A study of pine resin in softwood by 1D and 2D time-domain NMR

Time-domain nuclear magnetic resonance (TD-NMR) is widely used in the investigation of wood-water relationship. However, some ambiguities between the NMR signals and the components in wood remain unresolved, particularly the effect of pine resin on NMR signals. To clarify these ambiguities and increase the use of TD-NMR in wood research, different sample treatment methods were studied, including air-drying, low-temperature vacuum-drying, diethyl ether extraction and moisture isothermal adsorption. The corresponding one-dimensional (1D) T-1, T-2 and two-dimensional (2D) T-1, T-2 correlation relaxation time distributions of radiata pine and Douglas fir samples were investigated. The NMR signals accounted for "longer relaxation-time components" below the fiber saturation point (FSP), but overlaped in parts of the 1D relaxation time distributions making it difficult to distinguish between pine resin and moisture. The 2D T-1-T-2 correlation relaxation time distributions produced a better distinction between pine resin and bound water. This distinction established a quantitative relationship between pine resin, moisture and 2D NMR signal amplitudes.