High throughput characterization of biopolyol using DART-MS with ultra-fast polarity switching

Importance of the topic

Developing renewable alternatives to petroleum-derived materials is a critical goal in green chemistry. Biopolyols produced by liquefying starch and grafting propylene oxide offer a route to sustainable polyurethanes while reducing reliance on finite fossil resources.

Objectives and overview of the study

This work aimed to demonstrate a high-throughput, minimal-preparation approach for characterizing biopolyol and its polyurethane foam using Direct Analysis in Real Time mass spectrometry (DART-MS) combined with ultra-fast polarity switching. Key aims included identifying characteristic chemical structures, optimizing analysis conditions, and correlating mass spectral features with polymer properties.

Methodology

Samples analyzed included native starch, sucrose, liquefied starch, propylene oxide (PO)-modified liquefied starch (biopolyol), and biopolyol-based polyurethane foam. Small aliquots of each sample were introduced directly into the DART gas stream via a metal mesh or with forceps for foams. Analysis temperatures of 350 °C and 500 °C were compared to maximize decomposition and ionization of oligo- and polyhydroxyl compounds.

Instrumentation

• DART-SVP atmospheric pressure ion source (IonSense Inc.).
• Shimadzu LCMS-2020 single quadrupole mass spectrometer with ultra-fast polarity switching (15 ms) and scan rates up to 15 000 u/s.
• Shimadzu LCMS-IT-TOF hybrid ion-trap time-of-flight instrument for accurate mass confirmation.

Key findings and discussion

• In positive mode, starch and sucrose produced strong signals at m/z 342 and 504 corresponding to [Disaccharide+NH4–H2O]+ and [Trisaccharide+NH4–H2O]+. Negative mode revealed deprotonated oligosaccharide fragments.
• Optimal DART heater temperature was 500 °C, enhancing ion yield and spectral clarity for both polarities.
• Liquefied biomass showed dehydration products of glucose and glycerol, evidenced by ions at m/z 343 and 269 in negative mode, assigned to [Glucose+C3H6O3–H]– and [Glucose+C5H10O3–H]–.
• Biopolyol samples exhibited a characteristic 58 u mass interval in both polarities, indicating grafted propylene oxide units. Increased PO content correlated with lower viscosity and more frequent 58 u repeats.
• Polyurethane foam retained the same mass spectral pattern of biopolyol, confirming preservation of PO-modified structures after polymerization and foaming.

Benefits and practical applications of the method

The described DART-MS approach delivers rapid, high-throughput profiling of biomass-derived polyols and their polymer derivatives without chromatography or extensive sample prep. It enables real-time quality control of hydroxyl functionality, polymer modification degree, and reaction monitoring in industrial and research settings.

Future trends and potential applications

Advances may include coupling DART-MS with tandem MS for structural elucidation, extension to diverse biomass feedstocks (cellulose, lignin), integration into process analytics for continuous monitoring, and quantitative methods for polymer distribution and branching analysis.

Conclusion

Ultra-fast polarity switching DART-MS provides a powerful platform for direct, high-throughput characterization of biopolyol and derived polyurethane foams. The method reliably identifies oligosaccharide fragments and propylene oxide grafts, correlates spectral features with polymer properties, and supports sustainable material development.