2.4.5. Size exclusion chromatography
The molecular weights determinations were performed by
using a High performance liquid chromatography (HPLC)/SEC
instrument with four channels pomp JASCO PU-2089 Plus
equipped with a refraction index accessory JASCO RI 2031 Plus, a
multi-channel UV spectrometer JASCO UV-2077 Plus and an oven
for column model JASCO CO-2063 Plus interfaced with a personal
computer with the software Borwin 1.21.61 (JMBS DEVELOPMENT)
for the data elaboration.
Two columns of polystyrene/divinylbenzene of Polymer Labora-tories PLgel MIXED D and pre-column PL gel with a linearity range
of 1000–600 KDa were selected. The measurements were recordedby using thermostatic columns (30 C) with a flow of 1 m l/min. and
chloroform for HPLC (Carlo Erba – Italy) as eluent. The calibration
curve for the determination of the molecular weights was per-formed with monodisperse polystyrene samples as reference with
molecular weights: 254.000, 52.100, 24.300, 4.850 and 1.890 Da.
The PET sample preparation for HPLC/SEC analysis was done fol-lowing a procedure already reported in literature (Fox et al., 1997 ).