Dopant-Assisted APCI for Enhanced Sugar Analysis: Overcoming Ionization Bottlenecks

Area of Science:

• Analytical Chemistry
• Mass Spectrometry
• Biomass Analysis

Background:

• Atmospheric-pressure chemical ionization (APCI) mass spectrometry (MS) faces challenges in lignocellulosic biomass analysis, specifically with carbohydrate ionization and fragmentation during pyrolysis.
• Unequal ionization and significant fragmentation of carbohydrates hinder accurate biomass pyrolysis studies.

Purpose of the Study:

• To investigate and overcome ionization disturbances in carbohydrate analysis using APCI-MS.
• To improve the detection and reduce fragmentation of carbohydrates in biomass pyrolysis samples.

Main Methods:

• Employed direct infusion (DI) and modified direct insertion probe (DIP) APCI coupled with Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS).
• Assessed the influence of solvent proton affinity (PA) on ionization processes.
• Modified the DIP system to incorporate dopants into the ion source via an inert gas stream.

Main Results:

• A significant PA difference between solvent and analyte promotes carbohydrate dissociation post-ionization.
• Water formed during carbohydrate dehydration can self-induce ionization and dissociation.
• Introducing ammonia as a dopant formed [M+NH4]+ adducts, reducing dissociation and increasing carbohydrate signal intensity by over tenfold.
• Successfully applied the method to standards and cellulose pyrolysis samples.

Conclusions:

• Dopant-assisted APCI (dAPCI) is a promising technique for rapid biomass fast pyrolysis assessment, especially for highly oxygenated compounds.
• Careful selection of dopants and solvents is crucial for preserving carbohydrate structural integrity during ionization analysis.