Phospholipids, separation

Considering only the lipid phase as the transport pathway for the peptide, as the solute enters and diffuses across the membrane it will encounter a number of different microenvironments. The first is the aqueous membrane interface (Fig. 23). In this region, the hydrated polar headgroups of the membrane phospholipids separate the aqueous phase from the apolar membrane interior. It has been shown that this region is capable of satisfying up to 70% of the hydrophobic effect... 

Yip, H.S.H. Ashraf-Khorassani, M., and Taylor, L.T. Feasibility of phospholipid separation by packed column SFC with mass spectrometric and light scattering detection. 

A rapid method for phospholipid separation by HPLC using a light-scattering detector W. S. Letter, J. Liq. Chromatogr. 15 253 (1992)... 

Kim, L, Kim, J., Lee, K., and Tak, T. (2002) Phospholipids separation (degumming) from crude vegetable oil by poly-imide ultrafiltration membrane. Journal of Membrane Science 205, 113-123. 

Figure 11. Manifold for quantitation of phospholipids separated by HPLC by addition of diphenylhexatriene (DPH) to enhance fluorescence (after Ref. 218).

Eor phospholipids separation, various HPLC columns, e.g., silica, - - NH2,"° diol, " and polyvinyl alcohol" have been used. Silica columns were most often used. Both isocratic and gradient" mobile phases have been used. The most often used mobile phases are chloroform-methanol-water and hexane-isopropanol-water systems. The phospholipid classes can be separated very well by carefully adjusting the composition and time schedule of mobile phases. 

Precoated 20 X 20-cm silica glass plate (silica gel 60, layer thickness 0.25 mm, E. Merck). As discussed in Fried and Shapiro (1979), other layers may not be as satisfactory for phospholipid separations. 

Chloroform-methanol-water (65 25 4) for the phospholipid separation (see Experiment 3). 

Develop plates for neutral lipid separations as described in Experiment 1. Develop plates for phospholipid separations as described in Experiment 3. 

Figure 14 Two-dimensional scanning image of a phospholipid separated by TLC in an outside laboratory, transported to an analytical chromatography/SIMS instrument, and sputtered by cesium ions.

Table 6 Rf Values of Common Phospholipids Separated in Various Solvent Systems on Silica Gel...

Figure 6 Drawing of a thin-layer chromatogram of phospholipids separated from an extract of the digestive gland-gonad (DGG) complex of Biomphalaria glabrata snails. The silica gel G plate was developed in the first direction in chloroform-methanol-NH40H (65 35 5) and in the second direction in chloroform-methanol-water-acetic acid (65 25 4 1). Phospholipids were detected by using a variety of specific phospholipid detection reagents. Reproduced from Ref. 97 with the permission of Pergamon Press, Ltd.

Lipids may be quantified by charring with either dichromate or H2SO4 and then analyzed by photodensitometry (112). The charring technique may be combined with liquid scintillation, a procedure often used to quantify radiolabeled lipids (113). Phospholipids separated by TLC and then eluted from the plates may be quantified by classical wet chemical determination techniques for phosphorus (114). Similar techniques, although infrequently used, are also available for the hydrolysis products of various neutral lipids (46). Gravimetric methods can also be used to quantify lipids separated by TLC, but such methods may be unreliable since small amounts of sorbent, binder, or other... 

One of several bonded stationary phases to have been used in phospholipid separations with isocratic elution had a benzene sulfonate residue as the functional group. A column (4.6 x 250 mm) of Partisir -SCX and elution with acetonitrile-methanol-water (400 100 34 by volume) at a flow-rate of 2.5 mL/min were used to effect separation of the main ethanolamine- and choline-containing phospholipids of animal tissues [199,316]. While spectrophotometry at 203 nm was used to detect the components, phosphorus assay was preferred for quantification purposes. 

PC, PE, PI, PS, and phospha-tidic acid (PA) determination (after workup) in soybean lecithin separation according to acyl character observed MEKC Silica, 50 pm x 52 cm, 25 kV, 50-C for phospholipid separation 15-C for acyl distribution 0.035 M sodium deoxycho-late, 0.010 M Na2HP04, 0.006 M borax, 30% 2-PrOH, pH 8.5 UV,200nm 42... 

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