IDENTIFICATION BY HEADSPACE GAS-CHROMATOGRAPHY MASS-SPECTROMETRY OF IN-VITRO DEGRADATION PRODUCTS OF HOMOPOLYMERS AND COPOLYMERS OF L-LACTIDE AND D,L-LACTIDE AND 1,5-DIOXEPAN-2-ONE

Poly(L-lactide) (PLLA), poly(D,L-lactide) (PDLLA), poly(1,5-dioxepan-2 -one) (PDXO) and six different types of copolymers of L-LA-DXO and D,L -LA-DXO (80:20, 50:50 and 20:80) were hydrolysed in vitro in phosphate buffer (pH 7.4) at 37 degrees C for periods of up to 20 months and th e degradation products were identified by headspace gas chromatography -ion trap mass spectrometry. A suitable method to identify the decarbo xylic acids and hydroxy acids formed was developed using derivatizatio n with ert.-butyldimethylsilyl-N-methyltrifluoroacetamide reagent. The derivatives gave a single chromatographic peak with no tailing in the mass spectra. The main products identified in the in vitro buffers ar e lactic acid and 2-hydroxyethoxypropionic acid, which are the linear forms of the monomers D,L- or L-lactide and 1,5-dioxepan-2-one. The am ount of degradation products formed depends on the copolymer compositi on and the degradation time.