There are number of publications on soyabean lecithin. You need to check which one is exactly serving your purpose. See following links for details.

http://naldc.nal.usda.gov/download/26685/PDF

http://link.springer.com/article/10.1007/BF02568014#page-2

Bailey's Industrial Oil and Fat Products offers the following information:

[Table 17, pg 377] Approximate Chemical Composition of Natural Commercial

Soybean Lecithin:

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• Soybean oil 35%
• Phosphatidylcholine 16%
• Phosphatidylethanolamine 14%
• Phosphatidylinositol 10%
• Phytoglycolipids and other minor phosphatides and constituents 17%
• Carbohydrates 7%
• Moisture ~1%

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Due to Lecithins being used in a myriad of applications (food and non-food), the specifications may differ greatly between suppliers and manufacturers subject to the application needs. For instance, de-oiled Lecithins (achieved via solvent/acetone extraction) would result in the triglyceride fraction listed above (Soybean oil) to be removed in the final product, effectively raising the phosphatidylcholine fraction from 9-17% in natural lecithins to around 20-23% in de-oiled products (see Bueschelberger et al., 2015.

Source:

Szuhaj, B. (2005). Lecithins. In: F. Shahidi, ed., Bailey's Industrial Oil and Fat Products, 6th ed. Hoboken, N.J.: John Wiley & Sons.

Bueschelberger, H., Tirok, S., Stoffels, I. and Schoeppe, A. (2015). Lecithins. In: V. Norn, ed., Emulsifiers in Food Technology, 2nd ed. West Sussex, UK: John Wiley & Sons.

See following links...........

http://www.fao.org/docrep/t0532e/t0532e02.htm

http://naldc.nal.usda.gov/download/26685/PDF

Thanks a lot....