Determination of terpenes using NIRS

Background and Objective

The increased use of wood as a building material offers great potential for improving the carbon footprint in the construction industry. At the same time, improved insulation and reduced air permeability in buildings mean that volatile organic compounds (VOCs) from wood products can remain in the indoor air to a greater extent. Terpenes, which occur in coniferous woods, play a particularly important role in this context. According to the current standard method for determining VOCs (DIN EN 16516), it takes 28 days to obtain a measurement result. Storing the manufactured products for such a long period of time is not economically feasible.

The aim is therefore to develop an efficient procedure that enables faster quality control in industrial production. On the one hand, it should be possible to assess end products quickly; on the other hand, raw materials (e.g. sawn timber, boards) and intermediate products (e.g. dried or glued chips or strands) should also be tested in order to draw conclusions about the end product.

Target Group

Industry, Research

Approach

In this research project, we are developing a production-oriented method based on near-infrared spectroscopy and then comparing its measurements with the standardised chamber method. We are investigating the extent to which it is possible to reliably predict terpene emissions from pine wood (Pinus sylvestris) and which factors influence the quality of the model. Particular attention is paid to identifying the dominant emitters and to the question of whether the method is also suitable for heterogeneous wood materials.

Our Research Questions

Can terpene emissions be predicted using NIR spectroscopy?

Results

The study confirms that near-infrared spectroscopy (NIR) is a fast and reliable method for predicting terpene The investigations showed that near-infrared spectroscopy is a fast and reliable method for predicting terpene emissions from pine heartwood. Robust models were created for the dominant substances α-pinene and 3-carene in particular, enabling precise quantification. The model quality was checked using the coefficient of determination (R²CV), which was 0.77 for both α-pinene and 3-carene. These values confirmed the suitability of the method for emission analysis, especially for modelling individual terpenes. Analysis using principal component analysis (PCA) also identified clear spectral patterns that enable differentiation between wood samples with different emission values.

While the method proved to be reliable for solid wood, its transferability to heterogeneous wood-based materials was limited. Spectral variabilities and transmission effects made direct application of the models difficult, and the sensitivity of the method was also limited at low concentrations. Overall, the results show that NIR spectroscopy is a promising addition to the reference method. With further optimisation, particularly in the area of calibration strategies, the method could be extended to a broader spectrum of materials and substances in the future.