<p>In this paper, a low molecular weight lignin was separated under an alkali medium from Moroccan date palm waste. The reaction of glyoxal with the extracted lignin was studied by Matrix-Assisted Laser Desorption/Ionization Time-of-Flight (MALDI-ToF) mass spectrometry for its use as a phenol substitute in Phenol–Formaldehyde (PF) wood adhesives. Glyoxal is an environment-friendly, nonvolatile and nontoxic aldehyde. Different reactions were found to occur during glyoxalation, in particular lignin depolymerization and recombination through condensation reactions with glyoxal to form glyoxalene bridges linking both lignin units and mainly fractions of lignin units derived from degradation during depolymerization. Solid state CP MAS ¹³C NMR (Nuclear magnetic resonance) analysis confirmed the presence of functional groups pertaining to structures that are formed from glyoxalation of the lignin observed by MALDI-ToF. The mass spectrometry appears to be a suitable method for examining lignin-glyoxal reactions.</p> Graphical Abstract <p></p>