HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHIC DETERMINATION OF SOME OF THE HYDROLYTIC DECOMPOSITION PRODUCTS OF POLY(ALPHA-HYDROXYACID)S

An HPLC procedure is described for the separation and identification o f some hydrosoluble by-products resulting from the hydrolytic degradat ion of poly(alpha-hydroxyacid)s having biomedical interest: poly(L-lac tide), poly(DL-lactide), poly (glycolide) and poly(lactide-co-glycolid e). Peak identification was performed by comparing the respective rete ntion times with those of pure standards. It was observed that optimum shape and separation of peaks are considerably affected by the compos ition of the mobile phase, consisting of acetonitrile (A) and a 0.006 M K2HPO4 buffer (B), and, in particular, its pH and A:B ratio, which h ad to be adjusted to around 5.8 and 75:25 (v/v), respectively. Under t he investigated experimental conditions (aqueous suspension, 100 degre es C for 12 h under stirring), poly(L-lactide) is quite stable, poly(g lycolide) degrades easily to glycolic acid, whereas poly(DL-lactide) a nd poly(DL-lactide-co-glycolide) exhibit intermediate behaviour. Upon hydrolytic decomposition, these poly(alpha-hydroxyacid)s yield not onl y the corresponding acids, but also their linear dimers and, possibly, trimers, tetramers and higher oligomers.