INFRARED ANALYSIS OF LIPIDS OF THE $BRAIN^{*}$

Author Institution: Laboratories Philadelphia General HospitalBrain lipids (rat) were studied by infrared spectroscopy with the disc technique utilizing both adsorption and reversed-phase partition chromatography for lipid fractionation.Quantitative separation of phospholipids from cholesterol and fatty acids was obtained by chromatography with silica columns. The total phospholipid fraction thus obtained was dissolved in benzene and mixed with potassium bromide of small particle size (obtained by freeze drying of aqueous solutions of potassium bromide). Discs of 1/4-inch diameter were pressed from the frozen-dried mixture and studied by infrared spectroscopy with a beam-condensing unit. The resulting spectra clearly show the CO ester vibration of lecithin and cephalin at about $5.70 \mu$, the $NH_{2}$ vibration of sphingomyelin at about 6.40 $\mu$, and other characteristic bands at lower frequency. It is suggested that this technique may be useful for quantitative estimation of small amounts of phospholipids by infrared spectroscopy. Further separation of lipids was accomplished by reversed-phase partition chromatography using hexane as the stationary and aqueous methanol as the moving phase. Examination of the fractions thus obtained indicates that the combination of infrared spectroscopy and chromatography may permit accurate study of pure lipids