Evaluation of the Deterioration State of Archaeological Wooden Artifacts: A Nondestructive Protocol based on Direct Analysis in Real Time – Mass Spectrometry (DART-MS) Coupled to Chemometrics

Abstract

Evaluating the deterioration state of archeological wood is obligatory before the preservation of archeological wooden artifacts. Herein, a nondestructive, accurate, and rapid methodology is first developed via direct analysis in real time-mass spectrometry (DART-MS) with chemometrics to classify archeological wood and recent wood into 3 groups according to their deterioration states. As water in wooden artifacts probably affected the ion fragmentation process during DART-MS, ions responsible for evaluating the deterioration state were separately screened toward waterlogged archeological wood and dried archeological wood by partial least-squares discriminant analysis (PLS-DA). The well-defined separation of severely decayed archeological wood, moderately decayed archeological wood and recent wood was revealed in PLS-DA models. Twenty and 27 wood fragment ions were further screened as key variables to evaluate the deterioration state of waterlogged archeological wood and dried archeological wood, respectively. They were tentatively identified as ions of lignin monomeric compositions, lignin dimers, lignin trimers, and oligosaccharides. Results strongly suggested that differences in the structure and relative abundances of wood cell wall components accounts for the evaluation of deterioration state by DART-MS coupled to chemometrics. PLS-DA models provided R 2 Y = 0.836, Q 2 = 0.817, and R 2 Y = 0.754, Q 2 = 0.682 were then established separately using mass spectral fingerprints of respective potential predictive wood fragment ions. Furthermore, archeological woods, consisting of Castanopsis, Quercus, Idesia, Populus, and Cunninghamia species and with an average MWC range of 103–465%, were used as an external validation set and evaluated with the methodology developed herein and the MWC criteria. Results showed that DART-MS coupled to chemometrics could accurately predict the inhomogeneous deterioration states of archeological wooden artifacts and avoid the interference of inorganic deposits, in comparison with the MWC criteria.

Plasma‐based ambient mass spectrometry: Recent progress and applications

“…Dong et al utilized TD‐DART‐MS to classify Cannabis hemp cultivars with principal component analysis (PCA) and partial least squares discriminant analysis (PLS‐DA) models. In addition, DART‐MS coupled to chemometrics was also applied to achieve the nondestructive evaluation of the deterioration state of archeological wooden artifacts, and the analysis time was only 0.7 min per sample (Guo et al, 2020).…”

Rapid detection and classification of hongmu by atmospheric pressure ionization mass spectrometry

“…Atmospheric pressure ionization MS 22,23 attracts considerable attention due to its easy sample pretreatment in identifying mixtures. To a certain degree, the emergence of desorption electrospray ionization (DESI) 24 and direct analysis in real time (DART) 25 demonstrated the possibility of ionizing and sampling analytes directly from the sample surface.…”

“…V. Deklerck et al 26 studied DART-MS in combination with a random forest as a powerful tool for wood species identification. Yin et al 22 published a paper in which they described that DART-MS took 0.7 min for each wooden artifact and could accurately predict the inhomogeneous deterioration states of archeological wooden artifacts when coupled to chemometrics. Apart from that, desorption atmospheric pressure chemical ionization mass spectrometry (DAPCI-MS) was applied for the differential analysis of untreated camphor wood products with sufficient sensitivity and high throughput, allowing a confident differentiation of camphor wood products from other wood samples within 3 min.…”

Wood from Angiosperms and Gymnosperms Shows Distinctive Lignin Peaks in Direct Analysis in Real Time (DART) Mass Spectra

“…Adams proposed structures for the principal peaks arising from the DART-TOFMS analysis of lignin in an article about the analysis of printing and writing papers [20]. Guo et al detected lignin peaks by DART mass spectrometry in an evaluation of the deterioration state of archaeological wooden artifacts [21]. Crawford et al compared DART and spray ionization methods for lignin analysis mass spectrometry and concluded that spray methods produce more high-mass species than DART [22].…”