Raman spectroscopy for quantification of water-to-lipid ratio in phospholipid suspensions

In this paper, a way of quantification of the water-to-lipid ratio in aqueous suspensions of phospholipid vesicles by Raman spectroscopy is suggested. We measured the ratio of Raman intensities of the OH stretching band and the symmetric CH₂-stretching mode for series of water suspensions of different phosphatidylcholines with varied water-to-phospholipid ratio. It is shown that there is a simple linear relation between the ratio of Raman intensities and the water-to-lipid ratio if the number of CH₂ groups in the hydrocarbon chains is taken into account. The proportionality coefficient of this relation is determined for the gel and fluid phases of phospholipids.