Use of solid-phase microextraction for measuring oil-water partition coefficients and correlation with high-performance liquid chromatographic methods for lipophilicity.
For flavour compounds, lipophilicity is often estimated by the partition coefficient between oil and water (log Koil-water), which is highly relevant to food. A modification of the shake-flask method is reported here where compounds are quantified in the two phases using solid-phase microextraction (SPME). SPME's highly sensitivity to non-polar compounds facilitates quantification in the water phase. Twelve flavour compounds representing a broad range of lipophilicities and functional groups were analysed by two methods. Their log Koil-water was determined using SPME quantitation and their log k(w) using a reversed-phase HPLC methodology. The isocratic capacity factor at 60% methanol and predicted log P value also showed high correlation factors with other methods. The octadecyl silylated surface of the HPLC column provides a matrix that interacts with lipophilic compounds where the retention time is the indication of lipophilicity. Both methods gave reproducible results (median 3% and 4% RSD) and similar but not identical values for lipophilicity. The relationship between the two methods is log k(w) =0.85 log Koil-water +0.48 with a correlation coefficient of 0.94. The new SPME detection method, with the ability to quantify limonene and 2-pentylfuran at 1 ppm in the water phase, is preferred for flavour compound analysis due to the applicability of oil-water partitioning in food.
Pollien
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P
Nestlé Research Center, Vers Chez les Blanc, Lausanne, Switzerland.
Roberts
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D
D002021:Buffers; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D005421:Flavoring Agents / Q000737:chemistry*; D008401:Gas Chromatography-Mass Spectrometry; D008055:Lipids / Q000737:chemistry*; D009821:Oils / Q000737:chemistry; D012995:Solubility; D014461:Ultracentrifugation; D014867:Water / Q000737:chemistry
D002021:Buffers; D005421:Flavoring Agents; D008055:Lipids; D009821:Oils; D014867:Water