By taking the integrated area of methine 1 and dividing
it by the sum of methine 2 area and 1/3 of vinyl 3 area, one
can obtain the Mn for the sample. In this way, the 97 %
poly(L-lactic acid) and the poly(DL-lactic acid) have been
shown to have Mn of 52,000 and 14,000, respectively.