Polymer Analysis by Micro-Scale Size-Exclusion Chromatography/MALDI Time-of-Flight Mass Spectrometry with a Robotic Interface

Polydisperse synthetic polymers cannot be characterized reliably by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI MS) alone. Coupling of size-exclusion chromatography (SEC) with MALDI MS provides both absolute mass calibration of the SEC column based on the polymer itself and determination of monomers and end groups from the mass spectra. Now a micro-scale SEC (μSEC) system has been developed in which the MALDI matrix solution is coaxially added to the column effluent and directly spotted onto the MALDI targets in a robotic interface. Each spot corresponds with a 10-s elution window from the μSEC column, thus yielding a narrow polymer distribution which is amenable to characterization by MALDI MS. This μSEC/MALDI MS system is less laborious and time-consuming and features very low solvent consumption and reduced solvent emission during the evaporation step as compared to the conventional-sized SEC/fraction collector systems applied in the past. The performance is demonstrated by the characterization of a polybisphenol A carbonate and a complex dipropoxylated bisphenol A/adipic acid/isophthalic acid copolyester resin.