Patent ID: 8324343

Claim:
A method for obtaining a purified biodegradable PLG polyester, comprising sequentially extracting PLG polyester having an average molecular weight (M w ) of about 15 kDa to about 45 kDa with a supercritical fluid comprising carbon dioxide at a temperature above about 50° C. and a pressure above about 1,000 psi to produce a series of purified biodegradable PLG polyester fractions dissolved in the supercritical fluid, recovering the series of fractions by evaporation of the supercritical fluid and collecting the PLG polyester fractions having a weight average molecular weight of about 20 kDa and about 35 kDa, respective polydispersity indices of less than about 1.65 and less than about 1.44, and respectively containing less than about 6.7 weight % and less than about 0.7 wt % of polymer having a weight average molecular weight of less than about 5 kDa.