Method of purifying eicosapentaenoic acid or the ester derivative thereof by fractional distillation

A continuous method for purifying eicosapentaenoic acid and esters of eicosapentaenoic acid, comprising:

• (a) feeding a starting mixture of eicosapentaenoic acid or esters of eicosapentaenoic acid to a first distillation column,
• (b) fractionally distilling the mixture using the first distillation column to obtain a bottom liquid fraction containing eicosapentaenoic acid or esters of eicosapentaenoic acid and higher-number carbon fatty acids and a top fraction containing lower-number carbon fatty acids,
• (c) condensing the top fraction and feeding it to a second distillation column, then fractionally distilling the condensed top fraction in the second column to obtain a top fraction containing the lower-number carbon fatty acids and a bottom liquid fraction, removing the top fraction from the second column to separate the fraction containing the lower-number carbon fatty acids from the system, and recycling the bottom liquid fraction in the second column to the first distillation column,
• while simultaneously feeding the bottom liquid fraction obtained in the first column to a third column, fractionally distilling the bottom liquid fraction in the third column to obtain a top fraction containing eicosapentaenoic acid or esters of eicosapentaenoic acid and a bottom liquid fraction containing the higher-number carbon fatty acids, removing the bottom liquid fraction from the third column to separate the fraction containing the higher-carbon number fatty acids from the system,
• (d) feeding the top fraction obtained in the third column to a fourth column, fractionally distilling the top fraction in the fourth column to obtain a top fraction containing purified eicosapentaenoic acid or esters of eicosapentaenoic acid,
• (e) collecting the top fraction containing purified eicosapentaenoic acid or esters of eicosapentaenoic acid, and
• (f) repeating steps (a) through (e),
• wherein the pressure in the distillation columns is maintained at 10 Torr or below and wherein the bottom temperature of the distillation columns is maintained at 210.degree. C. or below.

A method for purifying eicosapentaenoic acid and esters of eicosapentaenoic acid, comprising:

• fractionally distilling a mixture containing eicosapentaenoic acid or esters of eicosapentaenoic acid using a system of at least three distillation columns connected in flow arrangement to separate a fraction containing eicosapentaenoic acid or esters of eicosapentaenoic acid and other C.sub.20 fatty acids from a fraction containing lower-number carbon fatty acids and from a fraction containing higher-number carbon fatty acids,
• wherein the pressure in the distillation columns is maintained at 10 Torr or below and wherein the bottom temperature of the distillation columns is maintained at 210.degree. C. or below,
• collecting the fraction containing eicosapentaenoic acid or esters of eicosapentaenoic acid,
• treating the fraction containing eicosapentaenoic acid or esters of eicosapentaenoic acid with a solution of urea and a non-polar solvent to obtain a urea adduct, and
• removing the solvent by distillation to obtain a fraction containing concentrated eicosapentaenoic acid or esters of eicosapentaenoic acid.