^d values calculated using SciLogP Application, version 2.2 from ALCHEMY 2000 software (http://www.tripos.com).

^e values calculated using SciQSAR Application, version 3.0 from ALCHEMY 2000 software (http://www.tripos.com).

*Fragment methodology (Episuite).

**Fragment methodology (Marvin Sketch).

***Shake-flask experiments.

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