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.