Laser ablation with resonance-enhanced multiphoton ionization time-of-flight mass spectrometry for determining aromatic lignin volatilization products from biomass

Abstract

We have designed and developed a laser ablation∕pulsed sample introduction∕mass spectrometry platform that integrates pyrolysis (py) and∕or laser ablation (LA) with resonance-enhanced multiphoton ionization (REMPI) reflectron time-of-flight mass spectrometry (TOFMS). Using this apparatus, we measured lignin volatilization products of untreated biomass materials. Biomass vapors are produced by either a custom-built hot stage pyrolysis reactor or laser ablation using the third harmonic of an Nd:YAG laser (355 nm). The resulting vapors are entrained in a free jet expansion of He, then skimmed and introduced into an ionization region. One color resonance-enhanced multiphoton ionization (1+1 REMPI) is used, resulting in highly selective detection of lignin subunits from complex vapors of biomass materials. The spectra obtained by py-REMPI-TOFMS and LA-REMPI-TOFMS display high selectivity and decreased fragmentation compared to spectra recorded by an electron impact ionization molecular beam mass spectrometer (EI-MBMS). The laser ablation method demonstrates the ability to selectively isolate and volatilize specific tissues within the same plant material and then detect lignin-based products from the vapors with enhanced sensitivity. The identification of select products observed in the LA-REMPI-TOFMS experiment is confirmed by comparing their REMPI wavelength scans with that of known standards.

Resonant two-photon mass-analyzed threshold ionization spectroscopy of 1-fluoronaphthalene and 2-fluoronaphthalene

“…In contrast, the resonance-enhanced multi-photon ionization (REMPI) [24,25] and MATI [18,[26][27][28] methods involve detection of ions and provide similar spectroscopic date with mass information. Recently, Zhang et al [29] pointed out that under typical supersonic jet-cooled conditions, 1FN can form clusters when irradiated by UV lasers of wavelength shorter than 315 nm.…”

Recent innovations in analytical methods for the qualitative and quantitative assessment of lignin

“…Time-offlight (ToF) secondary ion mass spectrometry (SIMS) is one such MS design that provides enhanced sensitivity to surface measurements of solid analytes with high mass spectral and spatial resolution, requires limited sample preparation, and yields rapid analyses over wide mass ranges [69][70][71][72]74,76]. Goacher et al developed an improved library of secondary ions for the differentiation between lignin and polysaccharide mass fragments [69].…”

“…A novel instrument for the analysis of lignin volatilization products from raw biomass was constructed by conjoining pyrolysis or laser ablation with resonance-enhanced multiphoton ionization (REMPI) reflectron ToF-SIMS [72]. A comparison of this instrument with pyrolysis electron impact molecular beam mass spectrometry (pyEI-MBMS) using poplar wood displayed the validity of the REMPI ToF-SIMS to selectively measure lignin, as no peaks from polysaccharides were measured.…”

“…Mass spectrometry, in its numerous configurations, has been employed to characterize the structure of lignin [62,[67][68][69][70][71][72][73][74][75][76][77]. Time-offlight (ToF) secondary ion mass spectrometry (SIMS) is one such MS design that provides enhanced sensitivity to surface measurements of solid analytes with high mass spectral and spatial resolution, requires limited sample preparation, and yields rapid analyses over wide mass ranges [69][70][71][72]74,76].…”

Two-color resonant two-photon ionization and mass-analyzed threshold ionization spectroscopy of o-chloroanisole

“…These methods involve detection of either photons or electrons with high sensitivity and spectral resolution. In contrast, the resonance-enhanced multiphoton ionization (REMPI) [11,12] and mass-analyzed threshold ionization (MATI) [13][14][15] techniques are subject to detection of ions and can also be used to obtain the same experimental data. We adopted the latter methods which provide mass information and are suitable for studies of molecular isotopomers, free radicals, complexes, and clusters.…”