2.2.1. Performance of Electrospray Mass Spectrometry (ESI-MSn) Analyses

Electrospray mass spectra were acquired by directly infusing the polyester sample into the ESI source of a Finnigan LCQ TM ion trap mass spectrometer (Finnigan, San Jose, CA, USA) with a syringe pump at a flow rate of 10 mL min−1. Nitrogen was used as the nebulising gas. The LCQ ESI source was operated at 4.5 kV, and the capillary heater was set to 200 ◦C. The polyester samples were diluted in a chloroform/methanol system (1:1; *v*/*v*). For fragmentation experiments, the ions of interest were isolated monoisotopically in the ion trap and were collisionally activated. The helium damping gas that was present in the mass analyzer acted as the collision gas. The ring electrode radio-frequency (RF) amplitude with a significant voltage range was set to a value that caused the peak height of the molecular ion to decrease by at least 50%. The analyses were accomplished in the negative-ion mode.
